SERVER-25596 Rename SplittableDocumentSource to NeedsMergerDocumentSource

Closes #1237

Signed-off-by: Charlie Swanson <charlie.swanson@mongodb.com>

17 files changed, 32 insertions, 33 deletions

diff --git a/src/mongo/db/pipeline/cluster_aggregation_planner.cpp b/src/mongo/db/pipeline/cluster_aggregation_planner.cpp
index 3653b5b2638..53ea48dd68f 100644
--- a/src/mongo/db/pipeline/cluster_aggregation_planner.cpp
+++ b/src/mongo/db/pipeline/cluster_aggregation_planner.cpp
@@ -46,15 +46,15 @@ namespace {
  *
  * It is not safe to call this optimization multiple times.
  *
- * NOTE: looks for SplittableDocumentSources and uses that API
+ * NOTE: looks for NeedsMergerDocumentSources and uses that API
  */
 void findSplitPoint(Pipeline* shardPipe, Pipeline* mergePipe) {
     while (!mergePipe->getSources().empty()) {
         boost::intrusive_ptr<DocumentSource> current = mergePipe->popFront();
 
         // Check if this source is splittable.
-        SplittableDocumentSource* splittable =
-            dynamic_cast<SplittableDocumentSource*>(current.get());
+        NeedsMergerDocumentSource* splittable =
+            dynamic_cast<NeedsMergerDocumentSource*>(current.get());
 
         if (!splittable) {
             // Move the source from the merger _sources to the shard _sources.
diff --git a/src/mongo/db/pipeline/document_source.h b/src/mongo/db/pipeline/document_source.h
index 3b4b421f358..b6e52d447fb 100644
--- a/src/mongo/db/pipeline/document_source.h
+++ b/src/mongo/db/pipeline/document_source.h
@@ -706,7 +706,7 @@ private:
  * This class marks DocumentSources that should be split between the merger and the shards. See
  * Pipeline::Optimizations::Sharded::findSplitPoint() for details.
  */
-class SplittableDocumentSource {
+class NeedsMergerDocumentSource {
 public:
     /**
      * Returns a source to be run on the shards, or NULL if no work should be done on the shards for
@@ -719,17 +719,16 @@ public:
     virtual boost::intrusive_ptr<DocumentSource> getShardSource() = 0;
 
     /**
-     * Returns a list of stages that combine results from the shards, or an empty list if no work
-     * should be done in the merge pipeline for this stage. Must not mutate the existing source
-     * object; if different behaviour is required, a new source should be created and configured
-     * appropriately. It is an error for getMergeSources() to return a pointer to the same object as
-     * getShardSource().
+     * Returns a list of stages that combine results from the shards. Subclasses of this class
+     * should not return an empty list. Must not mutate the existing source object; if different
+     * behaviour is required, a new source should be created and configured appropriately. It is an
+     * error for getMergeSources() to return a pointer to the same object as getShardSource().
      */
     virtual std::list<boost::intrusive_ptr<DocumentSource>> getMergeSources() = 0;
 
 protected:
-    // It is invalid to delete through a SplittableDocumentSource-typed pointer.
-    virtual ~SplittableDocumentSource() {}
+    // It is invalid to delete through a NeedsMergerDocumentSource-typed pointer.
+    virtual ~NeedsMergerDocumentSource() {}
 };
 
 }  // namespace mongo
diff --git a/src/mongo/db/pipeline/document_source_bucket_auto.h b/src/mongo/db/pipeline/document_source_bucket_auto.h
index a5b041d741e..b2f46e2e7ae 100644
--- a/src/mongo/db/pipeline/document_source_bucket_auto.h
+++ b/src/mongo/db/pipeline/document_source_bucket_auto.h
@@ -41,7 +41,7 @@ namespace mongo {
  * The $bucketAuto stage takes a user-specified number of buckets and automatically determines
  * boundaries such that the values are approximately equally distributed between those buckets.
  */
-class DocumentSourceBucketAuto final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceBucketAuto final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final;
     GetDepsReturn getDependencies(DepsTracker* deps) const final;
diff --git a/src/mongo/db/pipeline/document_source_change_stream.cpp b/src/mongo/db/pipeline/document_source_change_stream.cpp
index 7992ab9ec3b..602fd1edd46 100644
--- a/src/mongo/db/pipeline/document_source_change_stream.cpp
+++ b/src/mongo/db/pipeline/document_source_change_stream.cpp
@@ -142,7 +142,7 @@ namespace {
  * "invalidate" entries.
  * It is not intended to be created by the user.
  */
-class DocumentSourceCloseCursor final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceCloseCursor final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     GetNextResult getNext() final;
 
diff --git a/src/mongo/db/pipeline/document_source_check_resume_token.h b/src/mongo/db/pipeline/document_source_check_resume_token.h
index 1c04472eb62..430f3c3a6ce 100644
--- a/src/mongo/db/pipeline/document_source_check_resume_token.h
+++ b/src/mongo/db/pipeline/document_source_check_resume_token.h
@@ -91,7 +91,7 @@ private:
  * stream.  It is not intended to be created by the user.
  */
 class DocumentSourceEnsureResumeTokenPresent final : public DocumentSource,
-                                                     public SplittableDocumentSource {
+                                                     public NeedsMergerDocumentSource {
 public:
     // Used to record the results of comparing the token data extracted from documents in the
     // resumed stream against the client's resume token.
@@ -118,9 +118,9 @@ public:
     }
 
     /**
-     * SplittableDocumentSource methods; this has to run on the merger, since the resume point could
-     * be at any shard. Also add a DocumentSourceShardCheckResumability stage on the shards pipeline
-     * to ensure that each shard has enough oplog history to resume the change stream.
+     * NeedsMergerDocumentSource methods; this has to run on the merger, since the resume point
+     * could be at any shard. Also add a DocumentSourceShardCheckResumability stage on the shards
+     * pipeline to ensure that each shard has enough oplog history to resume the change stream.
      */
     boost::intrusive_ptr<DocumentSource> getShardSource() final {
         return DocumentSourceShardCheckResumability::create(pExpCtx,
diff --git a/src/mongo/db/pipeline/document_source_facet.h b/src/mongo/db/pipeline/document_source_facet.h
index 32248772188..cfb0580090d 100644
--- a/src/mongo/db/pipeline/document_source_facet.h
+++ b/src/mongo/db/pipeline/document_source_facet.h
@@ -55,7 +55,7 @@ class NamespaceString;
  * stage which will produce a document like the following:
  * {facetA: [<all input documents except the first one>], facetB: [<the first document>]}.
  */
-class DocumentSourceFacet final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceFacet final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     struct FacetPipeline {
         FacetPipeline(std::string name, std::unique_ptr<Pipeline, PipelineDeleter> pipeline)
diff --git a/src/mongo/db/pipeline/document_source_geo_near.h b/src/mongo/db/pipeline/document_source_geo_near.h
index d390967af81..fa67ab1c71a 100644
--- a/src/mongo/db/pipeline/document_source_geo_near.h
+++ b/src/mongo/db/pipeline/document_source_geo_near.h
@@ -33,7 +33,7 @@
 
 namespace mongo {
 
-class DocumentSourceGeoNear : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceGeoNear : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     static const long long kDefaultLimit;
 
@@ -67,7 +67,7 @@ public:
             {BSON(distanceField->fullPath() << -1)});
     }
 
-    // Virtuals for SplittableDocumentSource
+    // Virtuals for NeedsMergerDocumentSource
     boost::intrusive_ptr<DocumentSource> getShardSource() final;
     std::list<boost::intrusive_ptr<DocumentSource>> getMergeSources() final;
 
diff --git a/src/mongo/db/pipeline/document_source_group.h b/src/mongo/db/pipeline/document_source_group.h
index af262fd739e..eeec779807f 100644
--- a/src/mongo/db/pipeline/document_source_group.h
+++ b/src/mongo/db/pipeline/document_source_group.h
@@ -38,7 +38,7 @@
 
 namespace mongo {
 
-class DocumentSourceGroup final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceGroup final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     using Accumulators = std::vector<boost::intrusive_ptr<Accumulator>>;
     using GroupsMap = ValueUnorderedMap<Accumulators>;
@@ -99,7 +99,7 @@ public:
         return _streaming;
     }
 
-    // Virtuals for SplittableDocumentSource.
+    // Virtuals for NeedsMergerDocumentSource.
     boost::intrusive_ptr<DocumentSource> getShardSource() final;
     std::list<boost::intrusive_ptr<DocumentSource>> getMergeSources() final;
 
diff --git a/src/mongo/db/pipeline/document_source_group_test.cpp b/src/mongo/db/pipeline/document_source_group_test.cpp
index 3f0bc9b6671..de99452f3d7 100644
--- a/src/mongo/db/pipeline/document_source_group_test.cpp
+++ b/src/mongo/db/pipeline/document_source_group_test.cpp
@@ -542,7 +542,7 @@ protected:
     intrusive_ptr<DocumentSource> createMerger() {
         // Set up a group merger to simulate merging results in the router.  In this
         // case only one shard is in use.
-        SplittableDocumentSource* splittable = dynamic_cast<SplittableDocumentSource*>(group());
+        NeedsMergerDocumentSource* splittable = dynamic_cast<NeedsMergerDocumentSource*>(group());
         ASSERT(splittable);
         auto routerSources = splittable->getMergeSources();
         ASSERT_EQ(routerSources.size(), 1UL);
diff --git a/src/mongo/db/pipeline/document_source_internal_split_pipeline.h b/src/mongo/db/pipeline/document_source_internal_split_pipeline.h
index bf93c58c100..2d5bf946ead 100644
--- a/src/mongo/db/pipeline/document_source_internal_split_pipeline.h
+++ b/src/mongo/db/pipeline/document_source_internal_split_pipeline.h
@@ -42,7 +42,7 @@ namespace mongo {
  * random participating shard otherwise.
  */
 class DocumentSourceInternalSplitPipeline final : public DocumentSource,
-                                                  public SplittableDocumentSource {
+                                                  public NeedsMergerDocumentSource {
 public:
     static constexpr StringData kStageName = "$_internalSplitPipeline"_sd;
 
diff --git a/src/mongo/db/pipeline/document_source_limit.h b/src/mongo/db/pipeline/document_source_limit.h
index 3c8c21c2511..cfdbbdec036 100644
--- a/src/mongo/db/pipeline/document_source_limit.h
+++ b/src/mongo/db/pipeline/document_source_limit.h
@@ -32,7 +32,7 @@
 
 namespace mongo {
 
-class DocumentSourceLimit final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceLimit final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     static constexpr StringData kStageName = "$limit"_sd;
 
diff --git a/src/mongo/db/pipeline/document_source_lookup.h b/src/mongo/db/pipeline/document_source_lookup.h
index c9f8872f580..db62fb9b9f4 100644
--- a/src/mongo/db/pipeline/document_source_lookup.h
+++ b/src/mongo/db/pipeline/document_source_lookup.h
@@ -45,7 +45,7 @@ namespace mongo {
  * Queries separate collection for equality matches with documents in the pipeline collection.
  * Adds matching documents to a new array field in the input document.
  */
-class DocumentSourceLookUp final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceLookUp final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     static constexpr size_t kMaxSubPipelineDepth = 20;
 
diff --git a/src/mongo/db/pipeline/document_source_out.h b/src/mongo/db/pipeline/document_source_out.h
index ad6659f42b0..d6732e59b9d 100644
--- a/src/mongo/db/pipeline/document_source_out.h
+++ b/src/mongo/db/pipeline/document_source_out.h
@@ -32,7 +32,7 @@
 
 namespace mongo {
 
-class DocumentSourceOut final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceOut final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     static std::unique_ptr<LiteParsedDocumentSourceForeignCollections> liteParse(
         const AggregationRequest& request, const BSONElement& spec);
@@ -53,7 +53,7 @@ public:
                 TransactionRequirement::kNotAllowed};
     }
 
-    // Virtuals for SplittableDocumentSource
+    // Virtuals for NeedsMergerDocumentSource
     boost::intrusive_ptr<DocumentSource> getShardSource() final {
         return NULL;
     }
diff --git a/src/mongo/db/pipeline/document_source_sample.h b/src/mongo/db/pipeline/document_source_sample.h
index 1ac496305ee..ddba846442d 100644
--- a/src/mongo/db/pipeline/document_source_sample.h
+++ b/src/mongo/db/pipeline/document_source_sample.h
@@ -33,7 +33,7 @@
 
 namespace mongo {
 
-class DocumentSourceSample final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceSample final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     static constexpr StringData kStageName = "$sample"_sd;
 
diff --git a/src/mongo/db/pipeline/document_source_skip.h b/src/mongo/db/pipeline/document_source_skip.h
index 760e887f8b4..bb14fd3966e 100644
--- a/src/mongo/db/pipeline/document_source_skip.h
+++ b/src/mongo/db/pipeline/document_source_skip.h
@@ -32,7 +32,7 @@
 
 namespace mongo {
 
-class DocumentSourceSkip final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceSkip final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     static constexpr StringData kStageName = "$skip"_sd;
 
@@ -82,7 +82,7 @@ public:
         return SEE_NEXT;  // This doesn't affect needed fields
     }
 
-    // Virtuals for SplittableDocumentSource
+    // Virtuals for NeedsMergerDocumentSource
     // Need to run on rounter. Can't run on shards.
     boost::intrusive_ptr<DocumentSource> getShardSource() final {
         return NULL;
diff --git a/src/mongo/db/pipeline/document_source_sort.h b/src/mongo/db/pipeline/document_source_sort.h
index d5846774be8..81871e7224c 100644
--- a/src/mongo/db/pipeline/document_source_sort.h
+++ b/src/mongo/db/pipeline/document_source_sort.h
@@ -36,7 +36,7 @@
 
 namespace mongo {
 
-class DocumentSourceSort final : public DocumentSource, public SplittableDocumentSource {
+class DocumentSourceSort final : public DocumentSource, public NeedsMergerDocumentSource {
 public:
     static const uint64_t kMaxMemoryUsageBytes = 100 * 1024 * 1024;
     static constexpr StringData kStageName = "$sort"_sd;
diff --git a/src/mongo/db/pipeline/pipeline.cpp b/src/mongo/db/pipeline/pipeline.cpp
index e63f15c147f..79dd962d871 100644
--- a/src/mongo/db/pipeline/pipeline.cpp
+++ b/src/mongo/db/pipeline/pipeline.cpp
@@ -384,7 +384,7 @@ bool Pipeline::requiredToRunOnMongos() const {
     for (auto&& stage : _sources) {
         // If this pipeline is capable of splitting before the mongoS-only stage, then the pipeline
         // as a whole is not required to run on mongoS.
-        if (isUnsplit() && dynamic_cast<SplittableDocumentSource*>(stage.get())) {
+        if (isUnsplit() && dynamic_cast<NeedsMergerDocumentSource*>(stage.get())) {
             return false;
         }