diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index 35ad10ffbf..95f01b2127 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -2821,6 +2821,8 @@ static void firstlastSaveTupleData(const SSDataBlock* pSrcBlock, int32_t rowInde
 
   if (!pInfo->hasResult) {
     pInfo->pos = saveTupleData(pCtx, rowIndex, pSrcBlock, NULL);
+    ASSERT(pCtx->subsidiaries.buf != NULL);
+    ASSERT(pCtx->subsidiaries.rowLen > 0);
   } else {
     updateTupleData(pCtx, rowIndex, pSrcBlock, &pInfo->pos);
   }
@@ -5111,7 +5113,6 @@ int32_t sampleFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
   return pInfo->numSampled;
 }
 
-
 bool getTailFuncEnv(SFunctionNode* pFunc, SFuncExecEnv* pEnv) {
 #if 0
   SColumnNode* pCol = (SColumnNode*)nodesListGetNode(pFunc->pParameterList, 0);