SERVER-25980 Merge parallel vectors into one.

Merges the three parallel vectors in DocumentSourceGroup and
DocumentSourceBucketAuto into one vector of AccumulationStatements.

Closes #1143

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

1 files changed, 2 insertions, 8 deletions

diff --git a/src/mongo/db/pipeline/document_source_bucket_auto.h b/src/mongo/db/pipeline/document_source_bucket_auto.h
index a60bf5cb752..2a40b092c1f 100644
--- a/src/mongo/db/pipeline/document_source_bucket_auto.h
+++ b/src/mongo/db/pipeline/document_source_bucket_auto.h
@@ -96,7 +96,7 @@ private:
         Bucket(const boost::intrusive_ptr<ExpressionContext>& expCtx,
                Value min,
                Value max,
-               std::vector<Accumulator::Factory> accumulatorFactories);
+               const std::vector<AccumulationStatement>& accumulationStatements);
         Value _min;
         Value _max;
         std::vector<boost::intrusive_ptr<Accumulator>> _accums;
@@ -139,13 +139,7 @@ private:
     std::unique_ptr<Sorter<Value, Document>> _sorter;
     std::unique_ptr<Sorter<Value, Document>::Iterator> _sortedInput;
 
-    // _fieldNames contains the field names for the result documents, _accumulatorFactories contains
-    // the accumulator factories for the result documents, and _expressions contains the common
-    // expressions used by each instance of each accumulator in order to find the right-hand side of
-    // what gets added to the accumulator. These three vectors parallel each other.
-    std::vector<std::string> _fieldNames;
-    std::vector<Accumulator::Factory> _accumulatorFactories;
-    std::vector<boost::intrusive_ptr<Expression>> _expressions;
+    std::vector<AccumulationStatement> _accumulatedFields;
 
     int _nBuckets;
     uint64_t _maxMemoryUsageBytes;