SERVER-51853 Always initialize the numInserted out-parameter in AbstractIndexAccessMethod::insertKeysr4.4.2-rc0

(cherry picked from commit 8177334703d89a19f38246c5ca95cbf3e5470d91)

2 files changed, 7 insertions, 1 deletions

diff --git a/src/mongo/db/index/index_access_method.cpp b/src/mongo/db/index/index_access_method.cpp
index f88d721ae16..b37c38e713c 100644
--- a/src/mongo/db/index/index_access_method.cpp
+++ b/src/mongo/db/index/index_access_method.cpp
@@ -183,6 +183,10 @@ Status AbstractIndexAccessMethod::insertKeys(OperationContext* opCtx,
                                              const InsertDeleteOptions& options,
                                              KeyHandlerFn&& onDuplicateKey,
                                              int64_t* numInserted) {
+    // Initialize the 'numInserted' out-parameter to zero in case the caller did not already do so.
+    if (numInserted) {
+        *numInserted = 0;
+    }
     // Add all new keys into the index. The RecordId for each is already encoded in the KeyString.
     for (const auto& keyString : keys) {
         bool unique = _descriptor->unique();
diff --git a/src/mongo/db/index/index_access_method.h b/src/mongo/db/index/index_access_method.h
index 63be0cf3186..3a58f512159 100644
--- a/src/mongo/db/index/index_access_method.h
+++ b/src/mongo/db/index/index_access_method.h
@@ -109,7 +109,9 @@ public:
 
     /**
      * Inserts the specified keys into the index. Does not attempt to determine whether the
-     * insertion of these keys should cause the index to become multikey.
+     * insertion of these keys should cause the index to become multikey. The 'numInserted' output
+     * parameter, if non-nullptr, will be reset to the number of keys inserted by this function
+     * call, or to zero in the case of either a non-OK return Status or an empty 'keys' argument.
      */
     virtual Status insertKeys(OperationContext* opCtx,
                               const KeyStringSet& keys,