diff --git a/source/libs/executor/src/executorimpl.c b/source/libs/executor/src/executorimpl.c
index 209ffb9101374b1a546876f3419900bd15553ff5..f3711034909a610038e7c290d6cdc8dff5c03260 100644
--- a/source/libs/executor/src/executorimpl.c
+++ b/source/libs/executor/src/executorimpl.c
@@ -6513,9 +6513,9 @@ SOperatorInfo* createSortOperatorInfo(SOperatorInfo* downstream, SSDataBlock* pR
     return NULL;
   }
 
-  pInfo->bufPageSize = rowSize < 1024 ? 1024 : rowSize;
+  pInfo->bufPageSize = rowSize < 1024 ? 1024 : rowSize*2;
 
-  pInfo->sortBufSize = pInfo->bufPageSize * 16;  // 1MB, TODO dynamic set the available sort buffer
+  pInfo->sortBufSize = pInfo->bufPageSize * 16;  // TODO dynamic set the available sort buffer
   pInfo->numOfRowsInRes = 1024;
   pInfo->pDataBlock = pResBlock;
   pInfo->pSortInfo = pSortInfo;
diff --git a/source/libs/executor/src/tsort.c b/source/libs/executor/src/tsort.c
index ba95aa0a47a926ad30c2c5b47b25d4a987959be4..cc7416bc876edd8e315198741df112bc964356a3 100644
--- a/source/libs/executor/src/tsort.c
+++ b/source/libs/executor/src/tsort.c
@@ -141,8 +141,8 @@ static int32_t doAddNewExternalMemSource(SDiskbasedBuf *pBuf, SArray* pAllSource
   (*sourceId) += 1;
 
   int32_t rowSize = blockDataGetSerialRowSize(pSource->src.pBlock);
-  int32_t numOfRows = (getBufPageSize(pBuf) - blockDataGetSerialMetaSize(pBlock))/rowSize;
-
+  int32_t numOfRows = (getBufPageSize(pBuf) - blockDataGetSerialMetaSize(pBlock))/rowSize;  // The value of numOfRows must be greater than 0, which is guaranteed by the previous memory allocation
+  ASSERT(numOfRows > 0);
   return blockDataEnsureCapacity(pSource->src.pBlock, numOfRows);
 }
 
@@ -421,7 +421,7 @@ static int32_t doInternalMergeSort(SSortHandle* pHandle) {
   size_t pgSize = pHandle->pageSize;
   int32_t numOfRows = (pgSize - blockDataGetSerialMetaSize(pHandle->pDataBlock))/ blockDataGetSerialRowSize(pHandle->pDataBlock);
 
-  // blockDataEnsureCapacity(pHandle->pDataBlock, numOfRows); // useless, it is already enough
+  blockDataEnsureCapacity(pHandle->pDataBlock, numOfRows); // useless, it is already enough
 
   size_t numOfSorted = taosArrayGetSize(pHandle->pOrderedSource);
   for(int32_t t = 0; t < sortPass; ++t) {
diff --git a/source/libs/executor/test/sortTests.cpp b/source/libs/executor/test/sortTests.cpp
index 73808f86b261f181e2f2653dc4ddfc6e47a4fef4..229b84b9235e0a613073a317825ed8cc17a94ec5 100644
--- a/source/libs/executor/test/sortTests.cpp
+++ b/source/libs/executor/test/sortTests.cpp
@@ -83,7 +83,7 @@ SSDataBlock* getSingleColStrBlock(void* param) {
 
   SColumnInfoData colInfo = {0};
   colInfo.info.type = TSDB_DATA_TYPE_NCHAR;
-  colInfo.info.bytes = TSDB_NCHAR_SIZE * 32;
+  colInfo.info.bytes = TSDB_NCHAR_SIZE * 16;
   colInfo.info.colId = 1;
   colInfo.varmeta.offset = static_cast<int32_t *>(taosMemoryCalloc(pInfo->pageRows, sizeof(int32_t)));
 
@@ -92,7 +92,7 @@ SSDataBlock* getSingleColStrBlock(void* param) {
   for (int32_t i = 0; i < pInfo->pageRows; ++i) {
     SColumnInfoData* pColInfo = static_cast<SColumnInfoData*>(TARRAY_GET_ELEM(pBlock->pDataBlock, 0));
 
-    int32_t size = taosRand() % 32;
+    int32_t size = taosRand() % 16;
     char str[64] = {0};
     taosRandStr(varDataVal(str), size);
     varDataSetLen(str, size);
@@ -101,6 +101,8 @@ SSDataBlock* getSingleColStrBlock(void* param) {
 
   pBlock->info.rows = pInfo->pageRows;
   pBlock->info.numOfCols = 1;
+  pBlock->info.hasVarCol = true;
+
   return pBlock;
 }
 
@@ -218,7 +220,7 @@ TEST(testCase, external_mem_sort_Test) {
   SArray* orderInfo = taosArrayInit(1, sizeof(SBlockOrderInfo));
   taosArrayPush(orderInfo, &oi);
 
-  SSortHandle* phandle = tsortCreateSortHandle(orderInfo, SORT_SINGLESOURCE_SORT, 32, 6, NULL, "test_abc");
+  SSortHandle* phandle = tsortCreateSortHandle(orderInfo, SORT_SINGLESOURCE_SORT, 128, 6, NULL, "test_abc");
   tsortSetFetchRawDataFp(phandle, getSingleColDummyBlock);
 
   _info* pInfo = (_info*) taosMemoryCalloc(1, sizeof(_info));