SERVER-41696 Remove the 'ns' field from index specs

64 files changed, 340 insertions, 845 deletions

diff --git a/jstests/noPassthrough/absent_ns_field_in_index_specs.js b/jstests/noPassthrough/absent_ns_field_in_index_specs.js
index 4428415e1b3..b36beab8746 100644
--- a/jstests/noPassthrough/absent_ns_field_in_index_specs.js
+++ b/jstests/noPassthrough/absent_ns_field_in_index_specs.js
@@ -1,10 +1,5 @@
 /**
- * Uses the 'disableIndexSpecNamespaceGeneration' server test parameter to disable the generation
- * of the 'ns' field for index specs to test the absence of the field.
- *
- * When the 'ns' field is missing from the index specs and the 'disableIndexSpecNamespaceGeneration'
- * server test parameter is disabled, the server should automatically add the 'ns' field to the
- * index specs missing it prior to returning them.
+ * Ensures that the 'ns' field for index specs is absent with its removal in SERVER-41696.
  *
  * @tags: [requires_replication, requires_persistence]
  */
@@ -25,10 +20,6 @@ const primaryColl = primaryDB.getCollection(collName);
 const secondary = replSet.getSecondary();
 const secondaryDB = secondary.getDB(dbName);
 
-// The primary will not generate the 'ns' field for index specs, but the secondary will.
-assert.commandWorked(
-    primary.getDB('admin').runCommand({setParameter: 1, disableIndexSpecNamespaceGeneration: 1}));
-
 assert.commandWorked(primaryColl.insert({x: 100}));
 assert.commandWorked(primaryColl.createIndex({x: 1}));
 
@@ -40,15 +31,11 @@ let specSecondary =
     assert.commandWorked(secondaryDB.runCommand({listIndexes: collName})).cursor.firstBatch[1];
 
 assert.eq(false, specPrimary.hasOwnProperty('ns'));
-assert.eq(true, specSecondary.hasOwnProperty('ns'));
-assert.eq(dbName + '.' + collName, specSecondary.ns);
+assert.eq(false, specSecondary.hasOwnProperty('ns'));
 
 replSet.stopSet(/*signal=*/null, /*forRestart=*/true);
 
-// The primaries index spec has no 'ns' field and the secondaries index spec does have the 'ns'
-// field. Restart the nodes as standalone and ensure that the primaries index spec gets updated
-// with the 'ns' field. No changes should be necessary to the secondaries index spec, but
-// verify that it still has the 'ns' field.
+// Both nodes should have no 'ns' field in the index spec on restart.
 const options = {
     dbpath: primary.dbpath,
     noCleanData: true
@@ -59,8 +46,7 @@ assert.neq(null, conn, 'mongod was unable to start up with options: ' + tojson(o
 let db = conn.getDB(dbName);
 let spec = assert.commandWorked(db.runCommand({listIndexes: collName})).cursor.firstBatch[1];
 
-assert.eq(true, spec.hasOwnProperty('ns'));
-assert.eq(dbName + '.' + collName, spec.ns);
+assert.eq(false, spec.hasOwnProperty('ns'));
 
 MongoRunner.stopMongod(conn);
 
@@ -71,8 +57,7 @@ assert.neq(null, conn, 'mongod was unable to start up with options: ' + tojson(o
 db = conn.getDB(dbName);
 spec = assert.commandWorked(db.runCommand({listIndexes: collName})).cursor.firstBatch[1];
 
-assert.eq(true, spec.hasOwnProperty('ns'));
-assert.eq(dbName + '.' + collName, spec.ns);
+assert.eq(false, spec.hasOwnProperty('ns'));
 
 MongoRunner.stopMongod(conn);
 }());
diff --git a/jstests/replsets/oplog_format_create_indexes.js b/jstests/replsets/oplog_format_create_indexes.js
index 117d5be04bb..5202a547e25 100644
--- a/jstests/replsets/oplog_format_create_indexes.js
+++ b/jstests/replsets/oplog_format_create_indexes.js
@@ -41,14 +41,10 @@ function testOplogEntryContainsIndexInfoObj(coll, keyPattern, indexOptions) {
 
     // Because of differences between the new and old oplog entries for createIndexes,
     // treat the namespace part separately and compare entries without ns field.
-    const indexSpecNs = indexSpec.ns;
-    delete indexSpec.ns;
     const found = allOplogEntries.filter((entry) => {
-        const entryNs = entry.o.ns || testDB.getName() + "." + entry.o.createIndexes;
         const entrySpec = entry.o;
-        delete entrySpec.ns;
         delete entrySpec.createIndexes;
-        return indexSpecNs === entryNs && bsonWoCompare(indexSpec, entrySpec) === 0;
+        return bsonWoCompare(indexSpec, entrySpec) === 0;
     });
     assert.eq(1,
               found.length,
diff --git a/src/mongo/db/catalog/SConscript b/src/mongo/db/catalog/SConscript
index c2a92d5acca..369017cd7d3 100644
--- a/src/mongo/db/catalog/SConscript
+++ b/src/mongo/db/catalog/SConscript
@@ -114,16 +114,6 @@ env.Library(
 )
 
 env.Library(
-        target='disable_index_spec_namespace_generation',
-        source=[
-            env.Idlc('disable_index_spec_namespace_generation.idl')[0],
-        ],
-        LIBDEPS_PRIVATE=[
-            '$BUILD_DIR/mongo/idl/server_parameter',
-        ],
-)
-
-env.Library(
     target='index_key_validate',
     source=[
         "index_key_validate.cpp",
@@ -138,9 +128,6 @@ env.Library(
         '$BUILD_DIR/mongo/db/query/collation/collator_factory_interface',
         '$BUILD_DIR/mongo/util/fail_point',
     ],
-    LIBDEPS_PRIVATE=[
-        'disable_index_spec_namespace_generation',
-    ],
 )
 
 env.Library(
@@ -331,7 +318,6 @@ env.Library(
     ],
     LIBDEPS_PRIVATE=[
         'index_build_block',
-        'disable_index_spec_namespace_generation',
         '$BUILD_DIR/mongo/db/catalog/collection_catalog_helper',
         '$BUILD_DIR/mongo/db/commands/server_status_core',
         '$BUILD_DIR/mongo/db/index/index_build_interceptor',
diff --git a/src/mongo/db/catalog/collection_impl.cpp b/src/mongo/db/catalog/collection_impl.cpp
index 6ebdaf1ec51..2d441c2b2f6 100644
--- a/src/mongo/db/catalog/collection_impl.cpp
+++ b/src/mongo/db/catalog/collection_impl.cpp
@@ -1051,7 +1051,6 @@ std::unique_ptr<PlanExecutor, PlanExecutor::Deleter> CollectionImpl::makePlanExe
 
 void CollectionImpl::setNs(NamespaceString nss) {
     _ns = std::move(nss);
-    _indexCatalog->setNs(_ns);
     _infoCache->setNs(_ns);
     _recordStore.get()->setNs(_ns);
 }
diff --git a/src/mongo/db/catalog/database_test.cpp b/src/mongo/db/catalog/database_test.cpp
index 542cae76e80..173e797851d 100644
--- a/src/mongo/db/catalog/database_test.cpp
+++ b/src/mongo/db/catalog/database_test.cpp
@@ -301,8 +301,7 @@ void _testDropCollectionThrowsExceptionIfThereAreIndexesInProgress(OperationCont
         ASSERT_EQUALS(indexCatalog->numIndexesInProgress(opCtx), 0);
         auto indexInfoObj = BSON("v" << int(IndexDescriptor::kLatestIndexVersion) << "key"
                                      << BSON("a" << 1) << "name"
-                                     << "a_1"
-                                     << "ns" << nss.ns());
+                                     << "a_1");
 
         auto indexBuildBlock = std::make_unique<IndexBuildBlock>(
             indexCatalog, collection->ns(), indexInfoObj, IndexBuildMethod::kHybrid);
diff --git a/src/mongo/db/catalog/disable_index_spec_namespace_generation.idl b/src/mongo/db/catalog/disable_index_spec_namespace_generation.idl
deleted file mode 100644
index c750956396c..00000000000
--- a/src/mongo/db/catalog/disable_index_spec_namespace_generation.idl
+++ /dev/null
@@ -1,41 +0,0 @@
-# Copyright (C) 2019-present MongoDB, Inc.
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the Server Side Public License, version 1,
-# as published by MongoDB, Inc.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# Server Side Public License for more details.
-#
-# You should have received a copy of the Server Side Public License
-# along with this program. If not, see
-# <http://www.mongodb.com/licensing/server-side-public-license>.
-#
-# As a special exception, the copyright holders give permission to link the
-# code of portions of this program with the OpenSSL library under certain
-# conditions as described in each individual source file and distribute
-# linked combinations including the program with the OpenSSL library. You
-# must comply with the Server Side Public License in all respects for
-# all of the code used other than as permitted herein. If you modify file(s)
-# with this exception, you may extend this exception to your version of the
-# file(s), but you are not obligated to do so. If you do not wish to do so,
-# delete this exception statement from your version. If you delete this
-# exception statement from all source files in the program, then also delete
-# it in the license file.
-#
-
-global:
-  cpp_namespace: "mongo"
-
-server_parameters:
-  disableIndexSpecNamespaceGeneration:
-    description: "If enabled, the 'ns' field will not be generated for index specs if it's missing."
-    set_at:
-      - startup
-      - runtime
-    cpp_vartype: AtomicWord<bool>
-    cpp_varname: "disableIndexSpecNamespaceGeneration"
-    default: false
-    test_only: true
diff --git a/src/mongo/db/catalog/index_builds_manager_test.cpp b/src/mongo/db/catalog/index_builds_manager_test.cpp
index df5e50d244c..3ca43d04039 100644
--- a/src/mongo/db/catalog/index_builds_manager_test.cpp
+++ b/src/mongo/db/catalog/index_builds_manager_test.cpp
@@ -75,8 +75,8 @@ std::vector<BSONObj> makeSpecs(const NamespaceString& nss, std::vector<std::stri
     ASSERT(keys.size());
     std::vector<BSONObj> indexSpecs;
     for (auto keyName : keys) {
-        indexSpecs.push_back(BSON("ns" << nss.toString() << "v" << 2 << "key" << BSON(keyName << 1)
-                                       << "name" << (keyName + "_1")));
+        indexSpecs.push_back(
+            BSON("v" << 2 << "key" << BSON(keyName << 1) << "name" << (keyName + "_1")));
     }
     return indexSpecs;
 }
diff --git a/src/mongo/db/catalog/index_catalog.h b/src/mongo/db/catalog/index_catalog.h
index de87ee6a172..8a069ea65a0 100644
--- a/src/mongo/db/catalog/index_catalog.h
+++ b/src/mongo/db/catalog/index_catalog.h
@@ -470,8 +470,6 @@ public:
                                             const IndexDescriptor* desc,
                                             InsertDeleteOptions* options) const = 0;
 
-    virtual void setNs(NamespaceString ns) = 0;
-
     virtual void indexBuildSuccess(OperationContext* opCtx, IndexCatalogEntry* index) = 0;
 };
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/index_catalog_entry.h b/src/mongo/db/catalog/index_catalog_entry.h
index de034469453..863718a57fc 100644
--- a/src/mongo/db/catalog/index_catalog_entry.h
+++ b/src/mongo/db/catalog/index_catalog_entry.h
@@ -138,8 +138,6 @@ public:
     virtual boost::optional<Timestamp> getMinimumVisibleSnapshot() = 0;
 
     virtual void setMinimumVisibleSnapshot(const Timestamp name) = 0;
-
-    virtual void setNs(NamespaceString ns) = 0;
 };
 
 class IndexCatalogEntryContainer {
diff --git a/src/mongo/db/catalog/index_catalog_entry_impl.cpp b/src/mongo/db/catalog/index_catalog_entry_impl.cpp
index 9a30dfc9687..1cd68cd0900 100644
--- a/src/mongo/db/catalog/index_catalog_entry_impl.cpp
+++ b/src/mongo/db/catalog/index_catalog_entry_impl.cpp
@@ -37,6 +37,7 @@
 #include <memory>
 
 #include "mongo/base/init.h"
+#include "mongo/db/catalog/collection.h"
 #include "mongo/db/catalog/collection_info_cache_impl.h"
 #include "mongo/db/concurrency/d_concurrency.h"
 #include "mongo/db/concurrency/write_conflict_exception.h"
@@ -59,15 +60,14 @@ namespace mongo {
 using std::string;
 
 IndexCatalogEntryImpl::IndexCatalogEntryImpl(OperationContext* const opCtx,
-                                             const NamespaceString& nss,
                                              std::unique_ptr<IndexDescriptor> descriptor,
                                              CollectionInfoCache* const infoCache)
-    : _ns(nss),
-      _descriptor(std::move(descriptor)),
+    : _descriptor(std::move(descriptor)),
       _infoCache(infoCache),
       _ordering(Ordering::make(_descriptor->keyPattern())),
       _isReady(false),
-      _prefix(DurableCatalog::get(opCtx)->getIndexPrefix(opCtx, nss, _descriptor->indexName())) {
+      _prefix(DurableCatalog::get(opCtx)->getIndexPrefix(
+          opCtx, _descriptor->parentNS(), _descriptor->indexName())) {
     _descriptor->_cachedEntry = this;
 
     _isReady = _catalogIsReady(opCtx);
@@ -104,7 +104,7 @@ IndexCatalogEntryImpl::IndexCatalogEntryImpl(OperationContext* const opCtx,
                                          MatchExpressionParser::kBanAllSpecialFeatures);
         invariant(statusWithMatcher.getStatus());
         _filterExpression = std::move(statusWithMatcher.getValue());
-        LOG(2) << "have filter expression for " << _ns << " " << _descriptor->indexName() << " "
+        LOG(2) << "have filter expression for " << ns() << " " << _descriptor->indexName() << " "
                << redact(filter);
     }
 }
@@ -115,6 +115,10 @@ IndexCatalogEntryImpl::~IndexCatalogEntryImpl() {
     _descriptor.reset();
 }
 
+const NamespaceString& IndexCatalogEntryImpl::ns() const {
+    return _descriptor->parentNS();
+}
+
 void IndexCatalogEntryImpl::init(std::unique_ptr<IndexAccessMethod> accessMethod) {
     invariant(!_accessMethod);
     _accessMethod = std::move(accessMethod);
@@ -157,7 +161,7 @@ bool IndexCatalogEntryImpl::isMultikey(OperationContext* opCtx) const {
     }
 
     for (const MultikeyPathInfo& path : txnParticipant.getUncommittedMultikeyPathInfos()) {
-        if (path.nss == NamespaceString(_ns) && path.indexName == _descriptor->indexName()) {
+        if (path.nss == ns() && path.indexName == _descriptor->indexName()) {
             return true;
         }
     }
@@ -175,7 +179,7 @@ MultikeyPaths IndexCatalogEntryImpl::getMultikeyPaths(OperationContext* opCtx) c
 
     MultikeyPaths ret = _indexMultikeyPaths;
     for (const MultikeyPathInfo& path : txnParticipant.getUncommittedMultikeyPathInfos()) {
-        if (path.nss == NamespaceString(_ns) && path.indexName == _descriptor->indexName()) {
+        if (path.nss == ns() && path.indexName == _descriptor->indexName()) {
             MultikeyPathTracker::mergeMultikeyPaths(&ret, path.multikeyPaths);
         }
     }
@@ -251,7 +255,7 @@ void IndexCatalogEntryImpl::setMultikey(OperationContext* opCtx,
     // OperationContext and we can safely defer that write to the end of the batch.
     if (MultikeyPathTracker::get(opCtx).isTrackingMultikeyPathInfo()) {
         MultikeyPathInfo info;
-        info.nss = _ns;
+        info.nss = ns();
         info.indexName = _descriptor->indexName();
         info.multikeyPaths = paths;
         MultikeyPathTracker::get(opCtx).addMultikeyPathInfo(info);
@@ -279,7 +283,7 @@ void IndexCatalogEntryImpl::setMultikey(OperationContext* opCtx,
         }
 
         if (indexMetadataHasChanged && _infoCache) {
-            LOG(1) << _ns << ": clearing plan cache - index " << _descriptor->keyPattern()
+            LOG(1) << ns() << ": clearing plan cache - index " << _descriptor->keyPattern()
                    << " set to multi key.";
             _infoCache->clearQueryCache();
         }
@@ -294,7 +298,7 @@ void IndexCatalogEntryImpl::setMultikey(OperationContext* opCtx,
     auto txnParticipant = TransactionParticipant::get(opCtx);
     if (txnParticipant && txnParticipant.inMultiDocumentTransaction()) {
         TransactionParticipant::SideTransactionBlock sideTxn(opCtx);
-        writeConflictRetry(opCtx, "set index multikey", _ns.ns(), [&] {
+        writeConflictRetry(opCtx, "set index multikey", ns().ns(), [&] {
             WriteUnitOfWork wuow(opCtx);
 
             // If we have a prepare optime for recovery, then we always use that. During recovery of
@@ -316,7 +320,7 @@ void IndexCatalogEntryImpl::setMultikey(OperationContext* opCtx,
             }
             fassert(31164, status);
             indexMetadataHasChanged = DurableCatalog::get(opCtx)->setIndexIsMultikey(
-                opCtx, _ns, _descriptor->indexName(), paths);
+                opCtx, ns(), _descriptor->indexName(), paths);
             opCtx->recoveryUnit()->onCommit(
                 [onMultikeyCommitFn, indexMetadataHasChanged](boost::optional<Timestamp>) {
                     onMultikeyCommitFn(indexMetadataHasChanged);
@@ -325,7 +329,7 @@ void IndexCatalogEntryImpl::setMultikey(OperationContext* opCtx,
         });
     } else {
         indexMetadataHasChanged = DurableCatalog::get(opCtx)->setIndexIsMultikey(
-            opCtx, _ns, _descriptor->indexName(), paths);
+            opCtx, ns(), _descriptor->indexName(), paths);
     }
 
     opCtx->recoveryUnit()->onCommit(
@@ -342,33 +346,28 @@ void IndexCatalogEntryImpl::setMultikey(OperationContext* opCtx,
     // previous write in the transaction.
     if (txnParticipant && txnParticipant.inMultiDocumentTransaction()) {
         txnParticipant.addUncommittedMultikeyPathInfo(
-            MultikeyPathInfo{_ns, _descriptor->indexName(), std::move(paths)});
+            MultikeyPathInfo{ns(), _descriptor->indexName(), std::move(paths)});
     }
 }
 
-void IndexCatalogEntryImpl::setNs(NamespaceString ns) {
-    _ns = ns;
-    _descriptor->setNs(std::move(ns));
-}
-
 // ----
 
 bool IndexCatalogEntryImpl::_catalogIsReady(OperationContext* opCtx) const {
-    return DurableCatalog::get(opCtx)->isIndexReady(opCtx, _ns, _descriptor->indexName());
+    return DurableCatalog::get(opCtx)->isIndexReady(opCtx, ns(), _descriptor->indexName());
 }
 
 bool IndexCatalogEntryImpl::_catalogIsPresent(OperationContext* opCtx) const {
-    return DurableCatalog::get(opCtx)->isIndexPresent(opCtx, _ns, _descriptor->indexName());
+    return DurableCatalog::get(opCtx)->isIndexPresent(opCtx, ns(), _descriptor->indexName());
 }
 
 bool IndexCatalogEntryImpl::_catalogIsMultikey(OperationContext* opCtx,
                                                MultikeyPaths* multikeyPaths) const {
     return DurableCatalog::get(opCtx)->isIndexMultikey(
-        opCtx, _ns, _descriptor->indexName(), multikeyPaths);
+        opCtx, ns(), _descriptor->indexName(), multikeyPaths);
 }
 
 KVPrefix IndexCatalogEntryImpl::_catalogGetPrefix(OperationContext* opCtx) const {
-    return DurableCatalog::get(opCtx)->getIndexPrefix(opCtx, _ns, _descriptor->indexName());
+    return DurableCatalog::get(opCtx)->getIndexPrefix(opCtx, ns(), _descriptor->indexName());
 }
 
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/index_catalog_entry_impl.h b/src/mongo/db/catalog/index_catalog_entry_impl.h
index cb697a3d177..525b003b878 100644
--- a/src/mongo/db/catalog/index_catalog_entry_impl.h
+++ b/src/mongo/db/catalog/index_catalog_entry_impl.h
@@ -59,17 +59,12 @@ class IndexCatalogEntryImpl : public IndexCatalogEntry {
 public:
     explicit IndexCatalogEntryImpl(
         OperationContext* opCtx,
-        const NamespaceString& nss,
         std::unique_ptr<IndexDescriptor> descriptor,  // ownership passes to me
         CollectionInfoCache* infoCache);              // not owned, optional
 
     ~IndexCatalogEntryImpl() final;
 
-    const NamespaceString& ns() const final {
-        return _ns;
-    }
-
-    void setNs(NamespaceString ns) final;
+    const NamespaceString& ns() const final;
 
     void init(std::unique_ptr<IndexAccessMethod> accessMethod) final;
 
@@ -192,8 +187,6 @@ private:
 
     // -----
 
-    NamespaceString _ns;
-
     std::unique_ptr<IndexDescriptor> _descriptor;  // owned here
 
     CollectionInfoCache* _infoCache;  // not owned here
diff --git a/src/mongo/db/catalog/index_catalog_impl.cpp b/src/mongo/db/catalog/index_catalog_impl.cpp
index a4d4c6ec5b8..261f656d77c 100644
--- a/src/mongo/db/catalog/index_catalog_impl.cpp
+++ b/src/mongo/db/catalog/index_catalog_impl.cpp
@@ -41,7 +41,6 @@
 #include "mongo/db/audit.h"
 #include "mongo/db/background.h"
 #include "mongo/db/catalog/collection.h"
-#include "mongo/db/catalog/disable_index_spec_namespace_generation_gen.h"
 #include "mongo/db/catalog/index_build_block.h"
 #include "mongo/db/catalog/index_catalog_entry_impl.h"
 #include "mongo/db/catalog/index_key_validate.h"
@@ -373,7 +372,7 @@ IndexCatalogEntry* IndexCatalogImpl::createIndexEntry(OperationContext* opCtx,
 
     auto* const descriptorPtr = descriptor.get();
     auto entry = std::make_shared<IndexCatalogEntryImpl>(
-        opCtx, _collection->ns(), std::move(descriptor), _collection->infoCache());
+        opCtx, std::move(descriptor), _collection->infoCache());
 
     IndexDescriptor* desc = entry->descriptor();
 
@@ -531,21 +530,6 @@ Status IndexCatalogImpl::_isSpecOk(OperationContext* opCtx, const BSONObj& spec)
     if (nss.isOplog())
         return Status(ErrorCodes::CannotCreateIndex, "cannot have an index on the oplog");
 
-    // If we stop generating the 'ns' field for index specs during testing, then we shouldn't
-    // validate that the 'ns' field is missing.
-    if (!disableIndexSpecNamespaceGeneration.load()) {
-        const BSONElement specNamespace = spec["ns"];
-        if (specNamespace.type() != String)
-            return Status(ErrorCodes::CannotCreateIndex,
-                          "the index spec is missing a \"ns\" string field");
-
-        if (nss.ns() != specNamespace.valueStringData())
-            return Status(ErrorCodes::CannotCreateIndex,
-                          str::stream() << "the \"ns\" field of the index spec '"
-                                        << specNamespace.valueStringData()
-                                        << "' does not match the collection name '" << nss << "'");
-    }
-
     // logical name of the index
     const BSONElement nameElem = spec["name"];
     if (nameElem.type() != String)
@@ -811,7 +795,6 @@ BSONObj IndexCatalogImpl::getDefaultIdIndexSpec() const {
     BSONObjBuilder b;
     b.append("v", static_cast<int>(indexVersion));
     b.append("name", "_id_");
-    b.append("ns", _collection->ns().ns());
     b.append("key", _idObj);
     if (_collection->getDefaultCollator() && indexVersion >= IndexVersion::kV2) {
         // Creating an index with the "collation" option requires a v=2 index.
@@ -1660,6 +1643,14 @@ StatusWith<BSONObj> IndexCatalogImpl::_fixIndexSpec(OperationContext* opCtx,
     }
     b.append("name", name);
 
+    // During repair, if the 'ns' field exists in the index spec, do not remove it as repair can be
+    // running on old data files from other mongod versions. Removing the 'ns' field during repair
+    // would prevent the data files from starting up on the original mongod version as the 'ns'
+    // field is required to be present in 3.6 and 4.0.
+    if (storageGlobalParams.repair && o.hasField("ns")) {
+        b.append("ns", o.getField("ns").String());
+    }
+
     {
         BSONObjIterator i(o);
         while (i.more()) {
@@ -1668,8 +1659,9 @@ StatusWith<BSONObj> IndexCatalogImpl::_fixIndexSpec(OperationContext* opCtx,
 
             if (s == "_id") {
                 // skip
-            } else if (s == "dropDups") {
+            } else if (s == "dropDups" || s == "ns") {
                 // dropDups is silently ignored and removed from the spec as of SERVER-14710.
+                // ns is removed from the spec as of 4.4.
             } else if (s == "v" || s == "unique" || s == "key" || s == "name") {
                 // covered above
             } else {
@@ -1681,13 +1673,4 @@ StatusWith<BSONObj> IndexCatalogImpl::_fixIndexSpec(OperationContext* opCtx,
     return b.obj();
 }
 
-void IndexCatalogImpl::setNs(NamespaceString ns) {
-    for (auto&& ice : _readyIndexes) {
-        ice->setNs(ns);
-    }
-
-    for (auto&& ice : _buildingIndexes) {
-        ice->setNs(ns);
-    }
-}
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/index_catalog_impl.h b/src/mongo/db/catalog/index_catalog_impl.h
index 813c90b3d4e..9eecee90e52 100644
--- a/src/mongo/db/catalog/index_catalog_impl.h
+++ b/src/mongo/db/catalog/index_catalog_impl.h
@@ -296,8 +296,6 @@ public:
                                     const IndexDescriptor* desc,
                                     InsertDeleteOptions* options) const override;
 
-    void setNs(NamespaceString ns) override;
-
     void indexBuildSuccess(OperationContext* opCtx, IndexCatalogEntry* index) override;
 
 private:
diff --git a/src/mongo/db/catalog/index_catalog_noop.h b/src/mongo/db/catalog/index_catalog_noop.h
index a9caf06f132..8590d18b37d 100644
--- a/src/mongo/db/catalog/index_catalog_noop.h
+++ b/src/mongo/db/catalog/index_catalog_noop.h
@@ -236,8 +236,6 @@ public:
                                     const IndexDescriptor* desc,
                                     InsertDeleteOptions* options) const override {}
 
-    void setNs(NamespaceString ns) override {}
-
     void indexBuildSuccess(OperationContext* opCtx, IndexCatalogEntry* index) override {}
 };
 
diff --git a/src/mongo/db/catalog/index_key_validate.cpp b/src/mongo/db/catalog/index_key_validate.cpp
index 2bc450516fb..83c6812f5b1 100644
--- a/src/mongo/db/catalog/index_key_validate.cpp
+++ b/src/mongo/db/catalog/index_key_validate.cpp
@@ -40,7 +40,6 @@
 
 #include "mongo/base/status.h"
 #include "mongo/base/status_with.h"
-#include "mongo/db/catalog/disable_index_spec_namespace_generation_gen.h"
 #include "mongo/db/field_ref.h"
 #include "mongo/db/index/index_descriptor.h"
 #include "mongo/db/index/wildcard_key_generator.h"
@@ -255,7 +254,6 @@ BSONObj removeUnknownFields(const BSONObj& indexSpec) {
 StatusWith<BSONObj> validateIndexSpec(
     OperationContext* opCtx,
     const BSONObj& indexSpec,
-    const NamespaceString& expectedNamespace,
     const ServerGlobalParams::FeatureCompatibility& featureCompatibility) {
     bool hasKeyPatternField = false;
     bool hasIndexNameField = false;
@@ -327,28 +325,6 @@ StatusWith<BSONObj> validateIndexSpec(
 
             hasIndexNameField = true;
         } else if (IndexDescriptor::kNamespaceFieldName == indexSpecElemFieldName) {
-            if (indexSpecElem.type() != BSONType::String) {
-                return {ErrorCodes::TypeMismatch,
-                        str::stream()
-                            << "The field '" << IndexDescriptor::kNamespaceFieldName
-                            << "' must be a string, but got " << typeName(indexSpecElem.type())};
-            }
-
-            StringData ns = indexSpecElem.valueStringData();
-            if (ns.empty()) {
-                return {ErrorCodes::BadValue,
-                        str::stream() << "The field '" << IndexDescriptor::kNamespaceFieldName
-                                      << "' cannot be an empty string"};
-            }
-
-            if (ns != expectedNamespace.ns()) {
-                return {ErrorCodes::BadValue,
-                        str::stream()
-                            << "The value of the field '" << IndexDescriptor::kNamespaceFieldName
-                            << "' (" << ns << ") doesn't match the namespace '" << expectedNamespace
-                            << "'"};
-            }
-
             hasNamespaceField = true;
         } else if (IndexDescriptor::kIndexVersionFieldName == indexSpecElemFieldName) {
             if (!indexSpecElem.isNumber()) {
@@ -485,29 +461,24 @@ StatusWith<BSONObj> validateIndexSpec(
                               << static_cast<int>(*resolvedIndexVersion)};
     }
 
-    if (!hasNamespaceField || !hasVersionField) {
-        BSONObjBuilder bob;
+    BSONObj modifiedSpec = indexSpec;
 
-        // Only generate the 'ns' field for the index spec if it's missing it and if the server test
-        // parameter to disable the generation isn't enabled.
-        if (!hasNamespaceField && !disableIndexSpecNamespaceGeneration.load()) {
-            // We create a new index specification with the 'ns' field set as 'expectedNamespace' if
-            // the field was omitted.
-            bob.append(IndexDescriptor::kNamespaceFieldName, expectedNamespace.ns());
-        }
-
-        if (!hasVersionField) {
-            // We create a new index specification with the 'v' field set as 'defaultIndexVersion'
-            // if the field was omitted.
-            bob.append(IndexDescriptor::kIndexVersionFieldName,
-                       static_cast<int>(*resolvedIndexVersion));
-        }
+    // Ignore any 'ns' field in the index spec because this field is dropped post-4.0. Don't remove
+    // the field during repair, as repair may run on old data files (version 3.6 and 4.0) that
+    // require the field to be present.
+    if (hasNamespaceField && !storageGlobalParams.repair) {
+        modifiedSpec = modifiedSpec.removeField(IndexDescriptor::kNamespaceFieldName);
+    }
 
-        bob.appendElements(indexSpec);
-        return bob.obj();
+    if (!hasVersionField) {
+        // We create a new index specification with the 'v' field set as 'defaultIndexVersion' if
+        // the field was omitted.
+        BSONObj versionObj = BSON(IndexDescriptor::kIndexVersionFieldName
+                                  << static_cast<int>(*resolvedIndexVersion));
+        modifiedSpec = modifiedSpec.addField(versionObj.firstElement());
     }
 
-    return indexSpec;
+    return modifiedSpec;
 }
 
 Status validateIdIndexSpec(const BSONObj& indexSpec) {
diff --git a/src/mongo/db/catalog/index_key_validate.h b/src/mongo/db/catalog/index_key_validate.h
index 52ba7fd3ed2..7c177c50355 100644
--- a/src/mongo/db/catalog/index_key_validate.h
+++ b/src/mongo/db/catalog/index_key_validate.h
@@ -58,7 +58,6 @@ Status validateKeyPattern(const BSONObj& key, IndexDescriptor::IndexVersion inde
 StatusWith<BSONObj> validateIndexSpec(
     OperationContext* opCtx,
     const BSONObj& indexSpec,
-    const NamespaceString& expectedNamespace,
     const ServerGlobalParams::FeatureCompatibility& featureCompatibility);
 
 /**
diff --git a/src/mongo/db/catalog/index_spec_validate_test.cpp b/src/mongo/db/catalog/index_spec_validate_test.cpp
index 6b472d09073..cb2d66df78f 100644
--- a/src/mongo/db/catalog/index_spec_validate_test.cpp
+++ b/src/mongo/db/catalog/index_spec_validate_test.cpp
@@ -55,7 +55,6 @@ using index_key_validate::validateIndexSpec;
 using index_key_validate::validateIndexSpecCollation;
 using unittest::EnsureFCV;
 
-const NamespaceString kTestNamespace("test", "index_spec_validate");
 constexpr OperationContext* kDefaultOpCtx = nullptr;
 
 /**
@@ -75,7 +74,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfKeyPatternIsNotAnObject) {
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << 1 << "name"
                                            << "indexName"),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::TypeMismatch,
               validateIndexSpec(kDefaultOpCtx,
@@ -83,13 +81,11 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfKeyPatternIsNotAnObject) {
                                      << "not an object"
                                      << "name"
                                      << "indexName"),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::TypeMismatch,
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSONArray() << "name"
                                            << "indexName"),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -98,7 +94,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfFieldRepeatedInKeyPattern) {
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSON("field" << 1 << "field" << 1) << "name"
                                            << "indexName"),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::BadValue,
               validateIndexSpec(kDefaultOpCtx,
@@ -106,7 +101,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfFieldRepeatedInKeyPattern) {
                                                            << "2dsphere")
                                            << "name"
                                            << "indexName"),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -115,7 +109,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfKeyPatternIsNotPresent) {
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("name"
                                      << "indexName"),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -123,7 +116,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfNameIsNotAString) {
     ASSERT_EQ(ErrorCodes::TypeMismatch,
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSON("field" << 1) << "name" << 1),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -131,93 +123,20 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfNameIsNotPresent) {
     ASSERT_EQ(ErrorCodes::FailedToParse,
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSON("field" << 1)),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
-TEST(IndexSpecValidateTest, ReturnsAnErrorIfNamespaceIsNotAString) {
-    ASSERT_EQ(ErrorCodes::TypeMismatch,
-              validateIndexSpec(kDefaultOpCtx,
-                                BSON("key" << BSON("field" << 1) << "name"
-                                           << "indexName"
-                                           << "ns" << 1),
-                                kTestNamespace,
-                                serverGlobalParams.featureCompatibility));
-    ASSERT_EQ(ErrorCodes::TypeMismatch,
-              validateIndexSpec(kDefaultOpCtx,
-                                BSON("key" << BSON("field" << 1) << "name"
-                                           << "indexName"
-                                           << "ns" << BSONObj()),
-                                kTestNamespace,
-                                serverGlobalParams.featureCompatibility));
-}
-
-TEST(IndexSpecValidateTest, ReturnsAnErrorIfNamespaceIsEmptyString) {
-    ASSERT_EQ(ErrorCodes::BadValue,
-              validateIndexSpec(kDefaultOpCtx,
-                                BSON("key" << BSON("field" << 1) << "name"
-                                           << "indexName"
-                                           << "ns"
-                                           << ""),
-                                NamespaceString(),
-                                serverGlobalParams.featureCompatibility));
-}
-
-TEST(IndexSpecValidateTest, ReturnsAnErrorIfNamespaceDoesNotMatch) {
-    ASSERT_EQ(ErrorCodes::BadValue,
-              validateIndexSpec(kDefaultOpCtx,
-                                BSON("key" << BSON("field" << 1) << "name"
-                                           << "indexName"
-                                           << "ns"
-                                           << "some string"),
-                                kTestNamespace,
-                                serverGlobalParams.featureCompatibility));
-
-    // Verify that we reject the index specification when the "ns" field only contains the
-    // collection name.
-    ASSERT_EQ(ErrorCodes::BadValue,
-              validateIndexSpec(kDefaultOpCtx,
-                                BSON("key" << BSON("field" << 1) << "name"
-                                           << "indexName"
-                                           << "ns" << kTestNamespace.coll()),
-                                kTestNamespace,
-                                serverGlobalParams.featureCompatibility));
-}
-
-TEST(IndexSpecValidateTest, ReturnsIndexSpecWithNamespaceFilledInIfItIsNotPresent) {
+TEST(IndexSpecValidateTest, ReturnsIndexSpecUnchangedIfVersionIsPresent) {
     auto result = validateIndexSpec(kDefaultOpCtx,
                                     BSON("key" << BSON("field" << 1) << "name"
                                                << "indexName"
                                                << "v" << 1),
-                                    kTestNamespace,
-                                    serverGlobalParams.featureCompatibility);
-    ASSERT_OK(result.getStatus());
-
-    // We don't care about the order of the fields in the resulting index specification.
-    ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
-                                        << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 1)),
-                      sorted(result.getValue()));
-
-    // Verify that the index specification we returned is still considered valid.
-    ASSERT_OK(validateIndexSpec(
-        kDefaultOpCtx, result.getValue(), kTestNamespace, serverGlobalParams.featureCompatibility));
-}
-
-TEST(IndexSpecValidateTest, ReturnsIndexSpecUnchangedIfNamespaceAndVersionArePresent) {
-    auto result = validateIndexSpec(kDefaultOpCtx,
-                                    BSON("key" << BSON("field" << 1) << "name"
-                                               << "indexName"
-                                               << "ns" << kTestNamespace.ns() << "v" << 1),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 
     // We don't care about the order of the fields in the resulting index specification.
     ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
                                         << "indexName"
-                                        << "ns"
-                                        << "test.index_spec_validate"
                                         << "v" << 1)),
                       sorted(result.getValue()));
 }
@@ -229,14 +148,12 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfVersionIsNotANumber) {
                                            << "indexName"
                                            << "v"
                                            << "not a number"),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::TypeMismatch,
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "v" << BSONObj()),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -246,28 +163,24 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfVersionIsNotRepresentableAsInt) {
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "v" << 2.2),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::BadValue,
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "v" << std::nan("1")),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::BadValue,
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "v" << std::numeric_limits<double>::infinity()),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::BadValue,
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "v" << std::numeric_limits<long long>::max()),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -277,7 +190,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfVersionIsV0) {
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "v" << 0),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -289,7 +201,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfVersionIsUnsupported) {
                                            << "v" << 3 << "collation"
                                            << BSON("locale"
                                                    << "en")),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 
     ASSERT_EQ(ErrorCodes::CannotCreateIndex,
@@ -297,7 +208,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfVersionIsUnsupported) {
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "v" << -3LL),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -306,49 +216,45 @@ TEST(IndexSpecValidateTest, AcceptsIndexVersionsThatAreAllowedForCreation) {
                                     BSON("key" << BSON("field" << 1) << "name"
                                                << "indexName"
                                                << "v" << 1),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 
     // We don't care about the order of the fields in the resulting index specification.
     ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
                                         << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 1)),
+                                        << "v" << 1)),
                       sorted(result.getValue()));
 
     result = validateIndexSpec(kDefaultOpCtx,
                                BSON("key" << BSON("field" << 1) << "name"
                                           << "indexName"
                                           << "v" << 2LL),
-                               kTestNamespace,
                                serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 
     // We don't care about the order of the fields in the resulting index specification.
     ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
                                         << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 2LL)),
+                                        << "v" << 2LL)),
                       sorted(result.getValue()));
 }
 
 TEST(IndexSpecValidateTest, DefaultIndexVersionIsV2) {
     auto result = validateIndexSpec(kDefaultOpCtx,
                                     BSON("key" << BSON("field" << 1) << "name"
-                                               << "indexName"
-                                               << "ns" << kTestNamespace.ns()),
-                                    kTestNamespace,
+                                               << "indexName"),
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 
     // We don't care about the order of the fields in the resulting index specification.
     ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
                                         << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 2)),
+                                        << "v" << 2)),
                       sorted(result.getValue()));
 
     // Verify that the index specification we returned is still considered valid.
     ASSERT_OK(validateIndexSpec(
-        kDefaultOpCtx, result.getValue(), kTestNamespace, serverGlobalParams.featureCompatibility));
+        kDefaultOpCtx, result.getValue(), serverGlobalParams.featureCompatibility));
 }
 
 TEST(IndexSpecValidateTest, AcceptsIndexVersionV1) {
@@ -356,14 +262,13 @@ TEST(IndexSpecValidateTest, AcceptsIndexVersionV1) {
                                     BSON("key" << BSON("field" << 1) << "name"
                                                << "indexName"
                                                << "v" << 1),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 
     // We don't care about the order of the fields in the resulting index specification.
     ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
                                         << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 1)),
+                                        << "v" << 1)),
                       sorted(result.getValue()));
 }
 
@@ -373,7 +278,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfCollationIsNotAnObject) {
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "collation" << 1),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::TypeMismatch,
               validateIndexSpec(kDefaultOpCtx,
@@ -381,14 +285,12 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfCollationIsNotAnObject) {
                                            << "indexName"
                                            << "collation"
                                            << "not an object"),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
     ASSERT_EQ(ErrorCodes::TypeMismatch,
               validateIndexSpec(kDefaultOpCtx,
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "collation" << BSONArray()),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -398,7 +300,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfCollationIsEmpty) {
                                 BSON("key" << BSON("field" << 1) << "name"
                                            << "indexName"
                                            << "collation" << BSONObj()),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -411,7 +312,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfCollationIsPresentAndVersionIsLessTh
                                            << BSON("locale"
                                                    << "simple")
                                            << "v" << 1),
-                                kTestNamespace,
                                 serverGlobalParams.featureCompatibility));
 }
 
@@ -422,14 +322,13 @@ TEST(IndexSpecValidateTest, AcceptsAnyNonEmptyObjectValueForCollation) {
                                                << "v" << 2 << "collation"
                                                << BSON("locale"
                                                        << "simple")),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 
     // We don't care about the order of the fields in the resulting index specification.
     ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
                                         << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 2 << "collation"
+                                        << "v" << 2 << "collation"
                                         << BSON("locale"
                                                 << "simple"))),
                       sorted(result.getValue()));
@@ -439,16 +338,15 @@ TEST(IndexSpecValidateTest, AcceptsAnyNonEmptyObjectValueForCollation) {
                                           << "indexName"
                                           << "v" << 2 << "collation"
                                           << BSON("unknownCollationOption" << true)),
-                               kTestNamespace,
                                serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 
     // We don't care about the order of the fields in the resulting index specification.
-    ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
-                                        << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 2 << "collation"
-                                        << BSON("unknownCollationOption" << true))),
-                      sorted(result.getValue()));
+    ASSERT_BSONOBJ_EQ(
+        sorted(BSON("key" << BSON("field" << 1) << "name"
+                          << "indexName"
+                          << "v" << 2 << "collation" << BSON("unknownCollationOption" << true))),
+        sorted(result.getValue()));
 }
 
 TEST(IndexSpecValidateTest, AcceptsIndexSpecIfCollationIsPresentAndVersionIsEqualToV2) {
@@ -458,14 +356,13 @@ TEST(IndexSpecValidateTest, AcceptsIndexSpecIfCollationIsPresentAndVersionIsEqua
                                                << "v" << 2 << "collation"
                                                << BSON("locale"
                                                        << "en")),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 
     // We don't care about the order of the fields in the resulting index specification.
     ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
                                         << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 2 << "collation"
+                                        << "v" << 2 << "collation"
                                         << BSON("locale"
                                                 << "en"))),
                       sorted(result.getValue()));
@@ -476,7 +373,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfUnknownFieldIsPresentInSpecV2) {
                                     BSON("key" << BSON("field" << 1) << "name"
                                                << "indexName"
                                                << "v" << 2 << "unknownField" << 1),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(ErrorCodes::InvalidIndexSpecificationOption, result);
 }
@@ -486,7 +382,6 @@ TEST(IndexSpecValidateTest, ReturnsAnErrorIfUnknownFieldIsPresentInSpecV1) {
                                     BSON("key" << BSON("field" << 1) << "name"
                                                << "indexName"
                                                << "v" << 1 << "unknownField" << 1),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(ErrorCodes::InvalidIndexSpecificationOption, result);
 }
@@ -495,59 +390,53 @@ TEST(IdIndexSpecValidateTest, ReturnsAnErrorIfKeyPatternIsIncorrectForIdIndex) {
     ASSERT_EQ(ErrorCodes::BadValue,
               validateIdIndexSpec(BSON("key" << BSON("_id" << -1) << "name"
                                              << "_id_"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2)));
+                                             << "v" << 2)));
     ASSERT_EQ(ErrorCodes::BadValue,
               validateIdIndexSpec(BSON("key" << BSON("a" << 1) << "name"
                                              << "_id_"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2)));
+                                             << "v" << 2)));
 }
 
 TEST(IdIndexSpecValidateTest, ReturnsOKStatusIfKeyPatternCorrectForIdIndex) {
     ASSERT_OK(validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
                                              << "anyname"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2)));
+                                             << "v" << 2)));
 }
 
 TEST(IdIndexSpecValidateTest, ReturnsAnErrorIfFieldNotAllowedForIdIndex) {
     ASSERT_EQ(ErrorCodes::InvalidIndexSpecificationOption,
               validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
                                              << "_id_"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2
-                                             << "background" << false)));
+                                             << "v" << 2 << "background" << false)));
     ASSERT_EQ(ErrorCodes::InvalidIndexSpecificationOption,
               validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
                                              << "_id_"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2 << "unique"
-                                             << true)));
+                                             << "v" << 2 << "unique" << true)));
     ASSERT_EQ(ErrorCodes::InvalidIndexSpecificationOption,
               validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
                                              << "_id_"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2
-                                             << "partialFilterExpression" << BSON("a" << 5))));
+                                             << "v" << 2 << "partialFilterExpression"
+                                             << BSON("a" << 5))));
     ASSERT_EQ(ErrorCodes::InvalidIndexSpecificationOption,
               validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
                                              << "_id_"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2 << "sparse"
-                                             << false)));
+                                             << "v" << 2 << "sparse" << false)));
     ASSERT_EQ(ErrorCodes::InvalidIndexSpecificationOption,
               validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
                                              << "_id_"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2
-                                             << "expireAfterSeconds" << 3600)));
+                                             << "v" << 2 << "expireAfterSeconds" << 3600)));
     ASSERT_EQ(ErrorCodes::InvalidIndexSpecificationOption,
               validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
                                              << "_id_"
-                                             << "ns" << kTestNamespace.ns() << "v" << 2
-                                             << "storageEngine" << BSONObj())));
+                                             << "v" << 2 << "storageEngine" << BSONObj())));
 }
 
 TEST(IdIndexSpecValidateTest, ReturnsOKStatusIfAllFieldsAllowedForIdIndex) {
-    ASSERT_OK(
-        validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
-                                       << "_id_"
-                                       << "ns" << kTestNamespace.ns() << "v" << 2 << "collation"
-                                       << BSON("locale"
-                                               << "simple"))));
+    ASSERT_OK(validateIdIndexSpec(BSON("key" << BSON("_id" << 1) << "name"
+                                             << "_id_"
+                                             << "v" << 2 << "collation"
+                                             << BSON("locale"
+                                                     << "simple"))));
 }
 
 TEST(IndexSpecCollationValidateTest, FillsInFullCollationSpec) {
@@ -559,8 +448,7 @@ TEST(IndexSpecCollationValidateTest, FillsInFullCollationSpec) {
     auto result = validateIndexSpecCollation(opCtx.get(),
                                              BSON("key" << BSON("field" << 1) << "name"
                                                         << "indexName"
-                                                        << "ns" << kTestNamespace.ns() << "v" << 2
-                                                        << "collation"
+                                                        << "v" << 2 << "collation"
                                                         << BSON("locale"
                                                                 << "mock_reverse_string")),
                                              defaultCollator);
@@ -570,7 +458,7 @@ TEST(IndexSpecCollationValidateTest, FillsInFullCollationSpec) {
     ASSERT_BSONOBJ_EQ(
         sorted(BSON("key" << BSON("field" << 1) << "name"
                           << "indexName"
-                          << "ns" << kTestNamespace.ns() << "v" << 2 << "collation"
+                          << "v" << 2 << "collation"
                           << BSON("locale"
                                   << "mock_reverse_string"
                                   << "caseLevel" << false << "caseFirst"
@@ -593,8 +481,7 @@ TEST(IndexSpecCollationValidateTest, RemovesCollationFieldIfSimple) {
     auto result = validateIndexSpecCollation(opCtx.get(),
                                              BSON("key" << BSON("field" << 1) << "name"
                                                         << "indexName"
-                                                        << "ns" << kTestNamespace.ns() << "v" << 2
-                                                        << "collation"
+                                                        << "v" << 2 << "collation"
                                                         << BSON("locale"
                                                                 << "simple")),
                                              defaultCollator);
@@ -603,7 +490,7 @@ TEST(IndexSpecCollationValidateTest, RemovesCollationFieldIfSimple) {
     // We don't care about the order of the fields in the resulting index specification.
     ASSERT_BSONOBJ_EQ(sorted(BSON("key" << BSON("field" << 1) << "name"
                                         << "indexName"
-                                        << "ns" << kTestNamespace.ns() << "v" << 2)),
+                                        << "v" << 2)),
                       sorted(result.getValue()));
 }
 
@@ -616,7 +503,7 @@ TEST(IndexSpecCollationValidateTest, FillsInCollationFieldWithCollectionDefaultI
     auto result = validateIndexSpecCollation(opCtx.get(),
                                              BSON("key" << BSON("field" << 1) << "name"
                                                         << "indexName"
-                                                        << "ns" << kTestNamespace.ns() << "v" << 2),
+                                                        << "v" << 2),
                                              &defaultCollator);
     ASSERT_OK(result.getStatus());
 
@@ -624,7 +511,7 @@ TEST(IndexSpecCollationValidateTest, FillsInCollationFieldWithCollectionDefaultI
     ASSERT_BSONOBJ_EQ(
         sorted(BSON("key" << BSON("field" << 1) << "name"
                           << "indexName"
-                          << "ns" << kTestNamespace.ns() << "v" << 2 << "collation"
+                          << "v" << 2 << "collation"
                           << BSON("locale"
                                   << "mock_reverse_string"
                                   << "caseLevel" << false << "caseFirst"
@@ -643,7 +530,6 @@ TEST(IndexSpecPartialFilterTest, FailsIfPartialFilterIsNotAnObject) {
                                     BSON("key" << BSON("field" << 1) << "name"
                                                << "indexName"
                                                << "partialFilterExpression" << 1),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus(), ErrorCodes::TypeMismatch);
 }
@@ -654,7 +540,6 @@ TEST(IndexSpecPartialFilterTest, FailsIfPartialFilterContainsBannedFeature) {
                                                << "indexName"
                                                << "partialFilterExpression"
                                                << BSON("$jsonSchema" << BSONObj())),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus(), ErrorCodes::QueryFeatureNotAllowed);
 }
@@ -664,7 +549,6 @@ TEST(IndexSpecPartialFilterTest, AcceptsValidPartialFilterExpression) {
                                     BSON("key" << BSON("field" << 1) << "name"
                                                << "indexName"
                                                << "partialFilterExpression" << BSON("a" << 1)),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 }
@@ -676,7 +560,6 @@ TEST(IndexSpecWildcard, SucceedsWithInclusion) {
                           BSON("key" << BSON("$**" << 1) << "name"
                                      << "indexName"
                                      << "wildcardProjection" << BSON("a" << 1 << "b" << 1)),
-                          kTestNamespace,
                           serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 }
@@ -688,7 +571,6 @@ TEST(IndexSpecWildcard, SucceedsWithExclusion) {
                           BSON("key" << BSON("$**" << 1) << "name"
                                      << "indexName"
                                      << "wildcardProjection" << BSON("a" << 0 << "b" << 0)),
-                          kTestNamespace,
                           serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 }
@@ -700,7 +582,6 @@ TEST(IndexSpecWildcard, SucceedsWithExclusionIncludingId) {
                                                << "indexName"
                                                << "wildcardProjection"
                                                << BSON("_id" << 1 << "a" << 0 << "b" << 0)),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 }
@@ -712,7 +593,6 @@ TEST(IndexSpecWildcard, SucceedsWithInclusionExcludingId) {
                                                << "indexName"
                                                << "wildcardProjection"
                                                << BSON("_id" << 0 << "a" << 1 << "b" << 1)),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_OK(result.getStatus());
 }
@@ -724,7 +604,6 @@ TEST(IndexSpecWildcard, FailsWithInclusionExcludingIdSubfield) {
                                                << "indexName"
                                                << "wildcardProjection"
                                                << BSON("_id.field" << 0 << "a" << 1 << "b" << 1)),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), 40179);
 }
@@ -736,7 +615,6 @@ TEST(IndexSpecWildcard, FailsWithExclusionIncludingIdSubfield) {
                                                << "indexName"
                                                << "wildcardProjection"
                                                << BSON("_id.field" << 1 << "a" << 0 << "b" << 0)),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), 40178);
 }
@@ -748,7 +626,6 @@ TEST(IndexSpecWildcard, FailsWithImproperFeatureCompatabilityVersion) {
     auto result = validateIndexSpec(kDefaultOpCtx,
                                     BSON("key" << BSON("$**" << 1) << "name"
                                                << "indexName"),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), ErrorCodes::CannotCreateIndex);
 }
@@ -760,7 +637,6 @@ TEST(IndexSpecWildcard, FailsWithMixedProjection) {
                           BSON("key" << BSON("$**" << 1) << "name"
                                      << "indexName"
                                      << "wildcardProjection" << BSON("a" << 1 << "b" << 0)),
-                          kTestNamespace,
                           serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), 40178);
 }
@@ -773,7 +649,6 @@ TEST(IndexSpecWildcard, FailsWithComputedFieldsInProjection) {
                                                << "wildcardProjection"
                                                << BSON("a" << 1 << "b"
                                                            << "string")),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), ErrorCodes::FailedToParse);
 }
@@ -784,7 +659,6 @@ TEST(IndexSpecWildcard, FailsWhenProjectionPluginNotWildcard) {
                                     BSON("key" << BSON("a" << 1) << "name"
                                                << "indexName"
                                                << "wildcardProjection" << BSON("a" << 1)),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), ErrorCodes::BadValue);
 }
@@ -795,7 +669,6 @@ TEST(IndexSpecWildcard, FailsWhenProjectionIsNotAnObject) {
                                     BSON("key" << BSON("$**" << 1) << "name"
                                                << "indexName"
                                                << "wildcardProjection" << 4),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), ErrorCodes::TypeMismatch);
 }
@@ -806,7 +679,6 @@ TEST(IndexSpecWildcard, FailsWithEmptyProjection) {
                                     BSON("key" << BSON("$**" << 1) << "name"
                                                << "indexName"
                                                << "wildcardProjection" << BSONObj()),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), ErrorCodes::FailedToParse);
 }
@@ -817,7 +689,6 @@ TEST(IndexSpecWildcard, FailsWhenInclusionWithSubpath) {
                                     BSON("key" << BSON("a.$**" << 1) << "name"
                                                << "indexName"
                                                << "wildcardProjection" << BSON("a" << 1)),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), ErrorCodes::FailedToParse);
 }
@@ -828,7 +699,6 @@ TEST(IndexSpecWildcard, FailsWhenExclusionWithSubpath) {
                                     BSON("key" << BSON("a.$**" << 1) << "name"
                                                << "indexName"
                                                << "wildcardProjection" << BSON("b" << 0)),
-                                    kTestNamespace,
                                     serverGlobalParams.featureCompatibility);
     ASSERT_EQ(result.getStatus().code(), ErrorCodes::FailedToParse);
 }
diff --git a/src/mongo/db/catalog/rename_collection.cpp b/src/mongo/db/catalog/rename_collection.cpp
index 8506619312b..d1df31a6dba 100644
--- a/src/mongo/db/catalog/rename_collection.cpp
+++ b/src/mongo/db/catalog/rename_collection.cpp
@@ -536,34 +536,21 @@ Status renameBetweenDBs(OperationContext* opCtx,
         }
     });
 
-    // Copy the index descriptions from the source collection, adjusting the ns field.
+    // Copy the index descriptions from the source collection.
     {
         std::vector<BSONObj> indexesToCopy;
         std::unique_ptr<IndexCatalog::IndexIterator> sourceIndIt =
             sourceColl->getIndexCatalog()->getIndexIterator(opCtx, true);
         while (sourceIndIt->more()) {
             auto descriptor = sourceIndIt->next()->descriptor();
-            if (descriptor->isIdIndex()) {
-                continue;
+            if (!descriptor->isIdIndex()) {
+                indexesToCopy.push_back(descriptor->infoObj());
             }
-
-            const BSONObj currIndex = descriptor->infoObj();
-
-            // Process the source index, adding fields in the same order as they were originally.
-            BSONObjBuilder newIndex;
-            for (auto&& elem : currIndex) {
-                if (elem.fieldNameStringData() == "ns") {
-                    newIndex.append("ns", tmpName.ns());
-                } else {
-                    newIndex.append(elem);
-                }
-            }
-            indexesToCopy.push_back(newIndex.obj());
         }
 
-        // Create indexes using the namespace-adjusted index specs on the empty temporary collection
-        // that was just created. Since each index build is possibly replicated to downstream nodes,
-        // each createIndex oplog entry must have a distinct timestamp to support correct rollback
+        // Create indexes using the index specs on the empty temporary collection that was just
+        // created. Since each index build is possibly replicated to downstream nodes, each
+        // createIndex oplog entry must have a distinct timestamp to support correct rollback
         // operation. This is achieved by writing the createIndexes oplog entry *before* creating
         // the index. Using IndexCatalog::createIndexOnEmptyCollection() for the index creation
         // allows us to add and commit the index within a single WriteUnitOfWork and avoids the
diff --git a/src/mongo/db/catalog/rename_collection_test.cpp b/src/mongo/db/catalog/rename_collection_test.cpp
index 4c7e994f061..a27769d799b 100644
--- a/src/mongo/db/catalog/rename_collection_test.cpp
+++ b/src/mongo/db/catalog/rename_collection_test.cpp
@@ -415,7 +415,7 @@ void _createIndexOnEmptyCollection(OperationContext* opCtx,
                                 << " because collection " << nss << " does not exist.";
 
         auto indexInfoObj = BSON("v" << int(IndexDescriptor::kLatestIndexVersion) << "key"
-                                     << BSON("a" << 1) << "name" << indexName << "ns" << nss.ns());
+                                     << BSON("a" << 1) << "name" << indexName);
 
         auto indexCatalog = collection->getIndexCatalog();
         WriteUnitOfWork wuow(opCtx);
diff --git a/src/mongo/db/cloner.cpp b/src/mongo/db/cloner.cpp
index 1d19746cd7f..2a9c6d70b24 100644
--- a/src/mongo/db/cloner.cpp
+++ b/src/mongo/db/cloner.cpp
@@ -81,33 +81,6 @@ MONGO_FAIL_POINT_DEFINE(movePrimaryFailPoint);
 
 BSONElement getErrField(const BSONObj& o);
 
-namespace {
-
-/* for index info object:
-     { "name" : "name_1" , "ns" : "foo.index3" , "key" :  { "name" : 1.0 } }
-   we need to fix up the value in the "ns" parameter so that the name prefix is correct on a
-   copy to a new name.
-*/
-BSONObj fixIndexSpec(const string& newDbName, BSONObj indexSpec) {
-    BSONObjBuilder bob;
-
-    for (auto&& indexSpecElem : indexSpec) {
-        auto indexSpecElemFieldName = indexSpecElem.fieldNameStringData();
-        if (IndexDescriptor::kNamespaceFieldName == indexSpecElemFieldName) {
-            uassert(10024, "bad ns field for index during dbcopy", indexSpecElem.type() == String);
-            const char* p = strchr(indexSpecElem.valuestr(), '.');
-            uassert(10025, "bad ns field for index during dbcopy [2]", p);
-            string newname = newDbName + p;
-            bob.append(IndexDescriptor::kNamespaceFieldName, newname);
-        } else {
-            bob.append(indexSpecElem);
-        }
-    }
-
-    return bob.obj();
-}
-}  // namespace
-
 BSONObj Cloner::getIdIndexSpec(const std::list<BSONObj>& indexSpecs) {
     for (auto&& indexSpec : indexSpecs) {
         BSONElement indexName;
@@ -156,12 +129,13 @@ struct Cloner::Fun {
                 const bool createDefaultIndexes = true;
                 CollectionOptions collectionOptions = uassertStatusOK(CollectionOptions::parse(
                     from_options, CollectionOptions::ParseKind::parseForCommand));
-                auto indexSpec = fixIndexSpec(to_collection.db().toString(), from_id_index);
-                invariant(
-                    db->userCreateNS(
-                        opCtx, to_collection, collectionOptions, createDefaultIndexes, indexSpec),
-                    str::stream() << "collection creation failed during clone ["
-                                  << to_collection.ns() << "]");
+                invariant(db->userCreateNS(opCtx,
+                                           to_collection,
+                                           collectionOptions,
+                                           createDefaultIndexes,
+                                           from_id_index),
+                          str::stream() << "collection creation failed during clone ["
+                                        << to_collection.ns() << "]");
                 wunit.commit();
                 collection = db->getCollection(opCtx, to_collection);
                 invariant(collection,
@@ -337,19 +311,13 @@ void Cloner::copyIndexes(OperationContext* opCtx,
     LOG(2) << "\t\t copyIndexes " << from_collection << " to " << to_collection << " on "
            << _conn->getServerAddress();
 
-    vector<BSONObj> indexesToBuild;
-    for (auto&& indexSpec : from_indexes) {
-        indexesToBuild.push_back(fixIndexSpec(to_collection.db().toString(), indexSpec));
-    }
-
     uassert(ErrorCodes::PrimarySteppedDown,
             str::stream() << "Not primary while copying indexes from " << from_collection.ns()
                           << " to " << to_collection.ns() << " (Cloner)",
             !opCtx->writesAreReplicated() ||
                 repl::ReplicationCoordinator::get(opCtx)->canAcceptWritesFor(opCtx, to_collection));
 
-
-    if (indexesToBuild.empty())
+    if (from_indexes.empty())
         return;
 
     // We are under lock here again, so reload the database in case it may have disappeared
@@ -370,8 +338,7 @@ void Cloner::copyIndexes(OperationContext* opCtx,
                                        to_collection,
                                        collectionOptions,
                                        createDefaultIndexes,
-                                       fixIndexSpec(to_collection.db().toString(),
-                                                    getIdIndexSpec(from_indexes))),
+                                       getIdIndexSpec(from_indexes)),
                       str::stream()
                           << "Collection creation failed while copying indexes from "
                           << from_collection.ns() << " to " << to_collection.ns() << " (Cloner)");
@@ -383,8 +350,9 @@ void Cloner::copyIndexes(OperationContext* opCtx,
     }
 
     auto indexCatalog = collection->getIndexCatalog();
-    auto prunedIndexesToBuild = indexCatalog->removeExistingIndexesNoChecks(opCtx, indexesToBuild);
-    if (prunedIndexesToBuild.empty()) {
+    auto indexesToBuild = indexCatalog->removeExistingIndexesNoChecks(
+        opCtx, {std::begin(from_indexes), std::end(from_indexes)});
+    if (indexesToBuild.empty()) {
         return;
     }
 
@@ -399,7 +367,7 @@ void Cloner::copyIndexes(OperationContext* opCtx,
     ON_BLOCK_EXIT([&] { indexer.cleanUpAfterBuild(opCtx, collection); });
 
     auto indexInfoObjs = uassertStatusOK(
-        indexer.init(opCtx, collection, prunedIndexesToBuild, MultiIndexBlock::kNoopOnInitFn));
+        indexer.init(opCtx, collection, indexesToBuild, MultiIndexBlock::kNoopOnInitFn));
     uassertStatusOK(indexer.insertAllDocumentsInCollection(opCtx, collection));
     uassertStatusOK(indexer.checkConstraints(opCtx));
 
@@ -624,9 +592,8 @@ Status Cloner::createCollectionsForDb(
 
             CollectionOptions collectionOptions = uassertStatusOK(
                 CollectionOptions::parse(options, CollectionOptions::ParseKind::parseForStorage));
-            auto indexSpec = fixIndexSpec(nss.db().toString(), params.idIndexSpec);
-            Status createStatus =
-                db->userCreateNS(opCtx, nss, collectionOptions, createDefaultIndexes, indexSpec);
+            Status createStatus = db->userCreateNS(
+                opCtx, nss, collectionOptions, createDefaultIndexes, params.idIndexSpec);
             if (!createStatus.isOK()) {
                 return createStatus;
             }
diff --git a/src/mongo/db/commands/create_indexes.cpp b/src/mongo/db/commands/create_indexes.cpp
index a29bf22316a..b9e872e7a4f 100644
--- a/src/mongo/db/commands/create_indexes.cpp
+++ b/src/mongo/db/commands/create_indexes.cpp
@@ -130,7 +130,7 @@ StatusWith<std::vector<BSONObj>> parseAndValidateIndexSpecs(
                 }
 
                 auto indexSpecStatus = index_key_validate::validateIndexSpec(
-                    opCtx, parsedIndexSpec, ns, featureCompatibility);
+                    opCtx, parsedIndexSpec, featureCompatibility);
                 if (!indexSpecStatus.isOK()) {
                     return indexSpecStatus.getStatus().withContext(
                         str::stream() << "Error in specification " << parsedIndexSpec.toString());
diff --git a/src/mongo/db/commands/dbcommands.cpp b/src/mongo/db/commands/dbcommands.cpp
index a08a951f5a4..327983b3bd4 100644
--- a/src/mongo/db/commands/dbcommands.cpp
+++ b/src/mongo/db/commands/dbcommands.cpp
@@ -360,7 +360,7 @@ public:
 
             // Perform index spec validation.
             idIndexSpec = uassertStatusOK(index_key_validate::validateIndexSpec(
-                opCtx, idIndexSpec, ns, serverGlobalParams.featureCompatibility));
+                opCtx, idIndexSpec, serverGlobalParams.featureCompatibility));
             uassertStatusOK(index_key_validate::validateIdIndexSpec(idIndexSpec));
 
             // Validate or fill in _id index collation.
diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index 0deaf4d262f..b7da9aaf4bf 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -532,11 +532,10 @@ void State::prepTempCollection() {
             auto incColl = db->createCollection(
                 _opCtx, _config.incLong, options, false /* force no _id index */);
 
-            auto rawIndexSpec =
-                BSON("key" << BSON("0" << 1) << "ns" << _config.incLong.ns() << "name"
-                           << "_temp_0");
+            auto rawIndexSpec = BSON("key" << BSON("0" << 1) << "name"
+                                           << "_temp_0");
             auto indexSpec = uassertStatusOK(index_key_validate::validateIndexSpec(
-                _opCtx, rawIndexSpec, _config.incLong, serverGlobalParams.featureCompatibility));
+                _opCtx, rawIndexSpec, serverGlobalParams.featureCompatibility));
 
             uassertStatusOKWithContext(
                 incColl->getIndexCatalog()->createIndexOnEmptyCollection(_opCtx, indexSpec),
@@ -566,13 +565,12 @@ void State::prepTempCollection() {
             while (ii->more()) {
                 const IndexDescriptor* currIndex = ii->next()->descriptor();
                 BSONObjBuilder b;
-                b.append("ns", _config.tempNamespace.ns());
 
                 // Copy over contents of the index descriptor's infoObj.
                 BSONObjIterator j(currIndex->infoObj());
                 while (j.more()) {
                     BSONElement e = j.next();
-                    if (e.fieldNameStringData() == "_id" || e.fieldNameStringData() == "ns")
+                    if (e.fieldNameStringData() == "_id")
                         continue;
                     b.append(e);
                 }
diff --git a/src/mongo/db/index/index_descriptor.cpp b/src/mongo/db/index/index_descriptor.cpp
index da27ca8a2e5..8ebf493ba00 100644
--- a/src/mongo/db/index/index_descriptor.cpp
+++ b/src/mongo/db/index/index_descriptor.cpp
@@ -52,7 +52,7 @@ void populateOptionsMap(std::map<StringData, BSONElement>& theMap, const BSONObj
 
         StringData fieldName = e.fieldNameStringData();
         if (fieldName == IndexDescriptor::kKeyPatternFieldName ||
-            fieldName == IndexDescriptor::kNamespaceFieldName ||
+            fieldName == IndexDescriptor::kNamespaceFieldName ||  // removed in 4.4
             fieldName == IndexDescriptor::kIndexNameFieldName ||
             fieldName ==
                 IndexDescriptor::kIndexVersionFieldName ||  // not considered for equivalence
@@ -107,7 +107,6 @@ IndexDescriptor::IndexDescriptor(Collection* collection,
       _keyPattern(infoObj.getObjectField(IndexDescriptor::kKeyPatternFieldName).getOwned()),
       _projection(infoObj.getObjectField(IndexDescriptor::kPathProjectionFieldName).getOwned()),
       _indexName(infoObj.getStringField(IndexDescriptor::kIndexNameFieldName)),
-      _parentNS(collection->ns()),
       _isIdIndex(isIdIndexPattern(_keyPattern)),
       _sparse(infoObj[IndexDescriptor::kSparseFieldName].trueValue()),
       _unique(_isIdIndex || infoObj[kUniqueFieldName].trueValue()),
@@ -171,6 +170,10 @@ const IndexCatalog* IndexDescriptor::getIndexCatalog() const {
     return _collection->getIndexCatalog();
 }
 
+const NamespaceString& IndexDescriptor::parentNS() const {
+    return _collection->ns();
+}
+
 bool IndexDescriptor::areIndexOptionsEquivalent(const IndexDescriptor* other) const {
     if (isSparse() != other->isSparse()) {
         return false;
@@ -201,23 +204,4 @@ bool IndexDescriptor::areIndexOptionsEquivalent(const IndexDescriptor* other) co
                    });
 }
 
-void IndexDescriptor::setNs(NamespaceString ns) {
-    _parentNS = ns;
-
-    // Construct a new infoObj with the namespace field replaced.
-    _infoObj = renameNsInIndexSpec(_infoObj, ns);
-}
-
-BSONObj IndexDescriptor::renameNsInIndexSpec(BSONObj spec, const NamespaceString& newNs) {
-    BSONObjBuilder builder;
-    for (auto&& elt : spec) {
-        if (elt.fieldNameStringData() == kNamespaceFieldName) {
-            builder.append(kNamespaceFieldName, newNs.ns());
-        } else {
-            builder.append(elt);
-        }
-    }
-    return builder.obj();
-}
-
 }  // namespace mongo
diff --git a/src/mongo/db/index/index_descriptor.h b/src/mongo/db/index/index_descriptor.h
index e7893e85553..7e955258ab7 100644
--- a/src/mongo/db/index/index_descriptor.h
+++ b/src/mongo/db/index/index_descriptor.h
@@ -75,7 +75,7 @@ public:
     static constexpr StringData kIndexVersionFieldName = "v"_sd;
     static constexpr StringData kKeyPatternFieldName = "key"_sd;
     static constexpr StringData kLanguageOverrideFieldName = "language_override"_sd;
-    static constexpr StringData kNamespaceFieldName = "ns"_sd;
+    static constexpr StringData kNamespaceFieldName = "ns"_sd;  // Removed in 4.4
     static constexpr StringData kPartialFilterExprFieldName = "partialFilterExpression"_sd;
     static constexpr StringData kPathProjectionFieldName = "wildcardProjection"_sd;
     static constexpr StringData kSparseFieldName = "sparse"_sd;
@@ -85,12 +85,6 @@ public:
     static constexpr StringData kWeightsFieldName = "weights"_sd;
 
     /**
-     * Given a BSONObj representing an index spec, returns a new owned BSONObj which is identical to
-     * 'spec' after replacing the 'ns' field with the value of 'newNs'.
-     */
-    static BSONObj renameNsInIndexSpec(BSONObj spec, const NamespaceString& newNs);
-
-    /**
      * infoObj is a copy of the index-describing BSONObj contained in the catalog.
      */
     IndexDescriptor(Collection* collection, const std::string& accessMethodName, BSONObj infoObj);
@@ -162,9 +156,7 @@ public:
     }
 
     // Return the name of the indexed collection.
-    const NamespaceString& parentNS() const {
-        return _parentNS;
-    }
+    const NamespaceString& parentNS() const;
 
     // Return the name of the access method we must use to access this index's data.
     const std::string& getAccessMethodName() const {
@@ -227,8 +219,6 @@ public:
 
     bool areIndexOptionsEquivalent(const IndexDescriptor* other) const;
 
-    void setNs(NamespaceString ns);
-
     const BSONObj& collation() const {
         return _collation;
     }
@@ -266,7 +256,6 @@ private:
     BSONObj _keyPattern;
     BSONObj _projection;
     std::string _indexName;
-    NamespaceString _parentNS;
     bool _isIdIndex;
     bool _sparse;
     bool _unique;
diff --git a/src/mongo/db/index_builder.cpp b/src/mongo/db/index_builder.cpp
index c741814a663..f7430beb84b 100644
--- a/src/mongo/db/index_builder.cpp
+++ b/src/mongo/db/index_builder.cpp
@@ -79,20 +79,11 @@ std::string IndexBuilder::name() const {
     return _name;
 }
 
-Status IndexBuilder::buildInForeground(OperationContext* opCtx, Database* db) const {
-    return _buildAndHandleErrors(opCtx, db, false /*buildInBackground */, nullptr);
-}
-
-Status IndexBuilder::_buildAndHandleErrors(OperationContext* opCtx,
-                                           Database* db,
-                                           bool buildInBackground,
-                                           Lock::DBLock* dbLock) const {
-    invariant(!buildInBackground);
-    invariant(!dbLock);
+Status IndexBuilder::buildInForeground(OperationContext* opCtx,
+                                       Database* db,
+                                       Collection* coll) const {
+    invariant(opCtx->lockState()->isCollectionLockedForMode(coll->ns(), MODE_X));
 
-    const NamespaceString ns(_index["ns"].String());
-
-    Collection* coll = db->getCollection(opCtx, ns);
     // Collections should not be implicitly created by the index builder.
     fassert(40409, coll);
 
@@ -101,17 +92,12 @@ Status IndexBuilder::_buildAndHandleErrors(OperationContext* opCtx,
     // The 'indexer' can throw, so ensure build cleanup occurs.
     ON_BLOCK_EXIT([&] { indexer.cleanUpAfterBuild(opCtx, coll); });
 
-    return _build(opCtx, buildInBackground, coll, indexer, dbLock);
+    return _build(opCtx, coll, indexer);
 }
 
 Status IndexBuilder::_build(OperationContext* opCtx,
-                            bool buildInBackground,
                             Collection* coll,
-                            MultiIndexBlock& indexer,
-                            Lock::DBLock* dbLock) const try {
-    invariant(!buildInBackground);
-    invariant(!dbLock);
-
+                            MultiIndexBlock& indexer) const try {
     auto ns = coll->ns();
 
     {
@@ -163,7 +149,6 @@ Status IndexBuilder::_build(OperationContext* opCtx,
     }
 
     {
-        Lock::CollectionLock collLock(opCtx, ns, MODE_IX);
         // WriteConflict exceptions and statuses are not expected to escape this method.
         status = indexer.insertAllDocumentsInCollection(opCtx, coll);
         if (!status.isOK()) {
diff --git a/src/mongo/db/index_builder.h b/src/mongo/db/index_builder.h
index 11eeeea971c..2b68cd5ee9a 100644
--- a/src/mongo/db/index_builder.h
+++ b/src/mongo/db/index_builder.h
@@ -92,21 +92,12 @@ public:
     /**
      * Instead of building the index in a background thread, build on the current thread.
      */
-    Status buildInForeground(OperationContext* opCtx, Database* db) const;
+    Status buildInForeground(OperationContext* opCtx, Database* db, Collection* coll) const;
 
     static bool canBuildInBackground();
 
 private:
-    Status _buildAndHandleErrors(OperationContext* opCtx,
-                                 Database* db,
-                                 bool buildInBackground,
-                                 Lock::DBLock* dbLock) const;
-
-    Status _build(OperationContext* opCtx,
-                  bool buildInBackground,
-                  Collection* coll,
-                  MultiIndexBlock& indexer,
-                  Lock::DBLock* dbLock) const;
+    Status _build(OperationContext* opCtx, Collection* coll, MultiIndexBlock& indexer) const;
     const BSONObj _index;
     const IndexConstraints _indexConstraints;
     const ReplicatedWrites _replicatedWrites;
diff --git a/src/mongo/db/index_builds_coordinator_mongod_test.cpp b/src/mongo/db/index_builds_coordinator_mongod_test.cpp
index 6ba35b27e6b..7d496ac6952 100644
--- a/src/mongo/db/index_builds_coordinator_mongod_test.cpp
+++ b/src/mongo/db/index_builds_coordinator_mongod_test.cpp
@@ -95,8 +95,8 @@ std::vector<BSONObj> makeSpecs(const NamespaceString& nss, std::vector<std::stri
     invariant(keys.size());
     std::vector<BSONObj> indexSpecs;
     for (auto keyName : keys) {
-        indexSpecs.push_back(BSON("ns" << nss.toString() << "v" << 2 << "key" << BSON(keyName << 1)
-                                       << "name" << (keyName + "_1")));
+        indexSpecs.push_back(
+            BSON("v" << 2 << "key" << BSON(keyName << 1) << "name" << (keyName + "_1")));
     }
     return indexSpecs;
 }
diff --git a/src/mongo/db/op_observer_impl.cpp b/src/mongo/db/op_observer_impl.cpp
index e44c135e7d2..23266878f34 100644
--- a/src/mongo/db/op_observer_impl.cpp
+++ b/src/mongo/db/op_observer_impl.cpp
@@ -243,11 +243,7 @@ void OpObserverImpl::onCreateIndex(OperationContext* opCtx,
                                    bool fromMigrate) {
     BSONObjBuilder builder;
     builder.append("createIndexes", nss.coll());
-
-    for (const auto& e : indexDoc) {
-        if (e.fieldNameStringData() != "ns"_sd)
-            builder.append(e);
-    }
+    builder.appendElements(indexDoc);
 
     MutableOplogEntry oplogEntry;
     oplogEntry.setOpType(repl::OpTypeEnum::kCommand);
@@ -271,12 +267,7 @@ void OpObserverImpl::onStartIndexBuild(OperationContext* opCtx,
 
     BSONArrayBuilder indexesArr(oplogEntryBuilder.subarrayStart("indexes"));
     for (auto indexDoc : indexes) {
-        BSONObjBuilder builder;
-        for (const auto& e : indexDoc) {
-            if (e.fieldNameStringData() != "ns"_sd)
-                builder.append(e);
-        }
-        indexesArr.append(builder.obj());
+        indexesArr.append(indexDoc);
     }
     indexesArr.done();
 
@@ -302,12 +293,7 @@ void OpObserverImpl::onCommitIndexBuild(OperationContext* opCtx,
 
     BSONArrayBuilder indexesArr(oplogEntryBuilder.subarrayStart("indexes"));
     for (auto indexDoc : indexes) {
-        BSONObjBuilder builder;
-        for (const auto& e : indexDoc) {
-            if (e.fieldNameStringData() != "ns"_sd)
-                builder.append(e);
-        }
-        indexesArr.append(builder.obj());
+        indexesArr.append(indexDoc);
     }
     indexesArr.done();
 
@@ -333,12 +319,7 @@ void OpObserverImpl::onAbortIndexBuild(OperationContext* opCtx,
 
     BSONArrayBuilder indexesArr(oplogEntryBuilder.subarrayStart("indexes"));
     for (auto indexDoc : indexes) {
-        BSONObjBuilder builder;
-        for (const auto& e : indexDoc) {
-            if (e.fieldNameStringData() != "ns"_sd)
-                builder.append(e);
-        }
-        indexesArr.append(builder.obj());
+        indexesArr.append(indexDoc);
     }
     indexesArr.done();
 
diff --git a/src/mongo/db/pipeline/document_source_out.cpp b/src/mongo/db/pipeline/document_source_out.cpp
index 2293294534c..f4b7127a83d 100644
--- a/src/mongo/db/pipeline/document_source_out.cpp
+++ b/src/mongo/db/pipeline/document_source_out.cpp
@@ -145,13 +145,9 @@ void DocumentSourceOut::initialize() {
     }
 
     // Copy the indexes of the output collection to the temp collection.
-    std::vector<BSONObj> tempNsIndexes;
-    for (const auto& indexSpec : _originalIndexes) {
-        // Replace the spec's 'ns' field value, which is the original collection, with the temp
-        // collection.
-        tempNsIndexes.push_back(indexSpec.addField(BSON("ns" << _tempNs.ns()).firstElement()));
-    }
     try {
+        std::vector<BSONObj> tempNsIndexes = {std::begin(_originalIndexes),
+                                              std::end(_originalIndexes)};
         conn->createIndexes(_tempNs.ns(), tempNsIndexes);
     } catch (DBException& ex) {
         ex.addContext("Copying indexes for $out failed");
diff --git a/src/mongo/db/repl/base_cloner_test_fixture.cpp b/src/mongo/db/repl/base_cloner_test_fixture.cpp
index 8d9fc63f6cd..24841605f83 100644
--- a/src/mongo/db/repl/base_cloner_test_fixture.cpp
+++ b/src/mongo/db/repl/base_cloner_test_fixture.cpp
@@ -46,8 +46,7 @@ using namespace unittest;
 const HostAndPort BaseClonerTest::target("localhost", -1);
 const NamespaceString BaseClonerTest::nss("db.coll");
 const BSONObj BaseClonerTest::idIndexSpec = BSON("v" << 1 << "key" << BSON("_id" << 1) << "name"
-                                                     << "_id_"
-                                                     << "ns" << nss.ns());
+                                                     << "_id_");
 
 // static
 BSONObj BaseClonerTest::createCountResponse(int documentCount) {
diff --git a/src/mongo/db/repl/collection_cloner.cpp b/src/mongo/db/repl/collection_cloner.cpp
index 84c7273f001..774c0e8b36a 100644
--- a/src/mongo/db/repl/collection_cloner.cpp
+++ b/src/mongo/db/repl/collection_cloner.cpp
@@ -396,22 +396,15 @@ void CollectionCloner::_listIndexesCallback(const Fetcher::QueryResponseStatus&
     }
 
     UniqueLock lk(_mutex);
-    // When listing indexes by UUID, the sync source may use a different name for the collection
-    // as result of renaming or two-phase drop. As the index spec also includes a 'ns' field, this
-    // must be rewritten.
-    BSONObjBuilder nsFieldReplacementBuilder;
-    nsFieldReplacementBuilder.append("ns", _sourceNss.ns());
-    BSONElement nsFieldReplacementElem = nsFieldReplacementBuilder.done().firstElement();
 
     // We may be called with multiple batches leading to a need to grow _indexSpecs.
     _indexSpecs.reserve(_indexSpecs.size() + documents.size());
     for (auto&& doc : documents) {
-        // The addField replaces the 'ns' field with the correct name, see above.
         if (StringData("_id_") == doc["name"].str()) {
-            _idIndexSpec = doc.addField(nsFieldReplacementElem);
+            _idIndexSpec = doc;
             continue;
         }
-        _indexSpecs.push_back(doc.addField(nsFieldReplacementElem));
+        _indexSpecs.push_back(doc);
     }
     lk.unlock();
 
diff --git a/src/mongo/db/repl/collection_cloner_test.cpp b/src/mongo/db/repl/collection_cloner_test.cpp
index 5fb4970c183..c15b95ed15f 100644
--- a/src/mongo/db/repl/collection_cloner_test.cpp
+++ b/src/mongo/db/repl/collection_cloner_test.cpp
@@ -281,11 +281,9 @@ void CollectionClonerTest::setUp() {
 // Return index specs to use for secondary indexes.
 std::vector<BSONObj> CollectionClonerTest::makeSecondaryIndexSpecs(const NamespaceString& nss) {
     return {BSON("v" << 1 << "key" << BSON("a" << 1) << "name"
-                     << "a_1"
-                     << "ns" << nss.ns()),
+                     << "a_1"),
             BSON("v" << 1 << "key" << BSON("b" << 1) << "name"
-                     << "b_1"
-                     << "ns" << nss.ns())};
+                     << "b_1")};
 }
 
 void CollectionClonerTest::tearDown() {
@@ -1399,8 +1397,7 @@ TEST_F(CollectionClonerRenamedBeforeStartTest, BeginCollectionWithUUID) {
     ASSERT_BSONOBJ_EQ(options.toBSON(), collOptions.toBSON());
 
     BSONObj expectedIdIndexSpec = BSON("v" << 1 << "key" << BSON("_id" << 1) << "name"
-                                           << "_id_"
-                                           << "ns" << alternateNss.ns());
+                                           << "_id_");
     ASSERT_BSONOBJ_EQ(collIdIndexSpec, expectedIdIndexSpec);
 
     auto expectedNonIdIndexSpecs = makeSecondaryIndexSpecs(alternateNss);
diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index ec1fa40c985..f5732e53227 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -170,9 +170,7 @@ StatusWith<std::vector<BSONObj>> parseBSONSpecsIntoVector(const BSONElement& bso
                                   << "' array must be objects, but found "
                                   << typeName(bsonElem.type())};
         }
-        BSONObjBuilder builder(bsonElem.Obj());
-        builder.append("ns", nss.toString());
-        vec.emplace_back(builder.obj());
+        vec.emplace_back(bsonElem.Obj().getOwned());
     }
     return vec;
 }
@@ -232,11 +230,8 @@ void createIndexForApplyOps(OperationContext* opCtx,
                             const NamespaceString& indexNss,
                             IncrementOpsAppliedStatsFn incrementOpsAppliedStats,
                             OplogApplication::Mode mode) {
-    // Lock the database if it's not locked.
-    boost::optional<Lock::DBLock> dbLock;
-    if (!opCtx->lockState()->isLocked()) {
-        dbLock.emplace(opCtx, indexNss.db(), MODE_X);
-    }
+    invariant(opCtx->lockState()->isCollectionLockedForMode(indexNss, MODE_X));
+
     // Check if collection exists.
     auto databaseHolder = DatabaseHolder::get(opCtx);
     auto db = databaseHolder->getDb(opCtx, indexNss.ns());
@@ -263,7 +258,7 @@ void createIndexForApplyOps(OperationContext* opCtx,
 
     if (shouldBuildInForeground(opCtx, indexSpec, indexNss, mode)) {
         IndexBuilder builder(indexSpec, constraints, replicatedWrites);
-        Status status = builder.buildInForeground(opCtx, db);
+        Status status = builder.buildInForeground(opCtx, db, indexCollection);
         uassertStatusOK(status);
     } else {
         Lock::TempRelease release(opCtx->lockState());
@@ -734,7 +729,6 @@ const StringMap<ApplyOpMetadata> kOpsMap = {
           idIndexSpecBuilder.append(IndexDescriptor::kIndexVersionFieldName,
                                     static_cast<int>(IndexVersion::kV1));
           idIndexSpecBuilder.append(IndexDescriptor::kIndexNameFieldName, "_id_");
-          idIndexSpecBuilder.append(IndexDescriptor::kNamespaceFieldName, nss.ns());
           idIndexSpecBuilder.append(IndexDescriptor::kKeyPatternFieldName, BSON("_id" << 1));
           return createCollectionForApplyOps(
               opCtx, nss.db().toString(), ui, cmd, idIndexSpecBuilder.done());
@@ -754,10 +748,8 @@ const StringMap<ApplyOpMetadata> kOpsMap = {
                   "createIndexes value must be a string",
                   first.type() == mongo::String);
           BSONObj indexSpec = cmd.removeField("createIndexes");
-          // The UUID determines the collection to build the index on, so create new 'ns' field.
-          BSONObj nsObj = BSON("ns" << nss.ns());
-          indexSpec = indexSpec.addField(nsObj.firstElement());
-
+          Lock::DBLock dbLock(opCtx, nss.db(), MODE_IX);
+          Lock::CollectionLock collLock(opCtx, nss, MODE_X);
           createIndexForApplyOps(opCtx, indexSpec, nss, {}, mode);
           return Status::OK();
       },
diff --git a/src/mongo/db/repl/rollback_impl_test.cpp b/src/mongo/db/repl/rollback_impl_test.cpp
index e7fa22eef19..1f514eda2e6 100644
--- a/src/mongo/db/repl/rollback_impl_test.cpp
+++ b/src/mongo/db/repl/rollback_impl_test.cpp
@@ -1638,7 +1638,7 @@ TEST_F(RollbackImplObserverInfoTest, NamespacesForOpsExtractsNamespaceOfDropColl
 TEST_F(RollbackImplObserverInfoTest, NamespacesForOpsExtractsNamespaceOfCreateIndexOplogEntry) {
     auto nss = NamespaceString("test", "coll");
     auto indexObj =
-        BSON("createIndexes" << nss.coll() << "ns" << nss.toString() << "v"
+        BSON("createIndexes" << nss.coll() << "v"
                              << static_cast<int>(IndexDescriptor::IndexVersion::kV2) << "key"
                              << "x"
                              << "name"
diff --git a/src/mongo/db/repl/rs_rollback.cpp b/src/mongo/db/repl/rs_rollback.cpp
index 491ace5de8b..d04bdea10b2 100644
--- a/src/mongo/db/repl/rs_rollback.cpp
+++ b/src/mongo/db/repl/rs_rollback.cpp
@@ -738,11 +738,12 @@ void rollbackCreateIndexes(OperationContext* opCtx, UUID uuid, std::set<std::str
 void rollbackDropIndexes(OperationContext* opCtx,
                          UUID uuid,
                          std::map<std::string, BSONObj> indexNames) {
-
     boost::optional<NamespaceString> nss = CollectionCatalog::get(opCtx).lookupNSSByUUID(uuid);
     invariant(nss);
-    Lock::DBLock dbLock(opCtx, nss->db(), MODE_X);
-    Collection* collection = CollectionCatalog::get(opCtx).lookupCollectionByUUID(uuid);
+    Lock::DBLock dbLock(opCtx, nss->db(), MODE_IX);
+    Lock::CollectionLock collLock(opCtx, *nss, MODE_X);
+    Collection* collection = CollectionCatalog::get(opCtx).lookupCollectionByNamespace(*nss);
+
     // If we cannot find the collection, we skip over dropping the index.
     if (!collection) {
         LOG(2) << "Cannot find the collection with uuid: " << uuid.toString()
@@ -751,17 +752,8 @@ void rollbackDropIndexes(OperationContext* opCtx,
     }
 
     for (auto itIndex = indexNames.begin(); itIndex != indexNames.end(); itIndex++) {
-
         const string indexName = itIndex->first;
         BSONObj indexSpec = itIndex->second;
-        // We replace the namespace field because it is possible that a
-        // renameCollection command has occurred, changing the namespace of the
-        // collection from what it initially was during the creation of this index.
-        BSONObjBuilder updatedNss;
-        updatedNss.append("ns", nss->ns());
-
-        BSONObj updatedNssObj = updatedNss.obj();
-        indexSpec = indexSpec.addField(updatedNssObj.firstElement());
 
         log() << "Creating index in rollback for collection: " << *nss << ", UUID: " << uuid
               << ", index: " << indexName;
diff --git a/src/mongo/db/repl/rs_rollback_test.cpp b/src/mongo/db/repl/rs_rollback_test.cpp
index 3d12a5bac28..6d1bfbda79a 100644
--- a/src/mongo/db/repl/rs_rollback_test.cpp
+++ b/src/mongo/db/repl/rs_rollback_test.cpp
@@ -81,8 +81,8 @@ OplogInterfaceMock::Operation makeDropIndexOplogEntry(Collection* collection,
                                                       BSONObj key,
                                                       std::string indexName,
                                                       int time) {
-    auto indexSpec = BSON("ns" << collection->ns().ns() << "key" << key << "name" << indexName
-                               << "v" << static_cast<int>(kIndexVersion));
+    auto indexSpec =
+        BSON("key" << key << "name" << indexName << "v" << static_cast<int>(kIndexVersion));
 
     return std::make_pair(
         BSON("ts" << Timestamp(Seconds(time), 0) << "op"
@@ -98,9 +98,9 @@ OplogInterfaceMock::Operation makeCreateIndexOplogEntry(Collection* collection,
                                                         BSONObj key,
                                                         std::string indexName,
                                                         int time) {
-    auto indexSpec = BSON(
-        "createIndexes" << collection->ns().coll() << "ns" << collection->ns().ns() << "v"
-                        << static_cast<int>(kIndexVersion) << "key" << key << "name" << indexName);
+    auto indexSpec =
+        BSON("createIndexes" << collection->ns().coll() << "v" << static_cast<int>(kIndexVersion)
+                             << "key" << key << "name" << indexName);
 
     return std::make_pair(BSON("ts" << Timestamp(Seconds(time), 0) << "op"
                                     << "c"
@@ -439,9 +439,9 @@ TEST_F(RSRollbackTest, RollbackCreateIndexCommand) {
     options.uuid = UUID::gen();
     NamespaceString nss("test", "coll");
     auto collection = _createCollection(_opCtx.get(), nss.toString(), options);
-    auto indexSpec = BSON("ns" << nss.toString() << "v" << static_cast<int>(kIndexVersion) << "key"
-                               << BSON("a" << 1) << "name"
-                               << "a_1");
+    auto indexSpec =
+        BSON("v" << static_cast<int>(kIndexVersion) << "key" << BSON("a" << 1) << "name"
+                 << "a_1");
 
     int numIndexes = _createIndexOnEmptyCollection(_opCtx.get(), collection, nss, indexSpec);
     ASSERT_EQUALS(2, numIndexes);
@@ -482,10 +482,8 @@ TEST_F(RSRollbackTest, RollbackCreateIndexCommandIndexNotInCatalog) {
     CollectionOptions options;
     options.uuid = UUID::gen();
     auto collection = _createCollection(_opCtx.get(), "test.t", options);
-    auto indexSpec = BSON("ns"
-                          << "test.t"
-                          << "key" << BSON("a" << 1) << "name"
-                          << "a_1");
+    auto indexSpec = BSON("key" << BSON("a" << 1) << "name"
+                                << "a_1");
     // Skip index creation to trigger warning during rollback.
     {
         Lock::DBLock dbLock(_opCtx.get(), "test", MODE_S);
@@ -632,8 +630,8 @@ TEST_F(RSRollbackTest, RollingBackCreateIndexAndRenameWithLongName) {
     auto collection = _createCollection(_opCtx.get(), nss.toString(), options);
 
     auto longName = std::string(115, 'a');
-    auto indexSpec = BSON("ns" << nss.toString() << "v" << static_cast<int>(kIndexVersion) << "key"
-                               << BSON("b" << 1) << "name" << longName);
+    auto indexSpec = BSON("v" << static_cast<int>(kIndexVersion) << "key" << BSON("b" << 1)
+                              << "name" << longName);
 
     int numIndexes = _createIndexOnEmptyCollection(_opCtx.get(), collection, nss, indexSpec);
     ASSERT_EQUALS(2, numIndexes);
@@ -680,9 +678,9 @@ TEST_F(RSRollbackTest, RollingBackDropAndCreateOfSameIndexNameWithDifferentSpecs
     NamespaceString nss("test", "coll");
     auto collection = _createCollection(_opCtx.get(), nss.toString(), options);
 
-    auto indexSpec = BSON("ns" << nss.toString() << "v" << static_cast<int>(kIndexVersion) << "key"
-                               << BSON("b" << 1) << "name"
-                               << "a_1");
+    auto indexSpec =
+        BSON("v" << static_cast<int>(kIndexVersion) << "key" << BSON("b" << 1) << "name"
+                 << "a_1");
 
     int numIndexes = _createIndexOnEmptyCollection(_opCtx.get(), collection, nss, indexSpec);
     ASSERT_EQUALS(2, numIndexes);
@@ -779,8 +777,8 @@ std::string idxName(std::string id) {
 
 // Create an index spec object given the namespace and the index 'id'.
 BSONObj idxSpec(NamespaceString nss, std::string id) {
-    return BSON("ns" << nss.toString() << "v" << static_cast<int>(kIndexVersion) << "key"
-                     << BSON(idxKey(id) << 1) << "name" << idxName(id));
+    return BSON("v" << static_cast<int>(kIndexVersion) << "key" << BSON(idxKey(id) << 1) << "name"
+                    << idxName(id));
 }
 
 // Returns the number of indexes that exist on the given collection.
@@ -902,8 +900,8 @@ TEST_F(RSRollbackTest, RollbackCreateDropRecreateIndexOnCollection) {
 
     // Create the necessary indexes. Index 0 is created, dropped, and created again in the
     // sequence of ops, so we create that index.
-    auto indexSpec = BSON("ns" << nss.toString() << "v" << static_cast<int>(kIndexVersion) << "key"
-                               << BSON(idxKey("0") << 1) << "name" << idxName("0"));
+    auto indexSpec = BSON("v" << static_cast<int>(kIndexVersion) << "key" << BSON(idxKey("0") << 1)
+                              << "name" << idxName("0"));
 
     int numIndexes = _createIndexOnEmptyCollection(_opCtx.get(), coll, nss, indexSpec);
     ASSERT_EQUALS(2, numIndexes);
diff --git a/src/mongo/db/repl/storage_interface_impl_test.cpp b/src/mongo/db/repl/storage_interface_impl_test.cpp
index aa021037cc8..451e809ef55 100644
--- a/src/mongo/db/repl/storage_interface_impl_test.cpp
+++ b/src/mongo/db/repl/storage_interface_impl_test.cpp
@@ -66,10 +66,10 @@ using namespace mongo::repl;
 const auto kIndexVersion = IndexDescriptor::IndexVersion::kV2;
 
 BSONObj makeIdIndexSpec(const NamespaceString& nss) {
-    return BSON("ns" << nss.toString() << "name"
-                     << "_id_"
-                     << "key" << BSON("_id" << 1) << "unique" << true << "v"
-                     << static_cast<int>(kIndexVersion));
+    return BSON("name"
+                << "_id_"
+                << "key" << BSON("_id" << 1) << "unique" << true << "v"
+                << static_cast<int>(kIndexVersion));
 }
 
 /**
@@ -616,8 +616,7 @@ TEST_F(StorageInterfaceImplTest, DestroyingUncommittedCollectionBulkLoaderDropsI
     auto opCtx = getOperationContext();
     auto nss = makeNamespace(_agent);
     std::vector<BSONObj> indexes = {BSON("v" << 1 << "key" << BSON("x" << 1) << "name"
-                                             << "x_1"
-                                             << "ns" << nss.ns())};
+                                             << "x_1")};
     auto destroyLoaderFn = [](std::unique_ptr<CollectionBulkLoader> loader) {
         // Destroy 'loader' by letting it go out of scope.
     };
@@ -640,8 +639,7 @@ TEST_F(StorageInterfaceImplTest,
     auto opCtx = getOperationContext();
     auto nss = makeNamespace(_agent);
     std::vector<BSONObj> indexes = {BSON("v" << 1 << "key" << BSON("x" << 1) << "name"
-                                             << "x_1"
-                                             << "ns" << nss.ns())};
+                                             << "x_1")};
     auto destroyLoaderFn = [](std::unique_ptr<CollectionBulkLoader> loader) {
         // Destroy 'loader' in a new thread that does not have a Client.
         stdx::thread([&loader]() { loader.reset(); }).join();
@@ -904,8 +902,7 @@ TEST_F(StorageInterfaceImplTest, FindDocumentsReturnsIndexOptionsConflictIfIndex
     auto nss = makeNamespace(_agent);
     std::vector<BSONObj> indexes = {BSON("v" << 1 << "key" << BSON("x" << 1) << "name"
                                              << "x_1"
-                                             << "ns" << nss.ns() << "partialFilterExpression"
-                                             << BSON("y" << 1))};
+                                             << "partialFilterExpression" << BSON("y" << 1))};
     auto loader = unittest::assertGet(storage.createCollectionForBulkLoading(
         nss, generateOptionsWithUuid(), makeIdIndexSpec(nss), indexes));
     std::vector<BSONObj> docs = {BSON("_id" << 1), BSON("_id" << 1), BSON("_id" << 2)};
@@ -2643,8 +2640,8 @@ TEST_F(StorageInterfaceImplTest, SetIndexIsMultikeySucceeds) {
     ASSERT_OK(storage.createCollection(opCtx, nss, CollectionOptions()));
 
     auto indexName = "a_b_1";
-    auto indexSpec = BSON("name" << indexName << "ns" << nss.ns() << "key" << BSON("a.b" << 1)
-                                 << "v" << static_cast<int>(kIndexVersion));
+    auto indexSpec = BSON("name" << indexName << "key" << BSON("a.b" << 1) << "v"
+                                 << static_cast<int>(kIndexVersion));
     ASSERT_EQUALS(_createIndexOnEmptyCollection(opCtx, nss, indexSpec), 2);
 
     MultikeyPaths paths = {{1}};
diff --git a/src/mongo/db/repl/sync_tail_test.cpp b/src/mongo/db/repl/sync_tail_test.cpp
index 79fbd315d3b..d6a194ba29d 100644
--- a/src/mongo/db/repl/sync_tail_test.cpp
+++ b/src/mongo/db/repl/sync_tail_test.cpp
@@ -2180,7 +2180,7 @@ TEST_F(IdempotencyTest, CreateCollectionWithIdIndex) {
 
     auto options1 = BSON("idIndex" << BSON("key" << fromjson("{_id: 1}") << "name"
                                                  << "_id_"
-                                                 << "v" << 2 << "ns" << nss.ns())
+                                                 << "v" << 2)
                                    << "uuid" << uuid);
     auto createColl1 = makeCreateCollectionOplogEntry(nextOpTime(), nss, options1);
     ASSERT_OK(runOpInitialSync(createColl1));
diff --git a/src/mongo/db/s/config/sharding_catalog_manager_config_initialization_test.cpp b/src/mongo/db/s/config/sharding_catalog_manager_config_initialization_test.cpp
index 8d4feacb60b..b88ff084d93 100644
--- a/src/mongo/db/s/config/sharding_catalog_manager_config_initialization_test.cpp
+++ b/src/mongo/db/s/config/sharding_catalog_manager_config_initialization_test.cpp
@@ -271,66 +271,38 @@ TEST_F(ConfigInitializationTest, BuildsNecessaryIndexes) {
 
     auto expectedChunksIndexes = std::vector<BSONObj>{
         BSON("v" << 2 << "key" << BSON("_id" << 1) << "name"
-                 << "_id_"
-                 << "ns"
-                 << "config.chunks"),
+                 << "_id_"),
         BSON("v" << 2 << "unique" << true << "key" << BSON("ns" << 1 << "min" << 1) << "name"
-                 << "ns_1_min_1"
-                 << "ns"
-                 << "config.chunks"),
+                 << "ns_1_min_1"),
         BSON("v" << 2 << "unique" << true << "key" << BSON("ns" << 1 << "shard" << 1 << "min" << 1)
                  << "name"
-                 << "ns_1_shard_1_min_1"
-                 << "ns"
-                 << "config.chunks"),
+                 << "ns_1_shard_1_min_1"),
         BSON("v" << 2 << "unique" << true << "key" << BSON("ns" << 1 << "lastmod" << 1) << "name"
-                 << "ns_1_lastmod_1"
-                 << "ns"
-                 << "config.chunks")};
+                 << "ns_1_lastmod_1")};
     auto expectedLockpingsIndexes =
         std::vector<BSONObj>{BSON("v" << 2 << "key" << BSON("_id" << 1) << "name"
-                                      << "_id_"
-                                      << "ns"
-                                      << "config.lockpings"),
+                                      << "_id_"),
                              BSON("v" << 2 << "key" << BSON("ping" << 1) << "name"
-                                      << "ping_1"
-                                      << "ns"
-                                      << "config.lockpings")};
+                                      << "ping_1")};
     auto expectedLocksIndexes = std::vector<BSONObj>{
         BSON("v" << 2 << "key" << BSON("_id" << 1) << "name"
-                 << "_id_"
-                 << "ns"
-                 << "config.locks"),
+                 << "_id_"),
         BSON("v" << 2 << "key" << BSON("ts" << 1) << "name"
-                 << "ts_1"
-                 << "ns"
-                 << "config.locks"),
+                 << "ts_1"),
         BSON("v" << 2 << "key" << BSON("state" << 1 << "process" << 1) << "name"
-                 << "state_1_process_1"
-                 << "ns"
-                 << "config.locks")};
+                 << "state_1_process_1")};
     auto expectedShardsIndexes = std::vector<BSONObj>{
         BSON("v" << 2 << "key" << BSON("_id" << 1) << "name"
-                 << "_id_"
-                 << "ns"
-                 << "config.shards"),
+                 << "_id_"),
         BSON("v" << 2 << "unique" << true << "key" << BSON("host" << 1) << "name"
-                 << "host_1"
-                 << "ns"
-                 << "config.shards")};
+                 << "host_1")};
     auto expectedTagsIndexes = std::vector<BSONObj>{
         BSON("v" << 2 << "key" << BSON("_id" << 1) << "name"
-                 << "_id_"
-                 << "ns"
-                 << "config.tags"),
+                 << "_id_"),
         BSON("v" << 2 << "unique" << true << "key" << BSON("ns" << 1 << "min" << 1) << "name"
-                 << "ns_1_min_1"
-                 << "ns"
-                 << "config.tags"),
+                 << "ns_1_min_1"),
         BSON("v" << 2 << "key" << BSON("ns" << 1 << "tag" << 1) << "name"
-                 << "ns_1_tag_1"
-                 << "ns"
-                 << "config.tags")};
+                 << "ns_1_tag_1")};
 
     auto foundChunksIndexes = assertGet(getIndexes(operationContext(), ChunkType::ConfigNS));
     assertBSONObjsSame(expectedChunksIndexes, foundChunksIndexes);
@@ -358,13 +330,9 @@ TEST_F(ConfigInitializationTest, CompatibleIndexAlreadyExists) {
 
     auto expectedShardsIndexes = std::vector<BSONObj>{
         BSON("v" << 2 << "key" << BSON("_id" << 1) << "name"
-                 << "_id_"
-                 << "ns"
-                 << "config.shards"),
+                 << "_id_"),
         BSON("v" << 2 << "unique" << true << "key" << BSON("host" << 1) << "name"
-                 << "host_1"
-                 << "ns"
-                 << "config.shards")};
+                 << "host_1")};
 
 
     auto foundShardsIndexes = assertGet(getIndexes(operationContext(), ShardType::ConfigNS));
diff --git a/src/mongo/db/s/shardsvr_shard_collection.cpp b/src/mongo/db/s/shardsvr_shard_collection.cpp
index e229badedbc..f58f6983280 100644
--- a/src/mongo/db/s/shardsvr_shard_collection.cpp
+++ b/src/mongo/db/s/shardsvr_shard_collection.cpp
@@ -258,7 +258,7 @@ void createCollectionOrValidateExisting(OperationContext* opCtx,
     // 3. If proposed key is required to be unique, additionally check for exact match.
 
     if (hasUsefulIndexForKey && request.getUnique()) {
-        BSONObj eqQuery = BSON("ns" << nss.ns() << "key" << proposedKey);
+        BSONObj eqQuery = BSON("key" << proposedKey);
         BSONObj eqQueryResult;
 
         for (const auto& idx : indexes) {
diff --git a/src/mongo/db/storage/SConscript b/src/mongo/db/storage/SConscript
index 871d3fa97db..0e933164833 100644
--- a/src/mongo/db/storage/SConscript
+++ b/src/mongo/db/storage/SConscript
@@ -79,9 +79,6 @@ env.Library(
         '$BUILD_DIR/mongo/db/service_context',
         '$BUILD_DIR/mongo/db/storage/kv/kv_prefix',
         ],
-    LIBDEPS_PRIVATE=[
-        '$BUILD_DIR/mongo/db/catalog/disable_index_spec_namespace_generation',
-        ],
     )
 
 env.Library(
@@ -425,9 +422,6 @@ env.Library(
         '$BUILD_DIR/mongo/db/storage/kv/kv_drop_pending_ident_reaper',
         '$BUILD_DIR/mongo/db/storage/kv/kv_prefix',
         '$BUILD_DIR/mongo/db/catalog/collection_catalog',
-    ],
-    LIBDEPS_PRIVATE=[
-        '$BUILD_DIR/mongo/db/catalog/disable_index_spec_namespace_generation',
     ]
 )
 
diff --git a/src/mongo/db/storage/biggie/biggie_sorted_impl.cpp b/src/mongo/db/storage/biggie/biggie_sorted_impl.cpp
index e4aa5eee384..15d604fe069 100644
--- a/src/mongo/db/storage/biggie/biggie_sorted_impl.cpp
+++ b/src/mongo/db/storage/biggie/biggie_sorted_impl.cpp
@@ -37,6 +37,7 @@
 
 #include "mongo/bson/bsonobj.h"
 #include "mongo/bson/bsonobjbuilder.h"
+#include "mongo/db/catalog/collection.h"
 #include "mongo/db/catalog/index_catalog_entry.h"
 #include "mongo/db/index/index_descriptor.h"
 #include "mongo/db/storage/biggie/biggie_recovery_unit.h"
@@ -293,7 +294,7 @@ SortedDataInterface::SortedDataInterface(OperationContext* opCtx,
       _prefix(ident.toString().append(1, '\1')),
       // Therefore, the string ident + \2 will be greater than all elements in this ident.
       _identEnd(ident.toString().append(1, '\2')),
-      _collectionNamespace(desc->parentNS()),
+      _collectionNamespace(desc->getCollection()->ns()),
       _indexName(desc->indexName()),
       _keyPattern(desc->keyPattern()),
       _isUnique(desc->unique()),
diff --git a/src/mongo/db/storage/biggie/biggie_sorted_impl_test.cpp b/src/mongo/db/storage/biggie/biggie_sorted_impl_test.cpp
index 03aa3330b60..18e6da89d58 100644
--- a/src/mongo/db/storage/biggie/biggie_sorted_impl_test.cpp
+++ b/src/mongo/db/storage/biggie/biggie_sorted_impl_test.cpp
@@ -60,7 +60,7 @@ public:
         BSONObj spec = BSON("key" << BSON("a" << 1) << "name"
                                   << "testIndex"
                                   << "v" << static_cast<int>(IndexDescriptor::kLatestIndexVersion)
-                                  << "ns" << ns << "unique" << unique);
+                                  << "unique" << unique);
         if (partial) {
             auto partialBSON =
                 BSON(IndexDescriptor::kPartialFilterExprFieldName.toString() << BSON(""
diff --git a/src/mongo/db/storage/bson_collection_catalog_entry.cpp b/src/mongo/db/storage/bson_collection_catalog_entry.cpp
index a90848175a0..9d07ddd60c9 100644
--- a/src/mongo/db/storage/bson_collection_catalog_entry.cpp
+++ b/src/mongo/db/storage/bson_collection_catalog_entry.cpp
@@ -32,7 +32,6 @@
 #include <algorithm>
 #include <numeric>
 
-#include "mongo/db/catalog/disable_index_spec_namespace_generation_gen.h"
 #include "mongo/db/field_ref.h"
 
 namespace mongo {
@@ -141,19 +140,6 @@ bool BSONCollectionCatalogEntry::MetaData::eraseIndex(StringData name) {
 
 void BSONCollectionCatalogEntry::MetaData::rename(StringData toNS) {
     ns = toNS.toString();
-    for (size_t i = 0; i < indexes.size(); i++) {
-        BSONObj spec = indexes[i].spec;
-        BSONObjBuilder b;
-        // Add the fields in the same order they were in the original specification.
-        for (auto&& elem : spec) {
-            if (elem.fieldNameStringData() == "ns") {
-                b.append("ns", toNS);
-            } else {
-                b.append(elem);
-            }
-        }
-        indexes[i].spec = b.obj();
-    }
 }
 
 KVPrefix BSONCollectionCatalogEntry::MetaData::getMaxPrefix() const {
diff --git a/src/mongo/db/storage/durable_catalog_impl.cpp b/src/mongo/db/storage/durable_catalog_impl.cpp
index c8b849206c1..a7e8b3f5fb1 100644
--- a/src/mongo/db/storage/durable_catalog_impl.cpp
+++ b/src/mongo/db/storage/durable_catalog_impl.cpp
@@ -36,7 +36,6 @@
 
 #include "mongo/bson/util/bson_extract.h"
 #include "mongo/bson/util/builder.h"
-#include "mongo/db/catalog/disable_index_spec_namespace_generation_gen.h"
 #include "mongo/db/concurrency/d_concurrency.h"
 #include "mongo/db/index/index_descriptor.h"
 #include "mongo/db/namespace_string.h"
@@ -1205,12 +1204,6 @@ BSONObj DurableCatalogImpl::getIndexSpec(OperationContext* opCtx,
     invariant(offset >= 0);
 
     BSONObj spec = md.indexes[offset].spec.getOwned();
-    if (spec.hasField("ns") || disableIndexSpecNamespaceGeneration.load()) {
-        return spec;
-    }
-
-    BSONObj nsObj = BSON("ns" << ns.ns());
-    spec = spec.addField(nsObj.firstElement());
     return spec;
 }
 
diff --git a/src/mongo/db/storage/kv/durable_catalog_test.cpp b/src/mongo/db/storage/kv/durable_catalog_test.cpp
index f76ad1830eb..2a93def21d7 100644
--- a/src/mongo/db/storage/kv/durable_catalog_test.cpp
+++ b/src/mongo/db/storage/kv/durable_catalog_test.cpp
@@ -108,10 +108,9 @@ public:
         std::string indexName = "idx" + std::to_string(numIndexesCreated);
 
         auto collection = std::make_unique<CollectionMock>(_nss);
-        IndexDescriptor desc(
-            collection.get(),
-            indexType,
-            BSON("v" << 1 << "key" << keyPattern << "name" << indexName << "ns" << _nss.ns()));
+        IndexDescriptor desc(collection.get(),
+                             indexType,
+                             BSON("v" << 1 << "key" << keyPattern << "name" << indexName));
 
         {
             WriteUnitOfWork wuow(opCtx.get());
diff --git a/src/mongo/db/storage/kv/kv_engine_test_harness.cpp b/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
index 7b9bfb7a5f4..034d7b673f5 100644
--- a/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
+++ b/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
@@ -167,8 +167,8 @@ TEST(KVEngineTestHarness, SimpleSorted1) {
 
     IndexDescriptor desc(collection.get(),
                          "",
-                         BSON("v" << static_cast<int>(IndexDescriptor::kLatestIndexVersion) << "ns"
-                                  << ns.ns() << "key" << BSON("a" << 1)));
+                         BSON("v" << static_cast<int>(IndexDescriptor::kLatestIndexVersion) << "key"
+                                  << BSON("a" << 1)));
     std::unique_ptr<SortedDataInterface> sorted;
     {
         MyOperationContext opCtx(engine);
@@ -704,7 +704,7 @@ DEATH_TEST_F(DurableCatalogImplTest, TerminateOnNonNumericIndexVersion, "Fatal A
                          "",
                          BSON("v"
                               << "1"
-                              << "ns" << ns.ns() << "key" << BSON("a" << 1)));
+                              << "key" << BSON("a" << 1)));
     std::unique_ptr<SortedDataInterface> sorted;
     {
         MyOperationContext opCtx(engine);
diff --git a/src/mongo/db/storage/storage_engine_test_fixture.h b/src/mongo/db/storage/storage_engine_test_fixture.h
index ffbb42ee70c..50cb70ae6df 100644
--- a/src/mongo/db/storage/storage_engine_test_fixture.h
+++ b/src/mongo/db/storage/storage_engine_test_fixture.h
@@ -128,7 +128,7 @@ public:
             BSONObjBuilder keyObj;
             builder.append("key", keyObj.append(key, 1).done());
         }
-        BSONObj spec = builder.append("name", key).append("ns", collNs.ns()).append("v", 2).done();
+        BSONObj spec = builder.append("name", key).append("v", 2).done();
 
         auto collection = std::make_unique<CollectionMock>(collNs);
         auto descriptor = std::make_unique<IndexDescriptor>(
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_index_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_index_test.cpp
index 4684e13e264..b86e2d60a85 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_index_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_index_test.cpp
@@ -77,7 +77,7 @@ public:
         BSONObj spec = BSON("key" << BSON("a" << 1) << "name"
                                   << "testIndex"
                                   << "v" << static_cast<int>(IndexDescriptor::kLatestIndexVersion)
-                                  << "ns" << ns << "unique" << unique);
+                                  << "unique" << unique);
 
         if (partial) {
             auto partialBSON =
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_standard_index_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_standard_index_test.cpp
index f03fc201827..1f683424598 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_standard_index_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_standard_index_test.cpp
@@ -77,7 +77,7 @@ public:
         BSONObj spec = BSON("key" << BSON("a" << 1) << "name"
                                   << "testIndex"
                                   << "v" << static_cast<int>(IndexDescriptor::kLatestIndexVersion)
-                                  << "ns" << ns << "unique" << unique);
+                                  << "unique" << unique);
 
         if (partial) {
             auto partialBSON =
diff --git a/src/mongo/db/system_index.cpp b/src/mongo/db/system_index.cpp
index 47433ac4d38..b3b8ed740a6 100644
--- a/src/mongo/db/system_index.cpp
+++ b/src/mongo/db/system_index.cpp
@@ -111,7 +111,7 @@ SharedSemiFuture<ReplIndexBuildState::IndexCatalogStats> generateSystemIndexForE
 
     try {
         auto indexSpecStatus = index_key_validate::validateIndexSpec(
-            opCtx, spec.toBSON(), ns, serverGlobalParams.featureCompatibility);
+            opCtx, spec.toBSON(), serverGlobalParams.featureCompatibility);
         BSONObj indexSpec = fassert(40452, indexSpecStatus);
 
         log() << "No authorization index detected on " << ns
@@ -232,20 +232,16 @@ void createSystemIndexes(OperationContext* opCtx, Collection* collection) {
     const NamespaceString& ns = collection->ns();
     BSONObj indexSpec;
     if (ns == AuthorizationManager::usersCollectionNamespace) {
-        indexSpec =
-            fassert(40455,
-                    index_key_validate::validateIndexSpec(opCtx,
-                                                          v3SystemUsersIndexSpec.toBSON(),
-                                                          ns,
-                                                          serverGlobalParams.featureCompatibility));
+        indexSpec = fassert(
+            40455,
+            index_key_validate::validateIndexSpec(
+                opCtx, v3SystemUsersIndexSpec.toBSON(), serverGlobalParams.featureCompatibility));
 
     } else if (ns == AuthorizationManager::rolesCollectionNamespace) {
-        indexSpec =
-            fassert(40457,
-                    index_key_validate::validateIndexSpec(opCtx,
-                                                          v3SystemRolesIndexSpec.toBSON(),
-                                                          ns,
-                                                          serverGlobalParams.featureCompatibility));
+        indexSpec = fassert(
+            40457,
+            index_key_validate::validateIndexSpec(
+                opCtx, v3SystemRolesIndexSpec.toBSON(), serverGlobalParams.featureCompatibility));
     }
     if (!indexSpec.isEmpty()) {
         opCtx->getServiceContext()->getOpObserver()->onCreateIndex(
diff --git a/src/mongo/dbtests/counttests.cpp b/src/mongo/dbtests/counttests.cpp
index 9f820418793..41ad97c5203 100644
--- a/src/mongo/dbtests/counttests.cpp
+++ b/src/mongo/dbtests/counttests.cpp
@@ -59,7 +59,7 @@ public:
 
             IndexCatalog* indexCatalog = _collection->getIndexCatalog();
             auto indexSpec = BSON("v" << static_cast<int>(IndexDescriptor::kLatestIndexVersion)
-                                      << "ns" << ns() << "key" << BSON("a" << 1) << "name"
+                                      << "key" << BSON("a" << 1) << "name"
                                       << "a_1");
             uassertStatusOK(indexCatalog->createIndexOnEmptyCollection(&_opCtx, indexSpec));
 
diff --git a/src/mongo/dbtests/dbtests.cpp b/src/mongo/dbtests/dbtests.cpp
index c61f4d390b2..6f33b22ebe8 100644
--- a/src/mongo/dbtests/dbtests.cpp
+++ b/src/mongo/dbtests/dbtests.cpp
@@ -86,7 +86,6 @@ void initWireSpec() {
 Status createIndex(OperationContext* opCtx, StringData ns, const BSONObj& keys, bool unique) {
     BSONObjBuilder specBuilder;
     specBuilder.append("name", DBClientBase::genIndexName(keys));
-    specBuilder.append("ns", ns);
     specBuilder.append("key", keys);
     specBuilder.append("v", static_cast<int>(kIndexVersion));
     if (unique) {
diff --git a/src/mongo/dbtests/indexcatalogtests.cpp b/src/mongo/dbtests/indexcatalogtests.cpp
index 9ac94209601..802a200ead9 100644
--- a/src/mongo/dbtests/indexcatalogtests.cpp
+++ b/src/mongo/dbtests/indexcatalogtests.cpp
@@ -143,11 +143,11 @@ public:
         dbtests::WriteContextForTests ctx(&opCtx, _nss.ns());
         const std::string indexName = "x_1";
 
-        ASSERT_OK(dbtests::createIndexFromSpec(
-            &opCtx,
-            _nss.ns(),
-            BSON("name" << indexName << "ns" << _nss.ns() << "key" << BSON("x" << 1) << "v"
-                        << static_cast<int>(kIndexVersion) << "expireAfterSeconds" << 5)));
+        ASSERT_OK(dbtests::createIndexFromSpec(&opCtx,
+                                               _nss.ns(),
+                                               BSON("name" << indexName << "key" << BSON("x" << 1)
+                                                           << "v" << static_cast<int>(kIndexVersion)
+                                                           << "expireAfterSeconds" << 5)));
 
         const IndexDescriptor* desc = _catalog->findIndexByName(&opCtx, indexName);
         ASSERT(desc);
diff --git a/src/mongo/dbtests/indexupdatetests.cpp b/src/mongo/dbtests/indexupdatetests.cpp
index 63ed34e3871..362b34ae44a 100644
--- a/src/mongo/dbtests/indexupdatetests.cpp
+++ b/src/mongo/dbtests/indexupdatetests.cpp
@@ -134,7 +134,7 @@ public:
 
         const BSONObj spec = BSON("name"
                                   << "a"
-                                  << "ns" << coll->ns().ns() << "key" << BSON("a" << 1) << "v"
+                                  << "key" << BSON("a" << 1) << "v"
                                   << static_cast<int>(kIndexVersion) << "unique" << true
                                   << "background" << background);
 
@@ -182,7 +182,7 @@ public:
 
         const BSONObj spec = BSON("name"
                                   << "a"
-                                  << "ns" << coll->ns().ns() << "key" << BSON("a" << 1) << "v"
+                                  << "key" << BSON("a" << 1) << "v"
                                   << static_cast<int>(kIndexVersion) << "unique" << true
                                   << "background" << background);
 
@@ -226,7 +226,7 @@ public:
         }
         // Request an interrupt.
         getGlobalServiceContext()->setKillAllOperations();
-        BSONObj indexInfo = BSON("key" << BSON("a" << 1) << "ns" << _ns << "name"
+        BSONObj indexInfo = BSON("key" << BSON("a" << 1) << "name"
                                        << "a_1"
                                        << "v" << static_cast<int>(kIndexVersion));
         // The call is interrupted because mayInterrupt == true.
@@ -269,7 +269,7 @@ public:
         }
         // Request an interrupt.
         getGlobalServiceContext()->setKillAllOperations();
-        BSONObj indexInfo = BSON("key" << BSON("_id" << 1) << "ns" << _ns << "name"
+        BSONObj indexInfo = BSON("key" << BSON("_id" << 1) << "name"
                                        << "_id_"
                                        << "v" << static_cast<int>(kIndexVersion));
         ASSERT_TRUE(buildIndexInterrupted(indexInfo));
@@ -317,7 +317,7 @@ public:
         ASSERT_OK(createIndex("unittest",
                               BSON("name"
                                    << "x"
-                                   << "ns" << _ns << "key" << BSON("x" << 1 << "y" << 1) << "v"
+                                   << "key" << BSON("x" << 1 << "y" << 1) << "v"
                                    << static_cast<int>(kIndexVersion))));
     }
 };
@@ -330,9 +330,8 @@ public:
                       createIndex("unittest",
                                   BSON("name"
                                        << "x"
-                                       << "ns" << _ns << "unique" << true << "key"
-                                       << BSON("x" << 1 << "y" << 1) << "v"
-                                       << static_cast<int>(kIndexVersion))));
+                                       << "unique" << true << "key" << BSON("x" << 1 << "y" << 1)
+                                       << "v" << static_cast<int>(kIndexVersion))));
     }
 };
 
@@ -342,7 +341,7 @@ public:
         ASSERT_OK(createIndex("unittest",
                               BSON("name"
                                    << "x"
-                                   << "ns" << _ns << "key" << BSON("x" << 1 << "y" << 1) << "v"
+                                   << "key" << BSON("x" << 1 << "y" << 1) << "v"
                                    << static_cast<int>(kIndexVersion))));
     }
 };
@@ -355,7 +354,7 @@ public:
                       createIndex("unittest",
                                   BSON("name"
                                        << "x"
-                                       << "ns" << _ns << "key" << BSON("y" << 1 << "x" << 1) << "v"
+                                       << "key" << BSON("y" << 1 << "x" << 1) << "v"
                                        << static_cast<int>(kIndexVersion))));
     }
 };
@@ -369,8 +368,8 @@ public:
         ASSERT_OK(createIndex("unittests",
                               BSON("name"
                                    << "super"
-                                   << "ns" << _ns << "unique" << 1 << "sparse" << true
-                                   << "expireAfterSeconds" << 3600 << "key"
+                                   << "unique" << 1 << "sparse" << true << "expireAfterSeconds"
+                                   << 3600 << "key"
                                    << BSON("superIdx"
                                            << "2d")
                                    << "v" << static_cast<int>(kIndexVersion))));
@@ -387,8 +386,8 @@ public:
                       createIndex("unittests",
                                   BSON("name"
                                        << "super2"
-                                       << "ns" << _ns << "expireAfterSeconds" << 3600 << "sparse"
-                                       << true << "unique" << 1 << "key"
+                                       << "expireAfterSeconds" << 3600 << "sparse" << true
+                                       << "unique" << 1 << "key"
                                        << BSON("superIdx"
                                                << "2d")
                                        << "v" << static_cast<int>(kIndexVersion))));
@@ -403,8 +402,8 @@ public:
         ASSERT_OK(createIndex("unittests",
                               BSON("name"
                                    << "super"
-                                   << "ns" << _ns << "expireAfterSeconds" << 3600 << "sparse"
-                                   << true << "unique" << 1 << "key"
+                                   << "expireAfterSeconds" << 3600 << "sparse" << true << "unique"
+                                   << 1 << "key"
                                    << BSON("superIdx"
                                            << "2d")
                                    << "v" << static_cast<int>(kIndexVersion))));
@@ -421,7 +420,7 @@ public:
                       createIndex("unittest",
                                   BSON("name"
                                        << "super2"
-                                       << "ns" << _ns << "unique" << false << "sparse" << true
+                                       << "unique" << false << "sparse" << true
                                        << "expireAfterSeconds" << 3600 << "key"
                                        << BSON("superIdx"
                                                << "2d")
@@ -432,16 +431,15 @@ public:
 class SameSpecDifferentSparse : public ComplexIndex {
 public:
     void run() {
-        ASSERT_EQUALS(
-            ErrorCodes::IndexOptionsConflict,
-            createIndex("unittest",
-                        BSON("name"
-                             << "super2"
-                             << "ns" << _ns << "unique" << 1 << "sparse" << false << "background"
-                             << true << "expireAfterSeconds" << 3600 << "key"
-                             << BSON("superIdx"
-                                     << "2d")
-                             << "v" << static_cast<int>(kIndexVersion))));
+        ASSERT_EQUALS(ErrorCodes::IndexOptionsConflict,
+                      createIndex("unittest",
+                                  BSON("name"
+                                       << "super2"
+                                       << "unique" << 1 << "sparse" << false << "background" << true
+                                       << "expireAfterSeconds" << 3600 << "key"
+                                       << BSON("superIdx"
+                                               << "2d")
+                                       << "v" << static_cast<int>(kIndexVersion))));
     }
 };
 
@@ -452,8 +450,8 @@ public:
                       createIndex("unittest",
                                   BSON("name"
                                        << "super2"
-                                       << "ns" << _ns << "unique" << 1 << "sparse" << true
-                                       << "expireAfterSeconds" << 2400 << "key"
+                                       << "unique" << 1 << "sparse" << true << "expireAfterSeconds"
+                                       << 2400 << "key"
                                        << BSON("superIdx"
                                                << "2d")
                                        << "v" << static_cast<int>(kIndexVersion))));
@@ -503,8 +501,8 @@ protected:
     BSONObj _createSpec(T storageEngineValue) {
         return BSON("name"
                     << "super2"
-                    << "ns" << _ns << "key" << BSON("a" << 1) << "v"
-                    << static_cast<int>(kIndexVersion) << "storageEngine" << storageEngineValue);
+                    << "key" << BSON("a" << 1) << "v" << static_cast<int>(kIndexVersion)
+                    << "storageEngine" << storageEngineValue);
     }
 };
 
diff --git a/src/mongo/dbtests/multikey_paths_test.cpp b/src/mongo/dbtests/multikey_paths_test.cpp
index 8f0759f69b1..6c72c3e8936 100644
--- a/src/mongo/dbtests/multikey_paths_test.cpp
+++ b/src/mongo/dbtests/multikey_paths_test.cpp
@@ -142,8 +142,7 @@ TEST_F(MultikeyPathsTest, PathsUpdatedOnIndexCreation) {
     createIndex(collection,
                 BSON("name"
                      << "a_1_b_1"
-                     << "ns" << _nss.ns() << "key" << keyPattern << "v"
-                     << static_cast<int>(kIndexVersion)))
+                     << "key" << keyPattern << "v" << static_cast<int>(kIndexVersion)))
         .transitional_ignore();
 
     assertMultikeyPaths(collection, keyPattern, {std::set<size_t>{}, {0U}});
@@ -172,8 +171,7 @@ TEST_F(MultikeyPathsTest, PathsUpdatedOnIndexCreationWithMultipleDocuments) {
     createIndex(collection,
                 BSON("name"
                      << "a_1_b_1"
-                     << "ns" << _nss.ns() << "key" << keyPattern << "v"
-                     << static_cast<int>(kIndexVersion)))
+                     << "key" << keyPattern << "v" << static_cast<int>(kIndexVersion)))
         .transitional_ignore();
 
     assertMultikeyPaths(collection, keyPattern, {{0U}, {0U}});
@@ -188,8 +186,7 @@ TEST_F(MultikeyPathsTest, PathsUpdatedOnDocumentInsert) {
     createIndex(collection,
                 BSON("name"
                      << "a_1_b_1"
-                     << "ns" << _nss.ns() << "key" << keyPattern << "v"
-                     << static_cast<int>(kIndexVersion)))
+                     << "key" << keyPattern << "v" << static_cast<int>(kIndexVersion)))
         .transitional_ignore();
 
     {
@@ -226,8 +223,7 @@ TEST_F(MultikeyPathsTest, PathsUpdatedOnDocumentUpdate) {
     createIndex(collection,
                 BSON("name"
                      << "a_1_b_1"
-                     << "ns" << _nss.ns() << "key" << keyPattern << "v"
-                     << static_cast<int>(kIndexVersion)))
+                     << "key" << keyPattern << "v" << static_cast<int>(kIndexVersion)))
         .transitional_ignore();
 
     {
@@ -275,8 +271,7 @@ TEST_F(MultikeyPathsTest, PathsNotUpdatedOnDocumentDelete) {
     createIndex(collection,
                 BSON("name"
                      << "a_1_b_1"
-                     << "ns" << _nss.ns() << "key" << keyPattern << "v"
-                     << static_cast<int>(kIndexVersion)))
+                     << "key" << keyPattern << "v" << static_cast<int>(kIndexVersion)))
         .transitional_ignore();
 
     {
@@ -316,16 +311,14 @@ TEST_F(MultikeyPathsTest, PathsUpdatedForMultipleIndexesOnDocumentInsert) {
     createIndex(collection,
                 BSON("name"
                      << "a_1_b_1"
-                     << "ns" << _nss.ns() << "key" << keyPatternAB << "v"
-                     << static_cast<int>(kIndexVersion)))
+                     << "key" << keyPatternAB << "v" << static_cast<int>(kIndexVersion)))
         .transitional_ignore();
 
     BSONObj keyPatternAC = BSON("a" << 1 << "c" << 1);
     createIndex(collection,
                 BSON("name"
                      << "a_1_c_1"
-                     << "ns" << _nss.ns() << "key" << keyPatternAC << "v"
-                     << static_cast<int>(kIndexVersion)))
+                     << "key" << keyPatternAC << "v" << static_cast<int>(kIndexVersion)))
         .transitional_ignore();
     {
         WriteUnitOfWork wuow(_opCtx.get());
diff --git a/src/mongo/dbtests/query_stage_count.cpp b/src/mongo/dbtests/query_stage_count.cpp
index 87e66a58918..6444ee4b9ea 100644
--- a/src/mongo/dbtests/query_stage_count.cpp
+++ b/src/mongo/dbtests/query_stage_count.cpp
@@ -75,7 +75,7 @@ public:
             ->createIndexOnEmptyCollection(&_opCtx,
                                            BSON("key" << BSON("x" << 1) << "name"
                                                       << "x_1"
-                                                      << "ns" << ns() << "v" << 1))
+                                                      << "v" << 1))
             .status_with_transitional_ignore();
 
         for (int i = 0; i < kDocuments; i++) {
diff --git a/src/mongo/dbtests/query_stage_ixscan.cpp b/src/mongo/dbtests/query_stage_ixscan.cpp
index 3217ebd979b..ca36a6710d7 100644
--- a/src/mongo/dbtests/query_stage_ixscan.cpp
+++ b/src/mongo/dbtests/query_stage_ixscan.cpp
@@ -61,9 +61,8 @@ public:
 
         ASSERT_OK(_coll->getIndexCatalog()->createIndexOnEmptyCollection(
             &_opCtx,
-            BSON("ns" << ns() << "key" << BSON("x" << 1) << "name"
-                      << DBClientBase::genIndexName(BSON("x" << 1)) << "v"
-                      << static_cast<int>(kIndexVersion))));
+            BSON("key" << BSON("x" << 1) << "name" << DBClientBase::genIndexName(BSON("x" << 1))
+                       << "v" << static_cast<int>(kIndexVersion))));
 
         wunit.commit();
     }
diff --git a/src/mongo/dbtests/querytests.cpp b/src/mongo/dbtests/querytests.cpp
index 6e74f6c1571..c91ab589923 100644
--- a/src/mongo/dbtests/querytests.cpp
+++ b/src/mongo/dbtests/querytests.cpp
@@ -100,7 +100,6 @@ protected:
     void addIndex(const IndexSpec& spec) {
         BSONObjBuilder builder(spec.toBSON());
         builder.append("v", int(IndexDescriptor::kLatestIndexVersion));
-        builder.append("ns", ns());
         auto specObj = builder.obj();
 
         MultiIndexBlock indexer;
diff --git a/src/mongo/dbtests/rollbacktests.cpp b/src/mongo/dbtests/rollbacktests.cpp
index 317be739e89..fd48e6f46a3 100644
--- a/src/mongo/dbtests/rollbacktests.cpp
+++ b/src/mongo/dbtests/rollbacktests.cpp
@@ -541,8 +541,8 @@ public:
         IndexCatalog* catalog = coll->getIndexCatalog();
 
         string idxName = "a";
-        BSONObj spec = BSON("ns" << ns << "key" << BSON("a" << 1) << "name" << idxName << "v"
-                                 << static_cast<int>(kIndexVersion));
+        BSONObj spec = BSON("key" << BSON("a" << 1) << "name" << idxName << "v"
+                                  << static_cast<int>(kIndexVersion));
 
         // END SETUP / START TEST
 
@@ -582,8 +582,8 @@ public:
         IndexCatalog* catalog = coll->getIndexCatalog();
 
         string idxName = "a";
-        BSONObj spec = BSON("ns" << ns << "key" << BSON("a" << 1) << "name" << idxName << "v"
-                                 << static_cast<int>(kIndexVersion));
+        BSONObj spec = BSON("key" << BSON("a" << 1) << "name" << idxName << "v"
+                                  << static_cast<int>(kIndexVersion));
 
         {
             WriteUnitOfWork uow(&opCtx);
@@ -635,8 +635,8 @@ public:
         IndexCatalog* catalog = coll->getIndexCatalog();
 
         string idxName = "a";
-        BSONObj spec = BSON("ns" << ns << "key" << BSON("a" << 1) << "name" << idxName << "v"
-                                 << static_cast<int>(kIndexVersion));
+        BSONObj spec = BSON("key" << BSON("a" << 1) << "name" << idxName << "v"
+                                  << static_cast<int>(kIndexVersion));
 
         // END SETUP / START TEST
 
@@ -678,12 +678,12 @@ public:
         string idxNameA = "indexA";
         string idxNameB = "indexB";
         string idxNameC = "indexC";
-        BSONObj specA = BSON("ns" << ns << "key" << BSON("a" << 1) << "name" << idxNameA << "v"
-                                  << static_cast<int>(kIndexVersion));
-        BSONObj specB = BSON("ns" << ns << "key" << BSON("b" << 1) << "name" << idxNameB << "v"
-                                  << static_cast<int>(kIndexVersion));
-        BSONObj specC = BSON("ns" << ns << "key" << BSON("c" << 1) << "name" << idxNameC << "v"
-                                  << static_cast<int>(kIndexVersion));
+        BSONObj specA = BSON("key" << BSON("a" << 1) << "name" << idxNameA << "v"
+                                   << static_cast<int>(kIndexVersion));
+        BSONObj specB = BSON("key" << BSON("b" << 1) << "name" << idxNameB << "v"
+                                   << static_cast<int>(kIndexVersion));
+        BSONObj specC = BSON("key" << BSON("c" << 1) << "name" << idxNameC << "v"
+                                   << static_cast<int>(kIndexVersion));
 
         // END SETUP / START TEST
 
diff --git a/src/mongo/dbtests/storage_timestamp_tests.cpp b/src/mongo/dbtests/storage_timestamp_tests.cpp
index 60d10e576f3..6e79c1b8ae3 100644
--- a/src/mongo/dbtests/storage_timestamp_tests.cpp
+++ b/src/mongo/dbtests/storage_timestamp_tests.cpp
@@ -261,8 +261,7 @@ public:
             auto swIndexInfoObj =
                 indexer.init(_opCtx,
                              coll,
-                             {BSON("v" << 2 << "name" << indexName << "ns" << coll->ns().ns()
-                                       << "key" << indexKey)},
+                             {BSON("v" << 2 << "name" << indexName << "key" << indexKey)},
                              MultiIndexBlock::makeTimestampedIndexOnInitFn(_opCtx, coll));
             ASSERT_OK(swIndexInfoObj.getStatus());
             indexInfoObj = std::move(swIndexInfoObj.getValue()[0]);
@@ -1260,8 +1259,8 @@ public:
             uuid = autoColl.getCollection()->uuid();
         }
         auto indexName = "a_1";
-        auto indexSpec = BSON("name" << indexName << "ns" << nss.ns() << "key" << BSON("a" << 1)
-                                     << "v" << static_cast<int>(kIndexVersion));
+        auto indexSpec = BSON("name" << indexName << "key" << BSON("a" << 1) << "v"
+                                     << static_cast<int>(kIndexVersion));
         ASSERT_OK(dbtests::createIndexFromSpec(_opCtx, nss.ns(), indexSpec));
 
         _coordinatorMock->alwaysAllowWrites(false);
@@ -1329,8 +1328,8 @@ public:
             uuid = autoColl.getCollection()->uuid();
         }
         auto indexName = "a_1";
-        auto indexSpec = BSON("name" << indexName << "ns" << nss.ns() << "key" << BSON("a" << 1)
-                                     << "v" << static_cast<int>(kIndexVersion));
+        auto indexSpec = BSON("name" << indexName << "key" << BSON("a" << 1) << "v"
+                                     << static_cast<int>(kIndexVersion));
         ASSERT_OK(dbtests::createIndexFromSpec(_opCtx, nss.ns(), indexSpec));
 
         _coordinatorMock->alwaysAllowWrites(false);
@@ -1357,10 +1356,10 @@ public:
                                               << "op"
                                               << "i"
                                               << "ns" << nss.ns() << "ui" << uuid << "o" << doc2));
-        auto indexSpec2 = BSON("createIndexes" << nss.coll() << "ns" << nss.ns() << "v"
-                                               << static_cast<int>(kIndexVersion) << "key"
-                                               << BSON("b" << 1) << "name"
-                                               << "b_1");
+        auto indexSpec2 =
+            BSON("createIndexes" << nss.coll() << "v" << static_cast<int>(kIndexVersion) << "key"
+                                 << BSON("b" << 1) << "name"
+                                 << "b_1");
         auto createIndexOp = repl::OplogEntry(
             BSON("ts" << indexBuildTime.asTimestamp() << "t" << 1LL << "v" << 2 << "op"
                       << "c"
@@ -1425,8 +1424,8 @@ public:
 
         AutoGetCollection autoColl(_opCtx, nss, LockMode::MODE_IX);
         auto indexName = "a_1";
-        auto indexSpec = BSON("name" << indexName << "ns" << nss.ns() << "key" << BSON("a" << 1)
-                                     << "v" << static_cast<int>(kIndexVersion));
+        auto indexSpec = BSON("name" << indexName << "key" << BSON("a" << 1) << "v"
+                                     << static_cast<int>(kIndexVersion));
         ASSERT_OK(dbtests::createIndexFromSpec(_opCtx, nss.ns(), indexSpec));
 
         const LogicalTime pastTime = _clock->reserveTicks(1);
@@ -1454,8 +1453,8 @@ public:
 
         AutoGetCollection autoColl(_opCtx, nss, LockMode::MODE_IX);
         auto indexName = "a_1";
-        auto indexSpec = BSON("name" << indexName << "ns" << nss.ns() << "key" << BSON("a" << 1)
-                                     << "v" << static_cast<int>(kIndexVersion));
+        auto indexSpec = BSON("name" << indexName << "key" << BSON("a" << 1) << "v"
+                                     << static_cast<int>(kIndexVersion));
         ASSERT_OK(dbtests::createIndexFromSpec(_opCtx, nss.ns(), indexSpec));
 
         const LogicalTime pastTime = _clock->reserveTicks(1);
@@ -1877,7 +1876,7 @@ public:
                 autoColl.getCollection(),
                 {BSON("v" << 2 << "unique" << true << "name"
                           << "a_1"
-                          << "ns" << nss.ns() << "key" << BSON("a" << 1))},
+                          << "key" << BSON("a" << 1))},
                 MultiIndexBlock::makeTimestampedIndexOnInitFn(_opCtx, autoColl.getCollection()));
             ASSERT_OK(swIndexInfoObj.getStatus());
             indexInfoObj = std::move(swIndexInfoObj.getValue()[0]);
@@ -2515,10 +2514,10 @@ public:
                 origIdents = durableCatalog->getAllIdents(_opCtx);
             }
 
-            auto indexSpec = BSON("createIndexes" << nss.coll() << "ns" << nss.ns() << "v"
-                                                  << static_cast<int>(kIndexVersion) << "key"
-                                                  << BSON("field" << 1) << "name"
-                                                  << "field_1");
+            auto indexSpec =
+                BSON("createIndexes" << nss.coll() << "v" << static_cast<int>(kIndexVersion)
+                                     << "key" << BSON("field" << 1) << "name"
+                                     << "field_1");
 
             auto createIndexOp = BSON("ts" << startBuildTs << "t" << 1LL << "v" << 2 << "op"
                                            << "c"
diff --git a/src/mongo/dbtests/validate_tests.cpp b/src/mongo/dbtests/validate_tests.cpp
index 39f48384421..ed805c905f7 100644
--- a/src/mongo/dbtests/validate_tests.cpp
+++ b/src/mongo/dbtests/validate_tests.cpp
@@ -229,14 +229,13 @@ public:
             wunit.commit();
         }
 
-        auto status =
-            dbtests::createIndexFromSpec(&_opCtx,
-                                         coll->ns().ns(),
-                                         BSON("name"
-                                              << "a"
-                                              << "ns" << coll->ns().ns() << "key" << BSON("a" << 1)
-                                              << "v" << static_cast<int>(kIndexVersion)
-                                              << "background" << false));
+        auto status = dbtests::createIndexFromSpec(&_opCtx,
+                                                   coll->ns().ns(),
+                                                   BSON("name"
+                                                        << "a"
+                                                        << "key" << BSON("a" << 1) << "v"
+                                                        << static_cast<int>(kIndexVersion)
+                                                        << "background" << false));
 
         ASSERT_OK(status);
         ASSERT_TRUE(checkValid());
@@ -301,14 +300,13 @@ public:
             wunit.commit();
         }
 
-        auto status =
-            dbtests::createIndexFromSpec(&_opCtx,
-                                         coll->ns().ns(),
-                                         BSON("name"
-                                              << "a"
-                                              << "ns" << coll->ns().ns() << "key" << BSON("a" << 1)
-                                              << "v" << static_cast<int>(kIndexVersion)
-                                              << "background" << false));
+        auto status = dbtests::createIndexFromSpec(&_opCtx,
+                                                   coll->ns().ns(),
+                                                   BSON("name"
+                                                        << "a"
+                                                        << "key" << BSON("a" << 1) << "v"
+                                                        << static_cast<int>(kIndexVersion)
+                                                        << "background" << false));
 
         ASSERT_OK(status);
         ASSERT_TRUE(checkValid());
@@ -459,8 +457,7 @@ public:
                                                    coll->ns().ns(),
                                                    BSON("name"
                                                         << "multikey_index"
-                                                        << "ns" << coll->ns().ns() << "key"
-                                                        << BSON("a.b" << 1) << "v"
+                                                        << "key" << BSON("a.b" << 1) << "v"
                                                         << static_cast<int>(kIndexVersion)
                                                         << "background" << false));
 
@@ -534,9 +531,9 @@ public:
                                          coll->ns().ns(),
                                          BSON("name"
                                               << "sparse_index"
-                                              << "ns" << coll->ns().ns() << "key" << BSON("a" << 1)
-                                              << "v" << static_cast<int>(kIndexVersion)
-                                              << "background" << false << "sparse" << true));
+                                              << "key" << BSON("a" << 1) << "v"
+                                              << static_cast<int>(kIndexVersion) << "background"
+                                              << false << "sparse" << true));
 
         ASSERT_OK(status);
         ASSERT_TRUE(checkValid());
@@ -601,9 +598,9 @@ public:
                                          coll->ns().ns(),
                                          BSON("name"
                                               << "partial_index"
-                                              << "ns" << coll->ns().ns() << "key" << BSON("a" << 1)
-                                              << "v" << static_cast<int>(kIndexVersion)
-                                              << "background" << false << "partialFilterExpression"
+                                              << "key" << BSON("a" << 1) << "v"
+                                              << static_cast<int>(kIndexVersion) << "background"
+                                              << false << "partialFilterExpression"
                                               << BSON("a" << BSON("$gt" << 1))));
 
         ASSERT_OK(status);
@@ -662,7 +659,7 @@ public:
                                          coll->ns().ns(),
                                          BSON("name"
                                               << "partial_index"
-                                              << "ns" << coll->ns().ns() << "key"
+                                              << "key"
                                               << BSON("x"
                                                       << "2dsphere")
                                               << "v" << static_cast<int>(kIndexVersion)
@@ -675,7 +672,7 @@ public:
                                          coll->ns().ns(),
                                          BSON("name"
                                               << "partial_index"
-                                              << "ns" << coll->ns().ns() << "key"
+                                              << "key"
                                               << BSON("x"
                                                       << "2dsphere")
                                               << "v" << static_cast<int>(kIndexVersion)
@@ -735,9 +732,8 @@ public:
                                                    coll->ns().ns(),
                                                    BSON("name"
                                                         << "compound_index_1"
-                                                        << "ns" << coll->ns().ns() << "key"
-                                                        << BSON("a" << 1 << "b" << -1) << "v"
-                                                        << static_cast<int>(kIndexVersion)
+                                                        << "key" << BSON("a" << 1 << "b" << -1)
+                                                        << "v" << static_cast<int>(kIndexVersion)
                                                         << "background" << false));
         ASSERT_OK(status);
 
@@ -745,8 +741,7 @@ public:
                                               coll->ns().ns(),
                                               BSON("name"
                                                    << "compound_index_2"
-                                                   << "ns" << coll->ns().ns() << "key"
-                                                   << BSON("a" << -1 << "b" << 1) << "v"
+                                                   << "key" << BSON("a" << -1 << "b" << 1) << "v"
                                                    << static_cast<int>(kIndexVersion)
                                                    << "background" << false));
 
@@ -806,7 +801,7 @@ public:
         auto status = dbtests::createIndexFromSpec(
             &_opCtx,
             coll->ns().ns(),
-            BSON("name" << indexName << "ns" << coll->ns().ns() << "key" << BSON("a" << 1) << "v"
+            BSON("name" << indexName << "key" << BSON("a" << 1) << "v"
                         << static_cast<int>(kIndexVersion) << "background" << false));
 
         ASSERT_OK(status);
@@ -888,7 +883,7 @@ public:
         auto status = dbtests::createIndexFromSpec(
             &_opCtx,
             coll->ns().ns(),
-            BSON("name" << indexName << "ns" << coll->ns().ns() << "key" << BSON("a" << 1) << "v"
+            BSON("name" << indexName << "key" << BSON("a" << 1) << "v"
                         << static_cast<int>(kIndexVersion) << "background" << false));
 
         ASSERT_OK(status);
@@ -935,8 +930,8 @@ public:
         auto status = dbtests::createIndexFromSpec(
             &_opCtx,
             coll->ns().ns(),
-            BSON("name" << indexName << "ns" << coll->ns().ns() << "key" << indexKey << "v"
-                        << static_cast<int>(kIndexVersion) << "background" << false));
+            BSON("name" << indexName << "key" << indexKey << "v" << static_cast<int>(kIndexVersion)
+                        << "background" << false));
         ASSERT_OK(status);
 
         // Insert non-multikey documents.
@@ -1044,8 +1039,8 @@ public:
         auto status = dbtests::createIndexFromSpec(
             &_opCtx,
             coll->ns().ns(),
-            BSON("name" << indexName << "ns" << coll->ns().ns() << "key" << indexKey << "v"
-                        << static_cast<int>(kIndexVersion) << "background" << false));
+            BSON("name" << indexName << "key" << indexKey << "v" << static_cast<int>(kIndexVersion)
+                        << "background" << false));
         ASSERT_OK(status);
 
         // Insert documents with indexed and not-indexed paths.
@@ -1135,8 +1130,8 @@ public:
         auto status = dbtests::createIndexFromSpec(
             &_opCtx,
             coll->ns().ns(),
-            BSON("name" << indexName << "ns" << coll->ns().ns() << "key" << indexKey << "v"
-                        << static_cast<int>(kIndexVersion) << "background" << false));
+            BSON("name" << indexName << "key" << indexKey << "v" << static_cast<int>(kIndexVersion)
+                        << "background" << false));
         ASSERT_OK(status);
 
         // Insert documents.
@@ -1222,8 +1217,8 @@ public:
         auto status = dbtests::createIndexFromSpec(
             &_opCtx,
             coll->ns().ns(),
-            BSON("name" << indexName << "ns" << coll->ns().ns() << "key" << indexKey << "v"
-                        << static_cast<int>(kIndexVersion) << "background" << false));
+            BSON("name" << indexName << "key" << indexKey << "v" << static_cast<int>(kIndexVersion)
+                        << "background" << false));
         ASSERT_OK(status);
 
         // Insert documents.
@@ -1328,8 +1323,8 @@ public:
         auto status = dbtests::createIndexFromSpec(
             &_opCtx,
             coll->ns().ns(),
-            BSON("name" << indexName << "ns" << coll->ns().ns() << "key" << indexKey << "v"
-                        << static_cast<int>(kIndexVersion) << "background" << false));
+            BSON("name" << indexName << "key" << indexKey << "v" << static_cast<int>(kIndexVersion)
+                        << "background" << false));
         ASSERT_OK(status);
 
         // Insert documents.
diff --git a/src/mongo/dbtests/wildcard_multikey_persistence_test.cpp b/src/mongo/dbtests/wildcard_multikey_persistence_test.cpp
index 8ace89874da..6731153ed88 100644
--- a/src/mongo/dbtests/wildcard_multikey_persistence_test.cpp
+++ b/src/mongo/dbtests/wildcard_multikey_persistence_test.cpp
@@ -181,8 +181,7 @@ protected:
                                   BSONObj key,
                                   BSONObj pathProjection,
                                   bool background) {
-        BSONObjBuilder bob =
-            std::move(BSONObjBuilder() << "ns" << nss.ns() << "name" << name << "key" << key);
+        BSONObjBuilder bob = std::move(BSONObjBuilder() << "name" << name << "key" << key);
 
         if (!pathProjection.isEmpty())
             bob << IndexDescriptor::kPathProjectionFieldName << pathProjection;