SERVER-56494: Fix handling of groupby min/max rewrite if unpackbucket is the first stage.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/mongo/db/pipeline/document_source_internal_unpack_bucket.cpp b/src/mongo/db/pipeline/document_source_internal_unpack_bucket.cpp
index 1006fcd2e42..877c88fad55 100644
--- a/src/mongo/db/pipeline/document_source_internal_unpack_bucket.cpp
+++ b/src/mongo/db/pipeline/document_source_internal_unpack_bucket.cpp
@@ -777,7 +777,14 @@ DocumentSourceInternalUnpackBucket::rewriteGroupByMinMax(Pipeline::SourceContain
         // group.
         container->erase(std::next(itr));
         *itr = std::move(newGroup);
-        return {true, std::prev(itr)};
+
+        if (itr == container->begin()) {
+            // Optimize group stage.
+            return {true, itr};
+        } else {
+            // Give chance of the previous stage to optimize against group stage.
+            return {true, std::prev(itr)};
+        }
     }
 
     return {};