diff --git a/src/kit/taosdemo/taosdemo.c b/src/kit/taosdemo/taosdemo.c
index f561c1d610afc1cfea149c35591ea0f65b5f0843..ae36bff81dcd2f8a9825fe0c599f9c70acb58c3b 100644
--- a/src/kit/taosdemo/taosdemo.c
+++ b/src/kit/taosdemo/taosdemo.c
@@ -1997,7 +1997,7 @@ static int getChildNameOfSuperTableWithLimitAndOffset(TAOS * taos,
 
   int childTblCount = (limit < 0)?10000:limit;
   int count = 0;
-  childTblName = (char*)calloc(1, childTblCount * TSDB_TABLE_NAME_LEN);
+//  childTblName = (char*)calloc(1, childTblCount * TSDB_TABLE_NAME_LEN);
   char* pTblName = childTblName;
   while ((row = taos_fetch_row(res)) != NULL) {
     int32_t* len = taos_fetch_lengths(res);
@@ -3955,7 +3955,7 @@ static int getRowDataFromSample(char*  dataBuf, int maxLen, int64_t timestamp,
   return dataLen;
 }
 
-int generateRowData(char*  dataBuf, int maxLen, int64_t timestamp, SSuperTable* stbInfo) {
+static int generateRowData(char*  dataBuf, int maxLen, int64_t timestamp, SSuperTable* stbInfo) {
   int    dataLen = 0;
   dataLen += snprintf(dataBuf + dataLen, maxLen - dataLen, "(%" PRId64 ", ", timestamp);
   for (int i = 0; i < stbInfo->columnCount; i++) {    
@@ -4343,26 +4343,22 @@ static int execInsert(threadInfo *winfo, char *buffer, int k)
 
   if (superTblInfo) {
     if (0 == strncasecmp(superTblInfo->insertMode, "taosc", strlen("taosc"))) {
-          verbosePrint("%s() LN%d %s\n", __func__, __LINE__, buffer);
-          affectedRows = queryDbExec(winfo->taos, buffer, INSERT_TYPE);
+      verbosePrint("%s() LN%d %s\n", __func__, __LINE__, buffer);
+      affectedRows = queryDbExec(winfo->taos, buffer, INSERT_TYPE);
     } else {
-          verbosePrint("%s() LN%d %s\n", __func__, __LINE__, buffer);
-          int retCode = postProceSql(g_Dbs.host, g_Dbs.port, buffer);
+      verbosePrint("%s() LN%d %s\n", __func__, __LINE__, buffer);
+      int retCode = postProceSql(g_Dbs.host, g_Dbs.port, buffer);
 
-          if (0 != retCode) {
-            affectedRows = -1;
-            printf("========restful return fail, threadID[%d]\n", winfo->threadID);
-          } else {
-          affectedRows = k;
-          }
+      if (0 != retCode) {
+        affectedRows = -1;
+        printf("========restful return fail, threadID[%d]\n", winfo->threadID);
+      } else {
+        affectedRows = k;
+      }
     }
   } else {
-        verbosePrint("%s() LN%d %s\n", __func__, __LINE__, buffer);
-        affectedRows = queryDbExec(winfo->taos, buffer, 1);
-  }
-
-  if (0 > affectedRows){
-            return affectedRows;
+    verbosePrint("%s() LN%d %s\n", __func__, __LINE__, buffer);
+    affectedRows = queryDbExec(winfo->taos, buffer, 1);
   }
 
   return affectedRows;
@@ -4390,6 +4386,12 @@ static int generateDataBuffer(int32_t tableSeq,
   char *pChildTblName;
   int childTblCount;
 
+  pChildTblName = calloc(TSDB_TABLE_NAME_LEN, 1);
+  if (NULL == pChildTblName) {
+    fprintf(stderr, "failed to alloc memory %d\n", TSDB_TABLE_NAME_LEN);
+    return -1;
+  }
+
   if (superTblInfo && (superTblInfo->childTblOffset > 0)) {
       // select tbname from stb limit 1 offset tableSeq
     getChildNameOfSuperTableWithLimitAndOffset(pThreadInfo->taos,
@@ -4397,11 +4399,6 @@ static int generateDataBuffer(int32_t tableSeq,
             &pChildTblName, &childTblCount,
             1, tableSeq);
   } else {
-      pChildTblName = calloc(TSDB_TABLE_NAME_LEN, 1);
-      if (NULL == pChildTblName) {
-          fprintf(stderr, "failed to alloc memory %d\n", TSDB_TABLE_NAME_LEN);
-          return -1;
-      }
       snprintf(pChildTblName, TSDB_TABLE_NAME_LEN, "%s%d",
         superTblInfo?superTblInfo->childTblPrefix:g_args.tb_prefix, tableSeq);
   }
@@ -4421,9 +4418,9 @@ static int generateDataBuffer(int32_t tableSeq,
                     tableSeq % superTblInfo->tagSampleCount);
       }
       if (NULL == tagsValBuf) {
-         fprintf(stderr, "tag buf failed to allocate  memory\n");
-         free(pChildTblName);
-         return -1;
+        free(pChildTblName);
+        fprintf(stderr, "tag buf failed to allocate  memory\n");
+        return -1;
       }
 
       pstr += snprintf(pstr,
@@ -4498,6 +4495,11 @@ static int generateDataBuffer(int32_t tableSeq,
         }
 
         len += retLen;
+
+        if (len >= (superTblInfo->maxSqlLen - 256)) {    // reserve for overwrite
+            k++;
+            break;
+        }
       }
     } else {
       int rand_num = taosRandom() % 100;
@@ -4518,15 +4520,15 @@ static int generateDataBuffer(int32_t tableSeq,
                   lenOfBinary);
       }
 
+      pstr += sprintf(pstr, " %s", data);
       //assert(len + pstr - buffer < BUFFER_SIZE);
-      if (len + pstr - buffer >= g_args.max_sql_len) { // too long
-            break;
+      if (len + pstr - buffer >= (g_args.max_sql_len - 256)) { // too long
+          k++;
+          break;
       }
-
-      pstr += sprintf(pstr, " %s", data);
     }
 
-    verbosePrint("%s() LN%d len=%d k=%d \nbuffer=%s\n", __func__, __LINE__, len, k, buffer);
+    verbosePrint("%s() LN%d len=%d k=%d \nbuffer=%p\n", __func__, __LINE__, len, k, buffer);
 
     k++;
     startFrom ++;
@@ -4535,7 +4537,8 @@ static int generateDataBuffer(int32_t tableSeq,
       break;
   }
 
-  free(pChildTblName);
+  if (pChildTblName)
+      free(pChildTblName);
 
   return k;
 }
@@ -4613,6 +4616,7 @@ static void* syncWrite(void *sarg) {
       if (affectedRows < 0)
         goto free_and_statistics_2;
 
+
       winfo->totalInsertRows += generated;
       winfo->totalAffectedRows += affectedRows;
 
@@ -4712,7 +4716,7 @@ void callBack(void *param, TAOS_RES *res, int code) {
       break;
     }
   }
-  
+
   if (insert_interval) {
     winfo->st = taosGetTimestampUs();
   }