diff --git a/src/query/src/qExecutor.c b/src/query/src/qExecutor.c
index 0c07149e8e0b20e91123d9491ab25acfff75f5d4..bcce7c50a81032b330e878adb21bc6dc017598c3 100644
--- a/src/query/src/qExecutor.c
+++ b/src/query/src/qExecutor.c
@@ -1372,8 +1372,12 @@ static int32_t setGroupResultOutputBuf(SQueryRuntimeEnv *pRuntimeEnv, char *pDat
   }
 
   if (type == TSDB_DATA_TYPE_BINARY || type == TSDB_DATA_TYPE_NCHAR) {
-    pResultRow->key = malloc(varDataTLen(pData));
-    varDataCopy(pResultRow->key, pData);
+    if (pResultRow->key == NULL) {
+      pResultRow->key = malloc(varDataTLen(pData));
+      varDataCopy(pResultRow->key, pData);
+    } else {
+      assert(memcmp(pResultRow->key, pData, varDataTLen(pData)) == 0);
+    }
   } else {
     pResultRow->win.skey = v;
     pResultRow->win.ekey = v;