SERVER-54332 [SBE] $elemMatch with object filter returns no documents

1 files changed, 9 insertions, 1 deletions

diff --git a/src/mongo/db/query/sbe_stage_builder_filter.cpp b/src/mongo/db/query/sbe_stage_builder_filter.cpp
index ec290338a93..1f4d65eb4ba 100644
--- a/src/mongo/db/query/sbe_stage_builder_filter.cpp
+++ b/src/mongo/db/query/sbe_stage_builder_filter.cpp
@@ -912,7 +912,15 @@ EvalExprStagePair elemMatchMakePredicate(MatchExpressionVisitorContext* context,
         context->planNodeId,
         context->frameIdGenerator);
 
-    return {traverseSlot, std::move(traverseStage)};
+    // There are some cases where 'traverseOutputSlot' gets set to Nothing when TraverseStage
+    // doesn't match anything. One  example of when this happens is when innerBranch->getNext()
+    // returns EOF every time it is called by TraverseStage. In these cases $elemMatch should return
+    // false instead of Nothing.
+    auto projectExpr = makeFunction("fillEmpty",
+                                    sbe::makeE<sbe::EVariable>(traverseSlot),
+                                    context->stateHelper.makeState(false));
+
+    return {std::move(projectExpr), std::move(traverseStage)};
 }
 
 /**