diff --git a/src/client/src/tscSubquery.c b/src/client/src/tscSubquery.c
index 6ebbeeef411f8922662e7045027cf55410cbf89d..819a323db5e947df46158b9665c0f5d5c491f532 100644
--- a/src/client/src/tscSubquery.c
+++ b/src/client/src/tscSubquery.c
@@ -2198,6 +2198,9 @@ int32_t tscHandleInsertRetry(SSqlObj* pSql) {
   STableDataBlocks* pTableDataBlock = taosArrayGetP(pCmd->pDataBlocks, pSupporter->index);
   int32_t code = tscCopyDataBlockToPayload(pSql, pTableDataBlock);
 
+  // free the data block created from insert sql string
+  pCmd->pDataBlocks = tscDestroyBlockArrayList(pCmd->pDataBlocks);
+
   if ((pRes->code = code)!= TSDB_CODE_SUCCESS) {
     tscQueueAsyncRes(pSql);
     return code;  // here the pSql may have been released already.
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index b35dbb47e678fd6039555247f9a90d7ee84f1149..703e266eb82c49ff46a154f80a87f8709e89a113 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -833,9 +833,14 @@ int32_t tscMergeTableDataBlocks(SSqlObj* pSql, SArray* pTableDataBlockList) {
     dataBuf->size += (finalLen + sizeof(SSubmitBlk));
     assert(dataBuf->size <= dataBuf->nAllocSize);
 
+    // free unnecessary memory resource ASAP.
+    char* p = realloc(dataBuf->pData, dataBuf->size);
+    if (p != NULL) {
+      dataBuf->pData = p;
+    }
+
     // the length does not include the SSubmitBlk structure
     pBlocks->dataLen = htonl(finalLen);
-
     dataBuf->numOfTables += 1;
   }