SERVER-45418 Avoid explicitly batching documents in $cursor for count-like aggregates.

2 files changed, 11 insertions, 7 deletions

diff --git a/src/mongo/db/exec/document_value/document.cpp b/src/mongo/db/exec/document_value/document.cpp
index 7400e88058d..d3b170368bc 100644
--- a/src/mongo/db/exec/document_value/document.cpp
+++ b/src/mongo/db/exec/document_value/document.cpp
@@ -594,10 +594,11 @@ const Value Document::getNestedField(const FieldPath& path, vector<Position>* po
 }
 
 size_t Document::getApproximateSize() const {
+    size_t size = sizeof(Document);
     if (!_storage)
-        return 0;  // we've allocated no memory
+        return size;
 
-    size_t size = sizeof(DocumentStorage);
+    size += sizeof(DocumentStorage);
     size += storage().allocatedBytes();
 
     for (auto it = storage().iteratorCacheOnly(); !it.atEnd(); it.advance()) {
diff --git a/src/mongo/db/exec/document_value/document.h b/src/mongo/db/exec/document_value/document.h
index 978d008cae0..a4be77a09e8 100644
--- a/src/mongo/db/exec/document_value/document.h
+++ b/src/mongo/db/exec/document_value/document.h
@@ -188,12 +188,15 @@ public:
     /// Convenience type for dealing with fields. Used by FieldIterator.
     typedef std::pair<StringData, Value> FieldPair;
 
-    /** Get the approximate storage size of the document and sub-values in bytes.
-     *  Note: Some memory may be shared with other Documents or between fields within
-     *        a single Document so this can overestimate usage.
+    /**
+     * Get the approximate size of the Document, plus its underlying storage and sub-values. Returns
+     * size in bytes.
+     *
+     * Note: Some memory may be shared with other Documents or between fields within a single
+     * Document so this can overestimate usage.
      *
-     *  Note: the value returned by this function includes the size of the metadata associated with
-     *  the document.
+     * Note: the value returned by this function includes the size of the metadata associated with
+     * the document.
      */
     size_t getApproximateSize() const;