diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 8394924caf00d56a5ed040149431d3a789a94614..b7914d68831f555609ea3848decb0513b8d1e2c0 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -429,6 +429,8 @@ 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 tscProcessMultiVnodesInsert(SSqlObj *pSql);
 void tscProcessMultiVnodesInsertFromFile(SSqlObj *pSql);
 void tscKillMetricQuery(SSqlObj *pSql);
@@ -448,7 +450,7 @@ void tscQueueAsyncFreeResult(SSqlObj *pSql);
 extern void *     pVnodeConn;
 extern void *     pTscMgmtConn;
 extern void *     tscCacheHandle;
-extern uint8_t    globalCode;
+extern int32_t    globalCode;
 extern int        slaveIndex;
 extern void *     tscTmr;
 extern void *     tscConnCache;
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index 9528097d207f7d2546c3702f2c2712591fb81cc6..1c5c21e85280aac1fcd2dc0a86371027f6228031 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -40,47 +40,22 @@ 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);
 
-// TODO return the correct error code to client in tscQueueAsyncError
-void taos_query_a(TAOS *taos, const char *sqlstr, void (*fp)(void *, TAOS_RES *, int), void *param) {
-  STscObj *pObj = (STscObj *)taos;
-  if (pObj == NULL || pObj->signature != pObj) {
-    tscError("bug!!! pObj:%p", pObj);
-    globalCode = TSDB_CODE_DISCONNECTED;
-    tscQueueAsyncError(fp, param);
-    return;
-  }
-
-  int32_t sqlLen = strlen(sqlstr);
-  if (sqlLen > tsMaxSQLStringLen) {
-    tscError("sql string too long");
-    tscQueueAsyncError(fp, param);
-    return;
-  }
-
-  taosNotePrintTsc(sqlstr);
-
-  SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
-  if (pSql == NULL) {
-    tscError("failed to malloc sqlObj");
-    tscQueueAsyncError(fp, param);
-    return;
-  }
-
+void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const char* sqlstr, int32_t sqlLen) {
   SSqlCmd *pCmd = &pSql->cmd;
   SSqlRes *pRes = &pSql->res;
-
+  
   pSql->signature = pSql;
   pSql->pTscObj = pObj;
   pSql->fp = fp;
   pSql->param = param;
-
+  
   if (TSDB_CODE_SUCCESS != tscAllocPayload(pCmd, TSDB_DEFAULT_PAYLOAD_SIZE)) {
     tscError("failed to malloc payload");
     tfree(pSql);
     tscQueueAsyncError(fp, param);
     return;
   }
-
+  
   pSql->sqlstr = malloc(sqlLen + 1);
   if (pSql->sqlstr == NULL) {
     tscError("%p failed to malloc sql string buffer", pSql);
@@ -89,25 +64,54 @@ void taos_query_a(TAOS *taos, const char *sqlstr, void (*fp)(void *, TAOS_RES *,
     free(pSql);
     return;
   }
-
+  
   pRes->qhandle = 0;
   pRes->numOfRows = 1;
-
+  
   strtolower(pSql->sqlstr, sqlstr);
   tscDump("%p pObj:%p, Async SQL: %s", pSql, pObj, pSql->sqlstr);
-
+  
   int32_t code = tsParseSql(pSql, true);
   if (code == TSDB_CODE_ACTION_IN_PROGRESS) return;
-
+  
   if (code != TSDB_CODE_SUCCESS) {
     pSql->res.code = (uint8_t)code;
     tscQueueAsyncRes(pSql);
     return;
   }
-
+  
   tscDoQuery(pSql);
 }
 
+// TODO return the correct error code to client in tscQueueAsyncError
+void taos_query_a(TAOS *taos, const char *sqlstr, void (*fp)(void *, TAOS_RES *, int), void *param) {
+  STscObj *pObj = (STscObj *)taos;
+  if (pObj == NULL || pObj->signature != pObj) {
+    tscError("bug!!! pObj:%p", pObj);
+    globalCode = TSDB_CODE_DISCONNECTED;
+    tscQueueAsyncError(fp, param);
+    return;
+  }
+  
+  int32_t sqlLen = strlen(sqlstr);
+  if (sqlLen > tsMaxSQLStringLen) {
+    tscError("sql string too long");
+    tscQueueAsyncError(fp, param);
+    return;
+  }
+  
+  taosNotePrintTsc(sqlstr);
+  
+  SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
+  if (pSql == NULL) {
+    tscError("failed to malloc sqlObj");
+    tscQueueAsyncError(fp, param);
+    return;
+  }
+  
+  doAsyncQuery(pObj, pSql, fp, param, sqlstr, sqlLen);
+}
+
 static void tscAsyncFetchRowsProxy(void *param, TAOS_RES *tres, int numOfRows) {
   if (tres == NULL) {
     return;
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index c6efafe3329ff57e6d5c3f1dfadd1b49952c4beb..efeabf57f80cf7bda22f75860b780e387af98580 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -181,16 +181,22 @@ int tscSendMsgToServer(SSqlObj *pSql) {
   }
 
   pSql->ipList->ip[0] = inet_addr("192.168.0.1");
+  SSqlCmd* pCmd = &pSql->cmd;
+  
   if (pSql->cmd.command < TSDB_SQL_MGMT) {
     pSql->ipList->port = tsVnodeShellPort;
     tscPrint("%p msg:%s is sent to server %d", pSql, taosMsg[pSql->cmd.msgType], pSql->ipList->port);
     memcpy(pMsg, pSql->cmd.payload + tsRpcHeadSize, pSql->cmd.payloadLen);
-    rpcSendRequest(pVnodeConn, pSql->ipList, pSql->cmd.msgType, pMsg, pSql->cmd.payloadLen, pSql);
+    
+    SRpcMsg msg = {.msgType = pCmd->msgType, .contLen = pCmd->payloadLen, .pCont = pMsg, .handle = pSql};
+    rpcSendRequest(pVnodeConn, pSql->ipList, &msg);
   } else {
     pSql->ipList->port = tsMgmtShellPort;
     tscPrint("%p msg:%s is sent to server %d", pSql, taosMsg[pSql->cmd.msgType], pSql->ipList->port);
     memcpy(pMsg, pSql->cmd.payload, pSql->cmd.payloadLen);
-    rpcSendRequest(pTscMgmtConn, pSql->ipList, pSql->cmd.msgType, pMsg, pSql->cmd.payloadLen, pSql);
+  
+    SRpcMsg msg = {.msgType = pCmd->msgType, .contLen = pCmd->payloadLen, .pCont = pMsg, .handle = pSql};
+    rpcSendRequest(pTscMgmtConn, pSql->ipList, &msg);
   }
 
   return TSDB_CODE_SUCCESS;
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index 2f3312b0b6dca5d8ec5db584b4ca732b91fcdcdf..d86ca40554aef1f1690cbd789e5bbcd8e3ef2a5c 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -238,39 +238,36 @@ 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);
+  
+  sem_post(&pObj->pSql->rspSem);
+}
+
 int taos_query(TAOS *taos, const char *sqlstr) {
   STscObj *pObj = (STscObj *)taos;
   if (pObj == NULL || pObj->signature != pObj) {
     globalCode = TSDB_CODE_DISCONNECTED;
     return TSDB_CODE_DISCONNECTED;
   }
-
-  SSqlObj *pSql = pObj->pSql;
-  SSqlRes *pRes = &pSql->res;
-
-  size_t sqlLen = strlen(sqlstr);
-  if (sqlLen > tsMaxSQLStringLen) {
-    pRes->code =
-        tscInvalidSQLErrMsg(pSql->cmd.payload, "sql too long", NULL);  // set the additional error msg for invalid sql
-    tscError("%p SQL result:%d, %s pObj:%p", pSql, pRes->code, taos_errstr(taos), pObj);
-
-    return pRes->code;
-  }
-
-  taosNotePrintTsc(sqlstr);
-
-  void *sql = realloc(pSql->sqlstr, sqlLen + 1);
-  if (sql == NULL) {
-    pRes->code = TSDB_CODE_CLI_OUT_OF_MEMORY;
-    tscError("%p failed to malloc sql string buffer, reason:%s", pSql, strerror(errno));
-
-    tscError("%p SQL result:%d, %s pObj:%p", pSql, pRes->code, taos_errstr(taos), pObj);
-    return pRes->code;
+  
+  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);
+  
+  int32_t sqlLen = strlen(sqlstr);
+  doAsyncQuery(pObj, pObj->pSql, syncQueryCallback, taos, sqlstr, sqlLen);
 
-  pSql->sqlstr = sql;
-  strtolower(pSql->sqlstr, sqlstr);
-  return taos_query_imp(pObj, pSql);
+  // wait for the callback function to post the semaphore
+  sem_wait(&pSql->rspSem);
+  
+  return pSql->res.code;
 }
 
 TAOS_RES *taos_use_result(TAOS *taos) {
@@ -683,33 +680,37 @@ TAOS_ROW taos_fetch_row_impl(TAOS_RES *res) {
   return doSetResultRowData(pSql);
 }
 
+static void asyncFetchCallback(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);
+}
+
 TAOS_ROW taos_fetch_row(TAOS_RES *res) {
   SSqlObj *pSql = (SSqlObj *)res;
-  SSqlCmd *pCmd = &pSql->cmd;
-
   if (pSql == NULL || pSql->signature != pSql) {
     globalCode = TSDB_CODE_DISCONNECTED;
     return NULL;
   }
-
-  /*
-   * projection query on super table, access each virtual node sequentially retrieve data from vnode list,
-   * instead of two-stage merge
-   */
-  TAOS_ROW rows = taos_fetch_row_impl(res);
-  if (rows != NULL) {
-    return rows;
+  
+  SSqlCmd *pCmd = &pSql->cmd;
+  SSqlRes *pRes = &pSql->res;
+  
+  if (pRes->qhandle == 0 || pCmd->command == TSDB_SQL_RETRIEVE_EMPTY_RESULT || pCmd->command == TSDB_SQL_INSERT) {
+    return NULL;
   }
-
-  // current subclause is completed, try the next subclause
-  while (rows == NULL && pCmd->clauseIndex < pCmd->numOfClause - 1) {
-    tscTryQueryNextClause(pSql, NULL);
-
-    // if the rows is not NULL, return immediately
-    rows = taos_fetch_row_impl(res);
+  
+  // current data are exhausted, fetch more data
+  if (pRes->data == NULL || (pRes->data != NULL && pRes->row >= pRes->numOfRows && pCmd->command == TSDB_SQL_RETRIEVE)) {
+    taos_fetch_rows_a(res, asyncFetchCallback, pSql->pTscObj);
+    sem_wait(&pSql->rspSem);
   }
-
-  return rows;
+  
+  return doSetResultRowData(pSql);
 }
 
 int taos_fetch_block(TAOS_RES *res, TAOS_ROW *rows) {
diff --git a/src/client/src/tscSystem.c b/src/client/src/tscSystem.c
index 6e4653c2d442e58e6d8cfa58a4ed402dc44b725a..300adb7005b01e3e1fdc04e5f14dd76eb9931ff7 100644
--- a/src/client/src/tscSystem.c
+++ b/src/client/src/tscSystem.c
@@ -33,7 +33,7 @@ void *  pVMeterConn;
 void *  pTscMgmtConn;
 void *  pSlaveConn;
 void *  tscCacheHandle;
-uint8_t globalCode = 0;
+int32_t globalCode = 0;
 int     initialized = 0;
 int     slaveIndex;
 void *  tscTmr;