[TD-225] reduce memory consumption.

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.

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;
   }