SERVER-43860 Always upsert exact source document for pipeline-insert $merge

1 files changed, 7 insertions, 2 deletions

diff --git a/src/mongo/db/query/internal_plans.cpp b/src/mongo/db/query/internal_plans.cpp
index 53328901c88..a9bc1b5021a 100644
--- a/src/mongo/db/query/internal_plans.cpp
+++ b/src/mongo/db/query/internal_plans.cpp
@@ -42,6 +42,7 @@
 #include "mongo/db/exec/idhack.h"
 #include "mongo/db/exec/index_scan.h"
 #include "mongo/db/exec/update_stage.h"
+#include "mongo/db/exec/upsert_stage.h"
 #include "mongo/db/query/get_executor.h"
 
 namespace mongo {
@@ -166,8 +167,12 @@ std::unique_ptr<PlanExecutor, PlanExecutor::Deleter> InternalPlanner::updateWith
     auto ws = std::make_unique<WorkingSet>();
 
     auto idHackStage = std::make_unique<IDHackStage>(opCtx, key, ws.get(), descriptor);
-    auto root =
-        std::make_unique<UpdateStage>(opCtx, params, ws.get(), collection, idHackStage.release());
+
+    const bool isUpsert = params.request->isUpsert();
+    auto root = (isUpsert ? std::make_unique<UpsertStage>(
+                                opCtx, params, ws.get(), collection, idHackStage.release())
+                          : std::make_unique<UpdateStage>(
+                                opCtx, params, ws.get(), collection, idHackStage.release()));
 
     auto executor =
         PlanExecutor::make(opCtx, std::move(ws), std::move(root), collection, yieldPolicy);