SERVER-28651 Don't hold Document ref across group iterationsr3.5.7

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mongo/db/pipeline/parsed_aggregation_projection.h b/src/mongo/db/pipeline/parsed_aggregation_projection.h
index 227663a1342..dfda0f66756 100644
--- a/src/mongo/db/pipeline/parsed_aggregation_projection.h
+++ b/src/mongo/db/pipeline/parsed_aggregation_projection.h
@@ -150,7 +150,7 @@ public:
     /**
      * Apply the projection transformation.
      */
-    Document applyTransformation(Document input) {
+    Document applyTransformation(const Document& input) {
         return applyProjection(input);
     }
 
@@ -161,7 +161,7 @@ protected:
     /**
      * Apply the projection to 'input'.
      */
-    virtual Document applyProjection(Document input) const = 0;
+    virtual Document applyProjection(const Document& input) const = 0;
 
     boost::intrusive_ptr<ExpressionContext> _expCtx;
 };