diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 9cb43a9f3666f330704d968528986b38246b7351..054b2894c5cff77b63f57b16b069aaf60e150ecc 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -357,7 +357,6 @@ typedef struct SSqlObj {
   char              freed : 4;
   char              listed : 4;
   tsem_t            rspSem;
-  tsem_t            emptyRspSem;
   SSqlCmd           cmd;
   SSqlRes           res;
   uint8_t           numOfSubs;
@@ -409,7 +408,7 @@ int  tscProcessSql(SSqlObj *pSql);
 int  tscRenewMeterMeta(SSqlObj *pSql, char *tableId);
 void tscQueueAsyncRes(SSqlObj *pSql);
 
-void tscQueueAsyncError(void(*fp), void *param);
+void tscQueueAsyncError(void(*fp), void *param, int32_t code);
 
 int tscProcessLocalCmd(SSqlObj *pSql);
 int tscCfgDynamicOptions(char *msg);
@@ -450,7 +449,7 @@ void tscFreeSqlObj(SSqlObj *pObj);
 
 void tscCloseTscObj(STscObj *pObj);
 
-void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const char* sqlstr, int32_t sqlLen);
+void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const char* sqlstr, size_t sqlLen);
 
 void tscProcessMultiVnodesInsert(SSqlObj *pSql);
 void tscProcessMultiVnodesInsertFromFile(SSqlObj *pSql);
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index c1738e6801607703e51a6c6ef95edd6e8305f703..10878ee37fc8eb8b2717973657965f3e26b1d31d 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -40,7 +40,7 @@ static void tscProcessAsyncRetrieveImpl(void *param, TAOS_RES *tres, int numOfRo
 static void tscAsyncFetchRowsProxy(void *param, TAOS_RES *tres, int numOfRows);
 static void tscAsyncFetchSingleRowProxy(void *param, TAOS_RES *tres, int numOfRows);
 
-void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const char* sqlstr, int32_t sqlLen) {
+void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const char* sqlstr, size_t sqlLen) {
   SSqlCmd *pCmd = &pSql->cmd;
   SSqlRes *pRes = &pSql->res;
   
@@ -51,17 +51,15 @@ void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const
   
   if (TSDB_CODE_SUCCESS != tscAllocPayload(pCmd, TSDB_DEFAULT_PAYLOAD_SIZE)) {
     tscError("failed to malloc payload");
-    tfree(pSql);
-    tscQueueAsyncError(fp, param);
+    tscQueueAsyncError(fp, param, TSDB_CODE_CLI_OUT_OF_MEMORY);
     return;
   }
   
-  pSql->sqlstr = malloc(sqlLen + 1);
+  pSql->sqlstr = realloc(pSql->sqlstr, sqlLen + 1);
   if (pSql->sqlstr == NULL) {
     tscError("%p failed to malloc sql string buffer", pSql);
-    tscQueueAsyncError(fp, param);
+    tscQueueAsyncError(fp, param, TSDB_CODE_CLI_OUT_OF_MEMORY);
     free(pCmd->payload);
-    free(pSql);
     return;
   }
   
@@ -75,7 +73,7 @@ void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const
   if (code == TSDB_CODE_ACTION_IN_PROGRESS) return;
   
   if (code != TSDB_CODE_SUCCESS) {
-    pSql->res.code = (uint8_t)code;
+    pSql->res.code = code;
     tscQueueAsyncRes(pSql);
     return;
   }
@@ -88,15 +86,16 @@ void taos_query_a(TAOS *taos, const char *sqlstr, __async_cb_func_t fp, void *pa
   STscObj *pObj = (STscObj *)taos;
   if (pObj == NULL || pObj->signature != pObj) {
     tscError("bug!!! pObj:%p", pObj);
-    globalCode = TSDB_CODE_DISCONNECTED;
-    tscQueueAsyncError(fp, param);
+    terrno = TSDB_CODE_DISCONNECTED;
+    tscQueueAsyncError(fp, param, TSDB_CODE_DISCONNECTED);
     return;
   }
   
   int32_t sqlLen = strlen(sqlstr);
   if (sqlLen > tsMaxSQLStringLen) {
     tscError("sql string too long");
-    tscQueueAsyncError(fp, param);
+    terrno = TSDB_CODE_INVALID_SQL;
+    tscQueueAsyncError(fp, param, TSDB_CODE_INVALID_SQL);
     return;
   }
   
@@ -105,7 +104,8 @@ void taos_query_a(TAOS *taos, const char *sqlstr, __async_cb_func_t fp, void *pa
   SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
   if (pSql == NULL) {
     tscError("failed to malloc sqlObj");
-    tscQueueAsyncError(fp, param);
+    terrno = TSDB_CODE_CLI_OUT_OF_MEMORY;
+    tscQueueAsyncError(fp, param, TSDB_CODE_CLI_OUT_OF_MEMORY);
     return;
   }
   
@@ -170,7 +170,7 @@ static void tscProcessAsyncRetrieveImpl(void *param, TAOS_RES *tres, int numOfRo
       pRes->code = numOfRows;
     }
 
-    tscQueueAsyncError(pSql->fetchFp, param);
+    tscQueueAsyncError(pSql->fetchFp, param, pRes->code);
     return;
   }
 
@@ -200,8 +200,8 @@ void taos_fetch_rows_a(TAOS_RES *taosa, void (*fp)(void *, TAOS_RES *, int), voi
   SSqlObj *pSql = (SSqlObj *)taosa;
   if (pSql == NULL || pSql->signature != pSql) {
     tscError("sql object is NULL");
-    globalCode = TSDB_CODE_DISCONNECTED;
-    tscQueueAsyncError(fp, param);
+//    globalCode = TSDB_CODE_DISCONNECTED;
+    tscQueueAsyncError(fp, param, TSDB_CODE_DISCONNECTED);
     return;
   }
 
@@ -210,7 +210,7 @@ void taos_fetch_rows_a(TAOS_RES *taosa, void (*fp)(void *, TAOS_RES *, int), voi
 
   if (pRes->qhandle == 0) {
     tscError("qhandle is NULL");
-    tscQueueAsyncError(fp, param);
+    tscQueueAsyncError(fp, param, TSDB_CODE_INVALID_QHANDLE);
     return;
   }
 
@@ -232,8 +232,8 @@ void taos_fetch_row_a(TAOS_RES *taosa, void (*fp)(void *, TAOS_RES *, TAOS_ROW),
   SSqlObj *pSql = (SSqlObj *)taosa;
   if (pSql == NULL || pSql->signature != pSql) {
     tscError("sql object is NULL");
-    globalCode = TSDB_CODE_DISCONNECTED;
-    tscQueueAsyncError(fp, param);
+//    globalCode = TSDB_CODE_DISCONNECTED;
+    tscQueueAsyncError(fp, param, TSDB_CODE_DISCONNECTED);
     return;
   }
 
@@ -242,7 +242,7 @@ void taos_fetch_row_a(TAOS_RES *taosa, void (*fp)(void *, TAOS_RES *, TAOS_ROW),
 
   if (pRes->qhandle == 0) {
     tscError("qhandle is NULL");
-    tscQueueAsyncError(fp, param);
+    tscQueueAsyncError(fp, param, TSDB_CODE_INVALID_QHANDLE);
     return;
   }
 
@@ -331,7 +331,7 @@ void tscProcessAsyncRes(SSchedMsg *pMsg) {
 
   // pCmd may be released, so cache pCmd->command
   int cmd = pCmd->command;
-  int code = pRes->code ? -pRes->code : pRes->numOfRows;
+  int code = pRes->code;// ? -pRes->code : pRes->numOfRows;
 
   // in case of async insert, restore the user specified callback function
   bool shouldFree = tscShouldFreeAsyncSqlObj(pSql);
@@ -349,18 +349,20 @@ void tscProcessAsyncRes(SSchedMsg *pMsg) {
   }
 }
 
-void tscProcessAsyncError(SSchedMsg *pMsg) {
+static void tscProcessAsyncError(SSchedMsg *pMsg) {
   void (*fp)() = pMsg->ahandle;
-
-  (*fp)(pMsg->thandle, NULL, -1);
+  (*fp)(pMsg->thandle, NULL, *(int32_t*)pMsg->msg);
 }
 
-void tscQueueAsyncError(void(*fp), void *param) {
+void tscQueueAsyncError(void(*fp), void *param, int32_t code) {
+  int32_t* c = malloc(sizeof(int32_t));
+  *c = code;
+  
   SSchedMsg schedMsg;
   schedMsg.fp = tscProcessAsyncError;
   schedMsg.ahandle = fp;
   schedMsg.thandle = param;
-  schedMsg.msg = NULL;
+  schedMsg.msg = c;
   taosScheduleTask(tscQhandle, &schedMsg);
 }
 
@@ -412,7 +414,7 @@ void tscTableMetaCallBack(void *param, TAOS_RES *res, int code) {
     if (code != 0) {
       pRes->code = code;
       tscTrace("%p failed to renew tableMeta", pSql);
-      tsem_post(&pSql->rspSem);
+//      tsem_post(&pSql->rspSem);
     } else {
       tscTrace("%p renew tableMeta successfully, command:%d, code:%d, retry:%d",
           pSql, pSql->cmd.command, pSql->res.code, pSql->retry);
@@ -424,7 +426,7 @@ void tscTableMetaCallBack(void *param, TAOS_RES *res, int code) {
       code = tscSendMsgToServer(pSql);
       if (code != 0) {
         pRes->code = code;
-        tsem_post(&pSql->rspSem);
+//        tsem_post(&pSql->rspSem);
       }
     }
 
diff --git a/src/client/src/tscPrepare.c b/src/client/src/tscPrepare.c
index 241f24a74777be21ffb557209f20d227ff4ef957..8b065fcf51e3115792a6312ea74e4e0a130206a9 100644
--- a/src/client/src/tscPrepare.c
+++ b/src/client/src/tscPrepare.c
@@ -488,7 +488,6 @@ TAOS_STMT* taos_stmt_init(TAOS* taos) {
   }
 
   tsem_init(&pSql->rspSem, 0, 0);
-  tsem_init(&pSql->emptyRspSem, 0, 1);
   pSql->signature = pSql;
   pSql->pTscObj = pObj;
 
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index bf186051e840104ca1e908381fdf404680766d65..5696611387049b890eeaf726d465b67d6dbc3a4d 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -215,7 +215,7 @@ int32_t tscToSQLCmd(SSqlObj* pSql, struct SSqlInfo* pInfo) {
   if (pQueryInfo->numOfTables == 0) {
     pTableMetaInfo = tscAddEmptyMetaInfo(pQueryInfo);
   } else {
-    pTableMetaInfo = &pQueryInfo->pTableMetaInfo[0];
+    pTableMetaInfo = pQueryInfo->pTableMetaInfo[0];
   }
 
   pCmd->command = pInfo->type;
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index e57f9cc4104d9dc7abd6f0131fc40a34c9bc5941..f651c3532414dd8d40cdc0a5620763268f217444 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -285,14 +285,16 @@ void tscProcessMsgFromServer(SRpcMsg *rpcMsg) {
     pRes->rspType = rpcMsg->msgType;
     pRes->rspLen  = rpcMsg->contLen;
 
-    char *tmp = (char *)realloc(pRes->pRsp, pRes->rspLen);
-    if (tmp == NULL) {
-      pRes->code = TSDB_CODE_CLI_OUT_OF_MEMORY;
-    } else {
-      pRes->pRsp = tmp;
-      if (pRes->rspLen) {
+    if (pRes->rspLen > 0) {
+      char *tmp = (char *)realloc(pRes->pRsp, pRes->rspLen);
+      if (tmp == NULL) {
+        pRes->code = TSDB_CODE_CLI_OUT_OF_MEMORY;
+      } else {
+        pRes->pRsp = tmp;
         memcpy(pRes->pRsp, rpcMsg->pCont, pRes->rspLen);
       }
+    } else {
+      pRes->pRsp = NULL;
     }
 
     // ignore the error information returned from mnode when set ignore flag in sql
@@ -327,7 +329,7 @@ void tscProcessMsgFromServer(SRpcMsg *rpcMsg) {
     void *taosres = tscKeepConn[pCmd->command] ? pSql : NULL;
     rpcMsg->code = pRes->code ? pRes->code : pRes->numOfRows;
     
-    tscTrace("%p Async SQL result:%s res:%p", pSql, tstrerror(pRes->code), taosres);
+    tscTrace("%p Async SQL result:%s res:%p", pSql, tstrerror(pRes->code), pSql);
 
     /*
      * Whether to free sqlObj or not should be decided before call the user defined function, since this SqlObj
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index bbf46a235365541de55bee314009fdd607253912..f33e589c82164ca2b09a63b478d83c66bc58e37d 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -155,6 +155,10 @@ static void syncConnCallback(void *param, TAOS_RES *tres, int code) {
   STscObj *pObj = (STscObj *)param;
   assert(pObj != NULL && pObj->pSql != NULL);
   
+  if (code < 0) {
+    pObj->pSql->res.code = code;
+  }
+  
   sem_post(&pObj->pSql->rspSem);
 }
 
@@ -177,17 +181,17 @@ TAOS *taos_connect(const char *ip, const char *user, const char *pass, const cha
     sem_wait(&pSql->rspSem);
     
     if (pSql->res.code != TSDB_CODE_SUCCESS) {
+      terrno = pSql->res.code;
       taos_close(pObj);
       return NULL;
     }
     
     tscTrace("%p DB connection is opening", pObj);
-
+    
     // version compare only requires the first 3 segments of the version string
     int code = taosCheckVersion(version, taos_get_server_info(pObj), 3);
     if (code != 0) {
-      pSql->res.code = code;
-      
+      terrno = code;
       taos_close(pObj);
       return NULL;
     } else {
@@ -267,31 +271,29 @@ int taos_query_imp(STscObj *pObj, SSqlObj *pSql) {
   return pRes->code;
 }
 
-static void syncQueryCallback(void *param, TAOS_RES *tres, int code) {
-  STscObj *pObj = (STscObj *)param;
-  assert(pObj != NULL && pObj->pSql != NULL);
+static void waitForQueryRsp(void *param, TAOS_RES *tres, int code) {
+  assert(param != NULL);
+  SSqlObj *pSql = ((STscObj *)param)->pSql;
   
-  sem_post(&pObj->pSql->rspSem);
+  // valid error code is less than 0
+  if (code < 0) {
+    pSql->res.code = code;
+  }
+  
+  sem_post(&pSql->rspSem);
 }
 
 int taos_query(TAOS *taos, const char *sqlstr) {
   STscObj *pObj = (STscObj *)taos;
   if (pObj == NULL || pObj->signature != pObj) {
-    globalCode = TSDB_CODE_DISCONNECTED;
+    terrno = TSDB_CODE_DISCONNECTED;
     return TSDB_CODE_DISCONNECTED;
   }
   
-  SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
-  if (pSql == NULL) {
-    tscError("failed to malloc sqlObj");
-    return TSDB_CODE_CLI_OUT_OF_MEMORY;
-  }
-  
-  pObj->pSql = pSql;
-  tsem_init(&pSql->rspSem, 0, 0);
+  SSqlObj* pSql = pObj->pSql;
   
-  int32_t sqlLen = strlen(sqlstr);
-  doAsyncQuery(pObj, pObj->pSql, syncQueryCallback, taos, sqlstr, sqlLen);
+  size_t sqlLen = strlen(sqlstr);
+  doAsyncQuery(pObj, pObj->pSql, waitForQueryRsp, taos, sqlstr, sqlLen);
 
   // wait for the callback function to post the semaphore
   sem_wait(&pSql->rspSem);
@@ -649,12 +651,12 @@ static void **tscBuildResFromSubqueries(SSqlObj *pSql) {
   return pRes->tsrow;
 }
 
-static void asyncFetchCallback(void *param, TAOS_RES *tres, int numOfRows) {
+static void waitForRetrieveRsp(void *param, TAOS_RES *tres, int numOfRows) {
   SSqlObj* pSql = (SSqlObj*) tres;
+  
   if (numOfRows < 0) { // set the error code
     pSql->res.code = -numOfRows;
   }
-  
   sem_post(&pSql->rspSem);
 }
 
@@ -677,7 +679,7 @@ TAOS_ROW taos_fetch_row(TAOS_RES *res) {
   // current data are exhausted, fetch more data
   if (pRes->data == NULL || (pRes->data != NULL && pRes->row >= pRes->numOfRows && pRes->completed != true &&
       (pCmd->command == TSDB_SQL_RETRIEVE || pCmd->command == TSDB_SQL_RETRIEVE_METRIC || pCmd->command == TSDB_SQL_FETCH))) {
-    taos_fetch_rows_a(res, asyncFetchCallback, pSql->pTscObj);
+    taos_fetch_rows_a(res, waitForRetrieveRsp, pSql->pTscObj);
     
     sem_wait(&pSql->rspSem);
   }
@@ -754,20 +756,18 @@ void taos_free_result_imp(TAOS_RES *res, int keepCmd) {
   if (pRes == NULL || pRes->qhandle == 0) {
     /* Query rsp is not received from vnode, so the qhandle is NULL */
     tscTrace("%p qhandle is null, abort free, fp:%p", pSql, pSql->fp);
-    if (pSql->fp != NULL) {
-      STscObj* pObj = pSql->pTscObj;
-  
-      if (pSql == pObj->pSql) {
-        pObj->pSql = NULL;
-        tscFreeSqlObj(pSql);
-      }
-      
+    
+    if (tscShouldFreeAsyncSqlObj(pSql)) {
+      tscFreeSqlObj(pSql);
       tscTrace("%p Async SqlObj is freed by app", pSql);
-    } else if (keepCmd) {
-      tscFreeSqlResult(pSql);
     } else {
-      tscFreeSqlObjPartial(pSql);
+      if (keepCmd) {
+        tscFreeSqlResult(pSql);
+      } else {
+        tscFreeSqlObjPartial(pSql);
+      }
     }
+    
     return;
   }
 
@@ -793,7 +793,7 @@ void taos_free_result_imp(TAOS_RES *res, int keepCmd) {
    *         be executed, and the retry efforts may result in double free the resources, e.g.,SRetrieveSupport
    */
   if (pRes->code != TSDB_CODE_QUERY_CANCELLED &&
-      ((pRes->numOfRows > 0 && pCmd->command < TSDB_SQL_LOCAL) ||
+      ((pRes->numOfRows > 0 && pCmd->command < TSDB_SQL_LOCAL && pRes->completed == false) ||
        (pRes->code == TSDB_CODE_SUCCESS && pRes->numOfRows == 0 && pCmd->command == TSDB_SQL_SELECT &&
         pSql->pStream == NULL && pTableMetaInfo->pTableMeta != NULL))) {
     pCmd->command = (pCmd->command > TSDB_SQL_MGMT) ? TSDB_SQL_RETRIEVE : TSDB_SQL_FETCH;
@@ -836,39 +836,37 @@ void taos_free_result_imp(TAOS_RES *res, int keepCmd) {
     }
   } else {
     // if no free resource msg is sent to vnode, we free this object immediately.
-
-    if (pSql->fp) {
+    bool free = tscShouldFreeAsyncSqlObj(pSql);
+    if (free) {
       assert(pRes->numOfRows == 0 || (pCmd->command > TSDB_SQL_LOCAL));
+  
       tscFreeSqlObj(pSql);
       tscTrace("%p Async sql result is freed by app", pSql);
-    } else if (keepCmd) {
-      tscFreeSqlResult(pSql);
-      tscTrace("%p sql result is freed while sql command is kept", pSql);
     } else {
-      tscFreeSqlObjPartial(pSql);
-      tscTrace("%p sql result is freed", pSql);
+      if (keepCmd) {
+        tscFreeSqlResult(pSql);
+        tscTrace("%p sql result is freed while sql command is kept", pSql);
+      } else {
+        tscFreeSqlObjPartial(pSql);
+        tscTrace("%p sql result is freed by app", pSql);
+      }
     }
   }
 }
 
 void taos_free_result(TAOS_RES *res) { taos_free_result_imp(res, 0); }
 
+// todo should not be used in async query
 int taos_errno(TAOS *taos) {
   STscObj *pObj = (STscObj *)taos;
-  int      code;
-
-  if (pObj == NULL || pObj->signature != pObj) return globalCode;
 
-  if ((int8_t)(pObj->pSql->res.code) == -1)
-    code = TSDB_CODE_OTHERS;
-  else
-    code = pObj->pSql->res.code;
+  if (pObj == NULL || pObj->signature != pObj) {
+    return terrno;
+  }
 
-  return code;
+  return pObj->pSql->res.code;
 }
 
-//static bool validErrorCode(int32_t code) { return code >= TSDB_CODE_SUCCESS && code < TSDB_CODE_MAX_ERROR_CODE; }
-
 /*
  * In case of invalid sql error, additional information is attached to explain
  * why the sql is invalid
@@ -888,13 +886,15 @@ static bool hasAdditionalErrorInfo(int32_t code, SSqlCmd *pCmd) {
   return z != NULL;
 }
 
+// todo should not be used in async model
 char *taos_errstr(TAOS *taos) {
   STscObj *pObj = (STscObj *)taos;
 
   if (pObj == NULL || pObj->signature != pObj)
-    return (char*)tstrerror(globalCode);
+    return (char*)tstrerror(terrno);
 
-  SSqlObj *pSql = pObj->pSql;
+  SSqlObj* pSql = pObj->pSql;
+  
   if (hasAdditionalErrorInfo(pSql->res.code, &pSql->cmd)) {
     return pSql->cmd.payload;
   } else {
diff --git a/src/client/src/tscSub.c b/src/client/src/tscSub.c
index 616bcbba504df2d949a4cbb3aee7ef84b7f6e082..9d172d4ea5279c648b636df0d8895c1a20bda7cd 100644
--- a/src/client/src/tscSub.c
+++ b/src/client/src/tscSub.c
@@ -124,7 +124,6 @@ static SSub* tscCreateSubscription(STscObj* pObj, const char* topic, const char*
   pSql->sqlstr = sqlstr;
 
   tsem_init(&pSql->rspSem, 0, 0);
-  tsem_init(&pSql->emptyRspSem, 0, 1);
 
   SSqlRes *pRes = &pSql->res;
   pRes->numOfRows = 1;
diff --git a/src/client/src/tscSubquery.c b/src/client/src/tscSubquery.c
index b0c7b68ab4cfc263f6728d4ff8e95c224ec988cf..ca6ca369e422b448728d8761d7d5dc17e8377b0c 100644
--- a/src/client/src/tscSubquery.c
+++ b/src/client/src/tscSubquery.c
@@ -392,10 +392,10 @@ void freeSubqueryObj(SSqlObj* pSql) {
 static void doQuitSubquery(SSqlObj* pParentSql) {
   freeSubqueryObj(pParentSql);
 
-  tsem_wait(&pParentSql->emptyRspSem);
-  tsem_wait(&pParentSql->emptyRspSem);
+//  tsem_wait(&pParentSql->emptyRspSem);
+//  tsem_wait(&pParentSql->emptyRspSem);
 
-  tsem_post(&pParentSql->rspSem);
+//  tsem_post(&pParentSql->rspSem);
 }
 
 static void quitAllSubquery(SSqlObj* pSqlObj, SJoinSubquerySupporter* pSupporter) {
@@ -567,7 +567,7 @@ static void joinRetrieveCallback(void* param, TAOS_RES* tres, int numOfRows) {
         freeSubqueryObj(pParentSql);
       }
 
-      tsem_post(&pParentSql->rspSem);
+//      tsem_post(&pParentSql->rspSem);
     } else {
       tscTrace("%p sub:%p completed, completed:%d, total:%d", pParentSql, tres, finished, numOfTotal);
     }
@@ -662,7 +662,7 @@ void tscFetchDatablockFromSubquery(SSqlObj* pSql) {
   }
 
   // wait for all subquery completed
-  tsem_wait(&pSql->rspSem);
+//  tsem_wait(&pSql->rspSem);
   
   // update the records for each subquery
   for(int32_t i = 0; i < pSql->numOfSubs; ++i) {
@@ -797,10 +797,7 @@ void tscJoinQueryCallback(void* param, TAOS_RES* tres, int code) {
           tscProcessSql(pSql);
         } else {  // first retrieve from vnode during the secondary stage sub-query
           if (pParentSql->fp == NULL) {
-            tsem_wait(&pParentSql->emptyRspSem);
-            tsem_wait(&pParentSql->emptyRspSem);
-
-            tsem_post(&pParentSql->rspSem);
+//            tsem_post(&pParentSql->rspSem);
           } else {
             // set the command flag must be after the semaphore been correctly set.
             //    pPObj->cmd.command = TSDB_SQL_RETRIEVE_METRIC;
@@ -954,10 +951,7 @@ int32_t tscHandleMasterJoinQuery(SSqlObj* pSql) {
     }
   }
   
-  tsem_post(&pSql->emptyRspSem);
-  tsem_wait(&pSql->rspSem);
-  
-  tsem_post(&pSql->emptyRspSem);
+//  tsem_wait(&pSql->rspSem);
   
   if (pSql->numOfSubs <= 0) {
     pSql->cmd.command = TSDB_SQL_RETRIEVE_EMPTY_RESULT;
diff --git a/src/client/src/tscSystem.c b/src/client/src/tscSystem.c
index 7a585bfa68a3b82af98ae0ff358235f0ea9ed2a4..ead8c09dec3062b74745318b29c6eb3af11b96f8 100644
--- a/src/client/src/tscSystem.c
+++ b/src/client/src/tscSystem.c
@@ -40,15 +40,10 @@ void *  tscQhandle;
 void *  tscCheckDiskUsageTmr;
 int     tsInsertHeadSize;
 
-extern int            tscEmbedded;
-int                   tscNumOfThreads;
-static pthread_once_t tscinit = PTHREAD_ONCE_INIT;
-static pthread_mutex_t tscMutex;
+int tscNumOfThreads;
 
-extern int  tsTscEnableRecordSql;
-extern int  tsNumOfLogLines;
+static pthread_once_t tscinit = PTHREAD_ONCE_INIT;
 void taosInitNote(int numOfNoteLines, int maxNotes, char* lable);
-void deltaToUtcInitOnce();
 
 void tscCheckDiskUsage(void *para, void *unused) {
   taosGetDisk();
@@ -60,7 +55,6 @@ int32_t tscInitRpc(const char *user, const char *secret) {
   char secretEncrypt[32] = {0};
   taosEncryptPass((uint8_t *)secret, strlen(secret), secretEncrypt);
 
-  pthread_mutex_lock(&tscMutex);
   if (pVnodeConn == NULL) {
     memset(&rpcInit, 0, sizeof(rpcInit));
     rpcInit.localIp = tsLocalIp;
@@ -78,7 +72,6 @@ int32_t tscInitRpc(const char *user, const char *secret) {
     pVnodeConn = rpcOpen(&rpcInit);
     if (pVnodeConn == NULL) {
       tscError("failed to init connection to vnode");
-      pthread_mutex_unlock(&tscMutex);
       return -1;
     }
   }
@@ -100,12 +93,10 @@ int32_t tscInitRpc(const char *user, const char *secret) {
     pTscMgmtConn = rpcOpen(&rpcInit);
     if (pTscMgmtConn == NULL) {
       tscError("failed to init connection to mgmt");
-      pthread_mutex_unlock(&tscMutex);
       return -1;
     }
   }
 
-  pthread_mutex_unlock(&tscMutex);
   return 0;
 }
 
@@ -113,7 +104,7 @@ void taos_init_imp() {
   char        temp[128];
   struct stat dirstat;
 
-  pthread_mutex_init(&tscMutex, NULL);
+  errno = TSDB_CODE_SUCCESS;
   srand(taosGetTimestampSec());
   deltaToUtcInitOnce();
 
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index d003a72774abdba5cbafc1628656fe161e1aef2c..5c7d8789eaa54d52e34dcb1d4e4c83eae7d23bbe 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -469,7 +469,7 @@ void tscFreeSqlObjPartial(SSqlObj* pSql) {
   pSql->freed = 0;
   tscFreeSqlCmdData(pCmd);
   
-  tscTrace("%p free sqlObj partial completed", pSql);
+  tscTrace("%p partially free sqlObj completed", pSql);
 }
 
 void tscFreeSqlObj(SSqlObj* pSql) {
@@ -487,8 +487,6 @@ void tscFreeSqlObj(SSqlObj* pSql) {
   tfree(pCmd->payload);
 
   pCmd->allocSize = 0;
-
-  tsem_destroy(&pSql->rspSem);
   free(pSql);
 }
 
@@ -820,7 +818,9 @@ void tscCloseTscObj(STscObj* pObj) {
   taosTmrStopA(&(pObj->pTimer));
   tscFreeSqlObj(pSql);
 
+  sem_destroy(&pSql->rspSem);
   pthread_mutex_destroy(&pObj->mutex);
+  
   tscTrace("%p DB connection is closed", pObj);
   tfree(pObj);
 }
@@ -842,10 +842,9 @@ int tscAllocPayload(SSqlCmd* pCmd, int size) {
   if (pCmd->payload == NULL) {
     assert(pCmd->allocSize == 0);
 
-    pCmd->payload = (char*)malloc(size);
+    pCmd->payload = (char*)calloc(1, size);
     if (pCmd->payload == NULL) return TSDB_CODE_CLI_OUT_OF_MEMORY;
     pCmd->allocSize = size;
-    memset(pCmd->payload, 0, pCmd->allocSize);
   } else {
     if (pCmd->allocSize < size) {
       char* b = realloc(pCmd->payload, size);
@@ -853,6 +852,8 @@ int tscAllocPayload(SSqlCmd* pCmd, int size) {
       pCmd->payload = b;
       pCmd->allocSize = size;
     }
+    
+    memset(pCmd->payload, 0, pCmd->payloadLen);
   }
 
   //memset(pCmd->payload, 0, pCmd->allocSize);
@@ -1742,7 +1743,7 @@ bool tscShouldFreeAsyncSqlObj(SSqlObj* pSql) {
   }
 
   STscObj* pTscObj = pSql->pTscObj;
-  if (pSql->pStream != NULL || pTscObj->pHb == pSql) {
+  if (pSql->pStream != NULL || pTscObj->pHb == pSql || pTscObj->pSql == pSql) {
     return false;
   }
 
@@ -1929,7 +1930,6 @@ STableMetaInfo* tscAddMeterMetaInfo(SQueryInfo* pQueryInfo, const char* name, ST
   }
 
   pTableMetaInfo->pTableMeta = pTableMeta;
-//  pTableMetaInfo->pMetricMeta = pMetricMeta;
   pTableMetaInfo->numOfTags = numOfTags;
 
   if (tags != NULL) {
@@ -1963,7 +1963,7 @@ void doRemoveMeterMetaInfo(SQueryInfo* pQueryInfo, int32_t index, bool removeFro
 }
 
 void tscRemoveAllMeterMetaInfo(SQueryInfo* pQueryInfo, const char* address, bool removeFromCache) {
-  tscTrace("%p deref the metric/meter meta in cache, numOfTables:%d", address, pQueryInfo->numOfTables);
+  tscTrace("%p deref the table meta in cache, numOfTables:%d", address, pQueryInfo->numOfTables);
 
   int32_t index = pQueryInfo->numOfTables;
   while (index >= 0) {
diff --git a/src/os/linux/src/tlinux.c b/src/os/linux/src/tlinux.c
index bce4a8f13db7727cda101943529ebbd23481a32a..780e2903a064c45211ea3877c3fb2fef3a6c8bef 100644
--- a/src/os/linux/src/tlinux.c
+++ b/src/os/linux/src/tlinux.c
@@ -236,7 +236,7 @@ void *taosProcessAlarmSignal(void *tharg) {
   void (*callback)(int) = tharg;
 
   timer_t         timerId;
-  struct sigevent sevent;
+  struct sigevent sevent = {0};
 
   #ifdef _ALPINE
     sevent.sigev_notify = SIGEV_THREAD;
diff --git a/src/query/src/queryExecutor.c b/src/query/src/queryExecutor.c
index 75823c4e2e95f5cfc1d458ceece7d2b4acb2d193..932c04337745fb4e36cc2b04a4b6829703f4e6ed 100644
--- a/src/query/src/queryExecutor.c
+++ b/src/query/src/queryExecutor.c
@@ -5148,7 +5148,7 @@ static void singleTableQueryImpl(SQInfo* pQInfo) {
   int64_t st = taosGetTimestampUs();
   
   // group by normal column, sliding window query, interval query are handled by interval query processor
-  if (pQuery->intervalTime != 0 || isGroupbyNormalCol(pQuery->pGroupbyExpr)) {  // interval (down sampling operation)
+  if (isIntervalQuery(pQuery) || isGroupbyNormalCol(pQuery->pGroupbyExpr)) {  // interval (down sampling operation)
     tableIntervalProcessor(pQInfo);
   } else {
     if (isFixedOutputQuery(pQuery)) {
diff --git a/src/vnode/tsdb/src/tsdbFile.c b/src/vnode/tsdb/src/tsdbFile.c
index ff8da1cdadd130dc28b6544f58620a50429c5643..bd6699eb8484b3ee9b1bbb9cb2415f10f1d7b8f3 100644
--- a/src/vnode/tsdb/src/tsdbFile.c
+++ b/src/vnode/tsdb/src/tsdbFile.c
@@ -147,6 +147,11 @@ void tsdbInitFileGroupIter(STsdbFileH *pFileH, SFileGroupIter *pIter, int direct
 }
 
 void tsdbSeekFileGroupIter(SFileGroupIter *pIter, int fid) {
+  if (pIter->numOfFGroups == 0) {
+    assert(pIter->pFileGroup == NULL);
+    return;
+  }
+  
   int flags = (pIter->direction == TSDB_FGROUP_ITER_FORWARD) ? TD_GE : TD_LE;
   void *ptr = taosbsearch(&fid, pIter->base, sizeof(SFileGroup), pIter->numOfFGroups, compFGroupKey, flags);
   if (ptr == NULL) {
diff --git a/src/vnode/tsdb/src/tsdbRead.c b/src/vnode/tsdb/src/tsdbRead.c
index c134ba257a7b252d56995d6ef5be44dc01120b87..599d8bd34738d047f2e3331d3a242f08976bf7b9 100644
--- a/src/vnode/tsdb/src/tsdbRead.c
+++ b/src/vnode/tsdb/src/tsdbRead.c
@@ -745,12 +745,23 @@ static bool getQualifiedDataBlock(STsdbQueryHandle *pQueryHandle, STableCheckInf
   int32_t index = -1;
 
   int32_t tid = pCheckInfo->tableId.tid;
-  SFile* pFile = &pCheckInfo->pFileGroup->files[TSDB_FILE_TYPE_DATA];
   
-  while (1) {
+  while (pCheckInfo->pFileGroup != NULL) {
     if ((fid = getFileCompInfo(pCheckInfo, pCheckInfo->pFileGroup)) < 0) {
       break;
     }
+  
+    SFile* pFile = &pCheckInfo->pFileGroup->files[TSDB_FILE_TYPE_DATA];
+  
+    // no data block in current file, try next
+    if (pCheckInfo->compIndex[tid].numOfSuperBlocks == 0) {
+      dTrace("QInfo:%p no data block in file, fid:%d, tid:%d, try next", pQueryHandle->qinfo,
+          pCheckInfo->pFileGroup->fileId, tid);
+      
+      pCheckInfo->pFileGroup = tsdbGetFileGroupNext(&pCheckInfo->fileIter);
+  
+      continue;
+    }
     
     index = binarySearchForBlockImpl(pCheckInfo->pCompInfo->blocks, pCheckInfo->compIndex[tid].numOfSuperBlocks, pQueryHandle->order, key);
     
@@ -792,6 +803,7 @@ static bool getQualifiedDataBlock(STsdbQueryHandle *pQueryHandle, STableCheckInf
   pCheckInfo->pDataCols = tdNewDataCols(1000, 2, 4096);
   tdInitDataCols(pCheckInfo->pDataCols, pCheckInfo->pTableObj->schema);
   
+  SFile* pFile = &pCheckInfo->pFileGroup->files[TSDB_FILE_TYPE_DATA];
   if (pFile->fd == FD_INITIALIZER) {
     pFile->fd = open(pFile->fname, O_RDONLY);
   }