diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index 4a593854d5e65a0fcead6198f2a4d60f33c2e49f..4c81f82269054c46fde8fa3d860683cd738be572 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -68,6 +68,7 @@ typedef struct STopBotResItem {
 typedef struct STopBotRes {
   int32_t maxSize;
   int16_t type;  //store the original input type, used in merge function
+  int32_t numOfItems;
   STopBotResItem* pItems;
 } STopBotRes;
 
@@ -2718,12 +2719,13 @@ int32_t topFunction(SqlFunctionCtx* pCtx) {
 }
 
 static void topTransferInfo(SqlFunctionCtx* pCtx, STopBotRes* pInput) {
-  for (int32_t i = 0; i < pInput->maxSize; i++) {
+  for (int32_t i = 0; i < pInput->numOfItems; i++) {
     addResult(pCtx, &pInput->pItems[i], pInput->type, true);
   }
 }
 
 int32_t topFunctionMerge(SqlFunctionCtx* pCtx) {
+  SResultRowEntryInfo* pEntryInfo = GET_RES_INFO(pCtx);
   SInputColumnInfoData* pInput = &pCtx->input;
   SColumnInfoData* pCol = pInput->pData[0];
   ASSERT(pCol->info.type == TSDB_DATA_TYPE_BINARY);
@@ -2736,7 +2738,7 @@ int32_t topFunctionMerge(SqlFunctionCtx* pCtx) {
   pInfo->maxSize = pInputInfo->maxSize;
   pInfo->type    = pInputInfo->type;
   topTransferInfo(pCtx, pInputInfo);
-  SET_VAL(GET_RES_INFO(pCtx), pInputInfo->maxSize, pInputInfo->maxSize);
+  SET_VAL(GET_RES_INFO(pCtx), pEntryInfo->numOfRes, pEntryInfo->numOfRes);
 
   return TSDB_CODE_SUCCESS;
 }
@@ -2812,6 +2814,8 @@ void doAddIntoResult(SqlFunctionCtx* pCtx, void* pData, int32_t rowIndex, SSData
 
     // allocate the buffer and keep the data of this row into the new allocated buffer
     pEntryInfo->numOfRes++;
+    // accumulate number of items for each vgroup, this info is needed for merge
+    pRes->numOfItems++;
     taosheapsort((void*)pItems, sizeof(STopBotResItem), pEntryInfo->numOfRes, (const void*)&type, topBotResComparFn,
                  !isTopQuery);
   } else {  // replace the minimum value in the result
@@ -2983,6 +2987,8 @@ void addResult(SqlFunctionCtx* pCtx, STopBotResItem* pSourceItem, int16_t type,
     pItem->tuplePos.pageId = -1;
     replaceTupleData(&pItem->tuplePos, &pSourceItem->tuplePos);
     pEntryInfo->numOfRes++;
+    // accumulate number of items for each vgroup, this info is needed for merge
+    pRes->numOfItems++;
     taosheapsort((void*)pItems, sizeof(STopBotResItem), pEntryInfo->numOfRes, (const void*)&type, topBotResComparFn,
                  !isTopQuery);
   } else {  // replace the minimum value in the result