SERVER-18137 Use NamespaceString for fully-qualified ns in sharding

87 files changed, 623 insertions, 680 deletions

diff --git a/src/mongo/db/catalog/coll_mod.cpp b/src/mongo/db/catalog/coll_mod.cpp
index 0f9ea8a543a..ee1de8b7627 100644
--- a/src/mongo/db/catalog/coll_mod.cpp
+++ b/src/mongo/db/catalog/coll_mod.cpp
@@ -595,7 +595,7 @@ void updateUUIDSchemaVersion(OperationContext* opCtx, bool upgrade) {
                     opCtx,
                     ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                     repl::ReadConcernLevel::kMajorityReadConcern,
-                    NamespaceString(CollectionType::ConfigNS),
+                    CollectionType::ConfigNS,
                     BSON("dropped" << false),  // query
                     BSONObj(),                 // sort
                     boost::none                // limit
diff --git a/src/mongo/db/key_generator_update_test.cpp b/src/mongo/db/key_generator_update_test.cpp
index 79b26326f18..ee33e8204bf 100644
--- a/src/mongo/db/key_generator_update_test.cpp
+++ b/src/mongo/db/key_generator_update_test.cpp
@@ -120,7 +120,7 @@ TEST_F(KeyGeneratorUpdateTest, ShouldCreateAnotherKeyIfOnlyOneKeyExists) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     {
         auto allKeys = getKeys(operationContext());
@@ -167,12 +167,12 @@ TEST_F(KeyGeneratorUpdateTest, ShouldCreateAnotherKeyIfNoValidKeyAfterCurrent) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     KeysCollectionDocument origKey2(
         2, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(110, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey2.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey2.toBSON()));
 
     {
         auto allKeys = getKeys(operationContext());
@@ -250,12 +250,12 @@ TEST_F(KeyGeneratorUpdateTest, ShouldCreate2KeysIfAllKeysAreExpired) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     KeysCollectionDocument origKey2(
         2, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(110, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey2.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey2.toBSON()));
 
     {
         auto allKeys = getKeys(operationContext());
@@ -347,12 +347,12 @@ TEST_F(KeyGeneratorUpdateTest, ShouldNotCreateNewKeyIfThereAre2UnexpiredKeys) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     KeysCollectionDocument origKey2(
         2, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(110, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey2.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey2.toBSON()));
 
     {
         auto allKeys = getKeys(operationContext());
diff --git a/src/mongo/db/keys_collection_cache_test.cpp b/src/mongo/db/keys_collection_cache_test.cpp
index 6f50180ac8d..5ecbd828915 100644
--- a/src/mongo/db/keys_collection_cache_test.cpp
+++ b/src/mongo/db/keys_collection_cache_test.cpp
@@ -78,7 +78,7 @@ TEST_F(CacheTest, GetKeyShouldReturnCorrectKeyAfterRefresh) {
     KeysCollectionDocument origKey1(
         1, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     auto refreshStatus = cache.refresh(operationContext());
     ASSERT_OK(refreshStatus.getStatus());
@@ -109,7 +109,7 @@ TEST_F(CacheTest, GetKeyShouldReturnErrorIfNoKeyIsValidForGivenTime) {
     KeysCollectionDocument origKey1(
         1, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     auto refreshStatus = cache.refresh(operationContext());
     ASSERT_OK(refreshStatus.getStatus());
@@ -132,17 +132,17 @@ TEST_F(CacheTest, GetKeyShouldReturnOldestKeyPossible) {
     KeysCollectionDocument origKey0(
         0, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(100, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey0.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey0.toBSON()));
 
     KeysCollectionDocument origKey1(
         1, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     KeysCollectionDocument origKey2(
         2, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(110, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey2.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey2.toBSON()));
 
     auto refreshStatus = cache.refresh(operationContext());
     ASSERT_OK(refreshStatus.getStatus());
@@ -173,7 +173,7 @@ TEST_F(CacheTest, RefreshShouldNotGetKeysForOtherPurpose) {
     KeysCollectionDocument origKey0(
         0, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(100, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey0.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey0.toBSON()));
 
     {
         auto refreshStatus = cache.refresh(operationContext());
@@ -186,7 +186,7 @@ TEST_F(CacheTest, RefreshShouldNotGetKeysForOtherPurpose) {
     KeysCollectionDocument origKey1(
         1, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     {
         auto refreshStatus = cache.refresh(operationContext());
@@ -217,7 +217,7 @@ TEST_F(CacheTest, RefreshCanIncrementallyGetNewKeys) {
     KeysCollectionDocument origKey0(
         0, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(100, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey0.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey0.toBSON()));
 
     {
         auto refreshStatus = cache.refresh(operationContext());
@@ -237,12 +237,12 @@ TEST_F(CacheTest, RefreshCanIncrementallyGetNewKeys) {
     KeysCollectionDocument origKey1(
         1, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     KeysCollectionDocument origKey2(
         2, "test", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(110, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey2.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey2.toBSON()));
 
     {
         auto refreshStatus = cache.refresh(operationContext());
diff --git a/src/mongo/db/keys_collection_client_direct.cpp b/src/mongo/db/keys_collection_client_direct.cpp
index bd97a92a20f..4148b589bab 100644
--- a/src/mongo/db/keys_collection_client_direct.cpp
+++ b/src/mongo/db/keys_collection_client_direct.cpp
@@ -83,7 +83,7 @@ StatusWith<std::vector<KeysCollectionDocument>> KeysCollectionClientDirect::getN
     auto findStatus = _query(opCtx,
                              ReadPreferenceSetting(ReadPreference::Nearest, TagSet{}),
                              repl::ReadConcernLevel::kLocalReadConcern,
-                             NamespaceString(KeysCollectionDocument::ConfigNS),
+                             KeysCollectionDocument::ConfigNS,
                              queryBuilder.obj(),
                              BSON("expiresAt" << 1),
                              boost::none);
@@ -130,10 +130,9 @@ StatusWith<Shard::QueryResponse> KeysCollectionClientDirect::_query(
 }
 
 Status KeysCollectionClientDirect::_insert(OperationContext* opCtx,
-                                           const std::string& ns,
+                                           const NamespaceString& nss,
                                            const BSONObj& doc,
                                            const WriteConcernOptions& writeConcern) {
-    const NamespaceString nss(ns);
     BatchedCommandRequest request([&] {
         write_ops::Insert insertOp(nss);
         insertOp.setDocuments({doc});
diff --git a/src/mongo/db/keys_collection_client_direct.h b/src/mongo/db/keys_collection_client_direct.h
index f588fcc9d6e..ff5784770cd 100644
--- a/src/mongo/db/keys_collection_client_direct.h
+++ b/src/mongo/db/keys_collection_client_direct.h
@@ -73,7 +73,7 @@ private:
                                             boost::optional<long long> limit);
 
     Status _insert(OperationContext* opCtx,
-                   const std::string& ns,
+                   const NamespaceString& nss,
                    const BSONObj& doc,
                    const WriteConcernOptions& writeConcern);
 
diff --git a/src/mongo/db/keys_collection_document.cpp b/src/mongo/db/keys_collection_document.cpp
index 155eb730a31..f9444250d57 100644
--- a/src/mongo/db/keys_collection_document.cpp
+++ b/src/mongo/db/keys_collection_document.cpp
@@ -47,7 +47,7 @@ const char kExpiresAtFieldName[] = "expiresAt";
 
 }  // namespace
 
-const std::string KeysCollectionDocument::ConfigNS = "admin.system.keys";
+const NamespaceString KeysCollectionDocument::ConfigNS("admin.system.keys");
 
 StatusWith<KeysCollectionDocument> KeysCollectionDocument::fromBSON(const BSONObj& source) {
     long long keyId;
diff --git a/src/mongo/db/keys_collection_document.h b/src/mongo/db/keys_collection_document.h
index 5571982fdac..c7fbae7ed79 100644
--- a/src/mongo/db/keys_collection_document.h
+++ b/src/mongo/db/keys_collection_document.h
@@ -30,6 +30,7 @@
 
 #include "mongo/base/status.h"
 #include "mongo/db/logical_time.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/db/time_proof_service.h"
 
 namespace mongo {
@@ -47,7 +48,7 @@ namespace mongo {
  */
 class KeysCollectionDocument {
 public:
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     KeysCollectionDocument(long long keyId,
                            std::string purpose,
diff --git a/src/mongo/db/keys_collection_manager_sharding_test.cpp b/src/mongo/db/keys_collection_manager_sharding_test.cpp
index ccdd0b653b8..4653653c836 100644
--- a/src/mongo/db/keys_collection_manager_sharding_test.cpp
+++ b/src/mongo/db/keys_collection_manager_sharding_test.cpp
@@ -109,7 +109,7 @@ TEST_F(KeysManagerShardedTest, GetKeyWithSingleKey) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     auto keyStatus =
         keyManager()->getKeyForValidation(operationContext(), 1, LogicalTime(Timestamp(100, 0)));
@@ -127,12 +127,12 @@ TEST_F(KeysManagerShardedTest, GetKeyWithMultipleKeys) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     KeysCollectionDocument origKey2(
         2, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(205, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey2.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey2.toBSON()));
 
     auto keyStatus =
         keyManager()->getKeyForValidation(operationContext(), 1, LogicalTime(Timestamp(100, 0)));
@@ -159,7 +159,7 @@ TEST_F(KeysManagerShardedTest, GetKeyShouldErrorIfKeyIdMismatchKey) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     auto keyStatus =
         keyManager()->getKeyForValidation(operationContext(), 2, LogicalTime(Timestamp(100, 0)));
@@ -172,11 +172,11 @@ TEST_F(KeysManagerShardedTest, GetKeyWithoutRefreshShouldReturnRightKey) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
     KeysCollectionDocument origKey2(
         2, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(110, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey2.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey2.toBSON()));
 
     {
         auto keyStatus = keyManager()->getKeyForValidation(
@@ -207,7 +207,7 @@ TEST_F(KeysManagerShardedTest, GetKeyForSigningShouldReturnRightKey) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     keyManager()->refreshNow(operationContext());
 
@@ -226,11 +226,11 @@ TEST_F(KeysManagerShardedTest, GetKeyForSigningShouldReturnRightOldKey) {
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
     KeysCollectionDocument origKey2(
         2, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(110, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey2.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey2.toBSON()));
 
     keyManager()->refreshNow(operationContext());
 
@@ -297,7 +297,7 @@ TEST_F(KeysManagerShardedTest, ShouldStillBeAbleToUpdateCacheEvenIfItCantCreateK
     KeysCollectionDocument origKey1(
         1, "dummy", TimeProofService::generateRandomKey(), LogicalTime(Timestamp(105, 0)));
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(KeysCollectionDocument::ConfigNS), origKey1.toBSON()));
+        operationContext(), KeysCollectionDocument::ConfigNS, origKey1.toBSON()));
 
     // Set the time to be very ahead so the updater will be forced to create new keys.
     const LogicalTime fakeTime(Timestamp(20000, 0));
diff --git a/src/mongo/db/s/balancer/balancer.cpp b/src/mongo/db/s/balancer/balancer.cpp
index 99fed7b8737..d537260c666 100644
--- a/src/mongo/db/s/balancer/balancer.cpp
+++ b/src/mongo/db/s/balancer/balancer.cpp
@@ -605,7 +605,7 @@ int Balancer::_moveChunks(OperationContext* opCtx,
             log() << "Performing a split because migration " << redact(requestIt->toString())
                   << " failed for size reasons" << causedBy(redact(status));
 
-            _splitOrMarkJumbo(opCtx, NamespaceString(requestIt->ns), requestIt->minKey);
+            _splitOrMarkJumbo(opCtx, requestIt->nss, requestIt->minKey);
             continue;
         }
 
@@ -650,7 +650,7 @@ void Balancer::_splitOrMarkJumbo(OperationContext* opCtx,
 
         chunk->markAsJumbo();
 
-        const std::string chunkName = ChunkType::genID(nss.ns(), chunk->getMin());
+        const std::string chunkName = ChunkType::genID(nss, chunk->getMin());
 
         auto status = Grid::get(opCtx)->catalogClient()->updateConfigDocument(
             opCtx,
diff --git a/src/mongo/db/s/balancer/balancer_chunk_selection_policy_impl.cpp b/src/mongo/db/s/balancer/balancer_chunk_selection_policy_impl.cpp
index c00455f05cd..5e89baca4e1 100644
--- a/src/mongo/db/s/balancer/balancer_chunk_selection_policy_impl.cpp
+++ b/src/mongo/db/s/balancer/balancer_chunk_selection_policy_impl.cpp
@@ -86,12 +86,11 @@ StatusWith<DistributionStatus> createCollectionDistributionStatus(
         Grid::get(opCtx)->catalogClient()->getTagsForCollection(opCtx, chunkMgr->getns());
     if (!swCollectionTags.isOK()) {
         return swCollectionTags.getStatus().withContext(
-            str::stream() << "Unable to load tags for collection " << chunkMgr->getns());
+            str::stream() << "Unable to load tags for collection " << chunkMgr->getns().ns());
     }
     const auto& collectionTags = swCollectionTags.getValue();
 
-    DistributionStatus distribution(NamespaceString(chunkMgr->getns()),
-                                    std::move(shardToChunksMap));
+    DistributionStatus distribution(chunkMgr->getns(), std::move(shardToChunksMap));
 
     // Cache the collection tags
     const auto& keyPattern = chunkMgr->getShardKeyPattern().getKeyPattern();
@@ -298,8 +297,8 @@ BalancerChunkSelectionPolicyImpl::selectSpecificChunkToMove(OperationContext* op
     const auto& shardStats = shardStatsStatus.getValue();
 
     auto routingInfoStatus =
-        Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(
-            opCtx, NamespaceString(chunk.getNS()));
+        Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(opCtx,
+                                                                                     chunk.getNS());
     if (!routingInfoStatus.isOK()) {
         return routingInfoStatus.getStatus();
     }
@@ -327,8 +326,8 @@ Status BalancerChunkSelectionPolicyImpl::checkMoveAllowed(OperationContext* opCt
     auto shardStats = std::move(shardStatsStatus.getValue());
 
     auto routingInfoStatus =
-        Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(
-            opCtx, NamespaceString(chunk.getNS()));
+        Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(opCtx,
+                                                                                     chunk.getNS());
     if (!routingInfoStatus.isOK()) {
         return routingInfoStatus.getStatus();
     }
diff --git a/src/mongo/db/s/balancer/balancer_policy.cpp b/src/mongo/db/s/balancer/balancer_policy.cpp
index 46a20de8676..7239f9b9e61 100644
--- a/src/mongo/db/s/balancer/balancer_policy.cpp
+++ b/src/mongo/db/s/balancer/balancer_policy.cpp
@@ -537,7 +537,7 @@ MigrateInfo::MigrateInfo(const ShardId& a_to, const ChunkType& a_chunk) {
 
     to = a_to;
 
-    ns = a_chunk.getNS();
+    nss = a_chunk.getNS();
     from = a_chunk.getShard();
     minKey = a_chunk.getMin();
     maxKey = a_chunk.getMax();
@@ -545,12 +545,12 @@ MigrateInfo::MigrateInfo(const ShardId& a_to, const ChunkType& a_chunk) {
 }
 
 std::string MigrateInfo::getName() const {
-    return ChunkType::genID(ns, minKey);
+    return ChunkType::genID(nss, minKey);
 }
 
 string MigrateInfo::toString() const {
-    return str::stream() << ns << ": [" << minKey << ", " << maxKey << "), from " << from << ", to "
-                         << to;
+    return str::stream() << nss.ns() << ": [" << minKey << ", " << maxKey << "), from " << from
+                         << ", to " << to;
 }
 
 }  // namespace mongo
diff --git a/src/mongo/db/s/balancer/balancer_policy.h b/src/mongo/db/s/balancer/balancer_policy.h
index afba1db4915..ed70c40d3c9 100644
--- a/src/mongo/db/s/balancer/balancer_policy.h
+++ b/src/mongo/db/s/balancer/balancer_policy.h
@@ -34,6 +34,7 @@
 #include "mongo/base/disallow_copying.h"
 #include "mongo/bson/bsonobj.h"
 #include "mongo/bson/simple_bsonobj_comparator.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/db/s/balancer/cluster_statistics.h"
 #include "mongo/s/catalog/type_chunk.h"
 #include "mongo/s/shard_id.h"
@@ -57,7 +58,7 @@ struct MigrateInfo {
 
     std::string toString() const;
 
-    std::string ns;
+    NamespaceString nss;
     ShardId to;
     ShardId from;
     BSONObj minKey;
diff --git a/src/mongo/db/s/balancer/balancer_policy_test.cpp b/src/mongo/db/s/balancer/balancer_policy_test.cpp
index f6abd7c8acf..14e34cf298a 100644
--- a/src/mongo/db/s/balancer/balancer_policy_test.cpp
+++ b/src/mongo/db/s/balancer/balancer_policy_test.cpp
@@ -91,7 +91,7 @@ std::pair<ShardStatisticsVector, ShardToChunksMap> generateCluster(
         for (size_t i = 0; i < numChunks; i++, currentChunk++) {
             ChunkType chunk;
 
-            chunk.setNS(kNamespace.ns());
+            chunk.setNS(kNamespace);
             chunk.setMin(currentChunk == 0 ? shardKeyPattern.globalMin()
                                            : BSON("x" << currentChunk));
             chunk.setMax(currentChunk == totalNumChunks - 1 ? shardKeyPattern.globalMax()
diff --git a/src/mongo/db/s/balancer/migration_manager.cpp b/src/mongo/db/s/balancer/migration_manager.cpp
index 0beffad2508..ce7ed13d743 100644
--- a/src/mongo/db/s/balancer/migration_manager.cpp
+++ b/src/mongo/db/s/balancer/migration_manager.cpp
@@ -183,7 +183,7 @@ Status MigrationManager::executeManualMigration(
 
     auto routingInfoStatus =
         Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(
-            opCtx, NamespaceString(migrateInfo.ns));
+            opCtx, migrateInfo.nss);
     if (!routingInfoStatus.isOK()) {
         return routingInfoStatus.getStatus();
     }
@@ -228,7 +228,7 @@ void MigrationManager::startRecoveryAndAcquireDistLocks(OperationContext* opCtx)
             opCtx,
             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
             repl::ReadConcernLevel::kLocalReadConcern,
-            NamespaceString(MigrationType::ConfigNS),
+            MigrationType::ConfigNS,
             BSONObj(),
             BSONObj(),
             boost::none);
@@ -417,7 +417,7 @@ shared_ptr<Notification<RemoteCommandResponse>> MigrationManager::_schedule(
     uint64_t maxChunkSizeBytes,
     const MigrationSecondaryThrottleOptions& secondaryThrottle,
     bool waitForDelete) {
-    const NamespaceString nss(migrateInfo.ns);
+    const NamespaceString& nss = migrateInfo.nss;
 
     // Ensure we are not stopped in order to avoid doing the extra work
     {
diff --git a/src/mongo/db/s/balancer/migration_manager_test.cpp b/src/mongo/db/s/balancer/migration_manager_test.cpp
index 70718a25504..515ebceb7b2 100644
--- a/src/mongo/db/s/balancer/migration_manager_test.cpp
+++ b/src/mongo/db/s/balancer/migration_manager_test.cpp
@@ -99,13 +99,13 @@ protected:
      * Inserts a document into the config.collections collection to indicate that "collName" is
      * sharded with version "version". The shard key pattern defaults to "_id".
      */
-    void setUpCollection(const std::string collName, ChunkVersion version);
+    void setUpCollection(const NamespaceString& collName, ChunkVersion version);
 
     /**
      * Inserts a document into the config.chunks collection so that the chunk defined by the
      * parameters exists. Returns a ChunkType defined by the parameters.
      */
-    ChunkType setUpChunk(const std::string& collName,
+    ChunkType setUpChunk(const NamespaceString& collName,
                          const BSONObj& chunkMin,
                          const BSONObj& chunkMax,
                          const ShardId& shardId,
@@ -188,9 +188,9 @@ void MigrationManagerTest::setUpDatabase(const std::string& dbName, const ShardI
         operationContext(), DatabaseType::ConfigNS, db.toBSON(), kMajorityWriteConcern));
 }
 
-void MigrationManagerTest::setUpCollection(const std::string collName, ChunkVersion version) {
+void MigrationManagerTest::setUpCollection(const NamespaceString& collName, ChunkVersion version) {
     CollectionType coll;
-    coll.setNs(NamespaceString(collName));
+    coll.setNs(collName);
     coll.setEpoch(version.epoch());
     coll.setUpdatedAt(Date_t::fromMillisSinceEpoch(version.toLong()));
     coll.setKeyPattern(kKeyPattern);
@@ -199,7 +199,7 @@ void MigrationManagerTest::setUpCollection(const std::string collName, ChunkVers
         operationContext(), CollectionType::ConfigNS, coll.toBSON(), kMajorityWriteConcern));
 }
 
-ChunkType MigrationManagerTest::setUpChunk(const std::string& collName,
+ChunkType MigrationManagerTest::setUpChunk(const NamespaceString& collName,
                                            const BSONObj& chunkMin,
                                            const BSONObj& chunkMax,
                                            const ShardId& shardId,
@@ -217,7 +217,7 @@ ChunkType MigrationManagerTest::setUpChunk(const std::string& collName,
 
 void MigrationManagerTest::setUpMigration(const ChunkType& chunk, const ShardId& toShard) {
     BSONObjBuilder builder;
-    builder.append(MigrationType::ns(), chunk.getNS());
+    builder.append(MigrationType::ns(), chunk.getNS().ns());
     builder.append(MigrationType::min(), chunk.getMin());
     builder.append(MigrationType::max(), chunk.getMax());
     builder.append(MigrationType::toShard(), toShard.toString());
@@ -237,7 +237,7 @@ void MigrationManagerTest::checkMigrationsCollectionIsEmptyAndLocksAreUnlocked()
             operationContext(),
             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
             repl::ReadConcernLevel::kMajorityReadConcern,
-            NamespaceString(MigrationType::ConfigNS),
+            MigrationType::ConfigNS,
             BSONObj(),
             BSONObj(),
             boost::none);
@@ -249,7 +249,7 @@ void MigrationManagerTest::checkMigrationsCollectionIsEmptyAndLocksAreUnlocked()
         operationContext(),
         ReadPreferenceSetting{ReadPreference::PrimaryOnly},
         repl::ReadConcernLevel::kMajorityReadConcern,
-        NamespaceString(LocksType::ConfigNS),
+        LocksType::ConfigNS,
         BSON(LocksType::state(LocksType::LOCKED) << LocksType::name("{ '$ne' : 'balancer'}")),
         BSONObj(),
         boost::none);
@@ -262,13 +262,13 @@ void MigrationManagerTest::expectMoveChunkCommand(const ChunkType& chunk,
                                                   const BSONObj& response) {
     onCommand([&chunk, &toShardId, &response](const RemoteCommandRequest& request) {
         NamespaceString nss(request.cmdObj.firstElement().valueStringData());
-        ASSERT_EQ(chunk.getNS(), nss.ns());
+        ASSERT_EQ(chunk.getNS(), nss);
 
         const StatusWith<MoveChunkRequest> moveChunkRequestWithStatus =
             MoveChunkRequest::createFromCommand(nss, request.cmdObj);
         ASSERT_OK(moveChunkRequestWithStatus.getStatus());
 
-        ASSERT_EQ(chunk.getNS(), moveChunkRequestWithStatus.getValue().getNss().ns());
+        ASSERT_EQ(chunk.getNS(), moveChunkRequestWithStatus.getValue().getNss());
         ASSERT_BSONOBJ_EQ(chunk.getMin(), moveChunkRequestWithStatus.getValue().getMinKey());
         ASSERT_BSONOBJ_EQ(chunk.getMax(), moveChunkRequestWithStatus.getValue().getMaxKey());
         ASSERT_EQ(chunk.getShard(), moveChunkRequestWithStatus.getValue().getFromShardId());
@@ -295,8 +295,8 @@ TEST_F(MigrationManagerTest, OneCollectionTwoMigrations) {
         operationContext(), ShardType::ConfigNS, kShard2, kMajorityWriteConcern));
 
     // Set up the database and collection as sharded in the metadata.
-    std::string dbName = "foo";
-    std::string collName = "foo.bar";
+    const std::string dbName = "foo";
+    const NamespaceString collName(dbName, "bar");
     ChunkVersion version(2, 0, OID::gen());
 
     setUpDatabase(dbName, kShardId0);
@@ -347,8 +347,8 @@ TEST_F(MigrationManagerTest, TwoCollectionsTwoMigrationsEach) {
 
     // Set up a database and two collections as sharded in the metadata.
     std::string dbName = "foo";
-    std::string collName1 = "foo.bar";
-    std::string collName2 = "foo.baz";
+    const NamespaceString collName1(dbName, "bar");
+    const NamespaceString collName2(dbName, "baz");
     ChunkVersion version1(2, 0, OID::gen());
     ChunkVersion version2(2, 0, OID::gen());
 
@@ -413,8 +413,8 @@ TEST_F(MigrationManagerTest, SourceShardNotFound) {
         operationContext(), ShardType::ConfigNS, kShard2, kMajorityWriteConcern));
 
     // Set up the database and collection as sharded in the metadata.
-    std::string dbName = "foo";
-    std::string collName = "foo.bar";
+    const std::string dbName = "foo";
+    const NamespaceString collName(dbName, "bar");
     ChunkVersion version(2, 0, OID::gen());
 
     setUpDatabase(dbName, kShardId0);
@@ -463,8 +463,8 @@ TEST_F(MigrationManagerTest, JumboChunkResponseBackwardsCompatibility) {
         operationContext(), ShardType::ConfigNS, kShard0, kMajorityWriteConcern));
 
     // Set up the database and collection as sharded in the metadata.
-    std::string dbName = "foo";
-    std::string collName = "foo.bar";
+    const std::string dbName = "foo";
+    const NamespaceString collName(dbName, "bar");
     ChunkVersion version(2, 0, OID::gen());
 
     setUpDatabase(dbName, kShardId0);
@@ -505,8 +505,8 @@ TEST_F(MigrationManagerTest, InterruptMigration) {
         operationContext(), ShardType::ConfigNS, kShard0, kMajorityWriteConcern));
 
     // Set up the database and collection as sharded in the metadata.
-    std::string dbName = "foo";
-    std::string collName = "foo.bar";
+    const std::string dbName = "foo";
+    const NamespaceString collName(dbName, "bar");
     ChunkVersion version(2, 0, OID::gen());
 
     setUpDatabase(dbName, kShardId0);
@@ -564,7 +564,7 @@ TEST_F(MigrationManagerTest, InterruptMigration) {
             operationContext(),
             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
             repl::ReadConcernLevel::kMajorityReadConcern,
-            NamespaceString(MigrationType::ConfigNS),
+            MigrationType::ConfigNS,
             BSON(MigrationType::name(chunk.getName())),
             BSONObj(),
             boost::none);
@@ -588,8 +588,8 @@ TEST_F(MigrationManagerTest, RestartMigrationManager) {
         operationContext(), ShardType::ConfigNS, kShard0, kMajorityWriteConcern));
 
     // Set up the database and collection as sharded in the metadata.
-    std::string dbName = "foo";
-    std::string collName = "foo.bar";
+    const std::string dbName = "foo";
+    const NamespaceString collName(dbName, "bar");
     ChunkVersion version(2, 0, OID::gen());
 
     setUpDatabase(dbName, kShardId0);
@@ -633,8 +633,8 @@ TEST_F(MigrationManagerTest, MigrationRecovery) {
         operationContext(), ShardType::ConfigNS, kShard2, kMajorityWriteConcern));
 
     // Set up the database and collection as sharded in the metadata.
-    std::string dbName = "foo";
-    std::string collName = "foo.bar";
+    const std::string dbName = "foo";
+    const NamespaceString collName(dbName, "bar");
     ChunkVersion version(1, 0, OID::gen());
 
     setUpDatabase(dbName, kShardId0);
@@ -689,8 +689,8 @@ TEST_F(MigrationManagerTest, FailMigrationRecovery) {
         operationContext(), ShardType::ConfigNS, kShard2, kMajorityWriteConcern));
 
     // Set up the database and collection as sharded in the metadata.
-    std::string dbName = "foo";
-    std::string collName = "foo.bar";
+    const std::string dbName = "foo";
+    const NamespaceString collName(dbName, "bar");
     ChunkVersion version(1, 0, OID::gen());
 
     setUpDatabase(dbName, kShardId0);
@@ -725,7 +725,7 @@ TEST_F(MigrationManagerTest, FailMigrationRecovery) {
     // session ID used here doesn't matter.
     ASSERT_OK(catalogClient()->getDistLockManager()->lockWithSessionID(
         operationContext(),
-        collName,
+        collName.ns(),
         "MigrationManagerTest",
         OID::gen(),
         DistLockManager::kSingleLockAttemptTimeout));
@@ -748,8 +748,8 @@ TEST_F(MigrationManagerTest, RemoteCallErrorConversionToOperationFailed) {
         operationContext(), ShardType::ConfigNS, kShard2, kMajorityWriteConcern));
 
     // Set up the database and collection as sharded in the metadata.
-    std::string dbName = "foo";
-    std::string collName = "foo.bar";
+    const std::string dbName = "foo";
+    const NamespaceString collName(dbName, "bar");
     ChunkVersion version(1, 0, OID::gen());
 
     setUpDatabase(dbName, kShardId0);
diff --git a/src/mongo/db/s/balancer/scoped_migration_request.cpp b/src/mongo/db/s/balancer/scoped_migration_request.cpp
index d55855b14b8..6cf19c1f4bf 100644
--- a/src/mongo/db/s/balancer/scoped_migration_request.cpp
+++ b/src/mongo/db/s/balancer/scoped_migration_request.cpp
@@ -110,7 +110,7 @@ StatusWith<ScopedMigrationRequest> ScopedMigrationRequest::writeMigration(
                     opCtx,
                     ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                     repl::ReadConcernLevel::kLocalReadConcern,
-                    NamespaceString(MigrationType::ConfigNS),
+                    MigrationType::ConfigNS,
                     BSON(MigrationType::name(migrateInfo.getName())),
                     BSONObj(),
                     boost::none);
@@ -156,8 +156,7 @@ StatusWith<ScopedMigrationRequest> ScopedMigrationRequest::writeMigration(
         // As long as there isn't a DuplicateKey error, the document may have been written, and it's
         // safe (won't delete another migration's document) and necessary to try to clean up the
         // document via the destructor.
-        ScopedMigrationRequest scopedMigrationRequest(
-            opCtx, NamespaceString(migrateInfo.ns), migrateInfo.minKey);
+        ScopedMigrationRequest scopedMigrationRequest(opCtx, migrateInfo.nss, migrateInfo.minKey);
 
         // If there was a write error, let the object go out of scope and clean up in the
         // destructor.
@@ -173,7 +172,7 @@ StatusWith<ScopedMigrationRequest> ScopedMigrationRequest::writeMigration(
                                 << "number of retries. Chunk '"
                                 << ChunkRange(migrateInfo.minKey, migrateInfo.maxKey).toString()
                                 << "' in collection '"
-                                << migrateInfo.ns
+                                << migrateInfo.nss.ns()
                                 << "' was being moved (somewhere) by another operation.");
 }
 
diff --git a/src/mongo/db/s/balancer/scoped_migration_request_test.cpp b/src/mongo/db/s/balancer/scoped_migration_request_test.cpp
index 1aab0157210..1d9b7ba6c7d 100644
--- a/src/mongo/db/s/balancer/scoped_migration_request_test.cpp
+++ b/src/mongo/db/s/balancer/scoped_migration_request_test.cpp
@@ -71,7 +71,7 @@ void ScopedMigrationRequestTest::checkMigrationsCollectionForDocument(
         operationContext(),
         ReadPreferenceSetting{ReadPreference::PrimaryOnly},
         repl::ReadConcernLevel::kMajorityReadConcern,
-        NamespaceString(MigrationType::ConfigNS),
+        MigrationType::ConfigNS,
         BSON(MigrationType::name(chunkName)),
         BSONObj(),
         boost::none);
@@ -161,7 +161,7 @@ TEST_F(ScopedMigrationRequestTest, CreateScopedMigrationRequestOnRecovery) {
     // still removes the document corresponding to the MigrationRequest.
     {
         ScopedMigrationRequest scopedMigrationRequest = ScopedMigrationRequest::createForRecovery(
-            operationContext(), NamespaceString(migrateInfo.ns), migrateInfo.minKey);
+            operationContext(), migrateInfo.nss, migrateInfo.minKey);
 
         checkMigrationsCollectionForDocument(migrateInfo.getName(), 1);
     }
diff --git a/src/mongo/db/s/balancer/type_migration.cpp b/src/mongo/db/s/balancer/type_migration.cpp
index efaf453048d..e6341b77685 100644
--- a/src/mongo/db/s/balancer/type_migration.cpp
+++ b/src/mongo/db/s/balancer/type_migration.cpp
@@ -40,7 +40,7 @@ const StringData kChunkVersion = "chunkVersion"_sd;
 
 }  // namespace
 
-const std::string MigrationType::ConfigNS = "config.migrations";
+const NamespaceString MigrationType::ConfigNS("config.migrations");
 
 const BSONField<std::string> MigrationType::name("_id");
 const BSONField<std::string> MigrationType::ns("ns");
@@ -53,7 +53,7 @@ const BSONField<bool> MigrationType::waitForDelete("waitForDelete");
 MigrationType::MigrationType() = default;
 
 MigrationType::MigrationType(MigrateInfo info, bool waitForDelete)
-    : _nss(NamespaceString(info.ns)),
+    : _nss(info.nss),
       _min(info.minKey),
       _max(info.maxKey),
       _fromShard(info.from),
@@ -138,7 +138,7 @@ BSONObj MigrationType::toBSON() const {
 
 MigrateInfo MigrationType::toMigrateInfo() const {
     ChunkType chunk;
-    chunk.setNS(_nss.ns());
+    chunk.setNS(_nss);
     chunk.setShard(_fromShard);
     chunk.setMin(_min);
     chunk.setMax(_max);
@@ -148,7 +148,7 @@ MigrateInfo MigrationType::toMigrateInfo() const {
 }
 
 std::string MigrationType::getName() const {
-    return ChunkType::genID(_nss.ns(), _min);
+    return ChunkType::genID(_nss, _min);
 }
 
 }  // namespace mongo
diff --git a/src/mongo/db/s/balancer/type_migration.h b/src/mongo/db/s/balancer/type_migration.h
index dd35bd9b844..000145c0941 100644
--- a/src/mongo/db/s/balancer/type_migration.h
+++ b/src/mongo/db/s/balancer/type_migration.h
@@ -29,6 +29,7 @@
 #pragma once
 
 #include "mongo/bson/bsonobj.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/db/s/balancer/balancer_policy.h"
 #include "mongo/s/chunk_version.h"
 #include "mongo/s/client/shard.h"
@@ -43,7 +44,7 @@ namespace mongo {
 class MigrationType {
 public:
     // Name of the migrations collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     // Field names and types in the migrations collection type.
     static const BSONField<std::string> name;
diff --git a/src/mongo/db/s/chunk_splitter.cpp b/src/mongo/db/s/chunk_splitter.cpp
index caea3e11fed..f36ed19a0ea 100644
--- a/src/mongo/db/s/chunk_splitter.cpp
+++ b/src/mongo/db/s/chunk_splitter.cpp
@@ -117,7 +117,7 @@ void moveChunk(OperationContext* opCtx, const NamespaceString& nss, const BSONOb
     const auto suggestedChunk = routingInfo.cm()->findIntersectingChunkWithSimpleCollation(minKey);
 
     ChunkType chunkToMove;
-    chunkToMove.setNS(nss.ns());
+    chunkToMove.setNS(nss);
     chunkToMove.setShard(suggestedChunk->getShardId());
     chunkToMove.setMin(suggestedChunk->getMin());
     chunkToMove.setMax(suggestedChunk->getMax());
@@ -201,7 +201,7 @@ bool isAutoBalanceEnabled(OperationContext* opCtx,
     if (!balancerConfig->shouldBalanceForAutoSplit())
         return false;
 
-    auto collStatus = Grid::get(opCtx)->catalogClient()->getCollection(opCtx, nss.ns());
+    auto collStatus = Grid::get(opCtx)->catalogClient()->getCollection(opCtx, nss);
     if (!collStatus.isOK()) {
         log() << "Auto-split for " << nss << " failed to load collection metadata"
               << causedBy(redact(collStatus.getStatus()));
diff --git a/src/mongo/db/s/collection_sharding_state.cpp b/src/mongo/db/s/collection_sharding_state.cpp
index e94547ccfe9..78e9c8b4d55 100644
--- a/src/mongo/db/s/collection_sharding_state.cpp
+++ b/src/mongo/db/s/collection_sharding_state.cpp
@@ -430,7 +430,7 @@ void CollectionShardingState::onDeleteOp(OperationContext* opCtx,
     }
 
     if (serverGlobalParams.clusterRole == ClusterRole::ConfigServer) {
-        if (_nss.ns() == VersionType::ConfigNS) {
+        if (_nss == VersionType::ConfigNS) {
             if (!repl::ReplicationCoordinator::get(opCtx)->getMemberState().rollback()) {
                 uasserted(40302, "cannot delete config.version document while in --configsvr mode");
             } else {
@@ -467,7 +467,7 @@ void CollectionShardingState::onDropCollection(OperationContext* opCtx,
     }
 
     if (serverGlobalParams.clusterRole == ClusterRole::ConfigServer) {
-        if (_nss.ns() == VersionType::ConfigNS) {
+        if (_nss == VersionType::ConfigNS) {
             if (!repl::ReplicationCoordinator::get(opCtx)->getMemberState().rollback()) {
                 uasserted(40303, "cannot drop config.version document while in --configsvr mode");
             } else {
diff --git a/src/mongo/db/s/config/configsvr_drop_collection_command.cpp b/src/mongo/db/s/config/configsvr_drop_collection_command.cpp
index fd2c5ca9b93..c5fd2ecfc0f 100644
--- a/src/mongo/db/s/config/configsvr_drop_collection_command.cpp
+++ b/src/mongo/db/s/config/configsvr_drop_collection_command.cpp
@@ -130,7 +130,7 @@ public:
             [opCtx, nss] { Grid::get(opCtx)->catalogCache()->invalidateShardedCollection(nss); });
 
         auto collStatus = catalogClient->getCollection(
-            opCtx, nss.toString(), repl::ReadConcernLevel::kLocalReadConcern);
+            opCtx, nss, repl::ReadConcernLevel::kLocalReadConcern);
         if (collStatus == ErrorCodes::NamespaceNotFound) {
             // We checked the sharding catalog and found that this collection doesn't exist.
             // This may be because it never existed, or because a drop command was sent
diff --git a/src/mongo/db/s/config/configsvr_shard_collection_command.cpp b/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
index 63b6f00a48d..d221a719bb8 100644
--- a/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
+++ b/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
@@ -261,7 +261,7 @@ boost::optional<CollectionType> checkIfAlreadyShardedWithSameOptions(
                             opCtx,
                             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                             repl::ReadConcernLevel::kLocalReadConcern,
-                            NamespaceString(CollectionType::ConfigNS),
+                            CollectionType::ConfigNS,
                             BSON("_id" << nss.ns() << "dropped" << false),
                             BSONObj(),
                             1))
@@ -569,7 +569,7 @@ void migrateAndFurtherSplitInitialChunks(OperationContext* opCtx,
         }
 
         ChunkType chunkType;
-        chunkType.setNS(nss.ns());
+        chunkType.setNS(nss);
         chunkType.setMin(chunk->getMin());
         chunkType.setMax(chunk->getMax());
         chunkType.setShard(chunk->getShardId());
@@ -881,7 +881,7 @@ public:
 
         // Step 6. Actually shard the collection.
         catalogManager->shardCollection(opCtx,
-                                        nss.ns(),
+                                        nss,
                                         uuid,
                                         shardKeyPattern,
                                         *request.getCollation(),
diff --git a/src/mongo/db/s/shard_metadata_util.cpp b/src/mongo/db/s/shard_metadata_util.cpp
index 88a3d761cee..de8140a76e1 100644
--- a/src/mongo/db/s/shard_metadata_util.cpp
+++ b/src/mongo/db/s/shard_metadata_util.cpp
@@ -148,11 +148,11 @@ StatusWith<ShardCollectionType> readShardCollectionsEntry(OperationContext* opCt
     try {
         DBDirectClient client(opCtx);
         std::unique_ptr<DBClientCursor> cursor =
-            client.query(ShardCollectionType::ConfigNS.c_str(), fullQuery, 1);
+            client.query(ShardCollectionType::ConfigNS.ns(), fullQuery, 1);
         if (!cursor) {
             return Status(ErrorCodes::OperationFailed,
                           str::stream() << "Failed to establish a cursor for reading "
-                                        << ShardCollectionType::ConfigNS
+                                        << ShardCollectionType::ConfigNS.ns()
                                         << " from local storage");
         }
 
diff --git a/src/mongo/db/s/shard_metadata_util_test.cpp b/src/mongo/db/s/shard_metadata_util_test.cpp
index fa86f74a4ec..0fc7d24d5b6 100644
--- a/src/mongo/db/s/shard_metadata_util_test.cpp
+++ b/src/mongo/db/s/shard_metadata_util_test.cpp
@@ -322,7 +322,7 @@ TEST_F(ShardMetadataUtilTest, DropChunksAndDeleteCollectionsEntry) {
     ASSERT_OK(dropChunksAndDeleteCollectionsEntry(operationContext(), kNss));
     checkCollectionIsEmpty(kChunkMetadataNss);
     // Collections collection should be empty because it only had one entry.
-    checkCollectionIsEmpty(NamespaceString(ShardCollectionType::ConfigNS));
+    checkCollectionIsEmpty(ShardCollectionType::ConfigNS);
 }
 
 }  // namespace
diff --git a/src/mongo/db/s/shard_server_catalog_cache_loader_test.cpp b/src/mongo/db/s/shard_server_catalog_cache_loader_test.cpp
index 8db0430fdfe..8eb3818c90e 100644
--- a/src/mongo/db/s/shard_server_catalog_cache_loader_test.cpp
+++ b/src/mongo/db/s/shard_server_catalog_cache_loader_test.cpp
@@ -125,7 +125,7 @@ vector<ChunkType> ShardServerCatalogCacheLoaderTest::makeFiveChunks(
         collVersion.incMajor();
 
         ChunkType chunk;
-        chunk.setNS(kNss.ns());
+        chunk.setNS(kNss);
         chunk.setMin(mins[i]);
         chunk.setMax(maxs[i]);
         chunk.setShard(kShardId);
@@ -148,7 +148,7 @@ vector<ChunkType> ShardServerCatalogCacheLoaderTest::makeThreeUpdatedChunksDiff(
     // dependent on a race between persistence and retrieving data because it combines enqueued and
     // persisted results without applying modifications.
     ChunkType oldChunk;
-    oldChunk.setNS(kNss.ns());
+    oldChunk.setNS(kNss);
     oldChunk.setMin(BSON("a" << 200));
     oldChunk.setMax(BSON("a" << MAXKEY));
     oldChunk.setShard(kShardId);
@@ -164,7 +164,7 @@ vector<ChunkType> ShardServerCatalogCacheLoaderTest::makeThreeUpdatedChunksDiff(
         collVersion.incMinor();
 
         ChunkType chunk;
-        chunk.setNS(kNss.ns());
+        chunk.setNS(kNss);
         chunk.setMin(mins[i]);
         chunk.setMax(maxs[i]);
         chunk.setShard(kShardId);
diff --git a/src/mongo/s/balancer_configuration.cpp b/src/mongo/s/balancer_configuration.cpp
index 50d7c219b11..9ab44694485 100644
--- a/src/mongo/s/balancer_configuration.cpp
+++ b/src/mongo/s/balancer_configuration.cpp
@@ -81,7 +81,7 @@ Status BalancerConfiguration::setBalancerMode(OperationContext* opCtx,
                                               BalancerSettingsType::BalancerMode mode) {
     auto updateStatus = Grid::get(opCtx)->catalogClient()->updateConfigDocument(
         opCtx,
-        kSettingsNamespace.ns(),
+        kSettingsNamespace,
         BSON("_id" << BalancerSettingsType::kKey),
         BSON("$set" << BSON(kStopped << (mode == BalancerSettingsType::kOff) << kMode
                                      << BalancerSettingsType::kBalancerModes[mode])),
diff --git a/src/mongo/s/catalog/dist_lock_catalog_impl_test.cpp b/src/mongo/s/catalog/dist_lock_catalog_impl_test.cpp
index 693ccf67b30..e584944658d 100644
--- a/src/mongo/s/catalog/dist_lock_catalog_impl_test.cpp
+++ b/src/mongo/s/catalog/dist_lock_catalog_impl_test.cpp
@@ -1126,7 +1126,7 @@ TEST_F(DistLockCatalogFixture, BasicUnlockAll) {
         ASSERT_BSONOBJ_EQ(BSON("w" << 1 << "wtimeout" << 0), commandRequest.getWriteConcern());
 
         const auto& updateOp = commandRequest.getUpdateRequest();
-        ASSERT_EQUALS(LocksType::ConfigNS, updateOp.getNamespace().ns());
+        ASSERT_EQUALS(LocksType::ConfigNS, updateOp.getNamespace());
 
         const auto& updates = updateOp.getUpdates();
         ASSERT_EQUALS(1U, updates.size());
diff --git a/src/mongo/s/catalog/sharding_catalog_assign_key_range_to_zone_test.cpp b/src/mongo/s/catalog/sharding_catalog_assign_key_range_to_zone_test.cpp
index 50ff6368f2a..fa65e3bd070 100644
--- a/src/mongo/s/catalog/sharding_catalog_assign_key_range_to_zone_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_assign_key_range_to_zone_test.cpp
@@ -66,17 +66,16 @@ public:
         shardedCollection.setEpoch(OID::gen());
         shardedCollection.setKeyPattern(BSON("x" << 1));
 
-        ASSERT_OK(insertToConfigCollection(operationContext(),
-                                           NamespaceString(CollectionType::ConfigNS),
-                                           shardedCollection.toBSON()));
+        ASSERT_OK(insertToConfigCollection(
+            operationContext(), CollectionType::ConfigNS, shardedCollection.toBSON()));
     }
 
     /**
      * Asserts that the config.tags collection is empty.
      */
     void assertNoZoneDoc() {
-        auto findStatus = findOneOnConfigCollection(
-            operationContext(), NamespaceString(TagsType::ConfigNS), BSONObj());
+        auto findStatus =
+            findOneOnConfigCollection(operationContext(), TagsType::ConfigNS, BSONObj());
         ASSERT_EQ(ErrorCodes::NoMatchingDocument, findStatus);
     }
 
@@ -90,7 +89,7 @@ public:
             getConfigShard()->exhaustiveFindOnConfig(operationContext(),
                                                      kReadPref,
                                                      repl::ReadConcernLevel::kMajorityReadConcern,
-                                                     NamespaceString(TagsType::ConfigNS),
+                                                     TagsType::ConfigNS,
                                                      BSONObj(),
                                                      BSONObj(),
                                                      1);
@@ -103,7 +102,7 @@ public:
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(ns.ns(), tagDoc.getNS());
+        ASSERT_EQ(ns, tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(range.getMin(), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(range.getMax(), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName, tagDoc.getTag());
@@ -145,9 +144,8 @@ TEST_F(AssignKeyRangeToZoneTestFixture, AssignKeyRangeOnDroppedShardedCollShould
     unshardedCollection.setKeyPattern(BSON("x" << 1));
     unshardedCollection.setDropped(true);
 
-    ASSERT_OK(insertToConfigCollection(operationContext(),
-                                       NamespaceString(CollectionType::ConfigNS),
-                                       unshardedCollection.toBSON()));
+    ASSERT_OK(insertToConfigCollection(
+        operationContext(), CollectionType::ConfigNS, unshardedCollection.toBSON()));
 
     auto status =
         ShardingCatalogManager::get(operationContext())
@@ -199,7 +197,7 @@ TEST_F(AssignKeyRangeToZoneTestFixture, MinThatIsAShardKeyPrefixShouldConvertToF
     shardedCollection.setKeyPattern(BSON("x" << 1 << "y" << 1));
 
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(CollectionType::ConfigNS), shardedCollection.toBSON()));
+        operationContext(), CollectionType::ConfigNS, shardedCollection.toBSON()));
 
     const ChunkRange newRange(BSON("x" << 0), BSON("x" << 10 << "y" << 10));
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
@@ -218,7 +216,7 @@ TEST_F(AssignKeyRangeToZoneTestFixture, MaxThatIsAShardKeyPrefixShouldConvertToF
     shardedCollection.setKeyPattern(BSON("x" << 1 << "y" << 1));
 
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(CollectionType::ConfigNS), shardedCollection.toBSON()));
+        operationContext(), CollectionType::ConfigNS, shardedCollection.toBSON()));
 
     const ChunkRange newRange(BSON("x" << 0 << "y" << 0), BSON("x" << 10));
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
@@ -272,7 +270,7 @@ TEST_F(AssignKeyRangeToZoneTestFixture, MinMaxThatIsAShardKeyPrefixShouldSucceed
     shardedCollection.setKeyPattern(BSON("x" << 1 << "y" << 1));
 
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(CollectionType::ConfigNS), shardedCollection.toBSON()));
+        operationContext(), CollectionType::ConfigNS, shardedCollection.toBSON()));
 
     const ChunkRange newRange(BSON("x" << 0 << "y" << 0), BSON("x" << 10 << "y" << 10));
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
@@ -314,14 +312,14 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, NewMaxAlignsWithExistingMinShouldSucce
 
     {
         auto findStatus = findOneOnConfigCollection(
-            operationContext(), NamespaceString(TagsType::ConfigNS), BSON("min" << BSON("x" << 2)));
+            operationContext(), TagsType::ConfigNS, BSON("min" << BSON("x" << 2)));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(shardedNS().ns(), tagDoc.getNS());
+        ASSERT_EQ(shardedNS(), tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(BSON("x" << 2), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(BSON("x" << 4), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
@@ -329,16 +327,15 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, NewMaxAlignsWithExistingMinShouldSucce
 
     {
         const auto existingRange = getExistingRange();
-        auto findStatus = findOneOnConfigCollection(operationContext(),
-                                                    NamespaceString(TagsType::ConfigNS),
-                                                    BSON("min" << existingRange.getMin()));
+        auto findStatus = findOneOnConfigCollection(
+            operationContext(), TagsType::ConfigNS, BSON("min" << existingRange.getMin()));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(shardedNS().ns(), tagDoc.getNS());
+        ASSERT_EQ(shardedNS(), tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(existingRange.getMin(), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(existingRange.getMax(), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
@@ -389,7 +386,7 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, NewRangeOverlappingWithDifferentNSShou
     shardedCollection.setKeyPattern(BSON("x" << 1));
 
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(CollectionType::ConfigNS), shardedCollection.toBSON()));
+        operationContext(), CollectionType::ConfigNS, shardedCollection.toBSON()));
 
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
                   ->assignKeyRangeToZone(operationContext(),
@@ -399,30 +396,29 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, NewRangeOverlappingWithDifferentNSShou
 
     {
         const auto existingRange = getExistingRange();
-        auto findStatus = findOneOnConfigCollection(operationContext(),
-                                                    NamespaceString(TagsType::ConfigNS),
-                                                    BSON("min" << existingRange.getMin()));
+        auto findStatus = findOneOnConfigCollection(
+            operationContext(), TagsType::ConfigNS, BSON("min" << existingRange.getMin()));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(shardedNS().ns(), tagDoc.getNS());
+        ASSERT_EQ(shardedNS(), tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(existingRange.getMin(), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(existingRange.getMax(), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
     }
     {
         auto findStatus = findOneOnConfigCollection(
-            operationContext(), NamespaceString(TagsType::ConfigNS), BSON("min" << BSON("x" << 5)));
+            operationContext(), TagsType::ConfigNS, BSON("min" << BSON("x" << 5)));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(shardedCollection.getNs().ns(), tagDoc.getNS());
+        ASSERT_EQ(shardedCollection.getNs(), tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(BSON("x" << 5), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(BSON("x" << 7), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
@@ -454,8 +450,7 @@ TEST_F(AssignKeyRangeWithOneRangeFixture,
     shard.setHost("b:1234");
     shard.setTags({"y"});
 
-    ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(ShardType::ConfigNS), shard.toBSON()));
+    ASSERT_OK(insertToConfigCollection(operationContext(), ShardType::ConfigNS, shard.toBSON()));
 
     auto status =
         ShardingCatalogManager::get(operationContext())
@@ -495,16 +490,15 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, NewMinAlignsWithExistingMaxShouldSucce
 
     {
         const auto existingRange = getExistingRange();
-        auto findStatus = findOneOnConfigCollection(operationContext(),
-                                                    NamespaceString(TagsType::ConfigNS),
-                                                    BSON("min" << existingRange.getMin()));
+        auto findStatus = findOneOnConfigCollection(
+            operationContext(), TagsType::ConfigNS, BSON("min" << existingRange.getMin()));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(shardedNS().ns(), tagDoc.getNS());
+        ASSERT_EQ(shardedNS(), tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(existingRange.getMin(), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(existingRange.getMax(), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
@@ -512,14 +506,14 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, NewMinAlignsWithExistingMaxShouldSucce
 
     {
         auto findStatus = findOneOnConfigCollection(
-            operationContext(), NamespaceString(TagsType::ConfigNS), BSON("min" << BSON("x" << 8)));
+            operationContext(), TagsType::ConfigNS, BSON("min" << BSON("x" << 8)));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(shardedNS().ns(), tagDoc.getNS());
+        ASSERT_EQ(shardedNS(), tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(BSON("x" << 8), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(BSON("x" << 10), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
@@ -551,13 +545,12 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, NewRangeIsSuperSetOfExistingShouldFail
  */
 TEST_F(AssignKeyRangeWithOneRangeFixture, AssignWithExistingOveralpShouldFail) {
     TagsType tagDoc;
-    tagDoc.setNS(shardedNS().ns());
+    tagDoc.setNS(shardedNS());
     tagDoc.setMinKey(BSON("x" << 0));
     tagDoc.setMaxKey(BSON("x" << 2));
     tagDoc.setTag("z");
 
-    ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(TagsType::ConfigNS), tagDoc.toBSON()));
+    ASSERT_OK(insertToConfigCollection(operationContext(), TagsType::ConfigNS, tagDoc.toBSON()));
 
     auto status = ShardingCatalogManager::get(operationContext())
                       ->assignKeyRangeToZone(operationContext(),
@@ -593,9 +586,8 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, RemoveKeyRangeOnDroppedShardedCollShou
     unshardedCollection.setKeyPattern(BSON("x" << 1));
     unshardedCollection.setDropped(true);
 
-    ASSERT_OK(insertToConfigCollection(operationContext(),
-                                       NamespaceString(CollectionType::ConfigNS),
-                                       unshardedCollection.toBSON()));
+    ASSERT_OK(insertToConfigCollection(
+        operationContext(), CollectionType::ConfigNS, unshardedCollection.toBSON()));
 
     auto status = ShardingCatalogManager::get(operationContext())
                       ->removeKeyRangeFromZone(
@@ -633,7 +625,7 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, RemoveThatIsOnlyMinPrefixOfExistingSho
     shardedCollection.setKeyPattern(BSON("x" << 1 << "y" << 1));
 
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(CollectionType::ConfigNS), shardedCollection.toBSON()));
+        operationContext(), CollectionType::ConfigNS, shardedCollection.toBSON()));
 
     const ChunkRange existingRange(fromjson("{ x: 0, y: { $minKey: 1 }}"),
                                    BSON("x" << 10 << "y" << 10));
@@ -646,16 +638,15 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, RemoveThatIsOnlyMinPrefixOfExistingSho
                 operationContext(), ns, ChunkRange(BSON("x" << 0), BSON("x" << 10 << "y" << 10))));
 
     {
-        auto findStatus = findOneOnConfigCollection(operationContext(),
-                                                    NamespaceString(TagsType::ConfigNS),
-                                                    BSON("min" << existingRange.getMin()));
+        auto findStatus = findOneOnConfigCollection(
+            operationContext(), TagsType::ConfigNS, BSON("min" << existingRange.getMin()));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(ns.ns(), tagDoc.getNS());
+        ASSERT_EQ(ns, tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(existingRange.getMin(), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(existingRange.getMax(), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
@@ -663,16 +654,15 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, RemoveThatIsOnlyMinPrefixOfExistingSho
 
     {
         const auto existingRange = getExistingRange();
-        auto findStatus = findOneOnConfigCollection(operationContext(),
-                                                    NamespaceString(TagsType::ConfigNS),
-                                                    BSON("min" << existingRange.getMin()));
+        auto findStatus = findOneOnConfigCollection(
+            operationContext(), TagsType::ConfigNS, BSON("min" << existingRange.getMin()));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(shardedNS().ns(), tagDoc.getNS());
+        ASSERT_EQ(shardedNS(), tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(existingRange.getMin(), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(existingRange.getMax(), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
@@ -687,7 +677,7 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, RemoveThatIsOnlyMaxPrefixOfExistingSho
     shardedCollection.setKeyPattern(BSON("x" << 1 << "y" << 1));
 
     ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(CollectionType::ConfigNS), shardedCollection.toBSON()));
+        operationContext(), CollectionType::ConfigNS, shardedCollection.toBSON()));
 
     const ChunkRange existingRange(BSON("x" << 0 << "y" << 0),
                                    fromjson("{ x: 10, y: { $minKey: 1 }}"));
@@ -700,16 +690,15 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, RemoveThatIsOnlyMaxPrefixOfExistingSho
                 operationContext(), ns, ChunkRange(BSON("x" << 0 << "y" << 0), BSON("x" << 10))));
 
     {
-        auto findStatus = findOneOnConfigCollection(operationContext(),
-                                                    NamespaceString(TagsType::ConfigNS),
-                                                    BSON("min" << existingRange.getMin()));
+        auto findStatus = findOneOnConfigCollection(
+            operationContext(), TagsType::ConfigNS, BSON("min" << existingRange.getMin()));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(ns.ns(), tagDoc.getNS());
+        ASSERT_EQ(ns, tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(existingRange.getMin(), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(existingRange.getMax(), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
@@ -717,16 +706,15 @@ TEST_F(AssignKeyRangeWithOneRangeFixture, RemoveThatIsOnlyMaxPrefixOfExistingSho
 
     {
         const auto existingRange = getExistingRange();
-        auto findStatus = findOneOnConfigCollection(operationContext(),
-                                                    NamespaceString(TagsType::ConfigNS),
-                                                    BSON("min" << existingRange.getMin()));
+        auto findStatus = findOneOnConfigCollection(
+            operationContext(), TagsType::ConfigNS, BSON("min" << existingRange.getMin()));
         ASSERT_OK(findStatus);
 
         auto tagDocStatus = TagsType::fromBSON(findStatus.getValue());
         ASSERT_OK(tagDocStatus.getStatus());
 
         auto tagDoc = tagDocStatus.getValue();
-        ASSERT_EQ(shardedNS().ns(), tagDoc.getNS());
+        ASSERT_EQ(shardedNS(), tagDoc.getNS());
         ASSERT_BSONOBJ_EQ(existingRange.getMin(), tagDoc.getMinKey());
         ASSERT_BSONOBJ_EQ(existingRange.getMax(), tagDoc.getMaxKey());
         ASSERT_EQ(zoneName(), tagDoc.getTag());
diff --git a/src/mongo/s/catalog/sharding_catalog_client.h b/src/mongo/s/catalog/sharding_catalog_client.h
index d4eac9da595..c5cf22a61eb 100644
--- a/src/mongo/s/catalog/sharding_catalog_client.h
+++ b/src/mongo/s/catalog/sharding_catalog_client.h
@@ -133,7 +133,7 @@ public:
     /**
      * Retrieves the metadata for a given collection, if it exists.
      *
-     * @param collectionNs fully qualified name of the collection (case sensitive)
+     * @param nss fully qualified name of the collection (case sensitive)
      *
      * Returns Status::OK along with the collection information and the OpTime of the config server
      * which the collection information was based upon. Otherwise, returns an error code indicating
@@ -142,7 +142,7 @@ public:
      */
     virtual StatusWith<repl::OpTimeWith<CollectionType>> getCollection(
         OperationContext* opCtx,
-        const std::string& collNs,
+        const NamespaceString& nss,
         repl::ReadConcernLevel readConcernLevel = repl::ReadConcernLevel::kMajorityReadConcern) = 0;
 
     /**
@@ -195,8 +195,8 @@ public:
      *
      * Returns a !OK status if an error occurs.
      */
-    virtual StatusWith<std::vector<TagsType>> getTagsForCollection(
-        OperationContext* opCtx, const std::string& collectionNs) = 0;
+    virtual StatusWith<std::vector<TagsType>> getTagsForCollection(OperationContext* opCtx,
+                                                                   const NamespaceString& nss) = 0;
 
     /**
      * Retrieves all shards in this sharded cluster.
@@ -250,7 +250,7 @@ public:
     virtual Status applyChunkOpsDeprecated(OperationContext* opCtx,
                                            const BSONArray& updateOps,
                                            const BSONArray& preCondition,
-                                           const std::string& nss,
+                                           const NamespaceString& nss,
                                            const ChunkVersion& lastChunkVersion,
                                            const WriteConcernOptions& writeConcern,
                                            repl::ReadConcernLevel readConcern) = 0;
@@ -321,7 +321,7 @@ public:
      * NOTE: Should not be used in new code outside the ShardingCatalogManager.
      */
     virtual Status insertConfigDocument(OperationContext* opCtx,
-                                        const std::string& ns,
+                                        const NamespaceString& nss,
                                         const BSONObj& doc,
                                         const WriteConcernOptions& writeConcern) = 0;
 
@@ -340,7 +340,7 @@ public:
      * NOTE: Should not be used in new code outside the ShardingCatalogManager.
      */
     virtual StatusWith<bool> updateConfigDocument(OperationContext* opCtx,
-                                                  const std::string& ns,
+                                                  const NamespaceString& nss,
                                                   const BSONObj& query,
                                                   const BSONObj& update,
                                                   bool upsert,
@@ -353,7 +353,7 @@ public:
      * NOTE: Should not be used in new code outside the ShardingCatalogManager.
      */
     virtual Status removeConfigDocuments(OperationContext* opCtx,
-                                         const std::string& ns,
+                                         const NamespaceString& nss,
                                          const BSONObj& query,
                                          const WriteConcernOptions& writeConcern) = 0;
 
diff --git a/src/mongo/s/catalog/sharding_catalog_client_impl.cpp b/src/mongo/s/catalog/sharding_catalog_client_impl.cpp
index 19e83ed737d..7da59f057c3 100644
--- a/src/mongo/s/catalog/sharding_catalog_client_impl.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_client_impl.cpp
@@ -144,14 +144,14 @@ void ShardingCatalogClientImpl::shutDown(OperationContext* opCtx) {
 
 Status ShardingCatalogClientImpl::updateShardingCatalogEntryForCollection(
     OperationContext* opCtx,
-    const std::string& collNs,
+    const NamespaceString& nss,
     const CollectionType& coll,
     const bool upsert) {
     fassert(28634, coll.validate());
 
     auto status = _updateConfigDocument(opCtx,
                                         CollectionType::ConfigNS,
-                                        BSON(CollectionType::fullNs(collNs)),
+                                        BSON(CollectionType::fullNs(nss.ns())),
                                         coll.toBSON(),
                                         upsert,
                                         ShardingCatalogClient::kMajorityWriteConcern);
@@ -241,7 +241,7 @@ Status ShardingCatalogClientImpl::_log(OperationContext* opCtx,
     log() << "about to log metadata event into " << logCollName << ": " << redact(changeLogBSON);
 
     const NamespaceString nss("config", logCollName);
-    Status result = insertConfigDocument(opCtx, nss.ns(), changeLogBSON, writeConcern);
+    Status result = insertConfigDocument(opCtx, nss, changeLogBSON, writeConcern);
 
     if (!result.isOK()) {
         warning() << "Error encountered while logging config change with ID [" << changeId
@@ -302,7 +302,7 @@ StatusWith<repl::OpTimeWith<DatabaseType>> ShardingCatalogClientImpl::_fetchData
     auto findStatus = _exhaustiveFindOnConfig(opCtx,
                                               readPref,
                                               readConcernLevel,
-                                              NamespaceString(DatabaseType::ConfigNS),
+                                              DatabaseType::ConfigNS,
                                               BSON(DatabaseType::name(dbName)),
                                               BSONObj(),
                                               boost::none);
@@ -326,12 +326,12 @@ StatusWith<repl::OpTimeWith<DatabaseType>> ShardingCatalogClientImpl::_fetchData
 }
 
 StatusWith<repl::OpTimeWith<CollectionType>> ShardingCatalogClientImpl::getCollection(
-    OperationContext* opCtx, const std::string& collNs, repl::ReadConcernLevel readConcernLevel) {
+    OperationContext* opCtx, const NamespaceString& nss, repl::ReadConcernLevel readConcernLevel) {
     auto statusFind = _exhaustiveFindOnConfig(opCtx,
                                               kConfigReadSelector,
                                               readConcernLevel,
-                                              NamespaceString(CollectionType::ConfigNS),
-                                              BSON(CollectionType::fullNs(collNs)),
+                                              CollectionType::ConfigNS,
+                                              BSON(CollectionType::fullNs(nss.ns())),
                                               BSONObj(),
                                               1);
     if (!statusFind.isOK()) {
@@ -342,7 +342,7 @@ StatusWith<repl::OpTimeWith<CollectionType>> ShardingCatalogClientImpl::getColle
     const auto& retVal = retOpTimePair.value;
     if (retVal.empty()) {
         return Status(ErrorCodes::NamespaceNotFound,
-                      stream() << "collection " << collNs << " not found");
+                      stream() << "collection " << nss.ns() << " not found");
     }
 
     invariant(retVal.size() == 1);
@@ -355,7 +355,7 @@ StatusWith<repl::OpTimeWith<CollectionType>> ShardingCatalogClientImpl::getColle
     auto collType = parseStatus.getValue();
     if (collType.getDropped()) {
         return Status(ErrorCodes::NamespaceNotFound,
-                      stream() << "collection " << collNs << " was dropped");
+                      stream() << "collection " << nss.ns() << " was dropped");
     }
 
     return repl::OpTimeWith<CollectionType>(collType, retOpTimePair.opTime);
@@ -376,7 +376,7 @@ StatusWith<std::vector<CollectionType>> ShardingCatalogClientImpl::getCollection
     auto findStatus = _exhaustiveFindOnConfig(opCtx,
                                               kConfigReadSelector,
                                               readConcernLevel,
-                                              NamespaceString(CollectionType::ConfigNS),
+                                              CollectionType::ConfigNS,
                                               b.obj(),
                                               BSONObj(),
                                               boost::none);  // no limit
@@ -391,7 +391,7 @@ StatusWith<std::vector<CollectionType>> ShardingCatalogClientImpl::getCollection
         const auto collectionResult = CollectionType::fromBSON(obj);
         if (!collectionResult.isOK()) {
             return {ErrorCodes::FailedToParse,
-                    str::stream() << "error while parsing " << CollectionType::ConfigNS
+                    str::stream() << "error while parsing " << CollectionType::ConfigNS.ns()
                                   << " document: "
                                   << obj
                                   << " : "
@@ -437,7 +437,7 @@ StatusWith<VersionType> ShardingCatalogClientImpl::getConfigVersion(
         opCtx,
         kConfigReadSelector,
         readConcern,
-        NamespaceString(VersionType::ConfigNS),
+        VersionType::ConfigNS,
         BSONObj(),
         BSONObj(),
         boost::none /* no limit */);
@@ -449,7 +449,7 @@ StatusWith<VersionType> ShardingCatalogClientImpl::getConfigVersion(
 
     if (queryResults.size() > 1) {
         return {ErrorCodes::TooManyMatchingDocuments,
-                str::stream() << "should only have 1 document in " << VersionType::ConfigNS};
+                str::stream() << "should only have 1 document in " << VersionType::ConfigNS.ns()};
     }
 
     if (queryResults.empty()) {
@@ -481,7 +481,7 @@ StatusWith<std::vector<std::string>> ShardingCatalogClientImpl::getDatabasesForS
     auto findStatus = _exhaustiveFindOnConfig(opCtx,
                                               kConfigReadSelector,
                                               repl::ReadConcernLevel::kMajorityReadConcern,
-                                              NamespaceString(DatabaseType::ConfigNS),
+                                              DatabaseType::ConfigNS,
                                               BSON(DatabaseType::primary(shardId.toString())),
                                               BSONObj(),
                                               boost::none);  // no limit
@@ -515,13 +515,8 @@ StatusWith<std::vector<ChunkType>> ShardingCatalogClientImpl::getChunks(
 
     // Convert boost::optional<int> to boost::optional<long long>.
     auto longLimit = limit ? boost::optional<long long>(*limit) : boost::none;
-    auto findStatus = _exhaustiveFindOnConfig(opCtx,
-                                              kConfigReadSelector,
-                                              readConcern,
-                                              NamespaceString(ChunkType::ConfigNS),
-                                              query,
-                                              sort,
-                                              longLimit);
+    auto findStatus = _exhaustiveFindOnConfig(
+        opCtx, kConfigReadSelector, readConcern, ChunkType::ConfigNS, query, sort, longLimit);
     if (!findStatus.isOK()) {
         return findStatus.getStatus().withContext("Failed to load chunks");
     }
@@ -547,12 +542,12 @@ StatusWith<std::vector<ChunkType>> ShardingCatalogClientImpl::getChunks(
 }
 
 StatusWith<std::vector<TagsType>> ShardingCatalogClientImpl::getTagsForCollection(
-    OperationContext* opCtx, const std::string& collectionNs) {
+    OperationContext* opCtx, const NamespaceString& nss) {
     auto findStatus = _exhaustiveFindOnConfig(opCtx,
                                               kConfigReadSelector,
                                               repl::ReadConcernLevel::kMajorityReadConcern,
-                                              NamespaceString(TagsType::ConfigNS),
-                                              BSON(TagsType::ns(collectionNs)),
+                                              TagsType::ConfigNS,
+                                              BSON(TagsType::ns(nss.ns())),
                                               BSON(TagsType::min() << 1),
                                               boost::none);  // no limit
     if (!findStatus.isOK()) {
@@ -581,7 +576,7 @@ StatusWith<repl::OpTimeWith<std::vector<ShardType>>> ShardingCatalogClientImpl::
     auto findStatus = _exhaustiveFindOnConfig(opCtx,
                                               kConfigReadSelector,
                                               readConcern,
-                                              NamespaceString(ShardType::ConfigNS),
+                                              ShardType::ConfigNS,
                                               BSONObj(),     // no query filter
                                               BSONObj(),     // no sort
                                               boost::none);  // no limit
@@ -725,7 +720,7 @@ bool ShardingCatalogClientImpl::runUserManagementReadCommand(OperationContext* o
 Status ShardingCatalogClientImpl::applyChunkOpsDeprecated(OperationContext* opCtx,
                                                           const BSONArray& updateOps,
                                                           const BSONArray& preCondition,
-                                                          const std::string& nss,
+                                                          const NamespaceString& nss,
                                                           const ChunkVersion& lastChunkVersion,
                                                           const WriteConcernOptions& writeConcern,
                                                           repl::ReadConcernLevel readConcern) {
@@ -775,7 +770,7 @@ Status ShardingCatalogClientImpl::applyChunkOpsDeprecated(OperationContext* opCt
         // mod made it to the config server, then transaction was successful.
         BSONObjBuilder query;
         lastChunkVersion.addToBSON(query, ChunkType::lastmod());
-        query.append(ChunkType::ns(), nss);
+        query.append(ChunkType::ns(), nss.ns());
         auto swChunks = getChunks(opCtx, query.obj(), BSONObj(), 1, nullptr, readConcern);
         const auto& newestChunk = swChunks.getValue();
 
@@ -791,7 +786,7 @@ Status ShardingCatalogClientImpl::applyChunkOpsDeprecated(OperationContext* opCt
         } else {
             errMsg = str::stream() << "chunk operation commit failed: version "
                                    << lastChunkVersion.toString()
-                                   << " doesn't exist in namespace: " << nss
+                                   << " doesn't exist in namespace: " << nss.ns()
                                    << ". Unable to save chunk ops. Command: " << cmd
                                    << ". Result: " << response.getValue().response;
         }
@@ -818,10 +813,9 @@ void ShardingCatalogClientImpl::writeConfigServerDirect(OperationContext* opCtx,
 }
 
 Status ShardingCatalogClientImpl::insertConfigDocument(OperationContext* opCtx,
-                                                       const std::string& ns,
+                                                       const NamespaceString& nss,
                                                        const BSONObj& doc,
                                                        const WriteConcernOptions& writeConcern) {
-    const NamespaceString nss(ns);
     invariant(nss.db() == NamespaceString::kAdminDb || nss.db() == NamespaceString::kConfigDb);
 
     const BSONElement idField = doc.getField("_id");
@@ -894,23 +888,22 @@ Status ShardingCatalogClientImpl::insertConfigDocument(OperationContext* opCtx,
 
 StatusWith<bool> ShardingCatalogClientImpl::updateConfigDocument(
     OperationContext* opCtx,
-    const string& ns,
+    const NamespaceString& nss,
     const BSONObj& query,
     const BSONObj& update,
     bool upsert,
     const WriteConcernOptions& writeConcern) {
-    return _updateConfigDocument(opCtx, ns, query, update, upsert, writeConcern);
+    return _updateConfigDocument(opCtx, nss, query, update, upsert, writeConcern);
 }
 
 StatusWith<bool> ShardingCatalogClientImpl::_updateConfigDocument(
     OperationContext* opCtx,
-    const string& ns,
+    const NamespaceString& nss,
     const BSONObj& query,
     const BSONObj& update,
     bool upsert,
     const WriteConcernOptions& writeConcern) {
-    const NamespaceString nss(ns);
-    invariant(nss.db() == "config");
+    invariant(nss.db() == NamespaceString::kConfigDb);
 
     const BSONElement idField = query.getField("_id");
     invariant(!idField.eoo());
@@ -944,11 +937,10 @@ StatusWith<bool> ShardingCatalogClientImpl::_updateConfigDocument(
 }
 
 Status ShardingCatalogClientImpl::removeConfigDocuments(OperationContext* opCtx,
-                                                        const string& ns,
+                                                        const NamespaceString& nss,
                                                         const BSONObj& query,
                                                         const WriteConcernOptions& writeConcern) {
-    const NamespaceString nss(ns);
-    invariant(nss.db() == "config");
+    invariant(nss.db() == NamespaceString::kConfigDb);
 
     BatchedCommandRequest request([&] {
         write_ops::Delete deleteOp(nss);
@@ -1040,14 +1032,13 @@ StatusWith<std::vector<KeysCollectionDocument>> ShardingCatalogClientImpl::getNe
     queryBuilder.append("purpose", purpose);
     queryBuilder.append("expiresAt", BSON("$gt" << newerThanThis.asTimestamp()));
 
-    auto findStatus =
-        config->exhaustiveFindOnConfig(opCtx,
-                                       kConfigReadSelector,
-                                       readConcernLevel,
-                                       NamespaceString(KeysCollectionDocument::ConfigNS),
-                                       queryBuilder.obj(),
-                                       BSON("expiresAt" << 1),
-                                       boost::none);
+    auto findStatus = config->exhaustiveFindOnConfig(opCtx,
+                                                     kConfigReadSelector,
+                                                     readConcernLevel,
+                                                     KeysCollectionDocument::ConfigNS,
+                                                     queryBuilder.obj(),
+                                                     BSON("expiresAt" << 1),
+                                                     boost::none);
 
     if (!findStatus.isOK()) {
         return findStatus.getStatus();
diff --git a/src/mongo/s/catalog/sharding_catalog_client_impl.h b/src/mongo/s/catalog/sharding_catalog_client_impl.h
index 0766a44b279..0c258666bb7 100644
--- a/src/mongo/s/catalog/sharding_catalog_client_impl.h
+++ b/src/mongo/s/catalog/sharding_catalog_client_impl.h
@@ -56,7 +56,7 @@ public:
      * described by "coll."
      */
     static Status updateShardingCatalogEntryForCollection(OperationContext* opCtx,
-                                                          const std::string& collNs,
+                                                          const NamespaceString& nss,
                                                           const CollectionType& coll,
                                                           const bool upsert);
 
@@ -93,7 +93,7 @@ public:
 
     StatusWith<repl::OpTimeWith<CollectionType>> getCollection(
         OperationContext* opCtx,
-        const std::string& collNs,
+        const NamespaceString& nss,
         repl::ReadConcernLevel readConcernLevel) override;
 
     StatusWith<std::vector<CollectionType>> getCollections(
@@ -112,8 +112,8 @@ public:
                                                  repl::OpTime* opTime,
                                                  repl::ReadConcernLevel readConcern) override;
 
-    StatusWith<std::vector<TagsType>> getTagsForCollection(
-        OperationContext* opCtx, const std::string& collectionNs) override;
+    StatusWith<std::vector<TagsType>> getTagsForCollection(OperationContext* opCtx,
+                                                           const NamespaceString& nss) override;
 
     StatusWith<repl::OpTimeWith<std::vector<ShardType>>> getAllShards(
         OperationContext* opCtx, repl::ReadConcernLevel readConcern) override;
@@ -132,7 +132,7 @@ public:
     Status applyChunkOpsDeprecated(OperationContext* opCtx,
                                    const BSONArray& updateOps,
                                    const BSONArray& preCondition,
-                                   const std::string& nss,
+                                   const NamespaceString& nss,
                                    const ChunkVersion& lastChunkVersion,
                                    const WriteConcernOptions& writeConcern,
                                    repl::ReadConcernLevel readConcern) override;
@@ -147,19 +147,19 @@ public:
                                  BatchedCommandResponse* response) override;
 
     Status insertConfigDocument(OperationContext* opCtx,
-                                const std::string& ns,
+                                const NamespaceString& nss,
                                 const BSONObj& doc,
                                 const WriteConcernOptions& writeConcern) override;
 
     StatusWith<bool> updateConfigDocument(OperationContext* opCtx,
-                                          const std::string& ns,
+                                          const NamespaceString& nss,
                                           const BSONObj& query,
                                           const BSONObj& update,
                                           bool upsert,
                                           const WriteConcernOptions& writeConcern) override;
 
     Status removeConfigDocuments(OperationContext* opCtx,
-                                 const std::string& ns,
+                                 const NamespaceString& nss,
                                  const BSONObj& query,
                                  const WriteConcernOptions& writeConcern) override;
 
@@ -193,7 +193,7 @@ private:
      * returns whether the update command's response update.n value is > 0).
      */
     static StatusWith<bool> _updateConfigDocument(OperationContext* opCtx,
-                                                  const std::string& ns,
+                                                  const NamespaceString& nss,
                                                   const BSONObj& query,
                                                   const BSONObj& update,
                                                   bool upsert,
@@ -246,7 +246,7 @@ private:
     Status _log(OperationContext* opCtx,
                 const StringData& logCollName,
                 const std::string& what,
-                const std::string& operationNS,
+                const std::string& operationNSS,
                 const BSONObj& detail,
                 const WriteConcernOptions& writeConcern);
 
diff --git a/src/mongo/s/catalog/sharding_catalog_client_mock.cpp b/src/mongo/s/catalog/sharding_catalog_client_mock.cpp
index 2fe043be4e4..0cc54ef7df7 100644
--- a/src/mongo/s/catalog/sharding_catalog_client_mock.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_client_mock.cpp
@@ -80,7 +80,7 @@ StatusWith<repl::OpTimeWith<DatabaseType>> ShardingCatalogClientMock::getDatabas
 }
 
 StatusWith<repl::OpTimeWith<CollectionType>> ShardingCatalogClientMock::getCollection(
-    OperationContext* opCtx, const string& collNs, repl::ReadConcernLevel readConcernLevel) {
+    OperationContext* opCtx, const NamespaceString& nss, repl::ReadConcernLevel readConcernLevel) {
     return {ErrorCodes::InternalError, "Method not implemented"};
 }
 
@@ -108,7 +108,7 @@ StatusWith<std::vector<ChunkType>> ShardingCatalogClientMock::getChunks(
 }
 
 StatusWith<std::vector<TagsType>> ShardingCatalogClientMock::getTagsForCollection(
-    OperationContext* opCtx, const string& collectionNs) {
+    OperationContext* opCtx, const NamespaceString& nss) {
     return {ErrorCodes::InternalError, "Method not implemented"};
 }
 
@@ -135,7 +135,7 @@ bool ShardingCatalogClientMock::runUserManagementReadCommand(OperationContext* o
 Status ShardingCatalogClientMock::applyChunkOpsDeprecated(OperationContext* opCtx,
                                                           const BSONArray& updateOps,
                                                           const BSONArray& preCondition,
-                                                          const std::string& nss,
+                                                          const NamespaceString& nss,
                                                           const ChunkVersion& lastChunkVersion,
                                                           const WriteConcernOptions& writeConcern,
                                                           repl::ReadConcernLevel readConcern) {
@@ -150,8 +150,8 @@ Status ShardingCatalogClientMock::logAction(OperationContext* opCtx,
 }
 
 Status ShardingCatalogClientMock::logChange(OperationContext* opCtx,
-                                            const string& what,
-                                            const string& ns,
+                                            const std::string& what,
+                                            const std::string& ns,
                                             const BSONObj& detail,
                                             const WriteConcernOptions& writeConcern) {
     return {ErrorCodes::InternalError, "Method not implemented"};
@@ -172,7 +172,7 @@ void ShardingCatalogClientMock::writeConfigServerDirect(OperationContext* opCtx,
                                                         BatchedCommandResponse* response) {}
 
 Status ShardingCatalogClientMock::insertConfigDocument(OperationContext* opCtx,
-                                                       const std::string& ns,
+                                                       const NamespaceString& nss,
                                                        const BSONObj& doc,
                                                        const WriteConcernOptions& writeConcern) {
     return {ErrorCodes::InternalError, "Method not implemented"};
@@ -180,7 +180,7 @@ Status ShardingCatalogClientMock::insertConfigDocument(OperationContext* opCtx,
 
 StatusWith<bool> ShardingCatalogClientMock::updateConfigDocument(
     OperationContext* opCtx,
-    const std::string& ns,
+    const NamespaceString& nss,
     const BSONObj& query,
     const BSONObj& update,
     bool upsert,
@@ -189,7 +189,7 @@ StatusWith<bool> ShardingCatalogClientMock::updateConfigDocument(
 }
 
 Status ShardingCatalogClientMock::removeConfigDocuments(OperationContext* opCtx,
-                                                        const std::string& ns,
+                                                        const NamespaceString& nss,
                                                         const BSONObj& query,
                                                         const WriteConcernOptions& writeConcern) {
     return {ErrorCodes::InternalError, "Method not implemented"};
diff --git a/src/mongo/s/catalog/sharding_catalog_client_mock.h b/src/mongo/s/catalog/sharding_catalog_client_mock.h
index 159d5d8c1b8..7ab8c63ddef 100644
--- a/src/mongo/s/catalog/sharding_catalog_client_mock.h
+++ b/src/mongo/s/catalog/sharding_catalog_client_mock.h
@@ -58,7 +58,7 @@ public:
 
     StatusWith<repl::OpTimeWith<CollectionType>> getCollection(
         OperationContext* opCtx,
-        const std::string& collNs,
+        const NamespaceString& nss,
         repl::ReadConcernLevel readConcernLevel) override;
 
     StatusWith<std::vector<CollectionType>> getCollections(
@@ -77,8 +77,8 @@ public:
                                                  repl::OpTime* opTime,
                                                  repl::ReadConcernLevel readConcern) override;
 
-    StatusWith<std::vector<TagsType>> getTagsForCollection(
-        OperationContext* opCtx, const std::string& collectionNs) override;
+    StatusWith<std::vector<TagsType>> getTagsForCollection(OperationContext* opCtx,
+                                                           const NamespaceString& nss) override;
 
     StatusWith<repl::OpTimeWith<std::vector<ShardType>>> getAllShards(
         OperationContext* opCtx, repl::ReadConcernLevel readConcern) override;
@@ -97,7 +97,7 @@ public:
     Status applyChunkOpsDeprecated(OperationContext* opCtx,
                                    const BSONArray& updateOps,
                                    const BSONArray& preCondition,
-                                   const std::string& nss,
+                                   const NamespaceString& nss,
                                    const ChunkVersion& lastChunkVersion,
                                    const WriteConcernOptions& writeConcern,
                                    repl::ReadConcernLevel readConcern) override;
@@ -123,19 +123,19 @@ public:
                                  BatchedCommandResponse* response) override;
 
     Status insertConfigDocument(OperationContext* opCtx,
-                                const std::string& ns,
+                                const NamespaceString& nss,
                                 const BSONObj& doc,
                                 const WriteConcernOptions& writeConcern) override;
 
     StatusWith<bool> updateConfigDocument(OperationContext* opCtx,
-                                          const std::string& ns,
+                                          const NamespaceString& nss,
                                           const BSONObj& query,
                                           const BSONObj& update,
                                           bool upsert,
                                           const WriteConcernOptions& writeConcern) override;
 
     Status removeConfigDocuments(OperationContext* opCtx,
-                                 const std::string& ns,
+                                 const NamespaceString& nss,
                                  const BSONObj& query,
                                  const WriteConcernOptions& writeConcern) override;
 
diff --git a/src/mongo/s/catalog/sharding_catalog_commit_chunk_migration_test.cpp b/src/mongo/s/catalog/sharding_catalog_commit_chunk_migration_test.cpp
index 7904b697ea5..c703bb6e9b1 100644
--- a/src/mongo/s/catalog/sharding_catalog_commit_chunk_migration_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_commit_chunk_migration_test.cpp
@@ -43,9 +43,9 @@ namespace {
 
 using CommitChunkMigrate = ConfigServerTestFixture;
 
-TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandWithCtl) {
+const NamespaceString kNamespace("TestDB.TestColl");
 
-    std::string const nss = "TestDB.TestColl";
+TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandWithCtl) {
 
     ShardType shard0;
     shard0.setName("shard0");
@@ -61,7 +61,7 @@ TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandWithCtl) {
     auto const origVersion = ChunkVersion(origMajorVersion, 7, OID::gen());
 
     ChunkType chunk0;
-    chunk0.setNS(nss);
+    chunk0.setNS(kNamespace);
     chunk0.setVersion(origVersion);
     chunk0.setShard(shard0.getName());
 
@@ -72,7 +72,7 @@ TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandWithCtl) {
     chunk0.setMax(chunkMax);
 
     ChunkType chunk1;
-    chunk1.setNS(nss);
+    chunk1.setNS(kNamespace);
     chunk1.setVersion(origVersion);
     chunk1.setShard(shard0.getName());
 
@@ -88,7 +88,7 @@ TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandWithCtl) {
 
     StatusWith<BSONObj> resultBSON = ShardingCatalogManager::get(operationContext())
                                          ->commitChunkMigration(operationContext(),
-                                                                NamespaceString(chunk0.getNS()),
+                                                                chunk0.getNS(),
                                                                 chunk0cref,
                                                                 chunk1cref,
                                                                 origVersion.epoch(),
@@ -119,8 +119,6 @@ TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandWithCtl) {
 
 TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandNoCtl) {
 
-    std::string const nss = "TestDB.TestColl";
-
     ShardType shard0;
     shard0.setName("shard0");
     shard0.setHost("shard0:12");
@@ -135,7 +133,7 @@ TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandNoCtl) {
     auto const origVersion = ChunkVersion(origMajorVersion, 4, OID::gen());
 
     ChunkType chunk0;
-    chunk0.setNS(nss);
+    chunk0.setNS(kNamespace);
     chunk0.setVersion(origVersion);
     chunk0.setShard(shard0.getName());
 
@@ -149,7 +147,7 @@ TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandNoCtl) {
 
     StatusWith<BSONObj> resultBSON = ShardingCatalogManager::get(operationContext())
                                          ->commitChunkMigration(operationContext(),
-                                                                NamespaceString(chunk0.getNS()),
+                                                                chunk0.getNS(),
                                                                 chunk0,
                                                                 boost::none,
                                                                 origVersion.epoch(),
@@ -175,8 +173,6 @@ TEST_F(CommitChunkMigrate, CheckCorrectOpsCommandNoCtl) {
 
 TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch0) {
 
-    std::string const nss = "TestDB.TestColl";
-
     ShardType shard0;
     shard0.setName("shard0");
     shard0.setHost("shard0:12");
@@ -191,7 +187,7 @@ TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch0) {
     auto const origVersion = ChunkVersion(origMajorVersion, 7, OID::gen());
 
     ChunkType chunk0;
-    chunk0.setNS(nss);
+    chunk0.setNS(kNamespace);
     chunk0.setVersion(origVersion);
     chunk0.setShard(shard0.getName());
 
@@ -202,7 +198,7 @@ TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch0) {
     chunk0.setMax(chunkMax);
 
     ChunkType chunk1;
-    chunk1.setNS(nss);
+    chunk1.setNS(kNamespace);
     chunk1.setVersion(origVersion);
     chunk1.setShard(shard0.getName());
 
@@ -214,7 +210,7 @@ TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch0) {
 
     StatusWith<BSONObj> resultBSON = ShardingCatalogManager::get(operationContext())
                                          ->commitChunkMigration(operationContext(),
-                                                                NamespaceString(chunk0.getNS()),
+                                                                chunk0.getNS(),
                                                                 chunk0,
                                                                 chunk1,
                                                                 OID::gen(),
@@ -226,8 +222,6 @@ TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch0) {
 
 TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch1) {
 
-    std::string const nss = "TestDB.TestColl";
-
     ShardType shard0;
     shard0.setName("shard0");
     shard0.setHost("shard0:12");
@@ -243,7 +237,7 @@ TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch1) {
     auto const otherVersion = ChunkVersion(origMajorVersion, 7, OID::gen());
 
     ChunkType chunk0;
-    chunk0.setNS(nss);
+    chunk0.setNS(kNamespace);
     chunk0.setVersion(origVersion);
     chunk0.setShard(shard0.getName());
 
@@ -254,7 +248,7 @@ TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch1) {
     chunk0.setMax(chunkMax);
 
     ChunkType chunk1;
-    chunk1.setNS(nss);
+    chunk1.setNS(kNamespace);
     chunk1.setVersion(otherVersion);
     chunk1.setShard(shard0.getName());
 
@@ -267,7 +261,7 @@ TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch1) {
 
     StatusWith<BSONObj> resultBSON = ShardingCatalogManager::get(operationContext())
                                          ->commitChunkMigration(operationContext(),
-                                                                NamespaceString(chunk0.getNS()),
+                                                                chunk0.getNS(),
                                                                 chunk0,
                                                                 chunk1,
                                                                 origVersion.epoch(),
@@ -279,8 +273,6 @@ TEST_F(CommitChunkMigrate, RejectWrongCollectionEpoch1) {
 
 TEST_F(CommitChunkMigrate, RejectChunkMissing0) {
 
-    std::string const nss = "TestDB.TestColl";
-
     ShardType shard0;
     shard0.setName("shard0");
     shard0.setHost("shard0:12");
@@ -295,7 +287,7 @@ TEST_F(CommitChunkMigrate, RejectChunkMissing0) {
     auto const origVersion = ChunkVersion(origMajorVersion, 7, OID::gen());
 
     ChunkType chunk0;
-    chunk0.setNS(nss);
+    chunk0.setNS(kNamespace);
     chunk0.setVersion(origVersion);
     chunk0.setShard(shard0.getName());
 
@@ -306,7 +298,7 @@ TEST_F(CommitChunkMigrate, RejectChunkMissing0) {
     chunk0.setMax(chunkMax);
 
     ChunkType chunk1;
-    chunk1.setNS(nss);
+    chunk1.setNS(kNamespace);
     chunk1.setVersion(origVersion);
     chunk1.setShard(shard0.getName());
 
@@ -318,7 +310,7 @@ TEST_F(CommitChunkMigrate, RejectChunkMissing0) {
 
     StatusWith<BSONObj> resultBSON = ShardingCatalogManager::get(operationContext())
                                          ->commitChunkMigration(operationContext(),
-                                                                NamespaceString(chunk0.getNS()),
+                                                                chunk0.getNS(),
                                                                 chunk0,
                                                                 chunk1,
                                                                 origVersion.epoch(),
@@ -330,8 +322,6 @@ TEST_F(CommitChunkMigrate, RejectChunkMissing0) {
 
 TEST_F(CommitChunkMigrate, RejectChunkMissing1) {
 
-    std::string const nss = "TestDB.TestColl";
-
     ShardType shard0;
     shard0.setName("shard0");
     shard0.setHost("shard0:12");
@@ -346,7 +336,7 @@ TEST_F(CommitChunkMigrate, RejectChunkMissing1) {
     auto const origVersion = ChunkVersion(origMajorVersion, 7, OID::gen());
 
     ChunkType chunk0;
-    chunk0.setNS(nss);
+    chunk0.setNS(kNamespace);
     chunk0.setVersion(origVersion);
     chunk0.setShard(shard0.getName());
 
@@ -357,7 +347,7 @@ TEST_F(CommitChunkMigrate, RejectChunkMissing1) {
     chunk0.setMax(chunkMax);
 
     ChunkType chunk1;
-    chunk1.setNS(nss);
+    chunk1.setNS(kNamespace);
     chunk1.setVersion(origVersion);
     chunk1.setShard(shard0.getName());
 
@@ -369,7 +359,7 @@ TEST_F(CommitChunkMigrate, RejectChunkMissing1) {
 
     StatusWith<BSONObj> resultBSON = ShardingCatalogManager::get(operationContext())
                                          ->commitChunkMigration(operationContext(),
-                                                                NamespaceString(chunk0.getNS()),
+                                                                chunk0.getNS(),
                                                                 chunk0,
                                                                 chunk1,
                                                                 origVersion.epoch(),
diff --git a/src/mongo/s/catalog/sharding_catalog_config_initialization_test.cpp b/src/mongo/s/catalog/sharding_catalog_config_initialization_test.cpp
index 71705b712eb..bfb5234823a 100644
--- a/src/mongo/s/catalog/sharding_catalog_config_initialization_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_config_initialization_test.cpp
@@ -84,14 +84,14 @@ TEST_F(ConfigInitializationTest, UpgradeNotNeeded) {
     version.setClusterId(OID::gen());
     version.setCurrentVersion(CURRENT_CONFIG_VERSION);
     version.setMinCompatibleVersion(MIN_COMPATIBLE_CONFIG_VERSION);
-    ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), version.toBSON()));
+    ASSERT_OK(
+        insertToConfigCollection(operationContext(), VersionType::ConfigNS, version.toBSON()));
 
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
                   ->initializeConfigDatabaseIfNeeded(operationContext()));
 
-    auto versionDoc = assertGet(findOneOnConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), BSONObj()));
+    auto versionDoc =
+        assertGet(findOneOnConfigCollection(operationContext(), VersionType::ConfigNS, BSONObj()));
 
     VersionType foundVersion = assertGet(VersionType::fromBSON(versionDoc));
 
@@ -105,15 +105,15 @@ TEST_F(ConfigInitializationTest, InitIncompatibleVersion) {
     version.setClusterId(OID::gen());
     version.setCurrentVersion(MIN_COMPATIBLE_CONFIG_VERSION - 1);
     version.setMinCompatibleVersion(MIN_COMPATIBLE_CONFIG_VERSION - 2);
-    ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), version.toBSON()));
+    ASSERT_OK(
+        insertToConfigCollection(operationContext(), VersionType::ConfigNS, version.toBSON()));
 
     ASSERT_EQ(ErrorCodes::IncompatibleShardingConfigVersion,
               ShardingCatalogManager::get(operationContext())
                   ->initializeConfigDatabaseIfNeeded(operationContext()));
 
-    auto versionDoc = assertGet(findOneOnConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), BSONObj()));
+    auto versionDoc =
+        assertGet(findOneOnConfigCollection(operationContext(), VersionType::ConfigNS, BSONObj()));
 
     VersionType foundVersion = assertGet(VersionType::fromBSON(versionDoc));
 
@@ -127,11 +127,11 @@ TEST_F(ConfigInitializationTest, InitClusterMultipleVersionDocs) {
     version.setClusterId(OID::gen());
     version.setCurrentVersion(MIN_COMPATIBLE_CONFIG_VERSION - 2);
     version.setMinCompatibleVersion(MIN_COMPATIBLE_CONFIG_VERSION - 3);
-    ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), version.toBSON()));
+    ASSERT_OK(
+        insertToConfigCollection(operationContext(), VersionType::ConfigNS, version.toBSON()));
 
     ASSERT_OK(insertToConfigCollection(operationContext(),
-                                       NamespaceString(VersionType::ConfigNS),
+                                       VersionType::ConfigNS,
                                        BSON("_id"
                                             << "a second document")));
 
@@ -147,8 +147,7 @@ TEST_F(ConfigInitializationTest, InitInvalidConfigVersionDoc) {
                     currentVersion: 7,
                     clusterId: ObjectId("55919cc6dbe86ce7ac056427")
                 })"));
-    ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), versionDoc));
+    ASSERT_OK(insertToConfigCollection(operationContext(), VersionType::ConfigNS, versionDoc));
 
     ASSERT_EQ(ErrorCodes::TypeMismatch,
               ShardingCatalogManager::get(operationContext())
@@ -159,14 +158,13 @@ TEST_F(ConfigInitializationTest, InitInvalidConfigVersionDoc) {
 TEST_F(ConfigInitializationTest, InitNoVersionDocEmptyConfig) {
     // Make sure there is no existing document
     ASSERT_EQUALS(ErrorCodes::NoMatchingDocument,
-                  findOneOnConfigCollection(
-                      operationContext(), NamespaceString(VersionType::ConfigNS), BSONObj()));
+                  findOneOnConfigCollection(operationContext(), VersionType::ConfigNS, BSONObj()));
 
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
                   ->initializeConfigDatabaseIfNeeded(operationContext()));
 
-    auto versionDoc = assertGet(findOneOnConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), BSONObj()));
+    auto versionDoc =
+        assertGet(findOneOnConfigCollection(operationContext(), VersionType::ConfigNS, BSONObj()));
 
     VersionType foundVersion = assertGet(VersionType::fromBSON(versionDoc));
 
@@ -180,8 +178,8 @@ TEST_F(ConfigInitializationTest, InitVersionTooHigh) {
     version.setClusterId(OID::gen());
     version.setCurrentVersion(10000);
     version.setMinCompatibleVersion(10000);
-    ASSERT_OK(insertToConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), version.toBSON()));
+    ASSERT_OK(
+        insertToConfigCollection(operationContext(), VersionType::ConfigNS, version.toBSON()));
 
     ASSERT_EQ(ErrorCodes::IncompatibleShardingConfigVersion,
               ShardingCatalogManager::get(operationContext())
@@ -192,8 +190,8 @@ TEST_F(ConfigInitializationTest, OnlyRunsOnce) {
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
                   ->initializeConfigDatabaseIfNeeded(operationContext()));
 
-    auto versionDoc = assertGet(findOneOnConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), BSONObj()));
+    auto versionDoc =
+        assertGet(findOneOnConfigCollection(operationContext(), VersionType::ConfigNS, BSONObj()));
 
     VersionType foundVersion = assertGet(VersionType::fromBSON(versionDoc));
 
@@ -210,8 +208,8 @@ TEST_F(ConfigInitializationTest, ReRunsIfDocRolledBackThenReElected) {
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
                   ->initializeConfigDatabaseIfNeeded(operationContext()));
 
-    auto versionDoc = assertGet(findOneOnConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), BSONObj()));
+    auto versionDoc =
+        assertGet(findOneOnConfigCollection(operationContext(), VersionType::ConfigNS, BSONObj()));
 
     VersionType foundVersion = assertGet(VersionType::fromBSON(versionDoc));
 
@@ -228,7 +226,7 @@ TEST_F(ConfigInitializationTest, ReRunsIfDocRolledBackThenReElected) {
         ASSERT_OK(replicationCoordinator()->setFollowerMode(repl::MemberState::RS_ROLLBACK));
         auto opCtx = operationContext();
         repl::UnreplicatedWritesBlock uwb(opCtx);
-        auto nss = NamespaceString(VersionType::ConfigNS);
+        auto nss = VersionType::ConfigNS;
         writeConflictRetry(opCtx, "removeConfigDocuments", nss.ns(), [&] {
             AutoGetCollection autoColl(opCtx, nss, MODE_IX);
             auto coll = autoColl.getCollection();
@@ -249,15 +247,14 @@ TEST_F(ConfigInitializationTest, ReRunsIfDocRolledBackThenReElected) {
 
     // Verify the document was actually removed.
     ASSERT_EQUALS(ErrorCodes::NoMatchingDocument,
-                  findOneOnConfigCollection(
-                      operationContext(), NamespaceString(VersionType::ConfigNS), BSONObj()));
+                  findOneOnConfigCollection(operationContext(), VersionType::ConfigNS, BSONObj()));
 
     // Re-create the config.version document.
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
                   ->initializeConfigDatabaseIfNeeded(operationContext()));
 
-    auto newVersionDoc = assertGet(findOneOnConfigCollection(
-        operationContext(), NamespaceString(VersionType::ConfigNS), BSONObj()));
+    auto newVersionDoc =
+        assertGet(findOneOnConfigCollection(operationContext(), VersionType::ConfigNS, BSONObj()));
 
     VersionType newFoundVersion = assertGet(VersionType::fromBSON(newVersionDoc));
 
@@ -334,31 +331,25 @@ TEST_F(ConfigInitializationTest, BuildsNecessaryIndexes) {
                  << "ns"
                  << "config.tags")};
 
-    auto foundChunksIndexes =
-        assertGet(getIndexes(operationContext(), NamespaceString(ChunkType::ConfigNS)));
+    auto foundChunksIndexes = assertGet(getIndexes(operationContext(), ChunkType::ConfigNS));
     assertBSONObjsSame(expectedChunksIndexes, foundChunksIndexes);
 
-    auto foundLockpingsIndexes =
-        assertGet(getIndexes(operationContext(), NamespaceString(LockpingsType::ConfigNS)));
+    auto foundLockpingsIndexes = assertGet(getIndexes(operationContext(), LockpingsType::ConfigNS));
     assertBSONObjsSame(expectedLockpingsIndexes, foundLockpingsIndexes);
 
-    auto foundLocksIndexes =
-        assertGet(getIndexes(operationContext(), NamespaceString(LocksType::ConfigNS)));
+    auto foundLocksIndexes = assertGet(getIndexes(operationContext(), LocksType::ConfigNS));
     assertBSONObjsSame(expectedLocksIndexes, foundLocksIndexes);
 
-    auto foundShardsIndexes =
-        assertGet(getIndexes(operationContext(), NamespaceString(ShardType::ConfigNS)));
+    auto foundShardsIndexes = assertGet(getIndexes(operationContext(), ShardType::ConfigNS));
     assertBSONObjsSame(expectedShardsIndexes, foundShardsIndexes);
 
-    auto foundTagsIndexes =
-        assertGet(getIndexes(operationContext(), NamespaceString(TagsType::ConfigNS)));
+    auto foundTagsIndexes = assertGet(getIndexes(operationContext(), TagsType::ConfigNS));
     assertBSONObjsSame(expectedTagsIndexes, foundTagsIndexes);
 }
 
 TEST_F(ConfigInitializationTest, CompatibleIndexAlreadyExists) {
     getConfigShard()
-        ->createIndexOnConfig(
-            operationContext(), NamespaceString(ShardType::ConfigNS), BSON("host" << 1), true)
+        ->createIndexOnConfig(operationContext(), ShardType::ConfigNS, BSON("host" << 1), true)
         .transitional_ignore();
 
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
@@ -375,8 +366,7 @@ TEST_F(ConfigInitializationTest, CompatibleIndexAlreadyExists) {
                  << "config.shards")};
 
 
-    auto foundShardsIndexes =
-        assertGet(getIndexes(operationContext(), NamespaceString(ShardType::ConfigNS)));
+    auto foundShardsIndexes = assertGet(getIndexes(operationContext(), ShardType::ConfigNS));
     assertBSONObjsSame(expectedShardsIndexes, foundShardsIndexes);
 }
 
@@ -384,8 +374,7 @@ TEST_F(ConfigInitializationTest, IncompatibleIndexAlreadyExists) {
     // Make the index non-unique even though its supposed to be unique, make sure initialization
     // fails
     getConfigShard()
-        ->createIndexOnConfig(
-            operationContext(), NamespaceString(ShardType::ConfigNS), BSON("host" << 1), false)
+        ->createIndexOnConfig(operationContext(), ShardType::ConfigNS, BSON("host" << 1), false)
         .transitional_ignore();
 
     ASSERT_EQUALS(ErrorCodes::IndexOptionsConflict,
diff --git a/src/mongo/s/catalog/sharding_catalog_manager.cpp b/src/mongo/s/catalog/sharding_catalog_manager.cpp
index b2fb3521f1d..18f616516e3 100644
--- a/src/mongo/s/catalog/sharding_catalog_manager.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_manager.cpp
@@ -210,18 +210,15 @@ Status ShardingCatalogManager::_initConfigIndexes(OperationContext* opCtx) {
     const bool unique = true;
     auto configShard = Grid::get(opCtx)->shardRegistry()->getConfigShard();
 
-    Status result =
-        configShard->createIndexOnConfig(opCtx,
-                                         NamespaceString(ChunkType::ConfigNS),
-                                         BSON(ChunkType::ns() << 1 << ChunkType::min() << 1),
-                                         unique);
+    Status result = configShard->createIndexOnConfig(
+        opCtx, ChunkType::ConfigNS, BSON(ChunkType::ns() << 1 << ChunkType::min() << 1), unique);
     if (!result.isOK()) {
         return result.withContext("couldn't create ns_1_min_1 index on config db");
     }
 
     result = configShard->createIndexOnConfig(
         opCtx,
-        NamespaceString(ChunkType::ConfigNS),
+        ChunkType::ConfigNS,
         BSON(ChunkType::ns() << 1 << ChunkType::shard() << 1 << ChunkType::min() << 1),
         unique);
     if (!result.isOK()) {
@@ -230,7 +227,7 @@ Status ShardingCatalogManager::_initConfigIndexes(OperationContext* opCtx) {
 
     result =
         configShard->createIndexOnConfig(opCtx,
-                                         NamespaceString(ChunkType::ConfigNS),
+                                         ChunkType::ConfigNS,
                                          BSON(ChunkType::ns() << 1 << ChunkType::lastmod() << 1),
                                          unique);
     if (!result.isOK()) {
@@ -239,7 +236,7 @@ Status ShardingCatalogManager::_initConfigIndexes(OperationContext* opCtx) {
 
     result = configShard->createIndexOnConfig(
         opCtx,
-        NamespaceString(MigrationType::ConfigNS),
+        MigrationType::ConfigNS,
         BSON(MigrationType::ns() << 1 << MigrationType::min() << 1),
         unique);
     if (!result.isOK()) {
@@ -247,20 +244,20 @@ Status ShardingCatalogManager::_initConfigIndexes(OperationContext* opCtx) {
     }
 
     result = configShard->createIndexOnConfig(
-        opCtx, NamespaceString(ShardType::ConfigNS), BSON(ShardType::host() << 1), unique);
+        opCtx, ShardType::ConfigNS, BSON(ShardType::host() << 1), unique);
     if (!result.isOK()) {
         return result.withContext("couldn't create host_1 index on config db");
     }
 
     result = configShard->createIndexOnConfig(
-        opCtx, NamespaceString(LocksType::ConfigNS), BSON(LocksType::lockID() << 1), !unique);
+        opCtx, LocksType::ConfigNS, BSON(LocksType::lockID() << 1), !unique);
     if (!result.isOK()) {
         return result.withContext("couldn't create lock id index on config db");
     }
 
     result =
         configShard->createIndexOnConfig(opCtx,
-                                         NamespaceString(LocksType::ConfigNS),
+                                         LocksType::ConfigNS,
                                          BSON(LocksType::state() << 1 << LocksType::process() << 1),
                                          !unique);
     if (!result.isOK()) {
@@ -268,23 +265,19 @@ Status ShardingCatalogManager::_initConfigIndexes(OperationContext* opCtx) {
     }
 
     result = configShard->createIndexOnConfig(
-        opCtx, NamespaceString(LockpingsType::ConfigNS), BSON(LockpingsType::ping() << 1), !unique);
+        opCtx, LockpingsType::ConfigNS, BSON(LockpingsType::ping() << 1), !unique);
     if (!result.isOK()) {
         return result.withContext("couldn't create lockping ping time index on config db");
     }
 
-    result = configShard->createIndexOnConfig(opCtx,
-                                              NamespaceString(TagsType::ConfigNS),
-                                              BSON(TagsType::ns() << 1 << TagsType::min() << 1),
-                                              unique);
+    result = configShard->createIndexOnConfig(
+        opCtx, TagsType::ConfigNS, BSON(TagsType::ns() << 1 << TagsType::min() << 1), unique);
     if (!result.isOK()) {
         return result.withContext("couldn't create ns_1_min_1 index on config db");
     }
 
-    result = configShard->createIndexOnConfig(opCtx,
-                                              NamespaceString(TagsType::ConfigNS),
-                                              BSON(TagsType::ns() << 1 << TagsType::tag() << 1),
-                                              !unique);
+    result = configShard->createIndexOnConfig(
+        opCtx, TagsType::ConfigNS, BSON(TagsType::ns() << 1 << TagsType::tag() << 1), !unique);
     if (!result.isOK()) {
         return result.withContext("couldn't create ns_1_tag_1 index on config db");
     }
diff --git a/src/mongo/s/catalog/sharding_catalog_manager.h b/src/mongo/s/catalog/sharding_catalog_manager.h
index 4c535825c7e..8893561f5c8 100644
--- a/src/mongo/s/catalog/sharding_catalog_manager.h
+++ b/src/mongo/s/catalog/sharding_catalog_manager.h
@@ -138,7 +138,7 @@ public:
      * MinKey values.
      */
     Status assignKeyRangeToZone(OperationContext* opCtx,
-                                const NamespaceString& ns,
+                                const NamespaceString& nss,
                                 const ChunkRange& range,
                                 const std::string& zoneName);
 
@@ -149,7 +149,7 @@ public:
      * full shard key.
      */
     Status removeKeyRangeFromZone(OperationContext* opCtx,
-                                  const NamespaceString& ns,
+                                  const NamespaceString& nss,
                                   const ChunkRange& range);
 
     //
@@ -161,7 +161,7 @@ public:
      * smaller chunks at the specified split points.
      */
     Status commitChunkSplit(OperationContext* opCtx,
-                            const NamespaceString& ns,
+                            const NamespaceString& nss,
                             const OID& requestEpoch,
                             const ChunkRange& range,
                             const std::vector<BSONObj>& splitPoints,
@@ -172,7 +172,7 @@ public:
      * merged into a single larger chunk.
      */
     Status commitChunkMerge(OperationContext* opCtx,
-                            const NamespaceString& ns,
+                            const NamespaceString& nss,
                             const OID& requestEpoch,
                             const std::vector<BSONObj>& chunkBoundaries,
                             const std::string& shardName);
@@ -229,7 +229,7 @@ public:
      * some of the known failures:
      *  - NamespaceNotFound - collection does not exist
      */
-    Status dropCollection(OperationContext* opCtx, const NamespaceString& ns);
+    Status dropCollection(OperationContext* opCtx, const NamespaceString& nss);
 
 
     /**
@@ -248,7 +248,7 @@ public:
      *     Otherwise all chunks will be assigned to the primary shard for the database.
      */
     void shardCollection(OperationContext* opCtx,
-                         const std::string& ns,
+                         const NamespaceString& nss,
                          const boost::optional<UUID> uuid,
                          const ShardKeyPattern& fieldsAndOrder,
                          const BSONObj& defaultCollation,
@@ -430,7 +430,7 @@ private:
      * handling.
      */
     StatusWith<long long> _runCountCommandOnConfig(OperationContext* opCtx,
-                                                   const NamespaceString& ns,
+                                                   const NamespaceString& nss,
                                                    BSONObj query);
 
     /**
diff --git a/src/mongo/s/catalog/sharding_catalog_manager_chunk_operations.cpp b/src/mongo/s/catalog/sharding_catalog_manager_chunk_operations.cpp
index 41b5c5973e2..72c92bc6625 100644
--- a/src/mongo/s/catalog/sharding_catalog_manager_chunk_operations.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_manager_chunk_operations.cpp
@@ -78,7 +78,7 @@ BSONArray buildMergeChunksTransactionUpdates(const std::vector<ChunkType>& chunk
         BSONObjBuilder op;
         op.append("op", "u");
         op.appendBool("b", false);  // no upsert
-        op.append("ns", ChunkType::ConfigNS);
+        op.append("ns", ChunkType::ConfigNS.ns());
 
         // expand first chunk into newly merged chunk
         ChunkType mergedChunk(chunksToMerge.front());
@@ -101,7 +101,7 @@ BSONArray buildMergeChunksTransactionUpdates(const std::vector<ChunkType>& chunk
     for (size_t i = 1; i < chunksToMerge.size(); ++i) {
         BSONObjBuilder op;
         op.append("op", "d");
-        op.append("ns", ChunkType::ConfigNS);
+        op.append("ns", ChunkType::ConfigNS.ns());
 
         op.append("o", BSON(ChunkType::name(chunksToMerge[i].getName())));
 
@@ -117,13 +117,13 @@ BSONArray buildMergeChunksTransactionPrecond(const std::vector<ChunkType>& chunk
 
     for (auto chunk : chunksToMerge) {
         BSONObjBuilder b;
-        b.append("ns", ChunkType::ConfigNS);
-        b.append(
-            "q",
-            BSON("query" << BSON(ChunkType::ns(chunk.getNS()) << ChunkType::min(chunk.getMin())
-                                                              << ChunkType::max(chunk.getMax()))
-                         << "orderby"
-                         << BSON(ChunkType::lastmod() << -1)));
+        b.append("ns", ChunkType::ConfigNS.ns());
+        b.append("q",
+                 BSON("query" << BSON(ChunkType::ns(chunk.getNS().ns())
+                                      << ChunkType::min(chunk.getMin())
+                                      << ChunkType::max(chunk.getMax()))
+                              << "orderby"
+                              << BSON(ChunkType::lastmod() << -1)));
         b.append("res",
                  BSON(ChunkType::epoch(collVersion.epoch())
                       << ChunkType::shard(chunk.getShard().toString())));
@@ -148,7 +148,7 @@ Status checkChunkIsOnShard(OperationContext* opCtx,
             opCtx,
             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
             repl::ReadConcernLevel::kLocalReadConcern,
-            NamespaceString(ChunkType::ConfigNS),
+            ChunkType::ConfigNS,
             chunkQuery,
             BSONObj(),
             1);
@@ -179,10 +179,10 @@ BSONObj makeCommitChunkTransactionCommand(const NamespaceString& nss,
         BSONObjBuilder op;
         op.append("op", "u");
         op.appendBool("b", false);  // No upserting
-        op.append("ns", ChunkType::ConfigNS);
+        op.append("ns", ChunkType::ConfigNS.ns());
 
         BSONObjBuilder n(op.subobjStart("o"));
-        n.append(ChunkType::name(), ChunkType::genID(nss.ns(), migratedChunk.getMin()));
+        n.append(ChunkType::name(), ChunkType::genID(nss, migratedChunk.getMin()));
         migratedChunk.getVersion().addToBSON(n, ChunkType::lastmod());
         n.append(ChunkType::ns(), nss.ns());
         n.append(ChunkType::min(), migratedChunk.getMin());
@@ -191,7 +191,7 @@ BSONObj makeCommitChunkTransactionCommand(const NamespaceString& nss,
         n.done();
 
         BSONObjBuilder q(op.subobjStart("o2"));
-        q.append(ChunkType::name(), ChunkType::genID(nss.ns(), migratedChunk.getMin()));
+        q.append(ChunkType::name(), ChunkType::genID(nss, migratedChunk.getMin()));
         q.done();
 
         updates.append(op.obj());
@@ -202,10 +202,10 @@ BSONObj makeCommitChunkTransactionCommand(const NamespaceString& nss,
         BSONObjBuilder op;
         op.append("op", "u");
         op.appendBool("b", false);
-        op.append("ns", ChunkType::ConfigNS);
+        op.append("ns", ChunkType::ConfigNS.ns());
 
         BSONObjBuilder n(op.subobjStart("o"));
-        n.append(ChunkType::name(), ChunkType::genID(nss.ns(), controlChunk->getMin()));
+        n.append(ChunkType::name(), ChunkType::genID(nss, controlChunk->getMin()));
         controlChunk->getVersion().addToBSON(n, ChunkType::lastmod());
         n.append(ChunkType::ns(), nss.ns());
         n.append(ChunkType::min(), controlChunk->getMin());
@@ -214,7 +214,7 @@ BSONObj makeCommitChunkTransactionCommand(const NamespaceString& nss,
         n.done();
 
         BSONObjBuilder q(op.subobjStart("o2"));
-        q.append(ChunkType::name(), ChunkType::genID(nss.ns(), controlChunk->getMin()));
+        q.append(ChunkType::name(), ChunkType::genID(nss, controlChunk->getMin()));
         q.done();
 
         updates.append(op.obj());
@@ -247,7 +247,7 @@ Status ShardingCatalogManager::commitChunkSplit(OperationContext* opCtx,
         opCtx,
         ReadPreferenceSetting{ReadPreference::PrimaryOnly},
         repl::ReadConcernLevel::kLocalReadConcern,
-        NamespaceString(ChunkType::ConfigNS),
+        ChunkType::ConfigNS,
         BSON("ns" << nss.ns()),
         BSON(ChunkType::lastmod << -1),
         1);
@@ -326,11 +326,11 @@ Status ShardingCatalogManager::commitChunkSplit(OperationContext* opCtx,
         BSONObjBuilder op;
         op.append("op", "u");
         op.appendBool("b", true);
-        op.append("ns", ChunkType::ConfigNS);
+        op.append("ns", ChunkType::ConfigNS.ns());
 
         // add the modified (new) chunk information as the update object
         BSONObjBuilder n(op.subobjStart("o"));
-        n.append(ChunkType::name(), ChunkType::genID(nss.ns(), startKey));
+        n.append(ChunkType::name(), ChunkType::genID(nss, startKey));
         currentMaxVersion.addToBSON(n, ChunkType::lastmod());
         n.append(ChunkType::ns(), nss.ns());
         n.append(ChunkType::min(), startKey);
@@ -340,7 +340,7 @@ Status ShardingCatalogManager::commitChunkSplit(OperationContext* opCtx,
 
         // add the chunk's _id as the query part of the update statement
         BSONObjBuilder q(op.subobjStart("o2"));
-        q.append(ChunkType::name(), ChunkType::genID(nss.ns(), startKey));
+        q.append(ChunkType::name(), ChunkType::genID(nss, startKey));
         q.done();
 
         updates.append(op.obj());
@@ -359,7 +359,7 @@ Status ShardingCatalogManager::commitChunkSplit(OperationContext* opCtx,
     BSONArrayBuilder preCond;
     {
         BSONObjBuilder b;
-        b.append("ns", ChunkType::ConfigNS);
+        b.append("ns", ChunkType::ConfigNS.ns());
         b.append("q",
                  BSON("query" << BSON(ChunkType::ns(nss.ns()) << ChunkType::min() << range.getMin()
                                                               << ChunkType::max()
@@ -379,7 +379,7 @@ Status ShardingCatalogManager::commitChunkSplit(OperationContext* opCtx,
         opCtx,
         updates.arr(),
         preCond.arr(),
-        nss.ns(),
+        nss,
         currentMaxVersion,
         WriteConcernOptions(),
         repl::ReadConcernLevel::kLocalReadConcern);
@@ -428,7 +428,7 @@ Status ShardingCatalogManager::commitChunkSplit(OperationContext* opCtx,
 }
 
 Status ShardingCatalogManager::commitChunkMerge(OperationContext* opCtx,
-                                                const NamespaceString& ns,
+                                                const NamespaceString& nss,
                                                 const OID& requestEpoch,
                                                 const std::vector<BSONObj>& chunkBoundaries,
                                                 const std::string& shardName) {
@@ -446,8 +446,8 @@ Status ShardingCatalogManager::commitChunkMerge(OperationContext* opCtx,
         opCtx,
         ReadPreferenceSetting{ReadPreference::PrimaryOnly},
         repl::ReadConcernLevel::kLocalReadConcern,
-        NamespaceString(ChunkType::ConfigNS),
-        BSON("ns" << ns.ns()),
+        ChunkType::ConfigNS,
+        BSON("ns" << nss.ns()),
         BSON(ChunkType::lastmod << -1),
         1);
 
@@ -474,7 +474,7 @@ Status ShardingCatalogManager::commitChunkMerge(OperationContext* opCtx,
 
     ChunkType itChunk;
     itChunk.setMax(chunkBoundaries.front());
-    itChunk.setNS(ns.ns());
+    itChunk.setNS(nss);
     itChunk.setShard(shardName);
 
     // Do not use the first chunk boundary as a max bound while building chunks
@@ -508,7 +508,7 @@ Status ShardingCatalogManager::commitChunkMerge(OperationContext* opCtx,
         opCtx,
         updates,
         preCond,
-        ns.ns(),
+        nss,
         mergeVersion,
         WriteConcernOptions(),
         repl::ReadConcernLevel::kLocalReadConcern);
@@ -529,7 +529,7 @@ Status ShardingCatalogManager::commitChunkMerge(OperationContext* opCtx,
 
     Grid::get(opCtx)
         ->catalogClient()
-        ->logChange(opCtx, "merge", ns.ns(), logDetail.obj(), WriteConcernOptions())
+        ->logChange(opCtx, "merge", nss.ns(), logDetail.obj(), WriteConcernOptions())
         .transitional_ignore();
 
     return doTxnStatus;
@@ -563,7 +563,7 @@ StatusWith<BSONObj> ShardingCatalogManager::commitChunkMigration(
         configShard->exhaustiveFindOnConfig(opCtx,
                                             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                             repl::ReadConcernLevel::kLocalReadConcern,
-                                            NamespaceString(ChunkType::ConfigNS),
+                                            ChunkType::ConfigNS,
                                             BSON("ns" << nss.ns()),
                                             BSON(ChunkType::lastmod << -1),
                                             1);
diff --git a/src/mongo/s/catalog/sharding_catalog_manager_collection_operations.cpp b/src/mongo/s/catalog/sharding_catalog_manager_collection_operations.cpp
index 0576f4d59bd..50895470fc8 100644
--- a/src/mongo/s/catalog/sharding_catalog_manager_collection_operations.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_manager_collection_operations.cpp
@@ -169,7 +169,7 @@ ChunkVersion createFirstChunks(OperationContext* opCtx,
         }
 
         ChunkType chunk;
-        chunk.setNS(nss.ns());
+        chunk.setNS(nss);
         chunk.setMin(min);
         chunk.setMax(max);
         chunk.setShard(shardIds[i % shardIds.size()]);
@@ -185,10 +185,10 @@ ChunkVersion createFirstChunks(OperationContext* opCtx,
     return version;
 }
 
-void checkForExistingChunks(OperationContext* opCtx, const string& ns) {
+void checkForExistingChunks(OperationContext* opCtx, const NamespaceString& nss) {
     BSONObjBuilder countBuilder;
-    countBuilder.append("count", NamespaceString(ChunkType::ConfigNS).coll());
-    countBuilder.append("query", BSON(ChunkType::ns(ns)));
+    countBuilder.append("count", ChunkType::ConfigNS.coll());
+    countBuilder.append("query", BSON(ChunkType::ns(nss.ns())));
 
     // OK to use limit=1, since if any chunks exist, we will fail.
     countBuilder.append("limit", 1);
@@ -203,7 +203,7 @@ void checkForExistingChunks(OperationContext* opCtx, const string& ns) {
         Grid::get(opCtx)->shardRegistry()->getConfigShard()->runCommandWithFixedRetryAttempts(
             opCtx,
             kConfigReadSelector,
-            NamespaceString(ChunkType::ConfigNS).db().toString(),
+            ChunkType::ConfigNS.db().toString(),
             countBuilder.done(),
             Shard::kDefaultConfigCommandTimeout,
             Shard::RetryPolicy::kIdempotent));
@@ -212,22 +212,22 @@ void checkForExistingChunks(OperationContext* opCtx, const string& ns) {
     long long numChunks;
     uassertStatusOK(bsonExtractIntegerField(cmdResponse.response, "n", &numChunks));
     uassert(ErrorCodes::ManualInterventionRequired,
-            str::stream() << "A previous attempt to shard collection " << ns
+            str::stream() << "A previous attempt to shard collection " << nss.ns()
                           << " failed after writing some initial chunks to config.chunks. Please "
                              "manually delete the partially written chunks for collection "
-                          << ns
+                          << nss.ns()
                           << " from config.chunks",
             numChunks == 0);
 }
 
 }  // namespace
 
-Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const NamespaceString& ns) {
+Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const NamespaceString& nss) {
     const auto catalogClient = Grid::get(opCtx)->catalogClient();
     catalogClient
         ->logChange(opCtx,
                     "dropCollection.start",
-                    ns.ns(),
+                    nss.ns(),
                     BSONObj(),
                     ShardingCatalogClientImpl::kMajorityWriteConcern)
         .ignore();
@@ -239,11 +239,11 @@ Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const Nam
     }
     vector<ShardType> allShards = std::move(shardsStatus.getValue().value);
 
-    LOG(1) << "dropCollection " << ns << " started";
+    LOG(1) << "dropCollection " << nss.ns() << " started";
 
-    const auto dropCommandBSON = [opCtx, &ns] {
+    const auto dropCommandBSON = [opCtx, &nss] {
         BSONObjBuilder builder;
-        builder.append("drop", ns.coll());
+        builder.append("drop", nss.coll());
 
         if (!opCtx->getWriteConcern().usedDefault) {
             builder.append(WriteConcernOptions::kWriteConcernField,
@@ -267,7 +267,7 @@ Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const Nam
         auto swDropResult = shard->runCommandWithFixedRetryAttempts(
             opCtx,
             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
-            ns.db().toString(),
+            nss.db().toString(),
             dropCommandBSON,
             Shard::RetryPolicy::kIdempotent);
 
@@ -311,35 +311,35 @@ Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const Nam
         return {ErrorCodes::OperationFailed, sb.str()};
     }
 
-    LOG(1) << "dropCollection " << ns << " shard data deleted";
+    LOG(1) << "dropCollection " << nss.ns() << " shard data deleted";
 
     // Remove chunk data
     Status result =
         catalogClient->removeConfigDocuments(opCtx,
                                              ChunkType::ConfigNS,
-                                             BSON(ChunkType::ns(ns.ns())),
+                                             BSON(ChunkType::ns(nss.ns())),
                                              ShardingCatalogClient::kMajorityWriteConcern);
     if (!result.isOK()) {
         return result;
     }
 
-    LOG(1) << "dropCollection " << ns << " chunk data deleted";
+    LOG(1) << "dropCollection " << nss.ns() << " chunk data deleted";
 
     // Mark the collection as dropped
     CollectionType coll;
-    coll.setNs(ns);
+    coll.setNs(nss);
     coll.setDropped(true);
     coll.setEpoch(ChunkVersion::DROPPED().epoch());
     coll.setUpdatedAt(Grid::get(opCtx)->getNetwork()->now());
 
     const bool upsert = false;
     result = ShardingCatalogClientImpl::updateShardingCatalogEntryForCollection(
-        opCtx, ns.ns(), coll, upsert);
+        opCtx, nss, coll, upsert);
     if (!result.isOK()) {
         return result;
     }
 
-    LOG(1) << "dropCollection " << ns << " collection marked as dropped";
+    LOG(1) << "dropCollection " << nss.ns() << " collection marked as dropped";
 
     for (const auto& shardEntry : allShards) {
         auto swShard = shardRegistry->getShard(opCtx, shardEntry.getName());
@@ -353,7 +353,7 @@ Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const Nam
             shardRegistry->getConfigServerConnectionString(),
             shardEntry.getName(),
             fassertStatusOK(28781, ConnectionString::parse(shardEntry.getHost())),
-            ns,
+            nss,
             ChunkVersion::DROPPED(),
             true);
 
@@ -390,12 +390,12 @@ Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const Nam
         }
     }
 
-    LOG(1) << "dropCollection " << ns << " completed";
+    LOG(1) << "dropCollection " << nss.ns() << " completed";
 
     catalogClient
         ->logChange(opCtx,
                     "dropCollection",
-                    ns.ns(),
+                    nss.ns(),
                     BSONObj(),
                     ShardingCatalogClientImpl::kMajorityWriteConcern)
         .ignore();
@@ -404,7 +404,7 @@ Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const Nam
 }
 
 void ShardingCatalogManager::shardCollection(OperationContext* opCtx,
-                                             const string& ns,
+                                             const NamespaceString& nss,
                                              const boost::optional<UUID> uuid,
                                              const ShardKeyPattern& fieldsAndOrder,
                                              const BSONObj& defaultCollation,
@@ -418,13 +418,13 @@ void ShardingCatalogManager::shardCollection(OperationContext* opCtx,
     const auto primaryShard = uassertStatusOK(shardRegistry->getShard(opCtx, dbPrimaryShardId));
 
     // Fail if there are partially written chunks from a previous failed shardCollection.
-    checkForExistingChunks(opCtx, ns);
+    checkForExistingChunks(opCtx, nss);
 
     // Record start in changelog
     {
         BSONObjBuilder collectionDetail;
         collectionDetail.append("shardKey", fieldsAndOrder.toBSON());
-        collectionDetail.append("collection", ns);
+        collectionDetail.append("collection", nss.ns());
         if (uuid) {
             uuid->appendToBuilder(&collectionDetail, "uuid");
         }
@@ -433,13 +433,13 @@ void ShardingCatalogManager::shardCollection(OperationContext* opCtx,
         catalogClient
             ->logChange(opCtx,
                         "shardCollection.start",
-                        ns,
+                        nss.ns(),
                         collectionDetail.obj(),
                         ShardingCatalogClient::kMajorityWriteConcern)
             .transitional_ignore();
     }
 
-    const NamespaceString nss(ns);
+    // const NamespaceString nss(ns);
 
     // Construct the collection default collator.
     std::unique_ptr<CollatorInterface> defaultCollator;
@@ -467,7 +467,7 @@ void ShardingCatalogManager::shardCollection(OperationContext* opCtx,
         coll.setUnique(unique);
 
         uassertStatusOK(ShardingCatalogClientImpl::updateShardingCatalogEntryForCollection(
-            opCtx, ns, coll, true /*upsert*/));
+            opCtx, nss, coll, true /*upsert*/));
     }
 
     auto shard = uassertStatusOK(shardRegistry->getShard(opCtx, dbPrimaryShardId));
@@ -480,7 +480,7 @@ void ShardingCatalogManager::shardCollection(OperationContext* opCtx,
         shardRegistry->getConfigServerConnectionString(),
         dbPrimaryShardId,
         primaryShard->getConnString(),
-        NamespaceString(ns),
+        nss,
         collVersion,
         true);
 
@@ -493,14 +493,14 @@ void ShardingCatalogManager::shardCollection(OperationContext* opCtx,
     auto status = ssvResponse.isOK() ? std::move(ssvResponse.getValue().commandStatus)
                                      : std::move(ssvResponse.getStatus());
     if (!status.isOK()) {
-        warning() << "could not update initial version of " << ns << " on shard primary "
+        warning() << "could not update initial version of " << nss.ns() << " on shard primary "
                   << dbPrimaryShardId << causedBy(redact(status));
     }
 
     catalogClient
         ->logChange(opCtx,
                     "shardCollection.end",
-                    ns,
+                    nss.ns(),
                     BSON("version" << collVersion.toString()),
                     ShardingCatalogClient::kMajorityWriteConcern)
         .transitional_ignore();
@@ -515,7 +515,7 @@ void ShardingCatalogManager::generateUUIDsForExistingShardedCollections(Operatio
                 opCtx,
                 ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                 repl::ReadConcernLevel::kLocalReadConcern,
-                NamespaceString(CollectionType::ConfigNS),
+                CollectionType::ConfigNS,
                 BSON(CollectionType::uuid.name() << BSON("$exists" << false) << "dropped" << false),
                 BSONObj(),   // sort
                 boost::none  // limit
@@ -545,7 +545,7 @@ void ShardingCatalogManager::generateUUIDsForExistingShardedCollections(Operatio
         collType.setUUID(uuid);
 
         uassertStatusOK(ShardingCatalogClientImpl::updateShardingCatalogEntryForCollection(
-            opCtx, collType.getNs().ns(), collType, false /* upsert */));
+            opCtx, collType.getNs(), collType, false /* upsert */));
         LOG(2) << "updated entry in config.collections for sharded collection " << collType.getNs()
                << " with generated UUID " << uuid;
     }
diff --git a/src/mongo/s/catalog/sharding_catalog_manager_database_operations.cpp b/src/mongo/s/catalog/sharding_catalog_manager_database_operations.cpp
index e0c4574e510..a3e5c724208 100644
--- a/src/mongo/s/catalog/sharding_catalog_manager_database_operations.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_manager_database_operations.cpp
@@ -74,7 +74,7 @@ DatabaseType ShardingCatalogManager::createDatabase(OperationContext* opCtx,
                                     opCtx,
                                     ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                     repl::ReadConcernLevel::kLocalReadConcern,
-                                    NamespaceString(DatabaseType::ConfigNS),
+                                    DatabaseType::ConfigNS,
                                     queryBuilder.obj(),
                                     BSONObj(),
                                     1))
@@ -144,7 +144,7 @@ StatusWith<std::vector<std::string>> ShardingCatalogManager::getDatabasesForShar
         opCtx,
         kConfigReadSelector,
         repl::ReadConcernLevel::kLocalReadConcern,
-        NamespaceString(DatabaseType::ConfigNS),
+        DatabaseType::ConfigNS,
         BSON(DatabaseType::primary(shardId.toString())),
         BSONObj(),
         boost::none);  // no limit
diff --git a/src/mongo/s/catalog/sharding_catalog_manager_shard_operations.cpp b/src/mongo/s/catalog/sharding_catalog_manager_shard_operations.cpp
index efee3b53771..ebbcb8d253a 100644
--- a/src/mongo/s/catalog/sharding_catalog_manager_shard_operations.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_manager_shard_operations.cpp
@@ -99,7 +99,7 @@ StatusWith<std::string> generateNewShardName(OperationContext* opCtx) {
         opCtx,
         kConfigReadSelector,
         repl::ReadConcernLevel::kMajorityReadConcern,
-        NamespaceString(ShardType::ConfigNS),
+        ShardType::ConfigNS,
         shardNameRegex.obj(),
         BSON(ShardType::name() << -1),
         1);
@@ -739,7 +739,7 @@ StatusWith<ShardDrainingStatus> ShardingCatalogManager::removeShard(OperationCon
     std::string name = shardId.toString();
     auto countStatus = _runCountCommandOnConfig(
         opCtx,
-        NamespaceString(ShardType::ConfigNS),
+        ShardType::ConfigNS,
         BSON(ShardType::name() << NE << name << ShardType::draining(true)));
     if (!countStatus.isOK()) {
         return countStatus.getStatus();
@@ -749,8 +749,8 @@ StatusWith<ShardDrainingStatus> ShardingCatalogManager::removeShard(OperationCon
                       "Can't have more than one draining shard at a time");
     }
 
-    countStatus = _runCountCommandOnConfig(
-        opCtx, NamespaceString(ShardType::ConfigNS), BSON(ShardType::name() << NE << name));
+    countStatus =
+        _runCountCommandOnConfig(opCtx, ShardType::ConfigNS, BSON(ShardType::name() << NE << name));
     if (!countStatus.isOK()) {
         return countStatus.getStatus();
     }
@@ -759,10 +759,8 @@ StatusWith<ShardDrainingStatus> ShardingCatalogManager::removeShard(OperationCon
     }
 
     // Figure out if shard is already draining
-    countStatus =
-        _runCountCommandOnConfig(opCtx,
-                                 NamespaceString(ShardType::ConfigNS),
-                                 BSON(ShardType::name() << name << ShardType::draining(true)));
+    countStatus = _runCountCommandOnConfig(
+        opCtx, ShardType::ConfigNS, BSON(ShardType::name() << name << ShardType::draining(true)));
     if (!countStatus.isOK()) {
         return countStatus.getStatus();
     }
@@ -802,15 +800,15 @@ StatusWith<ShardDrainingStatus> ShardingCatalogManager::removeShard(OperationCon
 
     // Draining has already started, now figure out how many chunks and databases are still on the
     // shard.
-    countStatus = _runCountCommandOnConfig(
-        opCtx, NamespaceString(ChunkType::ConfigNS), BSON(ChunkType::shard(name)));
+    countStatus =
+        _runCountCommandOnConfig(opCtx, ChunkType::ConfigNS, BSON(ChunkType::shard(name)));
     if (!countStatus.isOK()) {
         return countStatus.getStatus();
     }
     const long long chunkCount = countStatus.getValue();
 
-    countStatus = _runCountCommandOnConfig(
-        opCtx, NamespaceString(DatabaseType::ConfigNS), BSON(DatabaseType::primary(name)));
+    countStatus =
+        _runCountCommandOnConfig(opCtx, DatabaseType::ConfigNS, BSON(DatabaseType::primary(name)));
     if (!countStatus.isOK()) {
         return countStatus.getStatus();
     }
@@ -927,17 +925,17 @@ StatusWith<ShardId> ShardingCatalogManager::_selectShardForNewDatabase(
 }
 
 StatusWith<long long> ShardingCatalogManager::_runCountCommandOnConfig(OperationContext* opCtx,
-                                                                       const NamespaceString& ns,
+                                                                       const NamespaceString& nss,
                                                                        BSONObj query) {
     BSONObjBuilder countBuilder;
-    countBuilder.append("count", ns.coll());
+    countBuilder.append("count", nss.coll());
     countBuilder.append("query", query);
 
     auto configShard = Grid::get(opCtx)->shardRegistry()->getConfigShard();
     auto resultStatus =
         configShard->runCommandWithFixedRetryAttempts(opCtx,
                                                       kConfigReadSelector,
-                                                      ns.db().toString(),
+                                                      nss.db().toString(),
                                                       countBuilder.done(),
                                                       Shard::kDefaultConfigCommandTimeout,
                                                       Shard::RetryPolicy::kIdempotent);
diff --git a/src/mongo/s/catalog/sharding_catalog_manager_zone_operations.cpp b/src/mongo/s/catalog/sharding_catalog_manager_zone_operations.cpp
index 5b21ab927ab..b841c7d0ee0 100644
--- a/src/mongo/s/catalog/sharding_catalog_manager_zone_operations.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_manager_zone_operations.cpp
@@ -60,17 +60,17 @@ const WriteConcernOptions kNoWaitWriteConcern(1, WriteConcernOptions::SyncMode::
  */
 Status checkForOveralappedZonedKeyRange(OperationContext* opCtx,
                                         Shard* configServer,
-                                        const NamespaceString& ns,
+                                        const NamespaceString& nss,
                                         const ChunkRange& range,
                                         const std::string& zoneName,
                                         const KeyPattern& shardKeyPattern) {
-    DistributionStatus chunkDist(ns, ShardToChunksMap{});
+    DistributionStatus chunkDist(nss, ShardToChunksMap{});
 
     auto tagStatus = configServer->exhaustiveFindOnConfig(opCtx,
                                                           kConfigPrimarySelector,
                                                           repl::ReadConcernLevel::kLocalReadConcern,
-                                                          NamespaceString(TagsType::ConfigNS),
-                                                          BSON(TagsType::ns(ns.ns())),
+                                                          TagsType::ConfigNS,
+                                                          BSON(TagsType::ns(nss.ns())),
                                                           BSONObj(),
                                                           0);
     if (!tagStatus.isOK()) {
@@ -108,21 +108,21 @@ Status checkForOveralappedZonedKeyRange(OperationContext* opCtx,
 /**
  * Returns a new range based on the given range with the full shard key.
  * Returns:
- * - ErrorCodes::NamespaceNotSharded if ns is not sharded.
+ * - ErrorCodes::NamespaceNotSharded if nss is not sharded.
  * - ErrorCodes::ShardKeyNotFound if range is not compatible (for example, not a prefix of shard
- * key) with the shard key of ns.
+ * key) with the shard key of nss.
  */
 StatusWith<ChunkRange> includeFullShardKey(OperationContext* opCtx,
                                            Shard* configServer,
-                                           const NamespaceString& ns,
+                                           const NamespaceString& nss,
                                            const ChunkRange& range,
                                            KeyPattern* shardKeyPatternOut) {
     auto findCollStatus =
         configServer->exhaustiveFindOnConfig(opCtx,
                                              kConfigPrimarySelector,
                                              repl::ReadConcernLevel::kLocalReadConcern,
-                                             NamespaceString(CollectionType::ConfigNS),
-                                             BSON(CollectionType::fullNs(ns.ns())),
+                                             CollectionType::ConfigNS,
+                                             BSON(CollectionType::fullNs(nss.ns())),
                                              BSONObj(),
                                              1);
 
@@ -133,7 +133,7 @@ StatusWith<ChunkRange> includeFullShardKey(OperationContext* opCtx,
     const auto& findCollResult = findCollStatus.getValue().docs;
 
     if (findCollResult.size() < 1) {
-        return {ErrorCodes::NamespaceNotSharded, str::stream() << ns.ns() << " is not sharded"};
+        return {ErrorCodes::NamespaceNotSharded, str::stream() << nss.ns() << " is not sharded"};
     }
 
     auto parseStatus = CollectionType::fromBSON(findCollResult.front());
@@ -143,7 +143,7 @@ StatusWith<ChunkRange> includeFullShardKey(OperationContext* opCtx,
 
     auto collDoc = parseStatus.getValue();
     if (collDoc.getDropped()) {
-        return {ErrorCodes::NamespaceNotSharded, str::stream() << ns.ns() << " is not sharded"};
+        return {ErrorCodes::NamespaceNotSharded, str::stream() << nss.ns() << " is not sharded"};
     }
 
     const auto& shardKeyPattern = collDoc.getKeyPattern();
@@ -155,7 +155,7 @@ StatusWith<ChunkRange> includeFullShardKey(OperationContext* opCtx,
                 str::stream() << "min: " << range.getMin() << " is not a prefix of the shard key "
                               << shardKeyBSON
                               << " of ns: "
-                              << ns.ns()};
+                              << nss.ns()};
     }
 
     if (!range.getMax().isFieldNamePrefixOf(shardKeyBSON)) {
@@ -163,7 +163,7 @@ StatusWith<ChunkRange> includeFullShardKey(OperationContext* opCtx,
                 str::stream() << "max: " << range.getMax() << " is not a prefix of the shard key "
                               << shardKeyBSON
                               << " of ns: "
-                              << ns.ns()};
+                              << nss.ns()};
     }
 
     return ChunkRange(shardKeyPattern.extendRangeBound(range.getMin(), false),
@@ -268,7 +268,7 @@ Status ShardingCatalogManager::removeShardFromZone(OperationContext* opCtx,
             configShard->exhaustiveFindOnConfig(opCtx,
                                                 kConfigPrimarySelector,
                                                 repl::ReadConcernLevel::kLocalReadConcern,
-                                                NamespaceString(TagsType::ConfigNS),
+                                                TagsType::ConfigNS,
                                                 BSON(TagsType::tag() << zoneName),
                                                 BSONObj(),
                                                 1);
@@ -310,7 +310,7 @@ Status ShardingCatalogManager::removeShardFromZone(OperationContext* opCtx,
 
 
 Status ShardingCatalogManager::assignKeyRangeToZone(OperationContext* opCtx,
-                                                    const NamespaceString& ns,
+                                                    const NamespaceString& nss,
                                                     const ChunkRange& givenRange,
                                                     const std::string& zoneName) {
     Lock::ExclusiveLock lk(opCtx->lockState(), _kZoneOpLock);
@@ -319,7 +319,7 @@ Status ShardingCatalogManager::assignKeyRangeToZone(OperationContext* opCtx,
 
     KeyPattern shardKeyPattern{BSONObj()};
     auto fullShardKeyStatus =
-        includeFullShardKey(opCtx, configServer.get(), ns, givenRange, &shardKeyPattern);
+        includeFullShardKey(opCtx, configServer.get(), nss, givenRange, &shardKeyPattern);
     if (!fullShardKeyStatus.isOK()) {
         return fullShardKeyStatus.getStatus();
     }
@@ -330,7 +330,7 @@ Status ShardingCatalogManager::assignKeyRangeToZone(OperationContext* opCtx,
         configServer->exhaustiveFindOnConfig(opCtx,
                                              kConfigPrimarySelector,
                                              repl::ReadConcernLevel::kLocalReadConcern,
-                                             NamespaceString(ShardType::ConfigNS),
+                                             ShardType::ConfigNS,
                                              BSON(ShardType::tags() << zoneName),
                                              BSONObj(),
                                              1);
@@ -346,18 +346,18 @@ Status ShardingCatalogManager::assignKeyRangeToZone(OperationContext* opCtx,
     }
 
     auto overlapStatus = checkForOveralappedZonedKeyRange(
-        opCtx, configServer.get(), ns, fullShardKeyRange, zoneName, shardKeyPattern);
+        opCtx, configServer.get(), nss, fullShardKeyRange, zoneName, shardKeyPattern);
     if (!overlapStatus.isOK()) {
         return overlapStatus;
     }
 
     BSONObj updateQuery(
-        BSON("_id" << BSON(TagsType::ns(ns.ns()) << TagsType::min(fullShardKeyRange.getMin()))));
+        BSON("_id" << BSON(TagsType::ns(nss.ns()) << TagsType::min(fullShardKeyRange.getMin()))));
 
     BSONObjBuilder updateBuilder;
     updateBuilder.append("_id",
-                         BSON(TagsType::ns(ns.ns()) << TagsType::min(fullShardKeyRange.getMin())));
-    updateBuilder.append(TagsType::ns(), ns.ns());
+                         BSON(TagsType::ns(nss.ns()) << TagsType::min(fullShardKeyRange.getMin())));
+    updateBuilder.append(TagsType::ns(), nss.ns());
     updateBuilder.append(TagsType::min(), fullShardKeyRange.getMin());
     updateBuilder.append(TagsType::max(), fullShardKeyRange.getMax());
     updateBuilder.append(TagsType::tag(), zoneName);
@@ -373,7 +373,7 @@ Status ShardingCatalogManager::assignKeyRangeToZone(OperationContext* opCtx,
 }
 
 Status ShardingCatalogManager::removeKeyRangeFromZone(OperationContext* opCtx,
-                                                      const NamespaceString& ns,
+                                                      const NamespaceString& nss,
                                                       const ChunkRange& range) {
     Lock::ExclusiveLock lk(opCtx->lockState(), _kZoneOpLock);
 
@@ -381,13 +381,13 @@ Status ShardingCatalogManager::removeKeyRangeFromZone(OperationContext* opCtx,
 
     KeyPattern shardKeyPattern{BSONObj()};
     auto fullShardKeyStatus =
-        includeFullShardKey(opCtx, configServer.get(), ns, range, &shardKeyPattern);
+        includeFullShardKey(opCtx, configServer.get(), nss, range, &shardKeyPattern);
     if (!fullShardKeyStatus.isOK()) {
         return fullShardKeyStatus.getStatus();
     }
 
     BSONObjBuilder removeBuilder;
-    removeBuilder.append("_id", BSON(TagsType::ns(ns.ns()) << TagsType::min(range.getMin())));
+    removeBuilder.append("_id", BSON(TagsType::ns(nss.ns()) << TagsType::min(range.getMin())));
     removeBuilder.append(TagsType::max(), range.getMax());
 
     return Grid::get(opCtx)->catalogClient()->removeConfigDocuments(
diff --git a/src/mongo/s/catalog/sharding_catalog_merge_chunks_test.cpp b/src/mongo/s/catalog/sharding_catalog_merge_chunks_test.cpp
index 4e02dd07dfd..32bcb66778a 100644
--- a/src/mongo/s/catalog/sharding_catalog_merge_chunks_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_merge_chunks_test.cpp
@@ -40,9 +40,11 @@ namespace {
 
 using MergeChunkTest = ConfigServerTestFixture;
 
+const NamespaceString kNamespace("TestDB.TestColl");
+
 TEST_F(MergeChunkTest, MergeExistingChunksCorrectlyShouldSucceed) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -76,7 +78,7 @@ TEST_F(MergeChunkTest, MergeExistingChunksCorrectlyShouldSucceed) {
         getConfigShard()->exhaustiveFindOnConfig(operationContext(),
                                                  ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                                  repl::ReadConcernLevel::kLocalReadConcern,
-                                                 NamespaceString(ChunkType::ConfigNS),
+                                                 ChunkType::ConfigNS,
                                                  BSON(ChunkType::ns() << "TestDB.TestColl"),
                                                  BSON(ChunkType::lastmod << -1),
                                                  boost::none));
@@ -100,7 +102,7 @@ TEST_F(MergeChunkTest, MergeExistingChunksCorrectlyShouldSucceed) {
 
 TEST_F(MergeChunkTest, MergeSeveralChunksCorrectlyShouldSucceed) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -140,7 +142,7 @@ TEST_F(MergeChunkTest, MergeSeveralChunksCorrectlyShouldSucceed) {
         getConfigShard()->exhaustiveFindOnConfig(operationContext(),
                                                  ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                                  repl::ReadConcernLevel::kLocalReadConcern,
-                                                 NamespaceString(ChunkType::ConfigNS),
+                                                 ChunkType::ConfigNS,
                                                  BSON(ChunkType::ns() << "TestDB.TestColl"),
                                                  BSON(ChunkType::lastmod << -1),
                                                  boost::none));
@@ -164,8 +166,8 @@ TEST_F(MergeChunkTest, MergeSeveralChunksCorrectlyShouldSucceed) {
 
 TEST_F(MergeChunkTest, NewMergeShouldClaimHighestVersion) {
     ChunkType chunk, otherChunk;
-    chunk.setNS("TestDB.TestColl");
-    otherChunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
+    otherChunk.setNS(kNamespace);
     auto collEpoch = OID::gen();
 
     auto origVersion = ChunkVersion(1, 2, collEpoch);
@@ -208,7 +210,7 @@ TEST_F(MergeChunkTest, NewMergeShouldClaimHighestVersion) {
         getConfigShard()->exhaustiveFindOnConfig(operationContext(),
                                                  ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                                  repl::ReadConcernLevel::kLocalReadConcern,
-                                                 NamespaceString(ChunkType::ConfigNS),
+                                                 ChunkType::ConfigNS,
                                                  BSON(ChunkType::ns() << "TestDB.TestColl"),
                                                  BSON(ChunkType::lastmod << -1),
                                                  boost::none));
@@ -232,7 +234,7 @@ TEST_F(MergeChunkTest, NewMergeShouldClaimHighestVersion) {
 
 TEST_F(MergeChunkTest, MergeLeavesOtherChunksAlone) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 2, OID::gen());
     chunk.setVersion(origVersion);
@@ -272,7 +274,7 @@ TEST_F(MergeChunkTest, MergeLeavesOtherChunksAlone) {
         getConfigShard()->exhaustiveFindOnConfig(operationContext(),
                                                  ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                                  repl::ReadConcernLevel::kLocalReadConcern,
-                                                 NamespaceString(ChunkType::ConfigNS),
+                                                 ChunkType::ConfigNS,
                                                  BSON(ChunkType::ns() << "TestDB.TestColl"),
                                                  BSON(ChunkType::lastmod << -1),
                                                  boost::none));
@@ -301,7 +303,7 @@ TEST_F(MergeChunkTest, MergeLeavesOtherChunksAlone) {
 
 TEST_F(MergeChunkTest, NonExistingNamespace) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -335,7 +337,7 @@ TEST_F(MergeChunkTest, NonExistingNamespace) {
 
 TEST_F(MergeChunkTest, NonMatchingEpochsOfChunkAndRequestErrors) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -369,7 +371,7 @@ TEST_F(MergeChunkTest, NonMatchingEpochsOfChunkAndRequestErrors) {
 
 TEST_F(MergeChunkTest, MergeAlreadyHappenedFailsPrecondition) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -411,7 +413,7 @@ TEST_F(MergeChunkTest, MergeAlreadyHappenedFailsPrecondition) {
         getConfigShard()->exhaustiveFindOnConfig(operationContext(),
                                                  ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                                  repl::ReadConcernLevel::kLocalReadConcern,
-                                                 NamespaceString(ChunkType::ConfigNS),
+                                                 ChunkType::ConfigNS,
                                                  BSON(ChunkType::ns() << "TestDB.TestColl"),
                                                  BSON(ChunkType::lastmod << -1),
                                                  boost::none));
@@ -436,7 +438,7 @@ TEST_F(MergeChunkTest, ChunkBoundariesOutOfOrderFails) {
         ChunkVersion version = ChunkVersion(1, 0, epoch);
 
         ChunkType chunk;
-        chunk.setNS("TestDB.TestColl");
+        chunk.setNS(kNamespace);
         chunk.setShard(ShardId("shard0000"));
 
         chunk.setVersion(version);
diff --git a/src/mongo/s/catalog/sharding_catalog_remove_shard_from_zone_test.cpp b/src/mongo/s/catalog/sharding_catalog_remove_shard_from_zone_test.cpp
index cc181595b89..5d0a9ea668a 100644
--- a/src/mongo/s/catalog/sharding_catalog_remove_shard_from_zone_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_remove_shard_from_zone_test.cpp
@@ -108,12 +108,11 @@ TEST_F(RemoveShardFromZoneTest, RemoveLastZoneFromShardShouldSucceedWhenNoChunks
 
     // Insert a chunk range document referring to a different zone
     TagsType tagDoc;
-    tagDoc.setNS("test.foo");
+    tagDoc.setNS(NamespaceString("test.foo"));
     tagDoc.setMinKey(BSON("x" << 0));
     tagDoc.setMaxKey(BSON("x" << 10));
     tagDoc.setTag("y");
-    insertToConfigCollection(
-        operationContext(), NamespaceString(TagsType::ConfigNS), tagDoc.toBSON())
+    insertToConfigCollection(operationContext(), TagsType::ConfigNS, tagDoc.toBSON())
         .transitional_ignore();
 
     ASSERT_OK(ShardingCatalogManager::get(operationContext())
@@ -149,12 +148,11 @@ TEST_F(RemoveShardFromZoneTest, RemoveLastZoneFromShardShouldFailWhenAChunkRefer
     setupShards({shardA, shardB}).transitional_ignore();
 
     TagsType tagDoc;
-    tagDoc.setNS("test.foo");
+    tagDoc.setNS(NamespaceString("test.foo"));
     tagDoc.setMinKey(BSON("x" << 0));
     tagDoc.setMaxKey(BSON("x" << 10));
     tagDoc.setTag("z");
-    insertToConfigCollection(
-        operationContext(), NamespaceString(TagsType::ConfigNS), tagDoc.toBSON())
+    insertToConfigCollection(operationContext(), TagsType::ConfigNS, tagDoc.toBSON())
         .transitional_ignore();
 
     auto status = ShardingCatalogManager::get(operationContext())
@@ -250,7 +248,7 @@ TEST_F(RemoveShardFromZoneTest, RemoveZoneFromShardShouldErrorIfShardDocIsMalfor
                                  << "z"));
 
     insertToConfigCollection(
-        operationContext(), NamespaceString(ShardType::ConfigNS), invalidShardDoc);
+        operationContext(), ShardType::ConfigNS, invalidShardDoc);
 
 
     auto status =
diff --git a/src/mongo/s/catalog/sharding_catalog_remove_shard_test.cpp b/src/mongo/s/catalog/sharding_catalog_remove_shard_test.cpp
index 644631d4459..2db9d9658e0 100644
--- a/src/mongo/s/catalog/sharding_catalog_remove_shard_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_remove_shard_test.cpp
@@ -101,7 +101,7 @@ protected:
             operationContext(),
             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
             repl::ReadConcernLevel::kMajorityReadConcern,
-            NamespaceString(ShardType::ConfigNS),
+            ShardType::ConfigNS,
             BSON(ShardType::name() << shardName),
             BSONObj(),
             1));
@@ -314,7 +314,7 @@ TEST_F(RemoveShardTest, RemoveShardCompletion) {
         operationContext(),
         ReadPreferenceSetting{ReadPreference::PrimaryOnly},
         repl::ReadConcernLevel::kMajorityReadConcern,
-        NamespaceString(ShardType::ConfigNS),
+        ShardType::ConfigNS,
         BSON(ShardType::name() << shard1.getName()),
         BSONObj(),
         1));
diff --git a/src/mongo/s/catalog/sharding_catalog_shard_collection_test.cpp b/src/mongo/s/catalog/sharding_catalog_shard_collection_test.cpp
index 6170ce5bcb7..6bf42c0609f 100644
--- a/src/mongo/s/catalog/sharding_catalog_shard_collection_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_shard_collection_test.cpp
@@ -73,10 +73,12 @@ using unittest::assertGet;
 
 const ShardId testPrimaryShard = ShardId("shard0");
 
+const NamespaceString kNamespace("db1.foo");
+
 class ShardCollectionTest : public ConfigServerTestFixture {
 public:
     void expectCount(const HostAndPort& receivingHost,
-                     const NamespaceString& expectedNs,
+                     const NamespaceString& expectedNss,
                      const BSONObj& expectedQuery,
                      const StatusWith<long long>& response) {
         onCommand([&](const RemoteCommandRequest& request) {
@@ -86,7 +88,7 @@ public:
             ASSERT_EQUALS("count", cmdName);
 
             const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-            ASSERT_EQUALS(expectedNs.toString(), nss.toString());
+            ASSERT_EQUALS(expectedNss, nss);
 
             if (expectedQuery.isEmpty()) {
                 auto queryElem = request.cmdObj["query"];
@@ -112,19 +114,17 @@ private:
 };
 
 TEST_F(ShardCollectionTest, anotherMongosSharding) {
-    const auto nss = NamespaceString("db1.foo");
-
     ShardType shard;
     shard.setName("shard0");
     shard.setHost("shardHost");
     ASSERT_OK(setupShards(vector<ShardType>{shard}));
 
-    setupDatabase(nss.db().toString(), shard.getName(), true);
+    setupDatabase(kNamespace.db().toString(), shard.getName(), true);
 
     // Set up chunks in the collection, indicating that another mongos must have already started
     // sharding the collection.
     ChunkType chunk;
-    chunk.setNS(nss.ns());
+    chunk.setNS(kNamespace);
     chunk.setVersion(ChunkVersion(2, 0, OID::gen()));
     chunk.setShard(shard.getName());
     chunk.setMin(BSON("_id" << 1));
@@ -136,7 +136,7 @@ TEST_F(ShardCollectionTest, anotherMongosSharding) {
 
     ASSERT_THROWS_CODE(ShardingCatalogManager::get(operationContext())
                            ->shardCollection(operationContext(),
-                                             nss.ns(),
+                                             kNamespace,
                                              boost::none,  // UUID
                                              shardKeyPattern,
                                              defaultCollation,
@@ -163,9 +163,7 @@ TEST_F(ShardCollectionTest, noInitialChunksOrData) {
 
     ASSERT_OK(setupShards(vector<ShardType>{shard}));
 
-    const auto nss = NamespaceString("db1.foo");
-
-    setupDatabase(nss.db().toString(), shard.getName(), true);
+    setupDatabase(kNamespace.db().toString(), shard.getName(), true);
 
     ShardKeyPattern shardKeyPattern(BSON("_id" << 1));
     BSONObj defaultCollation;
@@ -177,7 +175,7 @@ TEST_F(ShardCollectionTest, noInitialChunksOrData) {
         auto opCtx = cc().makeOperationContext();
         ShardingCatalogManager::get(operationContext())
             ->shardCollection(opCtx.get(),
-                              nss.ns(),
+                              kNamespace,
                               boost::none,  // UUID
                               shardKeyPattern,
                               defaultCollation,
@@ -188,13 +186,13 @@ TEST_F(ShardCollectionTest, noInitialChunksOrData) {
     });
 
     // Report that no documents exist for the given collection on the primary shard
-    expectCount(shardHost, nss, BSONObj(), 0);
+    expectCount(shardHost, kNamespace, BSONObj(), 0);
 
     // Expect the set shard version for that namespace.
     // We do not check for a specific ChunkVersion, because we cannot easily know the OID that was
     // generated by shardCollection for the first chunk.
     // TODO SERVER-29451: add hooks to the mock storage engine to expect reads and writes.
-    expectSetShardVersion(shardHost, shard, nss, boost::none /* expected ChunkVersion */);
+    expectSetShardVersion(shardHost, shard, kNamespace, boost::none /* expected ChunkVersion */);
 
     future.timed_get(kFutureTimeout);
 }
@@ -235,14 +233,11 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
 
     ASSERT_OK(setupShards(vector<ShardType>{shard0, shard1, shard2}));
 
-    const auto nss = NamespaceString("db1.foo");
-    string ns = "db1.foo";
-
     DatabaseType db;
     db.setName("db1");
     db.setPrimary(shard0.getName());
     db.setSharded(true);
-    setupDatabase(nss.db().toString(), shard0.getName(), true);
+    setupDatabase(kNamespace.db().toString(), shard0.getName(), true);
 
     ShardKeyPattern keyPattern(BSON("_id" << 1));
 
@@ -254,7 +249,7 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
     ChunkVersion expectedVersion(1, 0, OID::gen());
 
     ChunkType expectedChunk0;
-    expectedChunk0.setNS(ns);
+    expectedChunk0.setNS(kNamespace);
     expectedChunk0.setShard(shard0.getName());
     expectedChunk0.setMin(keyPattern.getKeyPattern().globalMin());
     expectedChunk0.setMax(splitPoint0);
@@ -262,7 +257,7 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
     expectedVersion.incMinor();
 
     ChunkType expectedChunk1;
-    expectedChunk1.setNS(ns);
+    expectedChunk1.setNS(kNamespace);
     expectedChunk1.setShard(shard1.getName());
     expectedChunk1.setMin(splitPoint0);
     expectedChunk1.setMax(splitPoint1);
@@ -270,7 +265,7 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
     expectedVersion.incMinor();
 
     ChunkType expectedChunk2;
-    expectedChunk2.setNS(ns);
+    expectedChunk2.setNS(kNamespace);
     expectedChunk2.setShard(shard2.getName());
     expectedChunk2.setMin(splitPoint1);
     expectedChunk2.setMax(splitPoint2);
@@ -278,7 +273,7 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
     expectedVersion.incMinor();
 
     ChunkType expectedChunk3;
-    expectedChunk3.setNS(ns);
+    expectedChunk3.setNS(kNamespace);
     expectedChunk3.setShard(shard0.getName());
     expectedChunk3.setMin(splitPoint2);
     expectedChunk3.setMax(splitPoint3);
@@ -286,7 +281,7 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
     expectedVersion.incMinor();
 
     ChunkType expectedChunk4;
-    expectedChunk4.setNS(ns);
+    expectedChunk4.setNS(kNamespace);
     expectedChunk4.setShard(shard1.getName());
     expectedChunk4.setMin(splitPoint3);
     expectedChunk4.setMax(keyPattern.getKeyPattern().globalMax());
@@ -307,7 +302,7 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
         auto opCtx = cc().makeOperationContext();
         ShardingCatalogManager::get(operationContext())
             ->shardCollection(opCtx.get(),
-                              ns,
+                              kNamespace,
                               boost::none,  // UUID
                               keyPattern,
                               defaultCollation,
@@ -321,8 +316,7 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
     // We do not check for a specific ChunkVersion, because we cannot easily know the OID that was
     // generated by shardCollection for the first chunk.
     // TODO SERVER-29451: add hooks to the mock storage engine to expect reads and writes.
-    expectSetShardVersion(
-        shard0Host, shard0, NamespaceString(ns), boost::none /* expected ChunkVersion */);
+    expectSetShardVersion(shard0Host, shard0, kNamespace, boost::none /* expected ChunkVersion */);
 
     future.timed_get(kFutureTimeout);
 }
@@ -342,10 +336,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
 
     ASSERT_OK(setupShards(vector<ShardType>{shard}));
 
-    const auto nss = NamespaceString("db1.foo");
-    string ns = "db1.foo";
-
-    setupDatabase(nss.db().toString(), shard.getName(), true);
+    setupDatabase(kNamespace.db().toString(), shard.getName(), true);
 
     ShardKeyPattern keyPattern(BSON("_id" << 1));
 
@@ -357,7 +348,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
     ChunkVersion expectedVersion(1, 0, OID::gen());
 
     ChunkType expectedChunk0;
-    expectedChunk0.setNS(ns);
+    expectedChunk0.setNS(kNamespace);
     expectedChunk0.setShard(shard.getName());
     expectedChunk0.setMin(keyPattern.getKeyPattern().globalMin());
     expectedChunk0.setMax(splitPoint0);
@@ -365,7 +356,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
     expectedVersion.incMinor();
 
     ChunkType expectedChunk1;
-    expectedChunk1.setNS(ns);
+    expectedChunk1.setNS(kNamespace);
     expectedChunk1.setShard(shard.getName());
     expectedChunk1.setMin(splitPoint0);
     expectedChunk1.setMax(splitPoint1);
@@ -373,7 +364,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
     expectedVersion.incMinor();
 
     ChunkType expectedChunk2;
-    expectedChunk2.setNS(ns);
+    expectedChunk2.setNS(kNamespace);
     expectedChunk2.setShard(shard.getName());
     expectedChunk2.setMin(splitPoint1);
     expectedChunk2.setMax(splitPoint2);
@@ -381,7 +372,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
     expectedVersion.incMinor();
 
     ChunkType expectedChunk3;
-    expectedChunk3.setNS(ns);
+    expectedChunk3.setNS(kNamespace);
     expectedChunk3.setShard(shard.getName());
     expectedChunk3.setMin(splitPoint2);
     expectedChunk3.setMax(splitPoint3);
@@ -389,7 +380,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
     expectedVersion.incMinor();
 
     ChunkType expectedChunk4;
-    expectedChunk4.setNS(ns);
+    expectedChunk4.setNS(kNamespace);
     expectedChunk4.setShard(shard.getName());
     expectedChunk4.setMin(splitPoint3);
     expectedChunk4.setMax(keyPattern.getKeyPattern().globalMax());
@@ -407,7 +398,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
         auto opCtx = cc().makeOperationContext();
         ShardingCatalogManager::get(operationContext())
             ->shardCollection(opCtx.get(),
-                              ns,
+                              kNamespace,
                               boost::none,  // UUID
                               keyPattern,
                               defaultCollation,
@@ -419,14 +410,15 @@ TEST_F(ShardCollectionTest, withInitialData) {
 
     // Report that documents exist for the given collection on the primary shard, so that calling
     // splitVector is required for calculating the initial split points.
-    expectCount(shardHost, NamespaceString(ns), BSONObj(), 1000);
+    expectCount(shardHost, kNamespace, BSONObj(), 1000);
 
     // Respond to the splitVector command sent to the shard to figure out initial split points
     onCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQUALS(shardHost, request.target);
         string cmdName = request.cmdObj.firstElement().fieldName();
         ASSERT_EQUALS("splitVector", cmdName);
-        ASSERT_EQUALS(ns, request.cmdObj["splitVector"].String());  // splitVector uses full ns
+        ASSERT_EQUALS(kNamespace.ns(),
+                      request.cmdObj["splitVector"].String());  // splitVector uses full ns
 
         ASSERT_BSONOBJ_EQ(keyPattern.toBSON(), request.cmdObj["keyPattern"].Obj());
         ASSERT_BSONOBJ_EQ(keyPattern.getKeyPattern().globalMin(), request.cmdObj["min"].Obj());
@@ -448,7 +440,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
     // We do not check for a specific ChunkVersion, because we cannot easily know the OID that was
     // generated by shardCollection for the first chunk.
     // TODO SERVER-29451: add hooks to the mock storage engine to expect reads and writes.
-    expectSetShardVersion(shardHost, shard, NamespaceString(ns), boost::none);
+    expectSetShardVersion(shardHost, shard, kNamespace, boost::none);
 
     future.timed_get(kFutureTimeout);
 }
diff --git a/src/mongo/s/catalog/sharding_catalog_split_chunk_test.cpp b/src/mongo/s/catalog/sharding_catalog_split_chunk_test.cpp
index 1a9d8eb857c..07c2301d624 100644
--- a/src/mongo/s/catalog/sharding_catalog_split_chunk_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_split_chunk_test.cpp
@@ -39,9 +39,11 @@ namespace {
 
 using SplitChunkTest = ConfigServerTestFixture;
 
+const NamespaceString kNamespace("TestDB", "TestColl");
+
 TEST_F(SplitChunkTest, SplitExistingChunkCorrectlyShouldSucceed) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -90,7 +92,7 @@ TEST_F(SplitChunkTest, SplitExistingChunkCorrectlyShouldSucceed) {
 
 TEST_F(SplitChunkTest, MultipleSplitsOnExistingChunkShouldSucceed) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -151,8 +153,8 @@ TEST_F(SplitChunkTest, MultipleSplitsOnExistingChunkShouldSucceed) {
 
 TEST_F(SplitChunkTest, NewSplitShouldClaimHighestVersion) {
     ChunkType chunk, chunk2;
-    chunk.setNS("TestDB.TestColl");
-    chunk2.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
+    chunk2.setNS(kNamespace);
     auto collEpoch = OID::gen();
 
     // set up first chunk
@@ -211,7 +213,7 @@ TEST_F(SplitChunkTest, NewSplitShouldClaimHighestVersion) {
 
 TEST_F(SplitChunkTest, PreConditionFailErrors) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -240,7 +242,7 @@ TEST_F(SplitChunkTest, PreConditionFailErrors) {
 
 TEST_F(SplitChunkTest, NonExisingNamespaceErrors) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -267,7 +269,7 @@ TEST_F(SplitChunkTest, NonExisingNamespaceErrors) {
 
 TEST_F(SplitChunkTest, NonMatchingEpochsOfChunkAndRequestErrors) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -294,7 +296,7 @@ TEST_F(SplitChunkTest, NonMatchingEpochsOfChunkAndRequestErrors) {
 
 TEST_F(SplitChunkTest, SplitPointsOutOfOrderShouldFail) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -321,7 +323,7 @@ TEST_F(SplitChunkTest, SplitPointsOutOfOrderShouldFail) {
 
 TEST_F(SplitChunkTest, SplitPointsOutOfRangeAtMinShouldFail) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
@@ -348,7 +350,7 @@ TEST_F(SplitChunkTest, SplitPointsOutOfRangeAtMinShouldFail) {
 
 TEST_F(SplitChunkTest, SplitPointsOutOfRangeAtMaxShouldFail) {
     ChunkType chunk;
-    chunk.setNS("TestDB.TestColl");
+    chunk.setNS(kNamespace);
 
     auto origVersion = ChunkVersion(1, 0, OID::gen());
     chunk.setVersion(origVersion);
diff --git a/src/mongo/s/catalog/sharding_catalog_test.cpp b/src/mongo/s/catalog/sharding_catalog_test.cpp
index c460b66c93a..fbeb94d178d 100644
--- a/src/mongo/s/catalog/sharding_catalog_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_test.cpp
@@ -75,6 +75,7 @@ using unittest::assertGet;
 using ShardingCatalogClientTest = ShardingCatalogTestFixture;
 
 const int kMaxCommandRetry = 3;
+const NamespaceString kNamespace("TestDB", "TestColl");
 
 BSONObj getReplSecondaryOkMetadata() {
     BSONObjBuilder o;
@@ -95,8 +96,7 @@ TEST_F(ShardingCatalogClientTest, GetCollectionExisting) {
     const OpTime newOpTime(Timestamp(7, 6), 5);
 
     auto future = launchAsync([this, &expectedColl] {
-        return assertGet(
-            catalogClient()->getCollection(operationContext(), expectedColl.getNs().ns()));
+        return assertGet(catalogClient()->getCollection(operationContext(), expectedColl.getNs()));
     });
 
     onFindWithMetadataCommand(
@@ -106,12 +106,12 @@ TEST_F(ShardingCatalogClientTest, GetCollectionExisting) {
                               rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
             const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-            ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
+            ASSERT_EQ(nss, CollectionType::ConfigNS);
 
             auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
             // Ensure the query is correct
-            ASSERT_EQ(query->nss().ns(), CollectionType::ConfigNS);
+            ASSERT_EQ(query->nss(), CollectionType::ConfigNS);
             ASSERT_BSONOBJ_EQ(query->getFilter(),
                               BSON(CollectionType::fullNs(expectedColl.getNs().ns())));
             ASSERT_BSONOBJ_EQ(query->getSort(), BSONObj());
@@ -136,7 +136,8 @@ TEST_F(ShardingCatalogClientTest, GetCollectionNotExisting) {
     configTargeter()->setFindHostReturnValue(HostAndPort("TestHost1"));
 
     auto future = launchAsync([this] {
-        auto status = catalogClient()->getCollection(operationContext(), "NonExistent");
+        auto status =
+            catalogClient()->getCollection(operationContext(), NamespaceString("NonExistent"));
         ASSERT_EQUALS(status.getStatus(), ErrorCodes::NamespaceNotFound);
     });
 
@@ -175,14 +176,14 @@ TEST_F(ShardingCatalogClientTest, GetDatabaseExisting) {
 
     onFindWithMetadataCommand([this, &expectedDb, newOpTime](const RemoteCommandRequest& request) {
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(nss.ns(), DatabaseType::ConfigNS);
+        ASSERT_EQ(nss, DatabaseType::ConfigNS);
 
         ASSERT_BSONOBJ_EQ(getReplSecondaryOkMetadata(),
                           rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-        ASSERT_EQ(query->nss().ns(), DatabaseType::ConfigNS);
+        ASSERT_EQ(query->nss(), DatabaseType::ConfigNS);
         ASSERT_BSONOBJ_EQ(query->getFilter(), BSON(DatabaseType::name(expectedDb.getName())));
         ASSERT_BSONOBJ_EQ(query->getSort(), BSONObj());
         ASSERT(!query->getLimit());
@@ -304,11 +305,11 @@ TEST_F(ShardingCatalogClientTest, GetAllShardsValid) {
                           rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(nss.ns(), ShardType::ConfigNS);
+        ASSERT_EQ(nss, ShardType::ConfigNS);
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-        ASSERT_EQ(query->nss().ns(), ShardType::ConfigNS);
+        ASSERT_EQ(query->nss(), ShardType::ConfigNS);
         ASSERT_BSONOBJ_EQ(query->getFilter(), BSONObj());
         ASSERT_BSONOBJ_EQ(query->getSort(), BSONObj());
         ASSERT_FALSE(query->getLimit().is_initialized());
@@ -357,14 +358,14 @@ TEST_F(ShardingCatalogClientTest, GetChunksForNSWithSortAndLimit) {
     OID oid = OID::gen();
 
     ChunkType chunkA;
-    chunkA.setNS("TestDB.TestColl");
+    chunkA.setNS(kNamespace);
     chunkA.setMin(BSON("a" << 1));
     chunkA.setMax(BSON("a" << 100));
     chunkA.setVersion({1, 2, oid});
     chunkA.setShard(ShardId("shard0000"));
 
     ChunkType chunkB;
-    chunkB.setNS("TestDB.TestColl");
+    chunkB.setNS(kNamespace);
     chunkB.setMin(BSON("a" << 100));
     chunkB.setMax(BSON("a" << 200));
     chunkB.setVersion({3, 4, oid});
@@ -401,11 +402,11 @@ TEST_F(ShardingCatalogClientTest, GetChunksForNSWithSortAndLimit) {
                               rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
             const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-            ASSERT_EQ(nss.ns(), ChunkType::ConfigNS);
+            ASSERT_EQ(nss, ChunkType::ConfigNS);
 
             auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-            ASSERT_EQ(query->nss().ns(), ChunkType::ConfigNS);
+            ASSERT_EQ(query->nss(), ChunkType::ConfigNS);
             ASSERT_BSONOBJ_EQ(query->getFilter(), chunksQuery);
             ASSERT_BSONOBJ_EQ(query->getSort(), BSON(ChunkType::lastmod() << -1));
             ASSERT_EQ(query->getLimit().get(), 1);
@@ -453,11 +454,11 @@ TEST_F(ShardingCatalogClientTest, GetChunksForNSNoSortNoLimit) {
                           rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(nss.ns(), ChunkType::ConfigNS);
+        ASSERT_EQ(nss, ChunkType::ConfigNS);
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-        ASSERT_EQ(query->nss().ns(), ChunkType::ConfigNS);
+        ASSERT_EQ(query->nss(), ChunkType::ConfigNS);
         ASSERT_BSONOBJ_EQ(query->getFilter(), chunksQuery);
         ASSERT_BSONOBJ_EQ(query->getSort(), BSONObj());
         ASSERT_FALSE(query->getLimit().is_initialized());
@@ -494,14 +495,14 @@ TEST_F(ShardingCatalogClientTest, GetChunksForNSInvalidChunk) {
 
     onFindCommand([&chunksQuery](const RemoteCommandRequest& request) {
         ChunkType chunkA;
-        chunkA.setNS("TestDB.TestColl");
+        chunkA.setNS(kNamespace);
         chunkA.setMin(BSON("a" << 1));
         chunkA.setMax(BSON("a" << 100));
         chunkA.setVersion({1, 2, OID::gen()});
         chunkA.setShard(ShardId("shard0000"));
 
         ChunkType chunkB;
-        chunkB.setNS("TestDB.TestColl");
+        chunkB.setNS(kNamespace);
         chunkB.setMin(BSON("a" << 100));
         chunkB.setMax(BSON("a" << 200));
         chunkB.setVersion({3, 4, OID::gen()});
@@ -812,11 +813,11 @@ TEST_F(ShardingCatalogClientTest, GetCollectionsValidResultsNoDb) {
                               rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
             const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-            ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
+            ASSERT_EQ(nss, CollectionType::ConfigNS);
 
             auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-            ASSERT_EQ(query->nss().ns(), CollectionType::ConfigNS);
+            ASSERT_EQ(query->nss(), CollectionType::ConfigNS);
             ASSERT_BSONOBJ_EQ(query->getFilter(), BSONObj());
             ASSERT_BSONOBJ_EQ(query->getSort(), BSONObj());
 
@@ -865,11 +866,11 @@ TEST_F(ShardingCatalogClientTest, GetCollectionsValidResultsWithDb) {
                           rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
+        ASSERT_EQ(nss, CollectionType::ConfigNS);
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-        ASSERT_EQ(query->nss().ns(), CollectionType::ConfigNS);
+        ASSERT_EQ(query->nss(), CollectionType::ConfigNS);
         {
             BSONObjBuilder b;
             b.appendRegex(CollectionType::fullNs(), "^test\\.");
@@ -909,14 +910,14 @@ TEST_F(ShardingCatalogClientTest, GetCollectionsInvalidCollectionType) {
 
     onFindCommand([this, validColl](const RemoteCommandRequest& request) {
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
+        ASSERT_EQ(nss, CollectionType::ConfigNS);
 
         ASSERT_BSONOBJ_EQ(getReplSecondaryOkMetadata(),
                           rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-        ASSERT_EQ(query->nss().ns(), CollectionType::ConfigNS);
+        ASSERT_EQ(query->nss(), CollectionType::ConfigNS);
         {
             BSONObjBuilder b;
             b.appendRegex(CollectionType::fullNs(), "^test\\.");
@@ -955,11 +956,11 @@ TEST_F(ShardingCatalogClientTest, GetDatabasesForShardValid) {
                           rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(nss.ns(), DatabaseType::ConfigNS);
+        ASSERT_EQ(nss, DatabaseType::ConfigNS);
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-        ASSERT_EQ(query->nss().ns(), DatabaseType::ConfigNS);
+        ASSERT_EQ(query->nss(), DatabaseType::ConfigNS);
         ASSERT_BSONOBJ_EQ(query->getFilter(),
                           BSON(DatabaseType::primary(dbt1.getPrimary().toString())));
         ASSERT_BSONOBJ_EQ(query->getSort(), BSONObj());
@@ -1003,20 +1004,20 @@ TEST_F(ShardingCatalogClientTest, GetTagsForCollection) {
     configTargeter()->setFindHostReturnValue(HostAndPort("TestHost1"));
 
     TagsType tagA;
-    tagA.setNS("TestDB.TestColl");
+    tagA.setNS(NamespaceString("TestDB.TestColl"));
     tagA.setTag("TagA");
     tagA.setMinKey(BSON("a" << 100));
     tagA.setMaxKey(BSON("a" << 200));
 
     TagsType tagB;
-    tagB.setNS("TestDB.TestColl");
+    tagB.setNS(NamespaceString("TestDB.TestColl"));
     tagB.setTag("TagB");
     tagB.setMinKey(BSON("a" << 200));
     tagB.setMaxKey(BSON("a" << 300));
 
     auto future = launchAsync([this] {
-        const auto& tags =
-            assertGet(catalogClient()->getTagsForCollection(operationContext(), "TestDB.TestColl"));
+        const auto& tags = assertGet(catalogClient()->getTagsForCollection(
+            operationContext(), NamespaceString("TestDB.TestColl")));
 
         ASSERT_EQ(2U, tags.size());
 
@@ -1028,11 +1029,11 @@ TEST_F(ShardingCatalogClientTest, GetTagsForCollection) {
                           rpc::TrackingMetadata::removeTrackingData(request.metadata));
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(nss.ns(), TagsType::ConfigNS);
+        ASSERT_EQ(nss, TagsType::ConfigNS);
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
-        ASSERT_EQ(query->nss().ns(), TagsType::ConfigNS);
+        ASSERT_EQ(query->nss(), TagsType::ConfigNS);
         ASSERT_BSONOBJ_EQ(query->getFilter(), BSON(TagsType::ns("TestDB.TestColl")));
         ASSERT_BSONOBJ_EQ(query->getSort(), BSON(TagsType::min() << 1));
 
@@ -1050,8 +1051,8 @@ TEST_F(ShardingCatalogClientTest, GetTagsForCollectionNoTags) {
     configTargeter()->setFindHostReturnValue(HostAndPort("TestHost1"));
 
     auto future = launchAsync([this] {
-        const auto& tags =
-            assertGet(catalogClient()->getTagsForCollection(operationContext(), "TestDB.TestColl"));
+        const auto& tags = assertGet(catalogClient()->getTagsForCollection(
+            operationContext(), NamespaceString("TestDB.TestColl")));
 
         ASSERT_EQ(0U, tags.size());
 
@@ -1067,21 +1068,21 @@ TEST_F(ShardingCatalogClientTest, GetTagsForCollectionInvalidTag) {
     configTargeter()->setFindHostReturnValue(HostAndPort("TestHost1"));
 
     auto future = launchAsync([this] {
-        const auto swTags =
-            catalogClient()->getTagsForCollection(operationContext(), "TestDB.TestColl");
+        const auto swTags = catalogClient()->getTagsForCollection(
+            operationContext(), NamespaceString("TestDB.TestColl"));
 
         ASSERT_EQUALS(ErrorCodes::NoSuchKey, swTags.getStatus());
     });
 
     onFindCommand([](const RemoteCommandRequest& request) {
         TagsType tagA;
-        tagA.setNS("TestDB.TestColl");
+        tagA.setNS(NamespaceString("TestDB.TestColl"));
         tagA.setTag("TagA");
         tagA.setMinKey(BSON("a" << 100));
         tagA.setMaxKey(BSON("a" << 200));
 
         TagsType tagB;
-        tagB.setNS("TestDB.TestColl");
+        tagB.setNS(NamespaceString("TestDB.TestColl"));
         tagB.setTag("TagB");
         tagB.setMinKey(BSON("a" << 200));
         // Missing maxKey
@@ -1114,7 +1115,7 @@ TEST_F(ShardingCatalogClientTest, UpdateDatabase) {
 
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto updateOp = UpdateOp::parse(opMsgRequest);
-        ASSERT_EQUALS(DatabaseType::ConfigNS, updateOp.getNamespace().ns());
+        ASSERT_EQUALS(DatabaseType::ConfigNS, updateOp.getNamespace());
 
         const auto& updates = updateOp.getUpdates();
         ASSERT_EQUALS(1U, updates.size());
@@ -1174,7 +1175,7 @@ TEST_F(ShardingCatalogClientTest, ApplyChunkOpsDeprecatedSuccessful) {
                                              << "first precondition")
                                         << BSON("precondition2"
                                                 << "second precondition"));
-    std::string nss = "config.chunks";
+    const NamespaceString nss("config.chunks");
     ChunkVersion lastChunkVersion(0, 0, OID());
 
     auto future = launchAsync([this, updateOps, preCondition, nss, lastChunkVersion] {
@@ -1219,7 +1220,7 @@ TEST_F(ShardingCatalogClientTest, ApplyChunkOpsDeprecatedSuccessfulWithCheck) {
                                              << "first precondition")
                                         << BSON("precondition2"
                                                 << "second precondition"));
-    std::string nss = "config.chunks";
+    const NamespaceString nss("config.chunks");
     ChunkVersion lastChunkVersion(0, 0, OID());
 
     auto future = launchAsync([this, updateOps, preCondition, nss, lastChunkVersion] {
@@ -1244,7 +1245,7 @@ TEST_F(ShardingCatalogClientTest, ApplyChunkOpsDeprecatedSuccessfulWithCheck) {
     onFindCommand([this](const RemoteCommandRequest& request) {
         OID oid = OID::gen();
         ChunkType chunk;
-        chunk.setNS("TestDB.TestColl");
+        chunk.setNS(kNamespace);
         chunk.setMin(BSON("a" << 1));
         chunk.setMax(BSON("a" << 100));
         chunk.setVersion({1, 2, oid});
@@ -1267,7 +1268,7 @@ TEST_F(ShardingCatalogClientTest, ApplyChunkOpsDeprecatedFailedWithCheck) {
                                              << "first precondition")
                                         << BSON("precondition2"
                                                 << "second precondition"));
-    std::string nss = "config.chunks";
+    const NamespaceString nss("config.chunks");
     ChunkVersion lastChunkVersion(0, 0, OID());
 
     auto future = launchAsync([this, updateOps, preCondition, nss, lastChunkVersion] {
@@ -1660,7 +1661,7 @@ TEST_F(ShardingCatalogClientTest, GetNewKeys) {
         ASSERT_EQ("admin", request.dbname);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(KeysCollectionDocument::ConfigNS, nss.ns());
+        ASSERT_EQ(KeysCollectionDocument::ConfigNS, nss);
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
@@ -1668,7 +1669,7 @@ TEST_F(ShardingCatalogClientTest, GetNewKeys) {
             fromjson("{purpose: 'none',"
                      "expiresAt: {$gt: {$timestamp: {t: 1234, i: 5678}}}}"));
 
-        ASSERT_EQ(KeysCollectionDocument::ConfigNS, query->nss().ns());
+        ASSERT_EQ(KeysCollectionDocument::ConfigNS, query->nss());
         ASSERT_BSONOBJ_EQ(expectedQuery, query->getFilter());
         ASSERT_BSONOBJ_EQ(BSON("expiresAt" << 1), query->getSort());
         ASSERT_FALSE(query->getLimit().is_initialized());
@@ -1713,7 +1714,7 @@ TEST_F(ShardingCatalogClientTest, GetNewKeysWithEmptyCollection) {
         ASSERT_EQ("admin", request.dbname);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(KeysCollectionDocument::ConfigNS, nss.ns());
+        ASSERT_EQ(KeysCollectionDocument::ConfigNS, nss);
 
         auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
 
@@ -1721,7 +1722,7 @@ TEST_F(ShardingCatalogClientTest, GetNewKeysWithEmptyCollection) {
             fromjson("{purpose: 'none',"
                      "expiresAt: {$gt: {$timestamp: {t: 1234, i: 5678}}}}"));
 
-        ASSERT_EQ(KeysCollectionDocument::ConfigNS, query->nss().ns());
+        ASSERT_EQ(KeysCollectionDocument::ConfigNS, query->nss());
         ASSERT_BSONOBJ_EQ(expectedQuery, query->getFilter());
         ASSERT_BSONOBJ_EQ(BSON("expiresAt" << 1), query->getSort());
         ASSERT_FALSE(query->getLimit().is_initialized());
diff --git a/src/mongo/s/catalog/sharding_catalog_write_retry_test.cpp b/src/mongo/s/catalog/sharding_catalog_write_retry_test.cpp
index 94b913ec232..d32de61a18e 100644
--- a/src/mongo/s/catalog/sharding_catalog_write_retry_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_write_retry_test.cpp
@@ -85,7 +85,7 @@ TEST_F(InsertRetryTest, RetryOnInterruptedAndNetworkErrorSuccess) {
     auto future = launchAsync([&] {
         Status status =
             catalogClient()->insertConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToInsert,
                                                   ShardingCatalogClient::kMajorityWriteConcern);
         ASSERT_OK(status);
@@ -117,7 +117,7 @@ TEST_F(InsertRetryTest, RetryOnNetworkErrorFails) {
     auto future = launchAsync([&] {
         Status status =
             catalogClient()->insertConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToInsert,
                                                   ShardingCatalogClient::kMajorityWriteConcern);
         ASSERT_EQ(ErrorCodes::NetworkTimeout, status.code());
@@ -152,7 +152,7 @@ TEST_F(InsertRetryTest, DuplicateKeyErrorAfterNetworkErrorMatch) {
     auto future = launchAsync([&] {
         Status status =
             catalogClient()->insertConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToInsert,
                                                   ShardingCatalogClient::kMajorityWriteConcern);
         ASSERT_OK(status);
@@ -190,7 +190,7 @@ TEST_F(InsertRetryTest, DuplicateKeyErrorAfterNetworkErrorNotFound) {
     auto future = launchAsync([&] {
         Status status =
             catalogClient()->insertConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToInsert,
                                                   ShardingCatalogClient::kMajorityWriteConcern);
         ASSERT_EQ(ErrorCodes::DuplicateKey, status.code());
@@ -228,7 +228,7 @@ TEST_F(InsertRetryTest, DuplicateKeyErrorAfterNetworkErrorMismatch) {
     auto future = launchAsync([&] {
         Status status =
             catalogClient()->insertConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToInsert,
                                                   ShardingCatalogClient::kMajorityWriteConcern);
         ASSERT_EQ(ErrorCodes::DuplicateKey, status.code());
@@ -267,7 +267,7 @@ TEST_F(InsertRetryTest, DuplicateKeyErrorAfterWriteConcernFailureMatch) {
     auto future = launchAsync([&] {
         Status status =
             catalogClient()->insertConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToInsert,
                                                   ShardingCatalogClient::kMajorityWriteConcern);
         ASSERT_OK(status);
@@ -276,7 +276,7 @@ TEST_F(InsertRetryTest, DuplicateKeyErrorAfterWriteConcernFailureMatch) {
     onCommand([&](const RemoteCommandRequest& request) {
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto insertOp = InsertOp::parse(opMsgRequest);
-        ASSERT_EQUALS(kTestNamespace.ns(), insertOp.getNamespace().ns());
+        ASSERT_EQUALS(kTestNamespace, insertOp.getNamespace());
 
         BatchedCommandResponse response;
         response.setStatus(Status::OK());
@@ -324,7 +324,7 @@ TEST_F(UpdateRetryTest, Success) {
     auto future = launchAsync([&] {
         auto status =
             catalogClient()->updateConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToUpdate,
                                                   updateExpr,
                                                   false,
@@ -335,7 +335,7 @@ TEST_F(UpdateRetryTest, Success) {
     onCommand([&](const RemoteCommandRequest& request) {
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto updateOp = UpdateOp::parse(opMsgRequest);
-        ASSERT_EQUALS(kTestNamespace.ns(), updateOp.getNamespace().ns());
+        ASSERT_EQUALS(kTestNamespace, updateOp.getNamespace());
 
         BatchedCommandResponse response;
         response.setStatus(Status::OK());
@@ -358,7 +358,7 @@ TEST_F(UpdateRetryTest, NotMasterErrorReturnedPersistently) {
     auto future = launchAsync([&] {
         auto status =
             catalogClient()->updateConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToUpdate,
                                                   updateExpr,
                                                   false,
@@ -389,7 +389,7 @@ TEST_F(UpdateRetryTest, NotMasterReturnedFromTargeter) {
     auto future = launchAsync([&] {
         auto status =
             catalogClient()->updateConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToUpdate,
                                                   updateExpr,
                                                   false,
@@ -420,7 +420,7 @@ TEST_F(UpdateRetryTest, NotMasterOnceSuccessAfterRetry) {
     auto future = launchAsync([&] {
         ASSERT_OK(
             catalogClient()->updateConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToUpdate,
                                                   updateExpr,
                                                   false,
@@ -442,7 +442,7 @@ TEST_F(UpdateRetryTest, NotMasterOnceSuccessAfterRetry) {
     onCommand([&](const RemoteCommandRequest& request) {
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto updateOp = UpdateOp::parse(opMsgRequest);
-        ASSERT_EQUALS(kTestNamespace.ns(), updateOp.getNamespace().ns());
+        ASSERT_EQUALS(kTestNamespace, updateOp.getNamespace());
 
         BatchedCommandResponse response;
         response.setStatus(Status::OK());
@@ -465,7 +465,7 @@ TEST_F(UpdateRetryTest, OperationInterruptedDueToPrimaryStepDown) {
     auto future = launchAsync([&] {
         auto status =
             catalogClient()->updateConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToUpdate,
                                                   updateExpr,
                                                   false,
@@ -476,7 +476,7 @@ TEST_F(UpdateRetryTest, OperationInterruptedDueToPrimaryStepDown) {
     onCommand([&](const RemoteCommandRequest& request) {
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto updateOp = UpdateOp::parse(opMsgRequest);
-        ASSERT_EQUALS(kTestNamespace.ns(), updateOp.getNamespace().ns());
+        ASSERT_EQUALS(kTestNamespace, updateOp.getNamespace());
 
         BatchedCommandResponse response;
         response.setStatus(Status::OK());
@@ -493,7 +493,7 @@ TEST_F(UpdateRetryTest, OperationInterruptedDueToPrimaryStepDown) {
     onCommand([&](const RemoteCommandRequest& request) {
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto updateOp = UpdateOp::parse(opMsgRequest);
-        ASSERT_EQUALS(kTestNamespace.ns(), updateOp.getNamespace().ns());
+        ASSERT_EQUALS(kTestNamespace, updateOp.getNamespace());
 
         BatchedCommandResponse response;
         response.setStatus(Status::OK());
@@ -516,7 +516,7 @@ TEST_F(UpdateRetryTest, WriteConcernFailure) {
     auto future = launchAsync([&] {
         auto status =
             catalogClient()->updateConfigDocument(operationContext(),
-                                                  kTestNamespace.ns(),
+                                                  kTestNamespace,
                                                   objToUpdate,
                                                   updateExpr,
                                                   false,
@@ -527,7 +527,7 @@ TEST_F(UpdateRetryTest, WriteConcernFailure) {
     onCommand([&](const RemoteCommandRequest& request) {
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto updateOp = UpdateOp::parse(opMsgRequest);
-        ASSERT_EQUALS(kTestNamespace.ns(), updateOp.getNamespace().ns());
+        ASSERT_EQUALS(kTestNamespace, updateOp.getNamespace());
 
         BatchedCommandResponse response;
         response.setStatus(Status::OK());
@@ -550,7 +550,7 @@ TEST_F(UpdateRetryTest, WriteConcernFailure) {
     onCommand([&](const RemoteCommandRequest& request) {
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto updateOp = UpdateOp::parse(opMsgRequest);
-        ASSERT_EQUALS(kTestNamespace.ns(), updateOp.getNamespace().ns());
+        ASSERT_EQUALS(kTestNamespace, updateOp.getNamespace());
 
         BatchedCommandResponse response;
         response.setStatus(Status::OK());
diff --git a/src/mongo/s/catalog/type_chunk.cpp b/src/mongo/s/catalog/type_chunk.cpp
index 456771f4aff..abec9536642 100644
--- a/src/mongo/s/catalog/type_chunk.cpp
+++ b/src/mongo/s/catalog/type_chunk.cpp
@@ -42,7 +42,7 @@
 
 namespace mongo {
 
-const std::string ChunkType::ConfigNS = "config.chunks";
+const NamespaceString ChunkType::ConfigNS("config.chunks");
 const std::string ChunkType::ShardNSPrefix = "config.cache.chunks.";
 
 const BSONField<std::string> ChunkType::name("_id");
@@ -157,7 +157,7 @@ ChunkRange ChunkRange::unionWith(ChunkRange const& other) const {
 ChunkType::ChunkType() = default;
 
 ChunkType::ChunkType(NamespaceString nss, ChunkRange range, ChunkVersion version, ShardId shardId)
-    : _ns(nss.ns()),
+    : _nss(nss),
       _min(range.getMin()),
       _max(range.getMax()),
       _version(version),
@@ -171,7 +171,7 @@ StatusWith<ChunkType> ChunkType::fromConfigBSON(const BSONObj& source) {
         Status status = bsonExtractStringField(source, ns.name(), &chunkNS);
         if (!status.isOK())
             return status;
-        chunk._ns = chunkNS;
+        chunk._nss = NamespaceString(chunkNS);
     }
 
     {
@@ -217,10 +217,10 @@ StatusWith<ChunkType> ChunkType::fromConfigBSON(const BSONObj& source) {
 
 BSONObj ChunkType::toConfigBSON() const {
     BSONObjBuilder builder;
-    if (_ns && _min)
+    if (_nss && _min)
         builder.append(name.name(), getName());
-    if (_ns)
-        builder.append(ns.name(), getNS());
+    if (_nss)
+        builder.append(ns.name(), getNS().ns());
     if (_min)
         builder.append(min.name(), getMin());
     if (_max)
@@ -295,14 +295,14 @@ BSONObj ChunkType::toShardBSON() const {
 }
 
 std::string ChunkType::getName() const {
-    invariant(_ns);
+    invariant(_nss);
     invariant(_min);
-    return genID(*_ns, *_min);
+    return genID(*_nss, *_min);
 }
 
-void ChunkType::setNS(const std::string& ns) {
-    invariant(!ns.empty());
-    _ns = ns;
+void ChunkType::setNS(const NamespaceString& nss) {
+    invariant(nss.isValid());
+    _nss = nss;
 }
 
 void ChunkType::setMin(const BSONObj& min) {
@@ -329,9 +329,9 @@ void ChunkType::setJumbo(bool jumbo) {
     _jumbo = jumbo;
 }
 
-std::string ChunkType::genID(StringData ns, const BSONObj& o) {
+std::string ChunkType::genID(const NamespaceString& nss, const BSONObj& o) {
     StringBuilder buf;
-    buf << ns << "-";
+    buf << nss.ns() << "-";
 
     BSONObjIterator i(o);
     while (i.more()) {
diff --git a/src/mongo/s/catalog/type_chunk.h b/src/mongo/s/catalog/type_chunk.h
index 2852955deb6..b4998af3c9a 100644
--- a/src/mongo/s/catalog/type_chunk.h
+++ b/src/mongo/s/catalog/type_chunk.h
@@ -147,7 +147,7 @@ private:
 class ChunkType {
 public:
     // Name of the chunks collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     // The shard chunks collections' common namespace prefix.
     static const std::string ShardNSPrefix;
@@ -199,10 +199,10 @@ public:
     /**
      * Getters and setters.
      */
-    const std::string& getNS() const {
-        return _ns.get();
+    const NamespaceString& getNS() const {
+        return _nss.get();
     }
-    void setNS(const std::string& name);
+    void setNS(const NamespaceString& nss);
 
     const BSONObj& getMin() const {
         return _min.get();
@@ -239,7 +239,7 @@ public:
     /**
      * Generates chunk id based on the namespace name and the lower bound of the chunk.
      */
-    static std::string genID(StringData ns, const BSONObj& min);
+    static std::string genID(const NamespaceString& nss, const BSONObj& min);
 
     /**
      * Returns OK if all the mandatory fields have been set. Otherwise returns NoSuchKey and
@@ -256,7 +256,7 @@ private:
     // Convention: (M)andatory, (O)ptional, (S)pecial; (C)onfig, (S)hard.
 
     // (O)(C)     collection this chunk is in
-    boost::optional<std::string> _ns;
+    boost::optional<NamespaceString> _nss;
     // (M)(C)(S)  first key of the range, inclusive
     boost::optional<BSONObj> _min;
     // (M)(C)(S)  last key of the range, non-inclusive
diff --git a/src/mongo/s/catalog/type_chunk_test.cpp b/src/mongo/s/catalog/type_chunk_test.cpp
index eabce7ed879..8aa5cd1b20f 100644
--- a/src/mongo/s/catalog/type_chunk_test.cpp
+++ b/src/mongo/s/catalog/type_chunk_test.cpp
@@ -197,7 +197,7 @@ TEST(ChunkType, ToFromConfigBSON) {
 
     ASSERT_BSONOBJ_EQ(chunk.toConfigBSON(), obj);
 
-    ASSERT_EQUALS(chunk.getNS(), "test.mycol");
+    ASSERT_EQUALS(chunk.getNS().ns(), "test.mycol");
     ASSERT_BSONOBJ_EQ(chunk.getMin(), BSON("a" << 10));
     ASSERT_BSONOBJ_EQ(chunk.getMax(), BSON("a" << 20));
     ASSERT_EQUALS(chunk.getVersion().toLong(), chunkVersion.toLong());
@@ -221,7 +221,7 @@ TEST(ChunkType, Pre22Format) {
                                                                << "shard0001")));
 
     ASSERT_OK(chunk.validate());
-    ASSERT_EQUALS(chunk.getNS(), "test.mycol");
+    ASSERT_EQUALS(chunk.getNS().ns(), "test.mycol");
     ASSERT_BSONOBJ_EQ(chunk.getMin(), BSON("a" << 10));
     ASSERT_BSONOBJ_EQ(chunk.getMax(), BSON("a" << 20));
     ASSERT_EQUALS(chunk.getVersion().toLong(), 1ULL);
diff --git a/src/mongo/s/catalog/type_collection.cpp b/src/mongo/s/catalog/type_collection.cpp
index 6c9a0644327..79490a4494f 100644
--- a/src/mongo/s/catalog/type_collection.cpp
+++ b/src/mongo/s/catalog/type_collection.cpp
@@ -46,7 +46,7 @@ const auto kIsAssignedShardKey = "isAssignedShardKey"_sd;
 
 }  // namespace
 
-const std::string CollectionType::ConfigNS = "config.collections";
+const NamespaceString CollectionType::ConfigNS("config.collections");
 
 const BSONField<std::string> CollectionType::fullNs("_id");
 const BSONField<OID> CollectionType::epoch("lastmodEpoch");
diff --git a/src/mongo/s/catalog/type_collection.h b/src/mongo/s/catalog/type_collection.h
index 796b4f7707a..db7c7490a08 100644
--- a/src/mongo/s/catalog/type_collection.h
+++ b/src/mongo/s/catalog/type_collection.h
@@ -70,7 +70,7 @@ class StatusWith;
 class CollectionType {
 public:
     // Name of the collections collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     static const BSONField<std::string> fullNs;
     static const BSONField<OID> epoch;
diff --git a/src/mongo/s/catalog/type_config_version.cpp b/src/mongo/s/catalog/type_config_version.cpp
index 68fa14829ad..7e9ce649527 100644
--- a/src/mongo/s/catalog/type_config_version.cpp
+++ b/src/mongo/s/catalog/type_config_version.cpp
@@ -38,7 +38,7 @@
 
 namespace mongo {
 
-const std::string VersionType::ConfigNS = "config.version";
+const NamespaceString VersionType::ConfigNS("config.version");
 
 const BSONField<int> VersionType::minCompatibleVersion("minCompatibleVersion");
 const BSONField<int> VersionType::currentVersion("currentVersion");
diff --git a/src/mongo/s/catalog/type_config_version.h b/src/mongo/s/catalog/type_config_version.h
index e469ac57b7b..a412eaba571 100644
--- a/src/mongo/s/catalog/type_config_version.h
+++ b/src/mongo/s/catalog/type_config_version.h
@@ -33,6 +33,7 @@
 #include <vector>
 
 #include "mongo/db/jsobj.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/s/catalog/mongo_version_range.h"
 
 namespace mongo {
@@ -45,7 +46,7 @@ namespace mongo {
 class VersionType {
 public:
     // Name of the version collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     // Field names and types in the version collection type.
     static const BSONField<int> minCompatibleVersion;
diff --git a/src/mongo/s/catalog/type_database.cpp b/src/mongo/s/catalog/type_database.cpp
index 492077a9337..d3d807c89a1 100644
--- a/src/mongo/s/catalog/type_database.cpp
+++ b/src/mongo/s/catalog/type_database.cpp
@@ -41,7 +41,7 @@ namespace mongo {
 
 using std::string;
 
-const std::string DatabaseType::ConfigNS = "config.databases";
+const NamespaceString DatabaseType::ConfigNS("config.databases");
 
 const BSONField<std::string> DatabaseType::name("_id");
 const BSONField<std::string> DatabaseType::primary("primary");
diff --git a/src/mongo/s/catalog/type_database.h b/src/mongo/s/catalog/type_database.h
index 9525263a151..8b2fcf85c7b 100644
--- a/src/mongo/s/catalog/type_database.h
+++ b/src/mongo/s/catalog/type_database.h
@@ -32,6 +32,7 @@
 #include <string>
 
 #include "mongo/db/jsobj.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/s/database_version_gen.h"
 #include "mongo/s/shard_id.h"
 
@@ -51,7 +52,7 @@ class StatusWith;
 class DatabaseType {
 public:
     // Name of the databases collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     static const BSONField<std::string> name;
     static const BSONField<std::string> primary;
diff --git a/src/mongo/s/catalog/type_lockpings.cpp b/src/mongo/s/catalog/type_lockpings.cpp
index 67fab8a20e2..0d2b041df79 100644
--- a/src/mongo/s/catalog/type_lockpings.cpp
+++ b/src/mongo/s/catalog/type_lockpings.cpp
@@ -35,7 +35,7 @@
 #include "mongo/util/mongoutils/str.h"
 
 namespace mongo {
-const std::string LockpingsType::ConfigNS = "config.lockpings";
+const NamespaceString LockpingsType::ConfigNS("config.lockpings");
 
 const BSONField<std::string> LockpingsType::process("_id");
 const BSONField<Date_t> LockpingsType::ping("ping");
diff --git a/src/mongo/s/catalog/type_lockpings.h b/src/mongo/s/catalog/type_lockpings.h
index 66556963705..52814f8d6c6 100644
--- a/src/mongo/s/catalog/type_lockpings.h
+++ b/src/mongo/s/catalog/type_lockpings.h
@@ -32,6 +32,7 @@
 #include <string>
 
 #include "mongo/db/jsobj.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/util/time_support.h"
 
 namespace mongo {
@@ -44,7 +45,7 @@ namespace mongo {
 class LockpingsType {
 public:
     // Name of the lockpings collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     // Field names and types in the lockpings collection type.
     static const BSONField<std::string> process;
diff --git a/src/mongo/s/catalog/type_locks.cpp b/src/mongo/s/catalog/type_locks.cpp
index 9724ac92519..59e4aa02881 100644
--- a/src/mongo/s/catalog/type_locks.cpp
+++ b/src/mongo/s/catalog/type_locks.cpp
@@ -38,7 +38,7 @@
 #include "mongo/util/mongoutils/str.h"
 
 namespace mongo {
-const std::string LocksType::ConfigNS = "config.locks";
+const NamespaceString LocksType::ConfigNS("config.locks");
 
 const BSONField<std::string> LocksType::name("_id");
 const BSONField<LocksType::State> LocksType::state("state");
diff --git a/src/mongo/s/catalog/type_locks.h b/src/mongo/s/catalog/type_locks.h
index 9df7998d35d..f2d30afd349 100644
--- a/src/mongo/s/catalog/type_locks.h
+++ b/src/mongo/s/catalog/type_locks.h
@@ -32,6 +32,7 @@
 #include <string>
 
 #include "mongo/db/jsobj.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/util/time_support.h"
 
 namespace mongo {
@@ -51,7 +52,7 @@ public:
     };
 
     // Name of the locks collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     // Field names and types in the locks collection type.
     static const BSONField<std::string> name;
diff --git a/src/mongo/s/catalog/type_mongos.cpp b/src/mongo/s/catalog/type_mongos.cpp
index c656f59b4ee..3cbee67603f 100644
--- a/src/mongo/s/catalog/type_mongos.cpp
+++ b/src/mongo/s/catalog/type_mongos.cpp
@@ -35,7 +35,7 @@
 #include "mongo/util/mongoutils/str.h"
 
 namespace mongo {
-const std::string MongosType::ConfigNS = "config.mongos";
+const NamespaceString MongosType::ConfigNS("config.mongos");
 
 const BSONField<std::string> MongosType::name("_id");
 const BSONField<Date_t> MongosType::ping("ping");
diff --git a/src/mongo/s/catalog/type_mongos.h b/src/mongo/s/catalog/type_mongos.h
index 02e7fea601b..d48141ac156 100644
--- a/src/mongo/s/catalog/type_mongos.h
+++ b/src/mongo/s/catalog/type_mongos.h
@@ -32,6 +32,7 @@
 #include <string>
 
 #include "mongo/db/jsobj.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/util/time_support.h"
 
 namespace mongo {
@@ -44,7 +45,7 @@ namespace mongo {
 class MongosType {
 public:
     // Name of the mongos collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     // Field names and types in the mongos collection type.
     static const BSONField<std::string> name;
diff --git a/src/mongo/s/catalog/type_shard.cpp b/src/mongo/s/catalog/type_shard.cpp
index 0b97a3d3cd6..56d432cf43e 100644
--- a/src/mongo/s/catalog/type_shard.cpp
+++ b/src/mongo/s/catalog/type_shard.cpp
@@ -40,7 +40,7 @@
 
 namespace mongo {
 
-const std::string ShardType::ConfigNS = "config.shards";
+const NamespaceString ShardType::ConfigNS("config.shards");
 
 const BSONField<std::string> ShardType::name("_id");
 const BSONField<std::string> ShardType::host("host");
diff --git a/src/mongo/s/catalog/type_shard.h b/src/mongo/s/catalog/type_shard.h
index 5e3ca3d8989..29fe7922043 100644
--- a/src/mongo/s/catalog/type_shard.h
+++ b/src/mongo/s/catalog/type_shard.h
@@ -33,6 +33,7 @@
 #include <vector>
 
 #include "mongo/db/jsobj.h"
+#include "mongo/db/namespace_string.h"
 #include "mongo/s/shard_id.h"
 
 namespace mongo {
@@ -56,7 +57,7 @@ public:
     };
 
     // Name of the shards collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     // Field names and types in the shards collection type.
     static const BSONField<std::string> name;
diff --git a/src/mongo/s/catalog/type_shard_collection.cpp b/src/mongo/s/catalog/type_shard_collection.cpp
index 195606b0878..7343238a1b1 100644
--- a/src/mongo/s/catalog/type_shard_collection.cpp
+++ b/src/mongo/s/catalog/type_shard_collection.cpp
@@ -39,8 +39,8 @@
 
 namespace mongo {
 
-const std::string ShardCollectionType::ConfigNS =
-    NamespaceString::kShardConfigCollectionsCollectionName.toString();
+const NamespaceString ShardCollectionType::ConfigNS(
+    NamespaceString::kShardConfigCollectionsCollectionName);
 
 const BSONField<std::string> ShardCollectionType::ns("_id");
 const BSONField<UUID> ShardCollectionType::uuid("uuid");
diff --git a/src/mongo/s/catalog/type_shard_collection.h b/src/mongo/s/catalog/type_shard_collection.h
index 3f1da52eb9c..0df48ffe59b 100644
--- a/src/mongo/s/catalog/type_shard_collection.h
+++ b/src/mongo/s/catalog/type_shard_collection.h
@@ -71,7 +71,7 @@ class StatusWith;
 class ShardCollectionType {
 public:
     // Name of the collections collection on the shard server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     static const BSONField<std::string> ns;  // "_id"
     static const BSONField<UUID> uuid;
diff --git a/src/mongo/s/catalog/type_tags.cpp b/src/mongo/s/catalog/type_tags.cpp
index b0c72053cca..5701633a273 100644
--- a/src/mongo/s/catalog/type_tags.cpp
+++ b/src/mongo/s/catalog/type_tags.cpp
@@ -42,7 +42,7 @@ namespace mongo {
 
 using std::string;
 
-const std::string TagsType::ConfigNS = "config.tags";
+const NamespaceString TagsType::ConfigNS("config.tags");
 
 const BSONField<std::string> TagsType::ns("ns");
 const BSONField<std::string> TagsType::tag("tag");
@@ -60,7 +60,7 @@ StatusWith<TagsType> TagsType::fromBSON(const BSONObj& source) {
             return status;
         }
 
-        tags._ns = tagsNs;
+        tags._ns = NamespaceString(tagsNs);
     }
 
     {
@@ -87,7 +87,7 @@ StatusWith<TagsType> TagsType::fromBSON(const BSONObj& source) {
 }
 
 Status TagsType::validate() const {
-    if (!_ns.is_initialized() || _ns->empty()) {
+    if (!_ns.is_initialized() || !_ns->isValid()) {
         return Status(ErrorCodes::NoSuchKey, str::stream() << "missing " << ns.name() << " field");
     }
 
@@ -130,7 +130,7 @@ BSONObj TagsType::toBSON() const {
     BSONObjBuilder builder;
 
     if (_ns)
-        builder.append(ns.name(), getNS());
+        builder.append(ns.name(), getNS().ns());
     if (_tag)
         builder.append(tag.name(), getTag());
     if (_minKey)
@@ -145,8 +145,8 @@ std::string TagsType::toString() const {
     return toBSON().toString();
 }
 
-void TagsType::setNS(const std::string& ns) {
-    invariant(!ns.empty());
+void TagsType::setNS(const NamespaceString& ns) {
+    invariant(ns.isValid());
     _ns = ns;
 }
 
diff --git a/src/mongo/s/catalog/type_tags.h b/src/mongo/s/catalog/type_tags.h
index 8549af8fadd..b205e2d5646 100644
--- a/src/mongo/s/catalog/type_tags.h
+++ b/src/mongo/s/catalog/type_tags.h
@@ -32,6 +32,7 @@
 #include <string>
 
 #include "mongo/db/jsobj.h"
+#include "mongo/db/namespace_string.h"
 
 namespace mongo {
 
@@ -49,7 +50,7 @@ class StatusWith;
 class TagsType {
 public:
     // Name of the tags collection in the config server.
-    static const std::string ConfigNS;
+    static const NamespaceString ConfigNS;
 
     // Field names and types in the tags collection type.
     static const BSONField<std::string> ns;
@@ -80,10 +81,10 @@ public:
      */
     std::string toString() const;
 
-    const std::string& getNS() const {
+    const NamespaceString& getNS() const {
         return _ns.get();
     }
-    void setNS(const std::string& ns);
+    void setNS(const NamespaceString& ns);
 
     const std::string& getTag() const {
         return _tag.get();
@@ -102,7 +103,7 @@ public:
 
 private:
     // Required namespace to which this tag belongs
-    boost::optional<std::string> _ns;
+    boost::optional<NamespaceString> _ns;
 
     // Required tag name
     boost::optional<std::string> _tag;
diff --git a/src/mongo/s/catalog/type_tags_test.cpp b/src/mongo/s/catalog/type_tags_test.cpp
index 16a7c6dc2ee..e3529097730 100644
--- a/src/mongo/s/catalog/type_tags_test.cpp
+++ b/src/mongo/s/catalog/type_tags_test.cpp
@@ -50,7 +50,7 @@ TEST(TagsType, Valid) {
 
     TagsType tag = status.getValue();
 
-    ASSERT_EQUALS(tag.getNS(), "test.mycol");
+    ASSERT_EQUALS(tag.getNS().ns(), "test.mycol");
     ASSERT_EQUALS(tag.getTag(), "tag");
     ASSERT_BSONOBJ_EQ(tag.getMinKey(), BSON("a" << 10));
     ASSERT_BSONOBJ_EQ(tag.getMaxKey(), BSON("a" << 20));
diff --git a/src/mongo/s/catalog_cache.cpp b/src/mongo/s/catalog_cache.cpp
index 1f970c5dca6..bf072e10df4 100644
--- a/src/mongo/s/catalog_cache.cpp
+++ b/src/mongo/s/catalog_cache.cpp
@@ -241,7 +241,7 @@ void CatalogCache::onStaleConfigError(CachedCollectionRoutingInfo&& ccriToInvali
     // Here we received a stale config error for a collection which we previously though was sharded
     stdx::lock_guard<stdx::mutex> lg(_mutex);
 
-    auto it = _databases.find(NamespaceString(ccri._cm->getns()).db());
+    auto it = _databases.find(ccri._cm->getns().db());
     if (it == _databases.end()) {
         // If the database does not exist, the collection must have been dropped so there is
         // nothing to invalidate. The getCollectionRoutingInfo will handle the reload of the
@@ -251,7 +251,7 @@ void CatalogCache::onStaleConfigError(CachedCollectionRoutingInfo&& ccriToInvali
 
     auto& collections = it->second->collections;
 
-    auto itColl = collections.find(ccri._cm->getns());
+    auto itColl = collections.find(ccri._cm->getns().ns());
     if (itColl == collections.end()) {
         // If the collection does not exist, this means it must have been dropped since the last
         // time we retrieved a cache entry for it. Doing nothing in this case will cause the
diff --git a/src/mongo/s/chunk_manager.h b/src/mongo/s/chunk_manager.h
index ed7a34d5468..dc04c1b8548 100644
--- a/src/mongo/s/chunk_manager.h
+++ b/src/mongo/s/chunk_manager.h
@@ -139,8 +139,8 @@ public:
         return _sequenceNumber;
     }
 
-    const std::string& getns() const {
-        return _nss.ns();
+    const NamespaceString& getns() const {
+        return _nss;
     }
 
     const ShardKeyPattern& getShardKeyPattern() const {
diff --git a/src/mongo/s/client/parallel.cpp b/src/mongo/s/client/parallel.cpp
index 7c56b69c053..0c35d6f5c68 100644
--- a/src/mongo/s/client/parallel.cpp
+++ b/src/mongo/s/client/parallel.cpp
@@ -445,7 +445,7 @@ void ParallelSortClusteredCursor::startInit(OperationContext* opCtx) {
 
     if (manager) {
         if (MONGO_unlikely(shouldLog(pc))) {
-            vinfo = str::stream() << "[" << manager->getns() << " @ "
+            vinfo = str::stream() << "[" << manager->getns().ns() << " @ "
                                   << manager->getVersion().toString() << "]";
         }
 
@@ -1303,7 +1303,7 @@ BSONObj ParallelConnectionState::toBSON() const {
 
     BSONObj stateObj =
         BSON("conn" << (conn ? (conn->ok() ? conn->conn().toString() : "(done)") : "") << "vinfo"
-                    << (manager ? (str::stream() << manager->getns() << " @ "
+                    << (manager ? (str::stream() << manager->getns().ns() << " @ "
                                                  << manager->getVersion().toString())
                                 : primary->toString()));
 
diff --git a/src/mongo/s/client/shard_connection.cpp b/src/mongo/s/client/shard_connection.cpp
index fcb033b1025..c977467dbb0 100644
--- a/src/mongo/s/client/shard_connection.cpp
+++ b/src/mongo/s/client/shard_connection.cpp
@@ -406,7 +406,7 @@ ShardConnection::ShardConnection(const ConnectionString& connectionString,
 
     // Make sure we specified a manager for the correct namespace
     if (_ns.size() && _manager) {
-        invariant(_manager->getns() == _ns);
+        invariant(_manager->getns().ns() == _ns);
     }
 
     auto csString = _cs.toString();
diff --git a/src/mongo/s/commands/cluster_add_shard_to_zone_cmd.cpp b/src/mongo/s/commands/cluster_add_shard_to_zone_cmd.cpp
index 419ca7e2a0e..ca9f56b0ab7 100644
--- a/src/mongo/s/commands/cluster_add_shard_to_zone_cmd.cpp
+++ b/src/mongo/s/commands/cluster_add_shard_to_zone_cmd.cpp
@@ -89,8 +89,7 @@ public:
                                const std::string& dbname,
                                const BSONObj& cmdObj) override {
         if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
-                ResourcePattern::forExactNamespace(NamespaceString(ShardType::ConfigNS)),
-                ActionType::update)) {
+                ResourcePattern::forExactNamespace(ShardType::ConfigNS), ActionType::update)) {
             return Status(ErrorCodes::Unauthorized, "Unauthorized");
         }
         return Status::OK();
diff --git a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
index 5e58c1c0e68..9eed7db5fa2 100644
--- a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
+++ b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
@@ -476,7 +476,7 @@ public:
             } else {
                 // Collection is already sharded; read the collection's UUID from the config server.
                 const auto coll =
-                    uassertStatusOK(catalogClient->getCollection(opCtx, outputCollNss.ns())).value;
+                    uassertStatusOK(catalogClient->getCollection(opCtx, outputCollNss)).value;
                 shardedOutputCollUUID = coll.getUUID();
             }
 
diff --git a/src/mongo/s/commands/cluster_move_chunk_cmd.cpp b/src/mongo/s/commands/cluster_move_chunk_cmd.cpp
index e251376c920..88549b9f70a 100644
--- a/src/mongo/s/commands/cluster_move_chunk_cmd.cpp
+++ b/src/mongo/s/commands/cluster_move_chunk_cmd.cpp
@@ -182,7 +182,7 @@ public:
             uassertStatusOK(MigrationSecondaryThrottleOptions::createFromCommand(cmdObj));
 
         ChunkType chunkType;
-        chunkType.setNS(nss.ns());
+        chunkType.setNS(nss);
         chunkType.setMin(chunk->getMin());
         chunkType.setMax(chunk->getMax());
         chunkType.setShard(chunk->getShardId());
diff --git a/src/mongo/s/commands/cluster_remove_shard_from_zone_cmd.cpp b/src/mongo/s/commands/cluster_remove_shard_from_zone_cmd.cpp
index bc35d3c573c..6ba4dc36278 100644
--- a/src/mongo/s/commands/cluster_remove_shard_from_zone_cmd.cpp
+++ b/src/mongo/s/commands/cluster_remove_shard_from_zone_cmd.cpp
@@ -89,14 +89,12 @@ public:
                                const std::string& dbname,
                                const BSONObj& cmdObj) override {
         if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
-                ResourcePattern::forExactNamespace(NamespaceString(ShardType::ConfigNS)),
-                ActionType::update)) {
+                ResourcePattern::forExactNamespace(ShardType::ConfigNS), ActionType::update)) {
             return Status(ErrorCodes::Unauthorized, "Unauthorized");
         }
 
         if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
-                ResourcePattern::forExactNamespace(NamespaceString(TagsType::ConfigNS)),
-                ActionType::find)) {
+                ResourcePattern::forExactNamespace(TagsType::ConfigNS), ActionType::find)) {
             return Status(ErrorCodes::Unauthorized, "Unauthorized");
         }
 
diff --git a/src/mongo/s/commands/cluster_update_zone_key_range_cmd.cpp b/src/mongo/s/commands/cluster_update_zone_key_range_cmd.cpp
index f286abc6a6b..b573d937ddd 100644
--- a/src/mongo/s/commands/cluster_update_zone_key_range_cmd.cpp
+++ b/src/mongo/s/commands/cluster_update_zone_key_range_cmd.cpp
@@ -92,26 +92,22 @@ public:
                                const std::string& dbname,
                                const BSONObj& cmdObj) override {
         if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
-                ResourcePattern::forExactNamespace(NamespaceString(ShardType::ConfigNS)),
-                ActionType::find)) {
+                ResourcePattern::forExactNamespace(ShardType::ConfigNS), ActionType::find)) {
             return Status(ErrorCodes::Unauthorized, "Unauthorized");
         }
 
         if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
-                ResourcePattern::forExactNamespace(NamespaceString(TagsType::ConfigNS)),
-                ActionType::find)) {
+                ResourcePattern::forExactNamespace(TagsType::ConfigNS), ActionType::find)) {
             return Status(ErrorCodes::Unauthorized, "Unauthorized");
         }
 
         if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
-                ResourcePattern::forExactNamespace(NamespaceString(TagsType::ConfigNS)),
-                ActionType::update)) {
+                ResourcePattern::forExactNamespace(TagsType::ConfigNS), ActionType::update)) {
             return Status(ErrorCodes::Unauthorized, "Unauthorized");
         }
 
         if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
-                ResourcePattern::forExactNamespace(NamespaceString(TagsType::ConfigNS)),
-                ActionType::remove)) {
+                ResourcePattern::forExactNamespace(TagsType::ConfigNS), ActionType::remove)) {
             return Status(ErrorCodes::Unauthorized, "Unauthorized");
         }
 
diff --git a/src/mongo/s/commands/cluster_write.cpp b/src/mongo/s/commands/cluster_write.cpp
index 14a0482a268..012ec0b17d8 100644
--- a/src/mongo/s/commands/cluster_write.cpp
+++ b/src/mongo/s/commands/cluster_write.cpp
@@ -258,7 +258,7 @@ void updateChunkWriteStatsAndSplitIfNeeded(OperationContext* opCtx,
         return;
     }
 
-    const NamespaceString nss(manager->getns());
+    const NamespaceString& nss = manager->getns();
 
     if (!manager->_autoSplitThrottle._splitTickets.tryAcquire()) {
         LOG(1) << "won't auto split because not enough tickets: " << nss;
@@ -390,7 +390,7 @@ void updateChunkWriteStatsAndSplitIfNeeded(OperationContext* opCtx,
             suggestedMigrateChunk->getMin());
 
         ChunkType chunkToMove;
-        chunkToMove.setNS(nss.ns());
+        chunkToMove.setNS(nss);
         chunkToMove.setShard(suggestedChunk->getShardId());
         chunkToMove.setMin(suggestedChunk->getMin());
         chunkToMove.setMax(suggestedChunk->getMax());
diff --git a/src/mongo/s/commands/commands_public.cpp b/src/mongo/s/commands/commands_public.cpp
index c5e0ecb358d..1ce1611ff25 100644
--- a/src/mongo/s/commands/commands_public.cpp
+++ b/src/mongo/s/commands/commands_public.cpp
@@ -458,7 +458,7 @@ public:
         Strategy::commandOp(opCtx,
                             dbName,
                             CommandHelpers::filterCommandRequestForPassthrough(cmdObj),
-                            cm->getns(),
+                            cm->getns().ns(),
                             query,
                             CollationSpec::kSimpleSpec,
                             &results);
diff --git a/src/mongo/s/config_server_catalog_cache_loader.cpp b/src/mongo/s/config_server_catalog_cache_loader.cpp
index 5f46e72fb20..49bbe011939 100644
--- a/src/mongo/s/config_server_catalog_cache_loader.cpp
+++ b/src/mongo/s/config_server_catalog_cache_loader.cpp
@@ -93,7 +93,7 @@ CollectionAndChangedChunks getChangedChunks(OperationContext* opCtx,
     const auto catalogClient = Grid::get(opCtx)->catalogClient();
 
     // Decide whether to do a full or partial load based on the state of the collection
-    const auto coll = uassertStatusOK(catalogClient->getCollection(opCtx, nss.ns())).value;
+    const auto coll = uassertStatusOK(catalogClient->getCollection(opCtx, nss)).value;
     uassert(ErrorCodes::NamespaceNotFound,
             str::stream() << "Collection " << nss.ns() << " is dropped.",
             !coll.getDropped());
diff --git a/src/mongo/s/config_server_test_fixture.cpp b/src/mongo/s/config_server_test_fixture.cpp
index d6260b1984d..0ab892018bb 100644
--- a/src/mongo/s/config_server_test_fixture.cpp
+++ b/src/mongo/s/config_server_test_fixture.cpp
@@ -300,8 +300,8 @@ Status ConfigServerTestFixture::setupShards(const std::vector<ShardType>& shards
 
 StatusWith<ShardType> ConfigServerTestFixture::getShardDoc(OperationContext* opCtx,
                                                            const std::string& shardId) {
-    auto doc = findOneOnConfigCollection(
-        opCtx, NamespaceString(ShardType::ConfigNS), BSON(ShardType::name(shardId)));
+    auto doc =
+        findOneOnConfigCollection(opCtx, ShardType::ConfigNS, BSON(ShardType::name(shardId)));
     if (!doc.isOK()) {
         if (doc.getStatus() == ErrorCodes::NoMatchingDocument) {
             return {ErrorCodes::ShardNotFound,
@@ -327,8 +327,8 @@ Status ConfigServerTestFixture::setupChunks(const std::vector<ChunkType>& chunks
 
 StatusWith<ChunkType> ConfigServerTestFixture::getChunkDoc(OperationContext* opCtx,
                                                            const BSONObj& minKey) {
-    auto doc = findOneOnConfigCollection(
-        opCtx, NamespaceString(ChunkType::ConfigNS), BSON(ChunkType::min() << minKey));
+    auto doc =
+        findOneOnConfigCollection(opCtx, ChunkType::ConfigNS, BSON(ChunkType::min() << minKey));
     if (!doc.isOK())
         return doc.getStatus();
 
@@ -374,14 +374,13 @@ StatusWith<std::vector<BSONObj>> ConfigServerTestFixture::getIndexes(OperationCo
 
 std::vector<KeysCollectionDocument> ConfigServerTestFixture::getKeys(OperationContext* opCtx) {
     auto config = getConfigShard();
-    auto findStatus =
-        config->exhaustiveFindOnConfig(opCtx,
-                                       kReadPref,
-                                       repl::ReadConcernLevel::kMajorityReadConcern,
-                                       NamespaceString(KeysCollectionDocument::ConfigNS),
-                                       BSONObj(),
-                                       BSON("expiresAt" << 1),
-                                       boost::none);
+    auto findStatus = config->exhaustiveFindOnConfig(opCtx,
+                                                     kReadPref,
+                                                     repl::ReadConcernLevel::kMajorityReadConcern,
+                                                     KeysCollectionDocument::ConfigNS,
+                                                     BSONObj(),
+                                                     BSON("expiresAt" << 1),
+                                                     boost::none);
     ASSERT_OK(findStatus.getStatus());
 
     std::vector<KeysCollectionDocument> keys;
diff --git a/src/mongo/s/request_types/balance_chunk_request_test.cpp b/src/mongo/s/request_types/balance_chunk_request_test.cpp
index 97af5a292bf..4697853109f 100644
--- a/src/mongo/s/request_types/balance_chunk_request_test.cpp
+++ b/src/mongo/s/request_types/balance_chunk_request_test.cpp
@@ -57,7 +57,7 @@ TEST(BalanceChunkRequest, ParseFromConfigCommandNoSecondaryThrottle) {
                                    << "lastmodEpoch"
                                    << version.epoch())));
     const auto& chunk = request.getChunk();
-    ASSERT_EQ("TestDB.TestColl", chunk.getNS());
+    ASSERT_EQ("TestDB.TestColl", chunk.getNS().ns());
     ASSERT_BSONOBJ_EQ(BSON("a" << -100LL), chunk.getMin());
     ASSERT_BSONOBJ_EQ(BSON("a" << 100LL), chunk.getMax());
     ASSERT_EQ(ShardId("TestShard0000"), chunk.getShard());
@@ -87,7 +87,7 @@ TEST(BalanceChunkRequest, ParseFromConfigCommandWithSecondaryThrottle) {
                                    << BSON("_secondaryThrottle" << true << "writeConcern"
                                                                 << BSON("w" << 2)))));
     const auto& chunk = request.getChunk();
-    ASSERT_EQ("TestDB.TestColl", chunk.getNS());
+    ASSERT_EQ("TestDB.TestColl", chunk.getNS().ns());
     ASSERT_BSONOBJ_EQ(BSON("a" << -100LL), chunk.getMin());
     ASSERT_BSONOBJ_EQ(BSON("a" << 100LL), chunk.getMax());
     ASSERT_EQ(ShardId("TestShard0000"), chunk.getShard());
diff --git a/src/mongo/s/sharding_test_fixture.cpp b/src/mongo/s/sharding_test_fixture.cpp
index 8b053a7426f..235054b36c1 100644
--- a/src/mongo/s/sharding_test_fixture.cpp
+++ b/src/mongo/s/sharding_test_fixture.cpp
@@ -302,13 +302,13 @@ void ShardingTestFixture::setupShards(const std::vector<ShardType>& shards) {
 void ShardingTestFixture::expectGetShards(const std::vector<ShardType>& shards) {
     onFindCommand([this, &shards](const RemoteCommandRequest& request) {
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQ(nss.toString(), ShardType::ConfigNS);
+        ASSERT_EQ(nss, ShardType::ConfigNS);
 
         auto queryResult = QueryRequest::makeFromFindCommand(nss, request.cmdObj, false);
         ASSERT_OK(queryResult.getStatus());
 
         const auto& query = queryResult.getValue();
-        ASSERT_EQ(query->nss().ns(), ShardType::ConfigNS);
+        ASSERT_EQ(query->nss(), ShardType::ConfigNS);
 
         ASSERT_BSONOBJ_EQ(query->getFilter(), BSONObj());
         ASSERT_BSONOBJ_EQ(query->getSort(), BSONObj());
@@ -334,7 +334,7 @@ void ShardingTestFixture::expectInserts(const NamespaceString& nss,
 
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto insertOp = InsertOp::parse(opMsgRequest);
-        ASSERT_EQUALS(nss.ns(), insertOp.getNamespace().ns());
+        ASSERT_EQUALS(nss, insertOp.getNamespace());
 
         const auto& inserted = insertOp.getDocuments();
         ASSERT_EQUALS(expected.size(), inserted.size());
@@ -451,7 +451,7 @@ void ShardingTestFixture::expectUpdateCollection(const HostAndPort& expectedHost
 
         const auto opMsgRequest = OpMsgRequest::fromDBAndBody(request.dbname, request.cmdObj);
         const auto updateOp = UpdateOp::parse(opMsgRequest);
-        ASSERT_EQUALS(CollectionType::ConfigNS, updateOp.getNamespace().ns());
+        ASSERT_EQUALS(CollectionType::ConfigNS, updateOp.getNamespace());
 
         const auto& updates = updateOp.getUpdates();
         ASSERT_EQUALS(1U, updates.size());
@@ -485,7 +485,7 @@ void ShardingTestFixture::expectSetShardVersion(const HostAndPort& expectedHost,
         ASSERT(!ssv.isInit());
         ASSERT(ssv.isAuthoritative());
         ASSERT_EQ(expectedShard.getHost(), ssv.getShardConnectionString().toString());
-        ASSERT_EQ(expectedNs.toString(), ssv.getNS().ns());
+        ASSERT_EQ(expectedNs, ssv.getNS());
         ASSERT_EQ(expectedChunkVersion.toString(), ssv.getNSVersion().toString());
 
         return BSON("ok" << true);