SERVER-45599 Backport of SERVER-39495: Only return versioned filtering metadata for cases that actually need to do filtering

This is a partial cherry-pick from 851dad7902d6bb8c3ed25f99f565a2e2c8c8bc47, adapted for the 4.0 branch.

16 files changed, 168 insertions, 154 deletions

diff --git a/src/mongo/db/commands/count_cmd.cpp b/src/mongo/db/commands/count_cmd.cpp
index 50cd6752024..9a4fd7ff529 100644
--- a/src/mongo/db/commands/count_cmd.cpp
+++ b/src/mongo/db/commands/count_cmd.cpp
@@ -152,8 +152,7 @@ public:
 
         // Prevent chunks from being cleaned up during yields - this allows us to only check the
         // version on initial entry into count.
-        auto rangePreserver =
-            CollectionShardingState::get(opCtx, nss)->getMetadataForOperation(opCtx);
+        auto rangePreserver = CollectionShardingState::get(opCtx, nss)->getCurrentMetadata();
 
         auto statusWithPlanExecutor =
             getExecutorCount(opCtx, collection, request.getValue(), true /*explain*/);
@@ -206,8 +205,7 @@ public:
 
         // Prevent chunks from being cleaned up during yields - this allows us to only check the
         // version on initial entry into count.
-        auto rangePreserver =
-            CollectionShardingState::get(opCtx, nss)->getMetadataForOperation(opCtx);
+        auto rangePreserver = CollectionShardingState::get(opCtx, nss)->getCurrentMetadata();
 
         auto statusWithPlanExecutor =
             getExecutorCount(opCtx, collection, request.getValue(), false /*explain*/);
diff --git a/src/mongo/db/commands/geo_near_cmd.cpp b/src/mongo/db/commands/geo_near_cmd.cpp
index 336ce83ebba..e21ccc9860f 100644
--- a/src/mongo/db/commands/geo_near_cmd.cpp
+++ b/src/mongo/db/commands/geo_near_cmd.cpp
@@ -230,9 +230,9 @@ public:
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
 
         // Prevent chunks from being cleaned up during yields - this allows us to only check the
-        // version on initial entry into geoNear.
-        auto rangePreserver =
-            CollectionShardingState::get(opCtx, nss)->getMetadataForOperation(opCtx);
+        // version on initial entry into geoNear (which happens as part of
+        // AutoGetCollectionForReadCommand).
+        auto rangePreserver = CollectionShardingState::get(opCtx, nss)->getCurrentMetadata();
 
         const auto& readConcernArgs = repl::ReadConcernArgs::get(opCtx);
         const PlanExecutor::YieldPolicy yieldPolicy =
diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index 4a23c78b7fb..8d99882c92d 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -1434,7 +1434,7 @@ public:
 
         const auto metadata = [&] {
             AutoGetCollectionForReadCommand autoColl(opCtx, config.nss);
-            return CollectionShardingState::get(opCtx, config.nss)->getMetadataForOperation(opCtx);
+            return CollectionShardingState::get(opCtx, config.nss)->getCurrentMetadata();
         }();
 
         bool shouldHaveData = false;
diff --git a/src/mongo/db/exec/update.cpp b/src/mongo/db/exec/update.cpp
index eb568bfb8e4..e2b78460b59 100644
--- a/src/mongo/db/exec/update.cpp
+++ b/src/mongo/db/exec/update.cpp
@@ -281,7 +281,6 @@ BSONObj UpdateStage::transformAndUpdate(const Snapshotted<BSONObj>& oldObj, Reco
     }
 
     if (docWasModified) {
-
         // Prepare to write back the modified document
         WriteUnitOfWork wunit(getOpCtx());
 
diff --git a/src/mongo/db/op_observer_impl.cpp b/src/mongo/db/op_observer_impl.cpp
index 15abf920fa6..62a6d9699cf 100644
--- a/src/mongo/db/op_observer_impl.cpp
+++ b/src/mongo/db/op_observer_impl.cpp
@@ -311,7 +311,7 @@ OpTimeBundle replLogApplyOps(OperationContext* opCtx,
 BSONObj OpObserverImpl::getDocumentKey(OperationContext* opCtx,
                                        NamespaceString const& nss,
                                        BSONObj const& doc) {
-    auto metadata = CollectionShardingState::get(opCtx, nss)->getMetadataForOperation(opCtx);
+    auto metadata = CollectionShardingState::get(opCtx, nss)->getCurrentMetadata();
     return metadata->extractDocumentKey(doc).getOwned();
 }
 
diff --git a/src/mongo/db/pipeline/pipeline_d.cpp b/src/mongo/db/pipeline/pipeline_d.cpp
index 9523261eb8a..5b368e81af1 100644
--- a/src/mongo/db/pipeline/pipeline_d.cpp
+++ b/src/mongo/db/pipeline/pipeline_d.cpp
@@ -157,7 +157,7 @@ StatusWith<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> createRandomCursorEx
     if (ShardingState::get(opCtx)->needCollectionMetadata(opCtx, collection->ns().ns())) {
         auto shardFilterStage = stdx::make_unique<ShardFilterStage>(
             opCtx,
-            CollectionShardingState::get(opCtx, collection->ns())->getMetadataForOperation(opCtx),
+            CollectionShardingState::get(opCtx, collection->ns())->getOrphansFilter(opCtx),
             ws.get(),
             stage.release());
         return PlanExecutor::make(opCtx,
diff --git a/src/mongo/db/query/get_executor.cpp b/src/mongo/db/query/get_executor.cpp
index defba5f3c69..ea89990bd2c 100644
--- a/src/mongo/db/query/get_executor.cpp
+++ b/src/mongo/db/query/get_executor.cpp
@@ -178,8 +178,8 @@ void fillOutPlannerParams(OperationContext* opCtx,
 
     // If the caller wants a shard filter, make sure we're actually sharded.
     if (plannerParams->options & QueryPlannerParams::INCLUDE_SHARD_FILTER) {
-        auto collMetadata = CollectionShardingState::get(opCtx, canonicalQuery->nss())
-                                ->getMetadataForOperation(opCtx);
+        auto collMetadata =
+            CollectionShardingState::get(opCtx, canonicalQuery->nss())->getCurrentMetadata();
         if (collMetadata->isSharded()) {
             plannerParams->shardKey = collMetadata->getKeyPattern();
         } else {
@@ -313,8 +313,7 @@ StatusWith<PrepareExecutionResult> prepareExecution(OperationContext* opCtx,
         if (plannerParams.options & QueryPlannerParams::INCLUDE_SHARD_FILTER) {
             root = make_unique<ShardFilterStage>(
                 opCtx,
-                CollectionShardingState::get(opCtx, canonicalQuery->nss())
-                    ->getMetadataForOperation(opCtx),
+                CollectionShardingState::get(opCtx, canonicalQuery->nss())->getOrphansFilter(opCtx),
                 ws,
                 root.release());
         }
diff --git a/src/mongo/db/query/stage_builder.cpp b/src/mongo/db/query/stage_builder.cpp
index c1390d0d18c..89a996be968 100644
--- a/src/mongo/db/query/stage_builder.cpp
+++ b/src/mongo/db/query/stage_builder.cpp
@@ -302,11 +302,11 @@ PlanStage* buildStages(OperationContext* opCtx,
             if (nullptr == childStage) {
                 return nullptr;
             }
-            return new ShardFilterStage(opCtx,
-                                        CollectionShardingState::get(opCtx, collection->ns())
-                                            ->getMetadataForOperation(opCtx),
-                                        ws,
-                                        childStage);
+            return new ShardFilterStage(
+                opCtx,
+                CollectionShardingState::get(opCtx, collection->ns())->getOrphansFilter(opCtx),
+                ws,
+                childStage);
         }
         case STAGE_KEEP_MUTATIONS: {
             const KeepMutationsNode* km = static_cast<const KeepMutationsNode*>(root);
diff --git a/src/mongo/db/s/collection_metadata.cpp b/src/mongo/db/s/collection_metadata.cpp
index 19c7b60a759..108395683d8 100644
--- a/src/mongo/db/s/collection_metadata.cpp
+++ b/src/mongo/db/s/collection_metadata.cpp
@@ -47,6 +47,46 @@ namespace mongo {
 CollectionMetadata::CollectionMetadata(std::shared_ptr<ChunkManager> cm, const ShardId& thisShardId)
     : _cm(std::move(cm)), _thisShardId(thisShardId) {}
 
+BSONObj CollectionMetadata::extractDocumentKey(const BSONObj& doc) const {
+    BSONObj key;
+
+    if (isSharded()) {
+        auto const& pattern = _cm->getShardKeyPattern();
+        key = dotted_path_support::extractElementsBasedOnTemplate(doc, pattern.toBSON());
+        if (pattern.hasId()) {
+            return key;
+        }
+        // else, try to append an _id field from the document.
+    }
+
+    if (auto id = doc["_id"]) {
+        return key.isEmpty() ? id.wrap() : BSONObjBuilder(std::move(key)).append(id).obj();
+    }
+
+    // For legacy documents that lack an _id, use the document itself as its key.
+    return doc;
+}
+
+void CollectionMetadata::toBSONBasic(BSONObjBuilder& bb) const {
+    if (isSharded()) {
+        _cm->getVersion().appendLegacyWithField(&bb, "collVersion");
+        getShardVersion().appendLegacyWithField(&bb, "shardVersion");
+        bb.append("keyPattern", _cm->getShardKeyPattern().toBSON());
+    } else {
+        ChunkVersion::UNSHARDED().appendLegacyWithField(&bb, "collVersion");
+        ChunkVersion::UNSHARDED().appendLegacyWithField(&bb, "shardVersion");
+    }
+}
+
+std::string CollectionMetadata::toStringBasic() const {
+    if (isSharded()) {
+        return str::stream() << "collection version: " << _cm->getVersion().toString()
+                             << ", shard version: " << getShardVersion().toString();
+    } else {
+        return "collection version: <unsharded>";
+    }
+}
+
 RangeMap CollectionMetadata::getChunks() const {
     invariant(isSharded());
 
@@ -113,62 +153,8 @@ Status CollectionMetadata::checkChunkIsValid(const ChunkType& chunk) const {
     return Status::OK();
 }
 
-BSONObj CollectionMetadata::extractDocumentKey(BSONObj const& doc) const {
-    BSONObj key;
-
-    if (isSharded()) {
-        auto const& pattern = getChunkManager()->getShardKeyPattern();
-        key = dotted_path_support::extractElementsBasedOnTemplate(doc, pattern.toBSON());
-        if (pattern.hasId()) {
-            return key;
-        }
-        // else, try to append an _id field from the document.
-    }
-
-    if (auto id = doc["_id"]) {
-        return key.isEmpty() ? id.wrap() : BSONObjBuilder(std::move(key)).append(id).obj();
-    }
-
-    // For legacy documents that lack an _id, use the document itself as its key.
-    return doc;
-}
-
-void CollectionMetadata::toBSONBasic(BSONObjBuilder& bb) const {
-    if (isSharded()) {
-        _cm->getVersion().appendLegacyWithField(&bb, "collVersion");
-        getShardVersion().appendLegacyWithField(&bb, "shardVersion");
-        bb.append("keyPattern", _cm->getShardKeyPattern().toBSON());
-    } else {
-        ChunkVersion::UNSHARDED().appendLegacyWithField(&bb, "collVersion");
-        ChunkVersion::UNSHARDED().appendLegacyWithField(&bb, "shardVersion");
-    }
-}
-
-void CollectionMetadata::toBSONChunks(BSONArrayBuilder& bb) const {
-    if (!isSharded())
-        return;
-
-    for (const auto& chunk : _cm->chunks()) {
-        if (chunk.getShardId() == _thisShardId) {
-            BSONArrayBuilder chunkBB(bb.subarrayStart());
-            chunkBB.append(chunk.getMin());
-            chunkBB.append(chunk.getMax());
-            chunkBB.done();
-        }
-    }
-}
-
-std::string CollectionMetadata::toStringBasic() const {
-    if (isSharded()) {
-        return str::stream() << "collection version: " << _cm->getVersion().toString()
-                             << ", shard version: " << getShardVersion().toString();
-    } else {
-        return "collection version: <unsharded>";
-    }
-}
-
 boost::optional<ChunkRange> CollectionMetadata::getNextOrphanRange(
-    RangeMap const& receivingChunks, BSONObj const& origLookupKey) const {
+    const RangeMap& receivingChunks, const BSONObj& origLookupKey) const {
     invariant(isSharded());
 
     const BSONObj maxKey = getMaxKey();
@@ -236,4 +222,18 @@ boost::optional<ChunkRange> CollectionMetadata::getNextOrphanRange(
     return boost::none;
 }
 
+void CollectionMetadata::toBSONChunks(BSONArrayBuilder* builder) const {
+    if (!isSharded())
+        return;
+
+    for (const auto& chunk : _cm->chunks()) {
+        if (chunk.getShardId() == _thisShardId) {
+            BSONArrayBuilder chunkBB(builder->subarrayStart());
+            chunkBB.append(chunk.getMin());
+            chunkBB.append(chunk.getMax());
+            chunkBB.done();
+        }
+    }
+}
+
 }  // namespace mongo
diff --git a/src/mongo/db/s/collection_metadata.h b/src/mongo/db/s/collection_metadata.h
index ae72682ca49..f123af36e26 100644
--- a/src/mongo/db/s/collection_metadata.h
+++ b/src/mongo/db/s/collection_metadata.h
@@ -64,8 +64,7 @@ public:
     CollectionMetadata(std::shared_ptr<ChunkManager> cm, const ShardId& thisShardId);
 
     /**
-     * Returns whether this metadata object represents a sharded collection which requires
-     * filtering.
+     * Returns whether this metadata object represents a sharded or unsharded collection.
      */
     bool isSharded() const {
         return bool(_cm);
@@ -86,6 +85,47 @@ public:
     }
 
     /**
+     * Obtains the shard id with which this collection metadata is configured.
+     */
+    const ShardId& shardId() const {
+        invariant(isSharded());
+        return _thisShardId;
+    }
+
+    /**
+     * Returns true if 'key' contains exactly the same fields as the shard key pattern.
+     */
+    bool isValidKey(const BSONObj& key) const {
+        invariant(isSharded());
+        return _cm->getShardKeyPattern().isShardKey(key);
+    }
+
+    const BSONObj& getKeyPattern() const {
+        invariant(isSharded());
+        return _cm->getShardKeyPattern().toBSON();
+    }
+
+    const std::vector<std::unique_ptr<FieldRef>>& getKeyPatternFields() const {
+        invariant(isSharded());
+        return _cm->getShardKeyPattern().getKeyPatternFields();
+    }
+
+    BSONObj getMinKey() const {
+        invariant(isSharded());
+        return _cm->getShardKeyPattern().getKeyPattern().globalMin();
+    }
+
+    BSONObj getMaxKey() const {
+        invariant(isSharded());
+        return _cm->getShardKeyPattern().getKeyPattern().globalMax();
+    }
+
+    bool uuidMatches(UUID uuid) const {
+        invariant(isSharded());
+        return _cm->uuidMatches(uuid);
+    }
+
+    /**
      * Returns just the shard key fields, if the collection is sharded, and the _id field, from
      * `doc`. Does not alter any field values (e.g. by hashing); values are copied verbatim.
      */
@@ -97,29 +137,17 @@ public:
     void toBSONBasic(BSONObjBuilder& bb) const;
 
     /**
-     * BSON output of the chunks metadata into a BSONArray
-     */
-    void toBSONChunks(BSONArrayBuilder& bb) const;
-
-    /**
      * String output of the collection and shard versions.
      */
     std::string toStringBasic() const;
 
-    /**
-     * Obtains the shard id with which this collection metadata is configured.
-     */
-    const ShardId& shardId() const {
-        invariant(isSharded());
-        return _thisShardId;
-    }
+    //
+    // Methods used for orphan filtering and general introspection of the chunks owned by the shard
+    //
 
-    /**
-     * Returns true if 'key' contains exactly the same fields as the shard key pattern.
-     */
-    bool isValidKey(const BSONObj& key) const {
+    ChunkManager* getChunkManager() const {
         invariant(isSharded());
-        return _cm->getShardKeyPattern().isShardKey(key);
+        return _cm.get();
     }
 
     /**
@@ -152,7 +180,7 @@ public:
     /**
      * Returns true if the argument range overlaps any chunk.
      */
-    bool rangeOverlapsChunk(ChunkRange const& range) const {
+    bool rangeOverlapsChunk(const ChunkRange& range) const {
         invariant(isSharded());
         return _cm->rangeOverlapsShard(range, _thisShardId);
     }
@@ -175,49 +203,25 @@ public:
      *
      * @return orphanRange the output range. Note that the NS is not set.
      */
-    boost::optional<ChunkRange> getNextOrphanRange(RangeMap const& receiveMap,
-                                                   BSONObj const& lookupKey) const;
+    boost::optional<ChunkRange> getNextOrphanRange(const RangeMap& receiveMap,
+                                                   const BSONObj& lookupKey) const;
 
     /**
      * Returns all the chunks which are contained on this shard.
      */
     RangeMap getChunks() const;
 
-    const BSONObj& getKeyPattern() const {
-        invariant(isSharded());
-        return _cm->getShardKeyPattern().toBSON();
-    }
-
-    const std::vector<std::unique_ptr<FieldRef>>& getKeyPatternFields() const {
-        invariant(isSharded());
-        return _cm->getShardKeyPattern().getKeyPatternFields();
-    }
-
-    BSONObj getMinKey() const {
-        invariant(isSharded());
-        return _cm->getShardKeyPattern().getKeyPattern().globalMin();
-    }
-
-    BSONObj getMaxKey() const {
-        invariant(isSharded());
-        return _cm->getShardKeyPattern().getKeyPattern().globalMax();
-    }
-
-    std::shared_ptr<ChunkManager> getChunkManager() const {
-        invariant(isSharded());
-        return _cm;
-    }
-
-    bool uuidMatches(UUID uuid) const {
-        invariant(isSharded());
-        return _cm->uuidMatches(uuid);
-    }
+    /**
+     * BSON output of the chunks metadata into a BSONArray
+     */
+    void toBSONChunks(BSONArrayBuilder* builder) const;
 
 private:
-    // The full routing table for the collection.
+    // The full routing table for the collection or nullptr if the collection is not sharded
     std::shared_ptr<ChunkManager> _cm;
 
-    // The identity of this shard, for the purpose of answering "key belongs to me" queries.
+    // The identity of this shard, for the purpose of answering "key belongs to me" queries. If the
+    // collection is not sharded (_cm is nullptr), then this value will be empty.
     ShardId _thisShardId;
 };
 
diff --git a/src/mongo/db/s/collection_metadata_filtering_test.cpp b/src/mongo/db/s/collection_metadata_filtering_test.cpp
index 46db156c36a..00c19583b17 100644
--- a/src/mongo/db/s/collection_metadata_filtering_test.cpp
+++ b/src/mongo/db/s/collection_metadata_filtering_test.cpp
@@ -141,7 +141,7 @@ TEST_F(CollectionMetadataFilteringTest, FilterDocumentsInTheFuture) {
 
         AutoGetCollection autoColl(operationContext(), kNss, MODE_IS);
         auto* const css = CollectionShardingState::get(operationContext(), kNss);
-        testFn(css->getMetadataForOperation(operationContext()));
+        testFn(css->getOrphansFilter(operationContext()));
     }
 
     {
@@ -172,7 +172,7 @@ TEST_F(CollectionMetadataFilteringTest, FilterDocumentsInThePast) {
 
         AutoGetCollection autoColl(operationContext(), kNss, MODE_IS);
         auto* const css = CollectionShardingState::get(operationContext(), kNss);
-        testFn(css->getMetadataForOperation(operationContext()));
+        testFn(css->getOrphansFilter(operationContext()));
     }
 
     {
@@ -211,7 +211,7 @@ TEST_F(CollectionMetadataFilteringTest, FilterDocumentsTooFarInThePastThrowsStal
 
         AutoGetCollection autoColl(operationContext(), kNss, MODE_IS);
         auto* const css = CollectionShardingState::get(operationContext(), kNss);
-        testFn(css->getMetadataForOperation(operationContext()));
+        testFn(css->getOrphansFilter(operationContext()));
     }
 
     {
diff --git a/src/mongo/db/s/collection_sharding_state.cpp b/src/mongo/db/s/collection_sharding_state.cpp
index f65f262a029..8a3e0304146 100644
--- a/src/mongo/db/s/collection_sharding_state.cpp
+++ b/src/mongo/db/s/collection_sharding_state.cpp
@@ -111,7 +111,8 @@ private:
 
 const auto kUnshardedCollection = std::make_shared<UnshardedCollection>();
 
-ChunkVersion getOperationReceivedVersion(OperationContext* opCtx, const NamespaceString& nss) {
+boost::optional<ChunkVersion> getOperationReceivedVersion(OperationContext* opCtx,
+                                                          const NamespaceString& nss) {
     auto& oss = OperationShardingState::get(opCtx);
 
     // If there is a version attached to the OperationContext, use it as the received version,
@@ -125,12 +126,12 @@ ChunkVersion getOperationReceivedVersion(OperationContext* opCtx, const Namespac
         // in a single call, the lack of version for a namespace on the collection must be treated
         // as UNSHARDED
         return connectionShardVersion.value_or(ChunkVersion::UNSHARDED());
-    } else {
-        // There is no shard version information on either 'opCtx' or 'client'. This means that the
-        // operation represented by 'opCtx' is unversioned, and the shard version is always OK for
-        // unversioned operations.
-        return ChunkVersion::IGNORED();
     }
+
+    // There is no shard version information on either 'opCtx' or 'client'. This means that the
+    // operation represented by 'opCtx' is unversioned, and the shard version is always OK for
+    // unversioned operations
+    return boost::none;
 }
 
 }  // namespace
@@ -151,12 +152,10 @@ void CollectionShardingState::report(OperationContext* opCtx, BSONObjBuilder* bu
     collectionsMap->report(opCtx, builder);
 }
 
-ScopedCollectionMetadata CollectionShardingState::getMetadataForOperation(OperationContext* opCtx) {
+ScopedCollectionMetadata CollectionShardingState::getOrphansFilter(OperationContext* opCtx) {
     const auto receivedShardVersion = getOperationReceivedVersion(opCtx, _nss);
-
-    if (ChunkVersion::isIgnoredVersion(receivedShardVersion)) {
+    if (!receivedShardVersion)
         return {kUnshardedCollection};
-    }
 
     const auto atClusterTime = repl::ReadConcernArgs::get(opCtx).getArgsAtClusterTime();
     auto optMetadata = _getMetadata(atClusterTime);
@@ -193,8 +192,12 @@ boost::optional<ChunkVersion> CollectionShardingState::getCurrentShardVersionIfK
 }
 
 void CollectionShardingState::checkShardVersionOrThrow(OperationContext* opCtx) {
-    const auto receivedShardVersion = getOperationReceivedVersion(opCtx, _nss);
+    const auto optReceivedShardVersion = getOperationReceivedVersion(opCtx, _nss);
+
+    if (!optReceivedShardVersion)
+        return;
 
+    const auto& receivedShardVersion = *optReceivedShardVersion;
     if (ChunkVersion::isIgnoredVersion(receivedShardVersion)) {
         return;
     }
@@ -203,7 +206,7 @@ void CollectionShardingState::checkShardVersionOrThrow(OperationContext* opCtx)
     invariant(repl::ReadConcernArgs::get(opCtx).getLevel() !=
               repl::ReadConcernLevel::kAvailableReadConcern);
 
-    const auto metadata = getMetadataForOperation(opCtx);
+    const auto metadata = getCurrentMetadata();
     const auto wantedShardVersion =
         metadata->isSharded() ? metadata->getShardVersion() : ChunkVersion::UNSHARDED();
 
diff --git a/src/mongo/db/s/collection_sharding_state.h b/src/mongo/db/s/collection_sharding_state.h
index e964dbced12..cbd7f9d563f 100644
--- a/src/mongo/db/s/collection_sharding_state.h
+++ b/src/mongo/db/s/collection_sharding_state.h
@@ -73,16 +73,26 @@ public:
     static void report(OperationContext* opCtx, BSONObjBuilder* builder);
 
     /**
-     * Returns the chunk filtering metadata that the current operation should be using for that
-     * collection or otherwise throws if it has not been loaded yet. If the operation does not
-     * require a specific shard version, returns an UNSHARDED metadata. The returned object is safe
-     * to access outside of collection lock.
+     * Returns the orphan chunk filtering metadata that the current operation should be using for
+     * the collection.
      *
-     * If the operation context contains an 'atClusterTime' property, the returned filtering
-     * metadata will be tied to a specific point in time. Otherwise it will reference the latest
-     * time available.
+     * If the operation context contains an 'atClusterTime', the returned filtering metadata will be
+     * tied to a specific point in time. Otherwise, it will reference the latest time available. If
+     * the operation is not associated with a shard version (refer to
+     * OperationShardingState::isOperationVersioned for more info on that), returns an UNSHARDED
+     * metadata object.
+     *
+     * The intended users of this method are callers which need to perform orphan filtering. Use
+     * 'getCurrentMetadata' for all other cases, where just sharding-related properties of the
+     * collection are necessary (e.g., isSharded or the shard key).
+     *
+     * The returned object is safe to access even after the collection lock has been dropped.
+     */
+    ScopedCollectionMetadata getOrphansFilter(OperationContext* opCtx);
+
+    /**
+     * See the comments for 'getOrphansFilter' above for more information on this method.
      */
-    ScopedCollectionMetadata getMetadataForOperation(OperationContext* opCtx);
     ScopedCollectionMetadata getCurrentMetadata();
 
     /**
diff --git a/src/mongo/db/s/get_shard_version_command.cpp b/src/mongo/db/s/get_shard_version_command.cpp
index a51ce749549..b986ffecb82 100644
--- a/src/mongo/db/s/get_shard_version_command.cpp
+++ b/src/mongo/db/s/get_shard_version_command.cpp
@@ -133,7 +133,7 @@ public:
                     metadata->toBSONBasic(metadataBuilder);
 
                     BSONArrayBuilder chunksArr(metadataBuilder.subarrayStart("chunks"));
-                    metadata->toBSONChunks(chunksArr);
+                    metadata->toBSONChunks(&chunksArr);
                     chunksArr.doneFast();
 
                     BSONArrayBuilder pendingArr(metadataBuilder.subarrayStart("pending"));
diff --git a/src/mongo/db/s/op_observer_sharding_impl.cpp b/src/mongo/db/s/op_observer_sharding_impl.cpp
index 0f6aaba48c4..70b090881de 100644
--- a/src/mongo/db/s/op_observer_sharding_impl.cpp
+++ b/src/mongo/db/s/op_observer_sharding_impl.cpp
@@ -63,6 +63,7 @@
 
 namespace mongo {
 namespace {
+
 const auto getIsMigrating = OperationContext::declareDecoration<bool>();
 }
 
diff --git a/src/mongo/db/s/shard_server_op_observer.cpp b/src/mongo/db/s/shard_server_op_observer.cpp
index 3078fd59396..5733763902c 100644
--- a/src/mongo/db/s/shard_server_op_observer.cpp
+++ b/src/mongo/db/s/shard_server_op_observer.cpp
@@ -207,7 +207,7 @@ void ShardServerOpObserver::onInserts(OperationContext* opCtx,
                                       std::vector<InsertStatement>::const_iterator end,
                                       bool fromMigrate) {
     auto* const css = CollectionShardingState::get(opCtx, nss);
-    const auto metadata = css->getMetadataForOperation(opCtx);
+    const auto metadata = css->getCurrentMetadata();
 
     for (auto it = begin; it != end; ++it) {
         const auto& insertedDoc = it->doc;
@@ -233,7 +233,7 @@ void ShardServerOpObserver::onInserts(OperationContext* opCtx,
 
 void ShardServerOpObserver::onUpdate(OperationContext* opCtx, const OplogUpdateEntryArgs& args) {
     auto* const css = CollectionShardingState::get(opCtx, args.nss);
-    const auto metadata = css->getMetadataForOperation(opCtx);
+    const auto metadata = css->getCurrentMetadata();
 
     if (args.nss == NamespaceString::kShardConfigCollectionsNamespace) {
         // Notification of routing table changes are only needed on secondaries