1 files changed, 17 insertions, 0 deletions
diff --git a/src/mongo/db/pipeline/document_source_sort.cpp b/src/mongo/db/pipeline/document_source_sort.cpp
index dcf40ba110b..02290179439 100644
--- a/src/mongo/db/pipeline/document_source_sort.cpp
+++ b/src/mongo/db/pipeline/document_source_sort.cpp
@@ -169,6 +169,23 @@ Pipeline::SourceContainer::iterator DocumentSourceSort::doOptimizeAt(
         _sortExecutor->setLimit(*limit);
     }
 
+    if (std::next(itr) == container->end()) {
+        return container->end();
+    }
+
+    if (auto nextSort = dynamic_cast<DocumentSourceSort*>((*std::next(itr)).get())) {
+        // If subsequent $sort stage exists, optimize by erasing the initial one.
+        // Since $sort is not guaranteed to be stable, we can blindly remove the first $sort.
+        auto thisLim = _sortExecutor->getLimit();
+        auto otherLim = nextSort->_sortExecutor->getLimit();
+        // When coalescing subsequent $sort stages, retain the existing/lower limit.
+        if (thisLim && (!otherLim || otherLim > thisLim)) {
+            nextSort->_sortExecutor->setLimit(thisLim);
+        }
+        Pipeline::SourceContainer::iterator ret = std::next(itr);
+        container->erase(itr);
+        return ret;
+    }
     return std::next(itr);
 }