diff --git a/src/client/inc/tscSubquery.h b/src/client/inc/tscSubquery.h
index 5293a176d85a0d928e3cf6211c31e301352ce2e7..41df0a4332eb8eceb4e3990b1e6ad7da18558851 100644
--- a/src/client/inc/tscSubquery.h
+++ b/src/client/inc/tscSubquery.h
@@ -50,7 +50,7 @@ void tscUnlockByThread(int64_t *lockedBy);
 
 int tsInsertInitialCheck(SSqlObj *pSql);
 
-void doCleanupSubqueries(SSqlObj *pSql, int32_t numOfSubs);
+void doCleanupSubqueries(SSqlObj *pSql);
 
 void tscFreeRetrieveSup(void **param);
 
diff --git a/src/client/inc/tscUtil.h b/src/client/inc/tscUtil.h
index 9f7ed63eb6b2681e6d0a8e6ca29975589331fecb..5d11a5b1edb34c10dfb51c2b1020a2eb04b3b673 100644
--- a/src/client/inc/tscUtil.h
+++ b/src/client/inc/tscUtil.h
@@ -342,7 +342,7 @@ void doAddGroupColumnForSubquery(SQueryInfo* pQueryInfo, int32_t tagIndex, SSqlC
 
 int16_t tscGetJoinTagColIdByUid(STagCond* pTagCond, uint64_t uid);
 int16_t tscGetTagColIndexById(STableMeta* pTableMeta, int16_t colId);
-int32_t doInitSubState(SSqlObj* pSql, int32_t numOfSubqueries);
+int32_t doReInitSubState(SSqlObj* pSql, int32_t numOfSubqueries);
 
 void tscPrintSelNodeList(SSqlObj* pSql, int32_t subClauseIndex);
 
diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index e3e1101332ae0ee1365c7cfe6fb12244db1323ed..d5f28871ea499e917aaa3cf3412641b936493038 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -359,6 +359,7 @@ typedef struct SSubqueryState {
   int8_t  *states;
   int32_t  numOfSub;            // the number of total sub-queries
   uint64_t numOfRetrievedRows;  // total number of points in this query
+  uint32_t version;
 } SSubqueryState;
 
 typedef struct SSqlObj {
@@ -386,7 +387,6 @@ typedef struct SSqlObj {
   SSqlRes          res;
 
   SSubqueryState   subState;
-  pthread_mutex_t  mtxSubs;      // avoid double access pSubs after failure
   struct SSqlObj **pSubs;
   struct SSqlObj  *rootObj;
 
@@ -434,6 +434,12 @@ typedef struct SSqlStream {
   struct SSqlStream *prev, *next;
 } SSqlStream;
 
+SSqlObj* tscAllocSqlObj();
+uint32_t tscGetVersionOfSubStateWithoutLock(SSqlObj *pSql);
+SSqlObj* tscAcquireRefOfSubobj(SSqlObj *pSql, int32_t idx, uint32_t stateVersion);
+void tscReleaseRefOfSubobj(SSqlObj *pSql);
+void tscResetAllSubStates(SSqlObj* pSql);
+
 void tscSetStreamDestTable(SSqlStream* pStream, const char* dstTable);
 
 int  tscAcquireRpc(const char *key, const char *user, const char *secret,void **pRpcObj);
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index 23b5a6e28ae0d6980168b2033e7ad51950bbac86..7e9869c4e75baa48fa8f1ce3304d4a654e414a6e 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -46,8 +46,6 @@ void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, __async_cb_func_t fp, void* para
   pSql->fetchFp   = fp;
   pSql->rootObj   = pSql;
 
-  pthread_mutex_init(&pSql->mtxSubs, NULL);
-
   registerSqlObj(pSql);
 
   pSql->sqlstr = calloc(1, sqlLen + 1);
@@ -108,7 +106,7 @@ TAOS_RES * taos_query_ra(TAOS *taos, const char *sqlstr, __async_cb_func_t fp, v
   
   nPrintTsc("%s", sqlstr);
   
-  SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
+  SSqlObj *pSql = tscAllocSqlObj();
   if (pSql == NULL) {
     tscError("failed to malloc sqlObj");
     tscQueueAsyncError(fp, param, TSDB_CODE_TSC_OUT_OF_MEMORY);
diff --git a/src/client/src/tscLocal.c b/src/client/src/tscLocal.c
index d0c3fb65e70c219337a3a94daceafbb88e5965ec..068e75a9c5eb15a53a7631dd56094bb7aa7bc6c1 100644
--- a/src/client/src/tscLocal.c
+++ b/src/client/src/tscLocal.c
@@ -611,7 +611,7 @@ static int32_t tscRebuildDDLForSubTable(SSqlObj *pSql, const char *tableName, ch
   STableMetaInfo *pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
   STableMeta *    pMeta = pTableMetaInfo->pTableMeta;
 
-  SSqlObj *pInterSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
+  SSqlObj *pInterSql = tscAllocSqlObj();
   if (pInterSql == NULL) {
     return TSDB_CODE_TSC_OUT_OF_MEMORY;
   }
@@ -763,7 +763,7 @@ static int32_t tscProcessShowCreateDatabase(SSqlObj *pSql) {
 
   STableMetaInfo *pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
 
-  SSqlObj *pInterSql = (SSqlObj *)calloc(1, sizeof(SSqlObj)); 
+  SSqlObj *pInterSql = tscAllocSqlObj();
   if (pInterSql == NULL) {
     return TSDB_CODE_TSC_OUT_OF_MEMORY;
   }  
diff --git a/src/client/src/tscParseLineProtocol.c b/src/client/src/tscParseLineProtocol.c
index 342ad8b7610cfabeab2b7e53371330a5ff94ca13..54e8124a4e0ee5b3310f3c36ac91fad56402e78e 100644
--- a/src/client/src/tscParseLineProtocol.c
+++ b/src/client/src/tscParseLineProtocol.c
@@ -558,7 +558,7 @@ static int32_t getSuperTableMetaFromLocalCache(TAOS* taos, char* tableName, STab
   int32_t     code = 0;
   STableMeta* tableMeta = NULL;
 
-  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+  SSqlObj* pSql = tscAllocSqlObj();
   if (pSql == NULL) {
     tscError("SML:0x%" PRIx64 " failed to allocate memory, reason:%s", info->id, strerror(errno));
     code = TSDB_CODE_TSC_OUT_OF_MEMORY;
@@ -2763,7 +2763,7 @@ static int32_t convertPrecisionType(int precision, SMLTimeStampType *tsType) {
 
 //make a dummy SSqlObj
 static SSqlObj* createSmlQueryObj(TAOS* taos, int32_t affected_rows, int32_t code) {
-  SSqlObj *pNew = (SSqlObj*)calloc(1, sizeof(SSqlObj));
+  SSqlObj *pNew = tscAllocSqlObj();
   if (pNew == NULL) {
     return NULL;
   }
@@ -2771,7 +2771,6 @@ static SSqlObj* createSmlQueryObj(TAOS* taos, int32_t affected_rows, int32_t cod
   pNew->pTscObj = taos;
   pNew->fp = NULL;
 
-  tsem_init(&pNew->rspSem, 0, 0);
   registerSqlObj(pNew);
 
   pNew->res.numOfRows = affected_rows;
diff --git a/src/client/src/tscPrepare.c b/src/client/src/tscPrepare.c
index e48e57ece4d027c47dcdcf2fb25f0912014b8590..3e364c4a52ed80bd5a4741435c500702a2e74496 100644
--- a/src/client/src/tscPrepare.c
+++ b/src/client/src/tscPrepare.c
@@ -1261,8 +1261,6 @@ static void insertBatchClean(STscStmt* pStmt) {
   taosHashClear(pCmd->insertParam.pTableBlockHashList);
   tscFreeSqlResult(pSql);
   tscFreeSubobj(pSql);
-  tfree(pSql->pSubs);
-  pSql->subState.numOfSub = 0;
 }
 
 static int insertBatchStmtExecute(STscStmt* pStmt) {
@@ -1589,7 +1587,7 @@ TAOS_STMT* taos_stmt_init(TAOS* taos) {
   }
   pStmt->taos = pObj;
 
-  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+  SSqlObj* pSql = tscAllocSqlObj();
 
   if (pSql == NULL) {
     free(pStmt);
@@ -1606,7 +1604,6 @@ TAOS_STMT* taos_stmt_init(TAOS* taos) {
     return NULL;
   }
 
-  tsem_init(&pSql->rspSem, 0, 0);
   pSql->signature   = pSql;
   pSql->pTscObj     = pObj;
   pSql->maxRetry    = TSDB_MAX_REPLICA;
diff --git a/src/client/src/tscProfile.c b/src/client/src/tscProfile.c
index 553c61d16049f7b087751116d88b656b103be8be..e594e8ecdfbba7b01ee889ca3ace420f6dbf0fb3 100644
--- a/src/client/src/tscProfile.c
+++ b/src/client/src/tscProfile.c
@@ -280,7 +280,8 @@ int tscBuildQueryStreamDesc(void *pMsg, STscObj *pObj) {
 //      } else {
 //        pQdesc->stableQuery = 0;
 //      }
-      pthread_mutex_lock(&pSql->subState.mutex);
+      { pthread_mutex_lock(&pSql->subState.mutex);
+
       if (pSql->pSubs != NULL && pSql->subState.states != NULL) {
         for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
           // because subState maybe free on anytime by any thread, check validate from here
@@ -297,7 +298,8 @@ int tscBuildQueryStreamDesc(void *pMsg, STscObj *pObj) {
         }
       }
       pQdesc->numOfSub = pSql->subState.numOfSub;
-      pthread_mutex_unlock(&pSql->subState.mutex);
+
+      pthread_mutex_unlock(&pSql->subState.mutex); }
     }
 
     pQdesc->numOfSub = htonl(pQdesc->numOfSub);
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index 9cd36cce2ba83b9dacebd7297b06e0c7e332e55e..4b564f381b799b129f8fc2521cee883441ad6181 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -353,8 +353,8 @@ void checkBrokenQueries(STscObj *pTscObj) {
         pSql->lastAlive = taosGetTimestampMs();
       }
     } else {
-      // lock subs
-      pthread_mutex_lock(&pSql->subState.mutex);
+      { pthread_mutex_lock(&pSql->subState.mutex);
+
       if (pSql->pSubs) {
         // have sub sql
         for (int i = 0; i < pSql->subState.numOfSub; i++) {
@@ -375,8 +375,8 @@ void checkBrokenQueries(STscObj *pTscObj) {
           }
         }
       }
-      // unlock
-      pthread_mutex_unlock(&pSql->subState.mutex);
+
+      pthread_mutex_unlock(&pSql->subState.mutex); }
     }
 
     // kill query
@@ -2708,7 +2708,7 @@ static void createHbObj(STscObj* pObj) {
     return;
   }
 
-  SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
+  SSqlObj *pSql = tscAllocSqlObj();
   if (NULL == pSql) return;
 
   pSql->fp = tscProcessHeartBeatRsp;
@@ -2977,7 +2977,7 @@ int tscProcessRetrieveRspFromNode(SSqlObj *pSql) {
 void tscTableMetaCallBack(void *param, TAOS_RES *res, int code);
 
 static int32_t getTableMetaFromMnode(SSqlObj *pSql, STableMetaInfo *pTableMetaInfo, bool autocreate) {
-  SSqlObj *pNew = calloc(1, sizeof(SSqlObj));
+  SSqlObj *pNew = tscAllocSqlObj();
   if (NULL == pNew) {
     tscError("0x%"PRIx64" malloc failed for new sqlobj to get table meta", pSql->self);
     return TSDB_CODE_TSC_OUT_OF_MEMORY;
@@ -3043,7 +3043,7 @@ static int32_t getTableMetaFromMnode(SSqlObj *pSql, STableMetaInfo *pTableMetaIn
 }
 
 int32_t getMultiTableMetaFromMnode(SSqlObj *pSql, SArray* pNameList, SArray* pVgroupNameList, SArray* pUdfList, __async_cb_func_t fp, bool metaClone) {
-  SSqlObj *pNew = calloc(1, sizeof(SSqlObj));
+  SSqlObj *pNew = tscAllocSqlObj();
   if (NULL == pNew) {
     tscError("0x%"PRIx64" failed to allocate sqlobj to get multiple table meta", pSql->self);
     return TSDB_CODE_TSC_OUT_OF_MEMORY;
@@ -3180,7 +3180,7 @@ int tscGetTableMetaEx(SSqlObj *pSql, STableMetaInfo *pTableMetaInfo, bool create
 }
 
 int32_t tscGetUdfFromNode(SSqlObj *pSql, SQueryInfo* pQueryInfo) {
-  SSqlObj *pNew = calloc(1, sizeof(SSqlObj));
+  SSqlObj *pNew = tscAllocSqlObj();
   if (NULL == pNew) {
     tscError("%p malloc failed for new sqlobj to get user-defined functions", pSql);
     return TSDB_CODE_TSC_OUT_OF_MEMORY;
@@ -3291,10 +3291,7 @@ int tscRenewTableMeta(SSqlObj *pSql) {
   pSql->rootObj->retryReason = pSql->retryReason;
 
   SSqlObj *rootSql = pSql->rootObj;
-  pthread_mutex_lock(&rootSql->mtxSubs);
   tscFreeSubobj(rootSql);
-  pthread_mutex_unlock(&rootSql->mtxSubs);
-  tfree(rootSql->pSubs);
   tscResetSqlCmd(&rootSql->cmd, true, rootSql->self);
 
   code = getMultiTableMetaFromMnode(rootSql, pNameList, vgroupList, NULL, tscTableMetaCallBack, true);
@@ -3321,7 +3318,7 @@ int tscGetSTableVgroupInfo(SSqlObj *pSql, SQueryInfo* pQueryInfo) {
   if (allVgroupInfoRetrieved(pQueryInfo)) {
     return TSDB_CODE_SUCCESS;
   }
-  SSqlObj *pNew = calloc(1, sizeof(SSqlObj));
+  SSqlObj *pNew = tscAllocSqlObj();
   pNew->pTscObj = pSql->pTscObj;
   pNew->signature = pNew;
 
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index 72349c8fba397207ebe0b06633f435a379813a12..d4dbec72236e1c7d321e4be139295cd6daad0bf3 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -143,7 +143,7 @@ static SSqlObj *taosConnectImpl(const char *ip, const char *user, const char *pa
 
   pthread_mutex_init(&pObj->mutex, NULL);
 
-  SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
+  SSqlObj *pSql = tscAllocSqlObj();
   if (NULL == pSql) {
     terrno = TSDB_CODE_TSC_OUT_OF_MEMORY;
     tscReleaseRpc(pRpcObj);
@@ -158,8 +158,6 @@ static SSqlObj *taosConnectImpl(const char *ip, const char *user, const char *pa
   pSql->param     = param;
   pSql->cmd.command = TSDB_SQL_CONNECT;
 
-  tsem_init(&pSql->rspSem, 0, 0);
-
   if (TSDB_CODE_SUCCESS != tscAllocPayload(&pSql->cmd, TSDB_DEFAULT_PAYLOAD_SIZE)) {
     terrno = TSDB_CODE_TSC_OUT_OF_MEMORY;
     tscReleaseRpc(pRpcObj);
@@ -307,10 +305,6 @@ void taos_close(TAOS *taos) {
 
       tscDebug("0x%"PRIx64" HB is freed", pHb->self);
       taosReleaseRef(tscObjRef, pHb->self);
-#ifdef __APPLE__
-      // to satisfy later tsem_destroy in taos_free_result
-      tsem_init(&pHb->rspSem, 0, 0);
-#endif // __APPLE__
       taos_free_result(pHb);
     }
   }
@@ -346,14 +340,13 @@ TAOS_RES* taos_query_c(TAOS *taos, const char *sqlstr, uint32_t sqlLen, int64_t*
 
   nPrintTsc("%s", sqlstr);
 
-  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+  SSqlObj* pSql = tscAllocSqlObj();
   if (pSql == NULL) {
     tscError("failed to malloc sqlObj");
     terrno = TSDB_CODE_TSC_OUT_OF_MEMORY;
     return NULL;
   }
   
-  tsem_init(&pSql->rspSem, 0, 0);
   doAsyncQuery(pObj, pSql, waitForQueryRsp, taos, sqlstr, sqlLen);
 
   if (res != NULL) {
@@ -730,7 +723,9 @@ static void tscKillSTableQuery(SSqlObj *pSql) {
   pSql->res.code = TSDB_CODE_TSC_QUERY_CANCELLED;
 
   tscLockByThread(&pSql->squeryLock);
-  
+
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
   for (int i = 0; i < pSql->subState.numOfSub; ++i) {
     // NOTE: pSub may have been released already here
     SSqlObj *pSub = pSql->pSubs[i];
@@ -750,6 +745,8 @@ static void tscKillSTableQuery(SSqlObj *pSql) {
     // taosRelekaseRef(tscObjRef, pSubObj->self);
   }
 
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+
   if (pSql->subState.numOfSub <= 0) {
     tscAsyncResultOnError(pSql);
   }
@@ -923,7 +920,7 @@ int taos_validate_sql(TAOS *taos, const char *sql) {
     return TSDB_CODE_TSC_DISCONNECTED;
   }
 
-  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+  SSqlObj* pSql = tscAllocSqlObj();
 
   pSql->pTscObj  = taos;
   pSql->signature = pSql;
@@ -1041,7 +1038,7 @@ int taos_load_table_info(TAOS *taos, const char *tableNameList) {
     return TSDB_CODE_TSC_OUT_OF_MEMORY;
   }
 
-  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+  SSqlObj* pSql = tscAllocSqlObj();
   tscAllocPayload(&pSql->cmd, 1024);
 
   pSql->pTscObj   = taos;
diff --git a/src/client/src/tscStream.c b/src/client/src/tscStream.c
index f8687c69687aa31af89ebbb139197627a7d6f675..592b29aa5f192c774a4ec1d60fb4f1a3c69a146c 100644
--- a/src/client/src/tscStream.c
+++ b/src/client/src/tscStream.c
@@ -208,8 +208,6 @@ static void tscProcessStreamQueryCallback(void *param, TAOS_RES *tres, int numOf
 
     tscFreeSqlResult(pSql);
     tscFreeSubobj(pSql);
-    tfree(pSql->pSubs);
-    pSql->subState.numOfSub = 0;
 
     pSql->parseRetry = 0;
     int32_t code = tsParseSql(pSql, true);
@@ -332,8 +330,6 @@ static void tscProcessStreamRetrieveResult(void *param, TAOS_RES *res, int numOf
 
     tscFreeSqlResult(pSql);
     tscFreeSubobj(pSql);    
-    tfree(pSql->pSubs);
-    pSql->subState.numOfSub = 0;
     pTableMetaInfo->vgroupList = tscVgroupInfoClear(pTableMetaInfo->vgroupList);
     tscSetNextLaunchTimer(pStream, pSql);
   }
@@ -677,7 +673,7 @@ TAOS_STREAM *taos_open_stream_withname(TAOS *taos, const char* dstTable, const c
     return NULL;
   }
 
-  SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
+  SSqlObj *pSql = tscAllocSqlObj();
   if (pSql == NULL) {
     return NULL;
   }
@@ -722,7 +718,6 @@ TAOS_STREAM *taos_open_stream_withname(TAOS *taos, const char* dstTable, const c
   pSql->fetchFp = tscCreateStream;
   pSql->cmd.resColumnId = TSDB_RES_COL_ID;
 
-  tsem_init(&pSql->rspSem, 0, 0);
   registerSqlObj(pSql);
 
   tscDebugL("0x%"PRIx64" SQL: %s", pSql->self, pSql->sqlstr);
diff --git a/src/client/src/tscSub.c b/src/client/src/tscSub.c
index b3d18f50114cd88e75e559323fed8c7d6f934289..d48a92cb962317dc1e6554a12a6aa474c6a1f193 100644
--- a/src/client/src/tscSub.c
+++ b/src/client/src/tscSub.c
@@ -83,7 +83,6 @@ void tscUpdateSubscriptionProgress(void* sub, int64_t uid, TSKEY ts) {
   }
 }
 
-
 static void asyncCallback(void *param, TAOS_RES *tres, int code) {
   assert(param != NULL);
   SSub *pSub = ((SSub *)param);
@@ -117,7 +116,7 @@ static SSub* tscCreateSubscription(STscObj* pObj, const char* topic, const char*
     goto fail;
   }
 
-  pSql = calloc(1, sizeof(SSqlObj));
+  pSql = tscAllocSqlObj();
   if (pSql == NULL) {
     line = __LINE__;
     code = TSDB_CODE_TSC_OUT_OF_MEMORY;
@@ -132,11 +131,6 @@ static SSub* tscCreateSubscription(STscObj* pObj, const char* topic, const char*
 
   SSqlCmd* pCmd = &pSql->cmd;
   SSqlRes* pRes = &pSql->res;
-  if (tsem_init(&pSql->rspSem, 0, 0) == -1) {
-    line = __LINE__;
-    code = TAOS_SYSTEM_ERROR(errno);
-    goto fail;
-  }
 
   pSql->param = pSub;
   pSql->maxRetry = TSDB_MAX_REPLICA;
@@ -432,7 +426,7 @@ TAOS_SUB *taos_subscribe(TAOS *taos, int restart, const char* topic, const char
 }
 
 SSqlObj* recreateSqlObj(SSub* pSub) {
-  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+  SSqlObj* pSql = tscAllocSqlObj();
   if (pSql == NULL) {
     return NULL;
   }
@@ -442,10 +436,6 @@ SSqlObj* recreateSqlObj(SSub* pSub) {
 
   SSqlCmd* pCmd = &pSql->cmd;
   SSqlRes* pRes = &pSql->res;
-  if (tsem_init(&pSql->rspSem, 0, 0) == -1) {
-    tscFreeSqlObj(pSql);
-    return NULL;
-  }
 
   pSql->param = pSub;
   pSql->maxRetry = TSDB_MAX_REPLICA;
diff --git a/src/client/src/tscSubquery.c b/src/client/src/tscSubquery.c
index 8306a47ffaa1779debbf42b65df323be5334704e..ae2a3f33f9b7afb3b1950c361a664051201dc4ef 100644
--- a/src/client/src/tscSubquery.c
+++ b/src/client/src/tscSubquery.c
@@ -66,16 +66,14 @@ static void skipRemainValue(STSBuf* pTSBuf, tVariant* tag1) {
   }
 }
 
-static void subquerySetState(SSqlObj *pSql, SSubqueryState *subState, int idx, int8_t state) {
+static void subquerySetStateWithoutLock(SSqlObj *pSql, SSubqueryState *subState, int idx, int8_t state) {
   assert(idx < subState->numOfSub && subState->states != NULL);
   tscDebug("subquery:0x%"PRIx64",%d state set to %d", pSql->self, idx, state);
 
-  pthread_mutex_lock(&subState->mutex);
   subState->states[idx] = state;
-  pthread_mutex_unlock(&subState->mutex);
 }
 
-static bool allSubqueryDone(SSqlObj *pParentSql) {
+static bool allSubqueryDoneWithoutLock(SSqlObj *pParentSql) {
   bool done = true;
   SSubqueryState *subState = &pParentSql->subState;
 
@@ -107,7 +105,7 @@ bool subAndCheckDone(SSqlObj *pSql, SSqlObj *pParentSql, int idx) {
     tscDebug("0x%"PRIx64" subquery:0x%"PRIx64", index:%d state set to 1", pParentSql->self, pSql->self, idx);
     subState->states[idx] = 1;
   }
-  bool done = allSubqueryDone(pParentSql);
+  bool done = allSubqueryDoneWithoutLock(pParentSql);
   if (!done) {
     tscDebug("0x%"PRIx64" sub:%p,%d completed, total:%d", pParentSql->self, pSql, idx, pParentSql->subState.numOfSub);
   }
@@ -115,8 +113,6 @@ bool subAndCheckDone(SSqlObj *pSql, SSqlObj *pParentSql, int idx) {
   return done;
 }
 
-
-
 static int64_t doTSBlockIntersect(SSqlObj* pSql, STimeWindow * win) {
   SQueryInfo* pQueryInfo = tscGetQueryInfo(&pSql->cmd);
 
@@ -125,7 +121,6 @@ static int64_t doTSBlockIntersect(SSqlObj* pSql, STimeWindow * win) {
 
   SLimitVal* pLimit = &pQueryInfo->limit;
   int32_t    order = pQueryInfo->order.order;
-  int32_t    joinNum = pSql->subState.numOfSub;
   SMergeTsCtx ctxlist[TSDB_MAX_JOIN_TABLE_NUM] = {{0}};
   SMergeTsCtx* ctxStack[TSDB_MAX_JOIN_TABLE_NUM] = {0};
   int32_t slot = 0;
@@ -140,25 +135,39 @@ static int64_t doTSBlockIntersect(SSqlObj* pSql, STimeWindow * win) {
   STSElem prev;
   SArray*   tsCond = NULL;
   int32_t mergeDone = 0;
+  int32_t  joinNum = 0;
+
+  int errflag = 0;
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
+  joinNum = pSql->subState.numOfSub;
 
   for (int32_t i = 0; i < joinNum; ++i) {
+    SSqlObj *pSub = pSql->pSubs[i];
+    if (!pSub) {
+        tscError("0x%"PRIx64" the %d'th of the (%d) sub queries is null.", pSql->self, i, joinNum);
+        errflag = 1;
+        break;
+    }
     STSBuf* output = tsBufCreate(true, pQueryInfo->order.order);
-    SQueryInfo* pSubQueryInfo = tscGetQueryInfo(&pSql->pSubs[i]->cmd);
+    SQueryInfo* pSubQueryInfo = tscGetQueryInfo(&pSub->cmd);
 
     pSubQueryInfo->tsBuf = output;
 
-    SJoinSupporter* pSupporter = pSql->pSubs[i]->param;
+    SJoinSupporter* pSupporter = pSub->param;
 
     if (pSupporter->pTSBuf == NULL) {
       tscDebug("0x%"PRIx64" at least one ts-comp is empty, 0 for secondary query after ts blocks intersecting", pSql->self);
-      return 0;
+      errflag = 1;
+      break;
     }
 
     tsBufResetPos(pSupporter->pTSBuf);
 
     if (!tsBufNextPos(pSupporter->pTSBuf)) {
       tscDebug("0x%"PRIx64" input1 is empty, 0 for secondary query after ts blocks intersecting", pSql->self);
-      return 0;
+      errflag = 1;
+      break;
     }
 
     tscDebug("0x%"PRIx64" sub:0x%"PRIx64" table idx:%d, input group number:%d", pSql->self,
@@ -168,6 +177,11 @@ static int64_t doTSBlockIntersect(SSqlObj* pSql, STimeWindow * win) {
     ctxlist[i].res = output;
   }
 
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+  if (errflag) {
+      return 0;
+  }
+
   TSKEY st = taosGetTimestampUs();
 
   for (int16_t tidx = 0; tidx < joinNum; tidx++) {
@@ -523,7 +537,11 @@ static SArray* buildVgroupTableByResult(SQueryInfo* pQueryInfo, SArray* pVgroupT
 static int32_t tscLaunchRealSubqueries(SSqlObj* pSql) {
   int32_t         numOfSub = 0;
   SJoinSupporter* pSupporter = NULL;
-  
+  bool success = true;
+  uint32_t stateVersion = 0;
+
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
   //If the columns are not involved in the final select clause, the corresponding query will not be issued.
   for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     pSupporter = pSql->pSubs[i]->param;
@@ -531,20 +549,19 @@ static int32_t tscLaunchRealSubqueries(SSqlObj* pSql) {
       ++numOfSub;
     }
   }
-  
+
   assert(numOfSub > 0);
-  
+
   // scan all subquery, if one sub query has only ts, ignore it
   tscDebug("0x%"PRIx64" start to launch secondary subqueries, %d out of %d needs to query", pSql->self, numOfSub, pSql->subState.numOfSub);
 
-  bool success = true;
-  
   for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     SSqlObj *pPrevSub = pSql->pSubs[i];
+    if (!pPrevSub) continue;
     pSql->pSubs[i] = NULL;
-    
+
     pSupporter = pPrevSub->param;
-  
+
     if (taosArrayGetSize(pSupporter->exprList) == 0) {
       tscDebug("0x%"PRIx64" subIndex: %d, no need to launch query, ignore it", pSql->self, i);
     
@@ -572,7 +589,7 @@ static int32_t tscLaunchRealSubqueries(SSqlObj* pSql) {
 
     tscClearSubqueryInfo(&pNew->cmd);
     pSql->pSubs[i] = pNew;
-  
+
     SQueryInfo *pQueryInfo = tscGetQueryInfo(&pNew->cmd);
     pQueryInfo->tsBuf = pTsBuf;  // transfer the ownership of timestamp comp-z data to the new created object
 
@@ -664,37 +681,55 @@ static int32_t tscLaunchRealSubqueries(SSqlObj* pSql) {
       pQueryInfo->stableQuery = true;
     }
 
-    subquerySetState(pNew, &pSql->subState, i, 0);
-    
+    subquerySetStateWithoutLock(pNew, &pSql->subState, i, 0);
+
     size_t numOfCols = taosArrayGetSize(pQueryInfo->colList);
     tscDebug("0x%"PRIx64" subquery:0x%"PRIx64" tableIndex:%d, vgroupIndex:%d, type:%d, exprInfo:%" PRIzu ", colList:%" PRIzu ", fieldsInfo:%d, name:%s",
              pSql->self, pNew->self, 0, pTableMetaInfo->vgroupIndex, pQueryInfo->type, taosArrayGetSize(pQueryInfo->exprList),
              numOfCols, pQueryInfo->fieldsInfo.numOfOutput, tNameGetTableName(&pTableMetaInfo->name));
   }
-  
+
+  stateVersion = tscGetVersionOfSubStateWithoutLock(pSql);
+
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+
   //prepare the subqueries object failed, abort
   if (!success) {
     pSql->res.code = TSDB_CODE_TSC_OUT_OF_MEMORY;
     tscError("0x%"PRIx64" failed to prepare subqueries objs for secondary phase query, numOfSub:%d, code:%d", pSql->self,
         pSql->subState.numOfSub, pSql->res.code);
-    freeJoinSubqueryObj(pSql);
-    
-    return pSql->res.code;
+    goto _error;
   }
-  
+
   for(int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
-    if (pSql->pSubs[i] == NULL) {
-      continue;
+    SSqlObj *pSub = tscAcquireRefOfSubobj(pSql, i, stateVersion); // ACQ ref
+    if (pSub == NULL) {
+        if (stateVersion == tscGetVersionOfSubStateWithoutLock(pSql)) {
+             continue;
+        }
+        pSql->res.code = TSDB_CODE_FAILED;
+        tscError("0x%"PRIx64"subqueries objs reset unexpectedly. numOfSub:%d", pSql->self, pSql->subState.numOfSub);
+        goto _error;
     }
-
-    SQueryInfo* pQueryInfo = tscGetQueryInfo(&pSql->pSubs[i]->cmd);
-    executeQuery(pSql->pSubs[i], pQueryInfo);
+    SQueryInfo* pQueryInfo = tscGetQueryInfo(&pSub->cmd);
+    executeQuery(pSub, pQueryInfo);
+    tscReleaseRefOfSubobj(pSub); // REL ref
   }
 
   return TSDB_CODE_SUCCESS;
+
+_error:
+  freeJoinSubqueryObj(pSql);
+  return pSql->res.code;
 }
 
 void freeJoinSubqueryObj(SSqlObj* pSql) {
+  pthread_mutex_lock(&pSql->subState.mutex);
+  if (pSql->subState.numOfSub == 0) {
+    goto _out;
+  }
+  pSql->subState.version ++;
+
   for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     SSqlObj* pSub = pSql->pSubs[i];
     if (pSub == NULL) {
@@ -707,13 +742,12 @@ void freeJoinSubqueryObj(SSqlObj* pSql) {
     taos_free_result(pSub);
     pSql->pSubs[i] = NULL;
   }
-
-  if (pSql->subState.states) {
-    pthread_mutex_destroy(&pSql->subState.mutex);
-  }
-  
+  tfree(pSql->pSubs);
   tfree(pSql->subState.states);
   pSql->subState.numOfSub = 0;
+
+_out:
+  pthread_mutex_unlock(&pSql->subState.mutex);
 }
 
 static int32_t quitAllSubquery(SSqlObj* pSqlSub, SSqlObj* pSqlObj, SJoinSupporter* pSupporter) {
@@ -901,7 +935,6 @@ bool tscReparseSql(SSqlObj *sql, int32_t code){
   }
 
   tscFreeSubobj(sql);      
-  tfree(sql->pSubs);
 
   sql->res.code = TSDB_CODE_SUCCESS;
   sql->retry++;
@@ -1026,18 +1059,24 @@ static int32_t tidTagsMergeSort(SArray *arr, int32_t start, int32_t end, const i
 }
 
 static int32_t getIntersectionOfTableTuple(SQueryInfo* pQueryInfo, SSqlObj* pParentSql, SArray* resList) {
-  int16_t joinNum = pParentSql->subState.numOfSub;
   STableMetaInfo* pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
   int16_t tagColId = tscGetJoinTagColIdByUid(&pQueryInfo->tagCond, pTableMetaInfo->pTableMeta->id.uid);
-  SJoinSupporter* p0 = pParentSql->pSubs[0]->param;
   SMergeCtx ctxlist[TSDB_MAX_JOIN_TABLE_NUM] = {{0}};
   SMergeCtx* ctxStack[TSDB_MAX_JOIN_TABLE_NUM] = {0};
+  SSchema* pColSchema = tscGetColumnSchemaById(pTableMetaInfo->pTableMeta, tagColId);
 
+  int16_t joinNum = 0;
+  SJoinSupporter* p0 = NULL;
+  int32_t size = 0;
+  int32_t code = TSDB_CODE_SUCCESS;
+
+ { pthread_mutex_lock(&pParentSql->subState.mutex);
+
+  joinNum = pParentSql->subState.numOfSub;
+  p0 = pParentSql->pSubs[0]->param;
   // int16_t for padding
-  int32_t size = p0->tagSize - sizeof(int16_t);
+  size = p0->tagSize - sizeof(int16_t);
 
-  SSchema* pColSchema = tscGetColumnSchemaById(pTableMetaInfo->pTableMeta, tagColId);
-  
   tscDebug("0x%"PRIx64" all subquery retrieve <tid, tags> complete, do tags match", pParentSql->self);
 
   for (int32_t i = 0; i < joinNum; i++) {
@@ -1059,10 +1098,16 @@ static int32_t getIntersectionOfTableTuple(SQueryInfo* pQueryInfo, SSqlObj* pPar
       for (int32_t j = 0; j <= i; j++) {
         taosArrayDestroy(&ctxlist[j].res);
       }
-      return TSDB_CODE_QRY_DUP_JOIN_KEY;
+      code = TSDB_CODE_QRY_DUP_JOIN_KEY;
+      break;
     }
   }
 
+  pthread_mutex_unlock(&pParentSql->subState.mutex); }
+  if (code != TSDB_CODE_SUCCESS) {
+      return code;
+  }
+
   int32_t slot = 0;
   size_t tableNum = 0;
   int16_t* tableMIdx = 0;
@@ -1379,22 +1424,34 @@ static void tidTagRetrieveCallback(void* param, TAOS_RES* tres, int32_t numOfRow
 
     (*pParentSql->fp)(pParentSql->param, pParentSql, 0);
   } else {
+    uint32_t stateVersion = tscGetVersionOfSubStateWithoutLock(pParentSql);
+
     for (int32_t m = 0; m < pParentSql->subState.numOfSub; ++m) {
+      SSqlObj *psub = tscAcquireRefOfSubobj(pParentSql, m, stateVersion); // ACQ ref
+      if (!psub) {
+          if (stateVersion == tscGetVersionOfSubStateWithoutLock(pParentSql)) {
+            continue;
+          }
+          tscError("0x%"PRIx64"subqueries objs reset unexpectedly. numOfSub:%d", pSql->self, pSql->subState.numOfSub);
+          break;
+      }
+
       // proceed to for ts_comp query
-      SSqlCmd* pSubCmd = &pParentSql->pSubs[m]->cmd;
+      SSqlCmd* pSubCmd = &psub->cmd;
       SArray** s = taosArrayGet(resList, m);
 
       SQueryInfo*     pQueryInfo1 = tscGetQueryInfo(pSubCmd);
       STableMetaInfo* pTableMetaInfo = tscGetMetaInfo(pQueryInfo1, 0);
       tscBuildVgroupTableInfo(pParentSql, pTableMetaInfo, *s);
 
-      SSqlObj* psub = pParentSql->pSubs[m];
       ((SJoinSupporter*)psub->param)->pVgroupTables =  tscVgroupTableInfoDup(pTableMetaInfo->pVgroupTables);
 
-      memset(pParentSql->subState.states, 0, sizeof(pParentSql->subState.states[0]) * pParentSql->subState.numOfSub);
+      tscResetAllSubStates(pParentSql);
       tscDebug("0x%"PRIx64" reset all sub states to 0", pParentSql->self);
-      
+
       issueTsCompQuery(psub, psub->param, pParentSql);
+
+      tscReleaseRefOfSubobj(psub); // REL ref
     }
   }
 
@@ -1690,12 +1747,14 @@ _return:
 }
 
 void tscFetchDatablockForSubquery(SSqlObj* pSql) {
-  assert(pSql->subState.numOfSub >= 1);
-  
   int32_t numOfFetch = 0;
   bool    hasData = true;
   bool    reachLimit = false;
 
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
+  assert(pSql->subState.numOfSub >= 1);
+
   // if the subquery is NULL, it does not involved in the final result generation
   for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     SSqlObj* pSub = pSql->pSubs[i];
@@ -1726,6 +1785,8 @@ void tscFetchDatablockForSubquery(SSqlObj* pSql) {
     }
   }
 
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+
   // has data remains in client side, and continue to return data to app
   if (hasData) {
     tscBuildResFromSubqueries(pSql);
@@ -1749,8 +1810,11 @@ void tscFetchDatablockForSubquery(SSqlObj* pSql) {
 
   if (numOfFetch <= 0) {
     bool tryNextVnode = false;
-
     bool orderedPrjQuery = false;
+    uint32_t stateVersion = 0;
+
+    { pthread_mutex_lock(&pSql->subState.mutex);
+
     for(int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
       SSqlObj* pSub = pSql->pSubs[i];
       if (pSub == NULL) {
@@ -1764,21 +1828,28 @@ void tscFetchDatablockForSubquery(SSqlObj* pSql) {
       }
     }
 
-
     if (orderedPrjQuery) {
       for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
         SSqlObj* pSub = pSql->pSubs[i];
         if (pSub != NULL && pSub->res.row >= pSub->res.numOfRows && pSub->res.completed) {
-          subquerySetState(pSub, &pSql->subState, i, 0);
+          subquerySetStateWithoutLock(pSub, &pSql->subState, i, 0);
         }
       }
     }
-    
+
+    stateVersion = tscGetVersionOfSubStateWithoutLock(pSql);
+
+    pthread_mutex_unlock(&pSql->subState.mutex); }
 
     for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
-      SSqlObj* pSub = pSql->pSubs[i];
+      SSqlObj* pSub = tscAcquireRefOfSubobj(pSql, i, stateVersion); // ACQ ref
       if (pSub == NULL) {
-        continue;
+          if (stateVersion == tscGetVersionOfSubStateWithoutLock(pSql)) {
+              continue;
+          }
+          tscError("0x%"PRIx64"subqueries objs reset unexpectedly. numOfSub:%d", pSql->self, pSql->subState.numOfSub);
+          pSql->res.code = TSDB_CODE_FAILED;
+          break;
       }
 
       SQueryInfo* pQueryInfo = tscGetQueryInfo(&pSub->cmd);
@@ -1808,6 +1879,8 @@ void tscFetchDatablockForSubquery(SSqlObj* pSql) {
           tscDebug("0x%"PRIx64" no result in current subquery anymore", pSub->self);
         }
       }
+
+      tscReleaseRefOfSubobj(pSub); // REL ref
     }
 
     if (tryNextVnode) {
@@ -1831,24 +1904,34 @@ void tscFetchDatablockForSubquery(SSqlObj* pSql) {
   tscDebug("0x%"PRIx64" retrieve data from %d subqueries", pSql->self, numOfFetch);
   SJoinSupporter* pSupporter = NULL;
 
+  uint32_t stateVersion = 0;
+
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
   for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     SSqlObj* pSql1 = pSql->pSubs[i];
     if (pSql1 == NULL) {
       continue;
     }
 
-
-
     SSqlRes* pRes1 = &pSql1->res;
     if (pRes1->row >= pRes1->numOfRows && !pRes1->completed) {
-      subquerySetState(pSql1, &pSql->subState, i, 0);
+      subquerySetStateWithoutLock(pSql1, &pSql->subState, i, 0);
     }
   }
 
+  stateVersion = tscGetVersionOfSubStateWithoutLock(pSql);
+
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+
   for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
-    SSqlObj* pSql1 = pSql->pSubs[i];
+    SSqlObj* pSql1 = tscAcquireRefOfSubobj(pSql, i, stateVersion); // ACQ ref
     if (pSql1 == NULL) {
-      continue;
+      if (stateVersion == tscGetVersionOfSubStateWithoutLock(pSql)) {
+          continue;
+      }
+      tscError("0x%"PRIx64"subqueries objs reset unexpectedly. numOfSub:%d", pSql->self, pSql->subState.numOfSub);
+      break;
     }
 
     SSqlRes* pRes1 = &pSql1->res;
@@ -1875,6 +1958,7 @@ void tscFetchDatablockForSubquery(SSqlObj* pSql) {
 
       tscBuildAndSendRequest(pSql1, NULL);
     }
+    tscReleaseRefOfSubobj(pSql1); // REF ref
   }
 }
 
@@ -2038,39 +2122,32 @@ static SSqlObj *tscCreateSTableSubquery(SSqlObj *pSql, SRetrieveSupport *trsuppo
 int32_t tscCreateJoinSubquery(SSqlObj *pSql, int16_t tableIndex, SJoinSupporter *pSupporter) {
   SSqlCmd *   pCmd = &pSql->cmd;
   SQueryInfo *pQueryInfo = tscGetQueryInfo(pCmd);
-  
+
   pSql->res.qId = 0x1;
   assert(pSql->res.numOfRows == 0);
 
-  if (pSql->pSubs == NULL) {
-    pSql->pSubs = calloc(pSql->subState.numOfSub, POINTER_BYTES);
-    if (pSql->pSubs == NULL) {
-      return TSDB_CODE_TSC_OUT_OF_MEMORY;
-    }
-  }
-  
   SSqlObj *pNew = createSubqueryObj(pSql, tableIndex, tscJoinQueryCallback, pSupporter, TSDB_SQL_SELECT, NULL);
   if (pNew == NULL) {
     return TSDB_CODE_TSC_OUT_OF_MEMORY;
   }
-  
+
   pSql->pSubs[tableIndex] = pNew;
-  
+
   if (QUERY_IS_JOIN_QUERY(pQueryInfo->type)) {
     addGroupInfoForSubquery(pSql, pNew, 0, tableIndex);
-    
+
     // refactor as one method
     SQueryInfo *pNewQueryInfo = tscGetQueryInfo(&pNew->cmd);
     assert(pNewQueryInfo != NULL);
 
     pSupporter->colList = pNewQueryInfo->colList;
     pNewQueryInfo->colList = NULL;
-    
+
     pSupporter->exprList = pNewQueryInfo->exprList;
     pNewQueryInfo->exprList = NULL;
-    
+
     pSupporter->fieldsInfo = pNewQueryInfo->fieldsInfo;
-  
+
     // this data needs to be transfer to support struct
     memset(&pNewQueryInfo->fieldsInfo, 0, sizeof(SFieldInfo));
     if (tscTagCondCopy(&pSupporter->tagCond, &pNewQueryInfo->tagCond) != 0) {
@@ -2182,33 +2259,29 @@ void tscHandleMasterJoinQuery(SSqlObj* pSql) {
   assert((pQueryInfo->type & TSDB_QUERY_TYPE_SUBQUERY) == 0);
 
   int32_t code = TSDB_CODE_SUCCESS;
-  pSql->subState.numOfSub = pQueryInfo->numOfTables;
 
-  if (pSql->subState.states == NULL) {
-    pSql->subState.states = calloc(pSql->subState.numOfSub, sizeof(*pSql->subState.states));
-    if (pSql->subState.states == NULL) {
-      code = TSDB_CODE_TSC_OUT_OF_MEMORY;
-      goto _error;
-    }
-    
-    pthread_mutex_init(&pSql->subState.mutex, NULL);
-  }
+  code = doReInitSubState(pSql, pQueryInfo->numOfTables);
+  assert (code == TSDB_CODE_SUCCESS && "Out of memory");
 
-  memset(pSql->subState.states, 0, sizeof(*pSql->subState.states) * pSql->subState.numOfSub);
-  tscDebug("0x%"PRIx64" reset all sub states to 0, start subquery, total:%d", pSql->self, pQueryInfo->numOfTables);
+  uint32_t stateVersion = 0;
+  int errflag = 0;
 
-  for (int32_t i = 0; i < pQueryInfo->numOfTables; ++i) {
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
+  for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     SJoinSupporter *pSupporter = tscCreateJoinSupporter(pSql, i);
     if (pSupporter == NULL) {  // failed to create support struct, abort current query
       tscError("0x%"PRIx64" tableIndex:%d, failed to allocate join support object, abort further query", pSql->self, i);
       code = TSDB_CODE_TSC_OUT_OF_MEMORY;
-      goto _error;
+      errflag = 1;
+      break;
     }
-    
+
     code = tscCreateJoinSubquery(pSql, i, pSupporter);
     if (code != TSDB_CODE_SUCCESS) {  // failed to create subquery object, quit query
       tscDestroyJoinSupporter(pSupporter);
-      goto _error;
+      errflag = 1;
+      break;
     }
 
     SSqlObj* pSub = pSql->pSubs[i];
@@ -2219,23 +2292,38 @@ void tscHandleMasterJoinQuery(SSqlObj* pSql) {
     }
   }
 
+  stateVersion = tscGetVersionOfSubStateWithoutLock(pSql);
+
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+  if (errflag) {
+      goto _error;
+  }
+
   if (pSql->cmd.command == TSDB_SQL_RETRIEVE_EMPTY_RESULT) {  // at least one subquery is empty, do nothing and return
     freeJoinSubqueryObj(pSql);
     (*pSql->fp)(pSql->param, pSql, 0);
   } else {
     int fail = 0;
     for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
-      SSqlObj* pSub = pSql->pSubs[i];
+      SSqlObj* pSub = tscAcquireRefOfSubobj(pSql, i, stateVersion); // ACQ ref
+      if (!pSub) {
+        if (stateVersion == tscGetVersionOfSubStateWithoutLock(pSql)) {
+            continue;
+        }
+        code = TSDB_CODE_FAILED;
+        goto _error;
+      }
       if (fail) {
         (*pSub->fp)(pSub->param, pSub, 0);
         continue;
       }
-      
+
       if ((code = tscBuildAndSendRequest(pSub, NULL)) != TSDB_CODE_SUCCESS) {
         pRes->code = code;
         (*pSub->fp)(pSub->param, pSub, 0);
         fail = 1;
       }
+      tscReleaseRefOfSubobj(pSub); // REL ref
     }
 
     if(fail) {
@@ -2247,22 +2335,23 @@ void tscHandleMasterJoinQuery(SSqlObj* pSql) {
 
   return;
 
-  _error:
+_error:
   pRes->code = code;
   tscAsyncResultOnError(pSql);
 }
 
-void doCleanupSubqueries(SSqlObj *pSql, int32_t numOfSubs) {
-  assert(numOfSubs <= pSql->subState.numOfSub && numOfSubs >= 0);
-  
-  for(int32_t i = 0; i < numOfSubs; ++i) {
+void doCleanupSubqueries(SSqlObj *pSql) {
+  pthread_mutex_lock(&pSql->subState.mutex);
+  for(int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     SSqlObj* pSub = pSql->pSubs[i];
-    assert(pSub != NULL);
+    if (!pSub) continue;
+    pSql->pSubs[i] = NULL;
 
     tscFreeRetrieveSup(&pSub->param);
     
     taos_free_result(pSub);
   }
+  pthread_mutex_unlock(&pSql->subState.mutex);
 }
 
 void tscLockByThread(int64_t *lockedBy) {
@@ -2367,8 +2456,7 @@ void tscFirstRoundRetrieveCallback(void* param, TAOS_RES* tres, int numOfRows) {
   if (code != TSDB_CODE_SUCCESS) {
     tscFreeFirstRoundSup(&param);
     taos_free_result(pSql);
-    pParent->subState.numOfSub = 0;
-    tfree(pParent->pSubs);    
+    tscFreeSubobj(pParent);
     pParent->res.code = code;
     tscAsyncResultOnError(pParent);
     return;
@@ -2471,8 +2559,7 @@ void tscFirstRoundRetrieveCallback(void* param, TAOS_RES* tres, int numOfRows) {
   tscFreeFirstRoundSup(&param);
 
   taos_free_result(pSql);
-  pParent->subState.numOfSub = 0;
-  tfree(pParent->pSubs);    
+  tscFreeSubobj(pParent);
 
   if (resRows == 0) {
     pParent->cmd.command = TSDB_SQL_RETRIEVE_EMPTY_RESULT;
@@ -2495,8 +2582,7 @@ void tscFirstRoundCallback(void* param, TAOS_RES* tres, int code) {
 
     tscFreeFirstRoundSup(&param);
     taos_free_result(pSql);
-    parent->subState.numOfSub = 0;
-    tfree(parent->pSubs);
+    tscFreeSubobj(parent);
     parent->res.code = c;
     tscAsyncResultOnError(parent);
     return;
@@ -2661,14 +2747,11 @@ int32_t tscHandleFirstRoundStableQuery(SSqlObj *pSql) {
       pSql->self, pNew->self, 0, pTableMetaInfo->vgroupIndex, pTableMetaInfo->vgroupList->numOfVgroups, pNewQueryInfo->type,
       tscNumOfExprs(pNewQueryInfo), idx+1, pNewQueryInfo->fieldsInfo.numOfOutput, tNameGetTableName(&pTableMetaInfo->name));
 
-  pSql->pSubs = calloc(1, POINTER_BYTES);
-  if (pSql->pSubs == NULL) {
-    terrno = TSDB_CODE_TSC_OUT_OF_MEMORY;
+  int32_t code = doReInitSubState(pSql, 1);
+  if (code != TSDB_CODE_SUCCESS) {
     goto _error;
   }
 
-  pSql->subState.numOfSub = 1;
-
   pSql->pSubs[0] = pNew;
 
   tscHandleMasterSTableQuery(pNew);
@@ -2690,17 +2773,19 @@ typedef struct SPair {
 static void doSendQueryReqs(SSchedMsg* pSchedMsg) {
   SSqlObj* pSql = pSchedMsg->ahandle;
   SPair* p = pSchedMsg->msg;
+  uint32_t stateVersion = tscGetVersionOfSubStateWithoutLock(pSql);
 
   for (int32_t i = p->first; i < p->second; ++i) {
-   if (i >= pSql->subState.numOfSub) {
-      tfree(p);
-      return;
+    SSqlObj* pSub = tscAcquireRefOfSubobj(pSql, i, stateVersion); // ACQ ref
+    if (!pSub) {
+        tscError("0x%"PRIx64"subqueries objs reset unexpectedly. numOfSub:%d", pSql->self, pSql->subState.numOfSub);
+        break;
     }
-    SSqlObj* pSub = pSql->pSubs[i];
     SRetrieveSupport* pSupport = pSub->param;
 
     tscDebug("0x%"PRIx64" sub:0x%"PRIx64" launch subquery, orderOfSub:%d.", pSql->self, pSub->self, pSupport->subqueryIndex);
     tscBuildAndSendRequest(pSub, NULL);
+    tscReleaseRefOfSubobj(pSub); // REL ref
   }
 
   tfree(p);
@@ -2763,12 +2848,9 @@ int32_t tscHandleMasterSTableQuery(SSqlObj *pSql) {
   SQueryInfo     *pQueryInfo = tscGetQueryInfo(pCmd);
   STableMetaInfo *pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
 
-  SSubqueryState *pState = &pSql->subState;
-
   int32_t numOfSub = (pTableMetaInfo->pVgroupTables == NULL) ? pTableMetaInfo->vgroupList->numOfVgroups
                                                              : (int32_t)taosArrayGetSize(pTableMetaInfo->pVgroupTables);
-
-  int32_t ret = doInitSubState(pSql, numOfSub);
+  int32_t ret = doReInitSubState(pSql, numOfSub);
   if (ret != 0) {
     tscAsyncResultOnError(pSql);
     return ret;
@@ -2783,11 +2865,11 @@ int32_t tscHandleMasterSTableQuery(SSqlObj *pSql) {
     return ret;
   }
 
-  tscDebug("0x%"PRIx64" retrieved query data from %d vnode(s)", pSql->self, pState->numOfSub);
+  tscDebug("0x%"PRIx64" retrieved query data from %d vnode(s)", pSql->self, pSql->subState.numOfSub);
   pRes->code = TSDB_CODE_SUCCESS;
   
   int32_t i = 0;
-  for (; i < pState->numOfSub; ++i) {
+  for (; i < pSql->subState.numOfSub; ++i) {
     SRetrieveSupport *trs = (SRetrieveSupport *)calloc(1, sizeof(SRetrieveSupport));
     if (trs == NULL) {
       tscError("0x%"PRIx64" failed to malloc buffer for SRetrieveSupport, orderOfSub:%d, reason:%s", pSql->self, i, strerror(errno));
@@ -2827,24 +2909,19 @@ int32_t tscHandleMasterSTableQuery(SSqlObj *pSql) {
     tscDebug("0x%"PRIx64" sub:0x%"PRIx64" create subquery success. orderOfSub:%d", pSql->self, pNew->self,
         trs->subqueryIndex);
   }
-  
-  if (i < pState->numOfSub) {
+
+  if (i < pSql->subState.numOfSub) {
     tscError("0x%"PRIx64" failed to prepare subquery structure and launch subqueries", pSql->self);
     pRes->code = TSDB_CODE_TSC_OUT_OF_MEMORY;
-    
-    tscDestroyGlobalMergerEnv(pMemoryBuf, pDesc, pState->numOfSub);
-    doCleanupSubqueries(pSql, i);
-    return pRes->code;   // free all allocated resource
   }
-  
-  if (pRes->code == TSDB_CODE_TSC_QUERY_CANCELLED) {
-    tscDestroyGlobalMergerEnv(pMemoryBuf, pDesc, pState->numOfSub);
-    doCleanupSubqueries(pSql, i);
+
+  if (pRes->code != TSDB_CODE_SUCCESS) {
+    tscDestroyGlobalMergerEnv(pMemoryBuf, pDesc, pSql->subState.numOfSub);
+    doCleanupSubqueries(pSql);
     return pRes->code;
   }
 
   doConcurrentlySendSubQueries(pSql);
-
   return TSDB_CODE_SUCCESS;
 }
 
@@ -3016,7 +3093,6 @@ void tscHandleSubqueryError(SRetrieveSupport *trsupport, SSqlObj *pSql, int numO
       }
 
       tscFreeSubobj(userSql);      
-      tfree(userSql->pSubs);
 
       userSql->res.code = TSDB_CODE_SUCCESS;
       userSql->retry++;
@@ -3288,7 +3364,7 @@ static SSqlObj *tscCreateSTableSubquery(SSqlObj *pSql, SRetrieveSupport *trsuppo
 
     pSql->pSubs[trsupport->subqueryIndex] = pNew;
   }
-  
+
   return pNew;
 }
 
@@ -3360,13 +3436,16 @@ void tscRetrieveDataRes(void *param, TAOS_RES *tres, int code) {
   }
 }
 
-static bool needRetryInsert(SSqlObj* pParentObj, int32_t numOfSub) {
+static bool needRetryInsert(SSqlObj* pParentObj) {
   if (pParentObj->retry > pParentObj->maxRetry) {
     tscError("0x%"PRIx64" max retry reached, abort the retry effort", pParentObj->self);
     return false;
   }
+  bool ret = true;
+
+  { pthread_mutex_lock(&pParentObj->subState.mutex);
 
-  for (int32_t i = 0; i < numOfSub; ++i) {
+  for (int32_t i = 0; i < pParentObj->subState.numOfSub; ++i) {
     int32_t code = pParentObj->pSubs[i]->res.code;
     if (code == TSDB_CODE_SUCCESS) {
       continue;
@@ -3376,11 +3455,14 @@ static bool needRetryInsert(SSqlObj* pParentObj, int32_t numOfSub) {
         code != TSDB_CODE_VND_INVALID_VGROUP_ID && code != TSDB_CODE_RPC_NETWORK_UNAVAIL &&
         code != TSDB_CODE_APP_NOT_READY) {
       pParentObj->res.code = code;
-      return false;
+      ret = false;
+      break;
     }
   }
 
-  return true;
+  pthread_mutex_unlock(&pParentObj->subState.mutex); }
+
+  return ret;
 }
 
 static void doFreeInsertSupporter(SSqlObj* pSqlObj) {
@@ -3425,7 +3507,6 @@ static void multiVnodeInsertFinalize(void* param, TAOS_RES* tres, int numOfRows)
 
   // restore user defined fp
   pParentObj->fp = pParentObj->fetchFp;
-  int32_t numOfSub = pParentObj->subState.numOfSub;
   doFreeInsertSupporter(pParentObj);
 
   if (pParentObj->res.code == TSDB_CODE_SUCCESS) {
@@ -3436,14 +3517,18 @@ static void multiVnodeInsertFinalize(void* param, TAOS_RES* tres, int numOfRows)
     int32_t v = (pParentObj->res.code != TSDB_CODE_SUCCESS) ? pParentObj->res.code : (int32_t)pParentObj->res.numOfRows;
     (*pParentObj->fp)(pParentObj->param, pParentObj, v);
   } else {
-    if (!needRetryInsert(pParentObj, numOfSub)) {
+    if (!needRetryInsert(pParentObj)) {
       tscAsyncResultOnError(pParentObj);
       return;
     }
 
     int32_t numOfFailed = 0;
-    for(int32_t i = 0; i < numOfSub; ++i) {
+
+    { pthread_mutex_lock(&pParentObj->subState.mutex);
+
+    for(int32_t i = 0; i < pParentObj->subState.numOfSub; ++i) {
       SSqlObj* pSql = pParentObj->pSubs[i];
+      if (!pSql) continue;
       if (pSql->res.code != TSDB_CODE_SUCCESS) {
         numOfFailed += 1;
 
@@ -3453,14 +3538,16 @@ static void multiVnodeInsertFinalize(void* param, TAOS_RES* tres, int numOfRows)
         STableMetaInfo* pMasterTableMetaInfo = tscGetTableMetaInfoFromCmd(&pParentObj->cmd, 0);
         tscAddTableMetaInfo(pQueryInfo, &pMasterTableMetaInfo->name, NULL, NULL, NULL, NULL);
 
-        subquerySetState(pSql, &pParentObj->subState, i, 0);
+        subquerySetStateWithoutLock(pSql, &pParentObj->subState, i, 0);
 
         tscDebug("0x%"PRIx64", failed sub:%d, %p", pParentObj->self, i, pSql);
       }
     }
 
+    pthread_mutex_unlock(&pParentObj->subState.mutex); }
+
     tscWarn("0x%"PRIx64" Async insertion completed, total inserted:%d rows, numOfFailed:%d, numOfTotal:%d", pParentObj->self,
-             pParentObj->res.numOfRows, numOfFailed, numOfSub);
+             pParentObj->res.numOfRows, numOfFailed, pParentObj->subState.numOfSub);
 
     tscDebug("0x%"PRIx64" cleanup %d tableMeta in hashTable before reparse sql", pParentObj->self, pParentObj->cmd.insertParam.numOfTables);
     for(int32_t i = 0; i < pParentObj->cmd.insertParam.numOfTables; ++i) {
@@ -3527,8 +3614,15 @@ int32_t tscHandleMultivnodeInsert(SSqlObj *pSql) {
       return pRes->code;
     }
 
+    uint32_t stateVersion = tscGetVersionOfSubStateWithoutLock(pSql);
+
     for(int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
-      SSqlObj* pSub = pSql->pSubs[i];
+      SSqlObj* pSub = tscAcquireRefOfSubobj(pSql, i, stateVersion); // ACQ ref
+      if (!pSub)  {
+        tscError("0x%"PRIx64"subqueries objs reset unexpectedly. numOfSub:%d", pSql->self, pSql->subState.numOfSub);
+        pRes->code = TSDB_CODE_FAILED;
+        return pRes->code;
+      }
       SInsertSupporter* pSup = calloc(1, sizeof(SInsertSupporter));
       pSup->index = i;
       pSup->pSql = pSql;
@@ -3538,43 +3632,33 @@ int32_t tscHandleMultivnodeInsert(SSqlObj *pSql) {
       if (pSub->res.code != TSDB_CODE_SUCCESS) {
         tscHandleInsertRetry(pSql, pSub);
       }
+      tscReleaseRefOfSubobj(pSub); // REL ref
     }
 
     return TSDB_CODE_SUCCESS;
   }
 
-  pSql->subState.numOfSub = (uint16_t)taosArrayGetSize(pCmd->insertParam.pDataBlocks);
-  assert(pSql->subState.numOfSub > 0);
-
   pRes->code = TSDB_CODE_SUCCESS;
 
-  // the number of already initialized subqueries
-  int32_t numOfSub = 0;
-
-  if (pSql->subState.states == NULL) {
-    pSql->subState.states = calloc(pSql->subState.numOfSub, sizeof(*pSql->subState.states));
-    if (pSql->subState.states == NULL) {
-      pRes->code = TSDB_CODE_TSC_OUT_OF_MEMORY;
-      goto _error;
-    }
-
-    pthread_mutex_init(&pSql->subState.mutex, NULL);
+  int32_t code = doReInitSubState(pSql, (int32_t)taosArrayGetSize(pCmd->insertParam.pDataBlocks));
+  if (code != TSDB_CODE_SUCCESS) {
+    goto _error;
   }
 
-  memset(pSql->subState.states, 0, sizeof(*pSql->subState.states) * pSql->subState.numOfSub);
-  tscDebug("0x%"PRIx64" reset all sub states to 0", pSql->self);
+  uint32_t stateVersion = 0;
+  int32_t numOfSub = 0;
+  int errflag = 0;
 
-  pSql->pSubs = calloc(pSql->subState.numOfSub, POINTER_BYTES);
-  if (pSql->pSubs == NULL) {
-    goto _error;
-  }
+  { pthread_mutex_lock(&pSql->subState.mutex);
 
+  assert(pSql->subState.numOfSub > 0);
   tscDebug("0x%"PRIx64" submit data to %d vnode(s)", pSql->self, pSql->subState.numOfSub);
 
   while(numOfSub < pSql->subState.numOfSub) {
     SInsertSupporter* pSupporter = calloc(1, sizeof(SInsertSupporter));
     if (pSupporter == NULL) {
-      goto _error;
+      errflag = 1;
+      break;
     }
 
     pSupporter->pSql   = pSql;
@@ -3583,7 +3667,8 @@ int32_t tscHandleMultivnodeInsert(SSqlObj *pSql) {
     SSqlObj *pNew = createSimpleSubObj(pSql, multiVnodeInsertFinalize, pSupporter, TSDB_SQL_INSERT);
     if (pNew == NULL) {
       tscError("0x%"PRIx64" failed to malloc buffer for subObj, orderOfSub:%d, reason:%s", pSql->self, numOfSub, strerror(errno));
-      goto _error;
+      errflag = 1;
+      break;
     }
   
     /*
@@ -3591,6 +3676,7 @@ int32_t tscHandleMultivnodeInsert(SSqlObj *pSql) {
      * the callback function (multiVnodeInsertFinalize) correctly.
      */
     pNew->fetchFp = pNew->fp;
+
     pSql->pSubs[numOfSub] = pNew;
 
     STableDataBlocks* pTableDataBlock = taosArrayGetP(pCmd->insertParam.pDataBlocks, numOfSub);
@@ -3601,28 +3687,44 @@ int32_t tscHandleMultivnodeInsert(SSqlObj *pSql) {
     } else {
       tscDebug("0x%"PRIx64" prepare submit data block failed in async insertion, vnodeIdx:%d, total:%d, code:%s", pSql->self, numOfSub,
                pSql->subState.numOfSub, tstrerror(pRes->code));
-      goto _error;
+      errflag = 1;
+      break;
     }
   }
-  
+
   if (numOfSub < pSql->subState.numOfSub) {
     tscError("0x%"PRIx64" failed to prepare subObj structure and launch sub-insertion", pSql->self);
     pRes->code = TSDB_CODE_TSC_OUT_OF_MEMORY;
-    goto _error;
+    errflag = 1;
+  }
+
+  stateVersion = tscGetVersionOfSubStateWithoutLock(pSql);
+
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+  if (errflag) {
+      goto _error;
   }
 
   pCmd->insertParam.pDataBlocks = tscDestroyBlockArrayList(pSql, pCmd->insertParam.pDataBlocks);
 
   // use the local variable
-  for (int32_t j = 0; j < numOfSub; ++j) {
-    SSqlObj *pSub = pSql->pSubs[j];
+  for (int32_t j = 0; j < pSql->subState.numOfSub; ++j) {
+    SSqlObj *pSub = tscAcquireRefOfSubobj(pSql, j, stateVersion); // ACQ ref
+    if (!pSub) {
+        if (stateVersion == tscGetVersionOfSubStateWithoutLock(pSql)) {
+            continue;
+        }
+        tscError("0x%"PRIx64"subqueries objs reset unexpectedly. numOfSub:%d", pSql->self, pSql->subState.numOfSub);
+        return TSDB_CODE_FAILED;
+    }
     tscDebug("0x%"PRIx64" sub:%p launch sub insert, orderOfSub:%d", pSql->self, pSub, j);
     tscBuildAndSendRequest(pSub, NULL);
+    tscReleaseRefOfSubobj(pSub); // REL ref
   }
 
   return TSDB_CODE_SUCCESS;
 
-  _error:
+_error:
   return TSDB_CODE_TSC_OUT_OF_MEMORY;
 }
 
@@ -3646,6 +3748,9 @@ static void doBuildResFromSubqueries(SSqlObj* pSql) {
   SQueryInfo *pQueryInfo = tscGetQueryInfo(&pSql->cmd);
 
   int32_t numOfRes = INT32_MAX;
+
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
   for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     SSqlObj* pSub = pSql->pSubs[i];
     if (pSub == NULL) {
@@ -3656,6 +3761,8 @@ static void doBuildResFromSubqueries(SSqlObj* pSql) {
     numOfRes = (int32_t)(MIN(numOfRes, remain));
   }
 
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+
   if (numOfRes == 0) {  // no result any more, free all subquery objects
     pSql->res.completed = true;
     freeJoinSubqueryObj(pSql);
@@ -3683,6 +3790,9 @@ static void doBuildResFromSubqueries(SSqlObj* pSql) {
 
   tscRestoreFuncForSTableQuery(pQueryInfo);
   tscFieldInfoUpdateOffset(pQueryInfo);
+
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
   for (int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
     SSqlObj* pSub = pSql->pSubs[i];
     if (pSub == NULL) {
@@ -3718,6 +3828,8 @@ static void doBuildResFromSubqueries(SSqlObj* pSql) {
     assert(pSub->res.row <= pSub->res.numOfRows);
   }
 
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+
   pRes->numOfRows = numOfRes;
   pRes->numOfClauseTotal += numOfRes;
 
@@ -3830,6 +3942,8 @@ static UNUSED_FUNC bool tscHasRemainDataInSubqueryResultSet(SSqlObj *pSql) {
   SSqlCmd *pCmd = &pSql->cmd;
   
   SQueryInfo *pQueryInfo = tscGetQueryInfo(pCmd);
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
   if (tscNonOrderedProjectionQueryOnSTable(pQueryInfo, 0)) {
     bool allSubqueryExhausted = true;
 
@@ -3876,6 +3990,8 @@ static UNUSED_FUNC bool tscHasRemainDataInSubqueryResultSet(SSqlObj *pSql) {
     }
   }
   
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+
   return hasData;
 }
 
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index bc0693bb30aef265d41eadb2c87ed5b4f4b40d70..6a33952a2f484ae049f7340a20f5d51a764e1a05 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -1656,29 +1656,30 @@ void tscFreeSqlResult(SSqlObj* pSql) {
 }
 
 void tscFreeSubobj(SSqlObj* pSql) {
+  pthread_mutex_lock(&pSql->subState.mutex);
   if (pSql->subState.numOfSub == 0) {
-    return;
+    goto _out;
   }
+  pSql->subState.version ++;
 
   tscDebug("0x%"PRIx64" start to free sub SqlObj, numOfSub:%d", pSql->self, pSql->subState.numOfSub);
 
   for(int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
-    if (pSql->pSubs[i] != NULL) {
-      tscDebug("0x%"PRIx64" free sub SqlObj:0x%"PRIx64", index:%d", pSql->self, pSql->pSubs[i]->self, i);
-    } else {
-      /* just for python error test case */
+    if (!pSql->pSubs[i]) {
       tscDebug("0x%"PRIx64" free sub SqlObj:0x0, index:%d", pSql->self, i);
+      continue;
     }
+    tscDebug("0x%"PRIx64" free sub SqlObj:0x%"PRIx64", index:%d", pSql->self, pSql->pSubs[i]->self, i);
     taos_free_result(pSql->pSubs[i]);
     pSql->pSubs[i] = NULL;
   }
 
-  if (pSql->subState.states) {
-    pthread_mutex_destroy(&pSql->subState.mutex);
-  }
-
+  tfree(pSql->pSubs);
   tfree(pSql->subState.states);
   pSql->subState.numOfSub = 0;
+
+_out:
+  pthread_mutex_unlock(&pSql->subState.mutex);
 }
 
 /**
@@ -1715,6 +1716,52 @@ void tscFreeMetaSqlObj(int64_t *rid){
   }
 }
 
+SSqlObj* tscAllocSqlObj() {
+    SSqlObj *pNew = calloc(1, sizeof(SSqlObj));
+    if (!pNew) {
+        return NULL;
+    }
+    int rc = tsem_init(&pNew->rspSem, 0, 0);
+    assert(rc == 0 && "tsem_init failure");
+    rc = pthread_mutex_init(&pNew->subState.mutex, NULL);
+    assert(rc == 0 && "pthread_mutex_init failure");
+    return pNew;
+}
+
+SSqlObj* tscAcquireRefOfSubobj(SSqlObj* pSql, int32_t idx, uint32_t stateVersion) {
+    assert (pSql != NULL);
+    SSqlObj *pSub = NULL;
+
+    { pthread_mutex_lock(&pSql->subState.mutex);
+    if (stateVersion != tscGetVersionOfSubStateWithoutLock(pSql) ||
+        idx < 0 ||
+        idx >= pSql->subState.numOfSub ||
+        !pSql->pSubs[idx]) {
+        goto _out;
+    }
+    pSub = taosAcquireRef(tscObjRef, pSql->pSubs[idx]->self);
+    assert (pSql->pSubs[idx] == pSub && "Refcounted subquery obj mismatch");
+
+_out:
+    pthread_mutex_unlock(&pSql->subState.mutex); }
+    return pSub;
+}
+
+void tscReleaseRefOfSubobj(SSqlObj* pSub) {
+    assert (pSub != NULL && pSub->self != 0 && "Subquery obj not refcounted");
+    taosReleaseRef(tscObjRef, pSub->self);
+}
+
+uint32_t tscGetVersionOfSubStateWithoutLock(SSqlObj *pSql) {
+    return pSql->subState.version;
+}
+
+void tscResetAllSubStates(SSqlObj* pSql) {
+    pthread_mutex_lock(&pSql->subState.mutex);
+    memset(pSql->subState.states, 0, sizeof(pSql->subState.states[0]) * pSql->subState.numOfSub);
+    pthread_mutex_unlock(&pSql->subState.mutex);
+}
+
 void tscFreeSqlObj(SSqlObj* pSql) {
   if (pSql == NULL || pSql->signature != pSql) {
     return;
@@ -1738,17 +1785,11 @@ void tscFreeSqlObj(SSqlObj* pSql) {
 
   tscFreeSubobj(pSql);
 
-  if (pSql && (pSql == pSql->rootObj)) {
-    pthread_mutex_destroy(&pSql->mtxSubs);
-  }
-
   pSql->signature = NULL;
   pSql->fp = NULL;
   tfree(pSql->sqlstr);
   tfree(pSql->pBuf);
 
-  tfree(pSql->pSubs);
-  pSql->subState.numOfSub = 0;
   pSql->self = 0;
 
   tscFreeSqlResult(pSql);
@@ -1759,6 +1800,7 @@ void tscFreeSqlObj(SSqlObj* pSql) {
 
   tscDebug("0x%"PRIx64" addr:%p free completed", sid, pSql);
 
+  pthread_mutex_destroy(&pSql->subState.mutex);
   tsem_destroy(&pSql->rspSem);
   memset(pSql, 0, sizeof(*pSql));
   free(pSql);
@@ -3744,7 +3786,7 @@ void registerSqlObj(SSqlObj* pSql) {
 }
 
 SSqlObj* createSimpleSubObj(SSqlObj* pSql, __async_cb_func_t fp, void* param, int32_t cmd) {
-  SSqlObj* pNew = (SSqlObj*)calloc(1, sizeof(SSqlObj));
+  SSqlObj* pNew = tscAllocSqlObj();
   if (pNew == NULL) {
     tscError("0x%"PRIx64" new subquery failed, tableIndex:%d", pSql->self, 0);
     return NULL;
@@ -3756,7 +3798,6 @@ SSqlObj* createSimpleSubObj(SSqlObj* pSql, __async_cb_func_t fp, void* param, in
 
   SSqlCmd* pCmd = &pNew->cmd;
   pCmd->command = cmd;
-  tsem_init(&pNew->rspSem, 0 ,0);
 
   if (tscAddQueryInfo(pCmd) != TSDB_CODE_SUCCESS) {
     tscFreeSqlObj(pNew);
@@ -3821,7 +3862,7 @@ static void doSetSqlExprAndResultFieldInfo(SQueryInfo* pNewQueryInfo, int64_t ui
 SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, __async_cb_func_t fp, void* param, int32_t cmd, SSqlObj* pPrevSql) {
   SSqlCmd* pCmd = &pSql->cmd;
 
-  SSqlObj* pNew = (SSqlObj*)calloc(1, sizeof(SSqlObj));
+  SSqlObj* pNew = tscAllocSqlObj();
   if (pNew == NULL) {
     tscError("0x%"PRIx64" new subquery failed, tableIndex:%d", pSql->self, tableIndex);
     terrno = TSDB_CODE_TSC_OUT_OF_MEMORY;
@@ -3835,7 +3876,6 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, __async_cb_func_t
   pNew->signature = pNew;
   pNew->sqlstr    = strdup(pSql->sqlstr);
   pNew->rootObj   = pSql->rootObj;
-  tsem_init(&pNew->rspSem, 0, 0);
 
   SSqlCmd* pnCmd  = &pNew->cmd;
   memcpy(pnCmd, pCmd, sizeof(SSqlCmd));
@@ -4124,10 +4164,7 @@ static void tscSubqueryCompleteCallback(void* param, TAOS_RES* tres, int code) {
     }
 
     tscFreeSubobj(pParentSql);
-    tfree(pParentSql->pSubs);
-
     tscFreeSubobj(rootObj);
-    tfree(rootObj->pSubs);
 
     rootObj->res.code = TSDB_CODE_SUCCESS;
     rootObj->retry++;
@@ -4163,34 +4200,25 @@ static void tscSubqueryCompleteCallback(void* param, TAOS_RES* tres, int code) {
     return;
   }
 
-
   taos_fetch_rows_a(tres, tscSubqueryRetrieveCallback, param);
 }
 
-int32_t doInitSubState(SSqlObj* pSql, int32_t numOfSubqueries) {
-  //bug fix. Above doInitSubState level, the loop invocation with the same SSqlObj will be fail.
-  //assert(pSql->subState.numOfSub == 0 && pSql->pSubs == NULL && pSql->subState.states == NULL);  
-  if(pSql->pSubs) {
-    free(pSql->pSubs);
-    pSql->pSubs = NULL;
-  }
-  
-  if(pSql->subState.states) {
-    free(pSql->subState.states);
-    pSql->subState.states = NULL;
-  }
-  
-  pSql->subState.numOfSub = numOfSubqueries;
-  
-  pSql->pSubs = calloc(pSql->subState.numOfSub, POINTER_BYTES);
-  pSql->subState.states = calloc(pSql->subState.numOfSub, sizeof(int8_t));
+int32_t doReInitSubState(SSqlObj* pSql, int32_t numOfSubqueries) {
+  tscFreeSubobj(pSql);
+  int32_t code = TSDB_CODE_SUCCESS;
 
-  int32_t code = pthread_mutex_init(&pSql->subState.mutex, NULL);
-  if (pSql->pSubs == NULL || pSql->subState.states == NULL || code != 0) {
-    return TSDB_CODE_TSC_OUT_OF_MEMORY;
+  { pthread_mutex_lock(&pSql->subState.mutex);
+
+  pSql->pSubs = calloc(numOfSubqueries, POINTER_BYTES);
+  pSql->subState.states = calloc(numOfSubqueries, sizeof(int8_t));
+  if (pSql->pSubs == NULL || pSql->subState.states == NULL) {
+    code = TSDB_CODE_TSC_OUT_OF_MEMORY;
   }
+  pSql->subState.numOfSub = numOfSubqueries;
+  pSql->subState.version ++;
 
-  return TSDB_CODE_SUCCESS;
+  pthread_mutex_unlock(&pSql->subState.mutex); }
+  return code;
 }
 
 // do execute the query according to the query execution plan
@@ -4209,21 +4237,26 @@ void executeQuery(SSqlObj* pSql, SQueryInfo* pQueryInfo) {
 
   // upstream may be freed before retry
   if (pQueryInfo->pUpstream && taosArrayGetSize(pQueryInfo->pUpstream) > 0) {  // nest query. do execute it firstly
-    code = doInitSubState(pSql, (int32_t) taosArrayGetSize(pQueryInfo->pUpstream));
+    code = doReInitSubState(pSql, (int32_t) taosArrayGetSize(pQueryInfo->pUpstream));
     if (code != TSDB_CODE_SUCCESS) {
       goto _error;
     }
 
+    uint32_t stateVersion = 0;
+    int errflag = 0;
+    { pthread_mutex_lock(&pSql->subState.mutex);
+
     for(int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
       SQueryInfo* pSub = taosArrayGetP(pQueryInfo->pUpstream, i);
 
       pSql->cmd.active = pSub;
       pSql->cmd.command = TSDB_SQL_SELECT;
 
-      SSqlObj* pNew = (SSqlObj*)calloc(1, sizeof(SSqlObj));
+      SSqlObj* pNew = tscAllocSqlObj();
       if (pNew == NULL) {
         code = TSDB_CODE_TSC_OUT_OF_MEMORY;
-        goto _error;
+        errflag = 1;
+        break;
       }
 
       pNew->pTscObj   = pSql->pTscObj;
@@ -4236,24 +4269,26 @@ void executeQuery(SSqlObj* pSql, SQueryInfo* pQueryInfo) {
 
       pNew->cmd.resColumnId = TSDB_RES_COL_ID;
 
-      tsem_init(&pNew->rspSem, 0, 0);
-
       SRetrieveSupport* ps = calloc(1, sizeof(SRetrieveSupport));  // todo use object id
       if (ps == NULL) {
         tscFreeSqlObj(pNew);
-        goto _error;
+        errflag = 1;
+        break;
       }
 
       ps->pParentSql = pSql;
       ps->subqueryIndex = i;
-
       pNew->param = ps;
+
+      registerSqlObj(pNew);
+
       pSql->pSubs[i] = pNew;
 
       SSqlCmd* pCmd = &pNew->cmd;
       pCmd->command = TSDB_SQL_SELECT;
       if ((code = tscAddQueryInfo(pCmd)) != TSDB_CODE_SUCCESS) {
-        goto _error;
+        errflag = 1;
+        break;
       }
 
       SQueryInfo* pNewQueryInfo = tscGetQueryInfo(pCmd);
@@ -4263,9 +4298,23 @@ void executeQuery(SSqlObj* pSql, SQueryInfo* pQueryInfo) {
       numOfInit++;
     }
 
+    stateVersion = tscGetVersionOfSubStateWithoutLock(pSql);
+
+    pthread_mutex_unlock(&pSql->subState.mutex); }
+    if (errflag) {
+        goto _error;
+    }
+
     for(int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
-      SSqlObj* psub = pSql->pSubs[i];
-      registerSqlObj(psub);
+      SSqlObj* psub = tscAcquireRefOfSubobj(pSql, i, stateVersion);  // ACQ ref
+      if (!psub) {
+        if (stateVersion == tscGetVersionOfSubStateWithoutLock(pSql)) {
+            continue;
+        }
+        tscError("0x%"PRIx64"subqueries objs reset unexpectedly. numOfSub:%d", pSql->self, pSql->subState.numOfSub);
+        code = TSDB_CODE_FAILED;
+        goto _error;
+      }
 
       // create sub query to handle the sub query.
       SQueryInfo* pq = tscGetQueryInfo(&psub->cmd);
@@ -4275,29 +4324,21 @@ void executeQuery(SSqlObj* pSql, SQueryInfo* pQueryInfo) {
         psub->cmd.command = TSDB_SQL_RETRIEVE_EMPTY_RESULT;
       }
       executeQuery(psub, pq);
+
+      tscReleaseRefOfSubobj(psub); // REL ref
     }
 
     return;
-  } else if (hasMoreClauseToTry(pSql)) {
-    if (pthread_mutex_init(&pSql->subState.mutex, NULL) != 0) {
-      goto _error;
-    }
   }
 
   pSql->cmd.active = pQueryInfo;
   doExecuteQuery(pSql, pQueryInfo);
   return;
 
-  _error:
-  for(int32_t i = 0; i < numOfInit; ++i) {
-    SSqlObj* p = pSql->pSubs[i];
-    tscFreeSqlObj(p);
-  }
-
+_error:
   pSql->res.code = code;
-  pSql->subState.numOfSub = 0;   // not initialized sub query object will not be freed
-  tfree(pSql->subState.states);
-  tfree(pSql->pSubs);
+  tscFreeSubobj(pSql);
+
   tscAsyncResultOnError(pSql);
 }
 
@@ -4532,7 +4573,7 @@ void tscTryQueryNextVnode(SSqlObj* pSql, __async_cb_func_t fp) {
      *
      * For super table join with projection query, if anyone of the subquery is exhausted, the query completed.
      */
-    pSql->subState.numOfSub = 0;
+    tscFreeSubobj(pSql);
     pCmd->command = TSDB_SQL_SELECT;
 
     tscResetForNextRetrieve(pRes);
@@ -4564,16 +4605,7 @@ void tscTryQueryNextClause(SSqlObj* pSql, __async_cb_func_t fp) {
   pRes->final = finalBk;
   pRes->numOfTotal = num;
 
-  pthread_mutex_lock(&pSql->subState.mutex);
-  for(int32_t i = 0; i < pSql->subState.numOfSub; ++i) {
-    taos_free_result(pSql->pSubs[i]);
-  }
-
-  tfree(pSql->pSubs);
-  tfree(pSql->subState.states);
-  pSql->subState.numOfSub = 0;
-  pthread_mutex_unlock(&pSql->subState.mutex);
-  pthread_mutex_destroy(&pSql->subState.mutex);
+  tscFreeSubobj(pSql);
 
   pSql->fp = fp;
 
diff --git a/src/util/src/tref.c b/src/util/src/tref.c
index a828820870374c8bf9cadcc7bfb00d6950494560..37671c62b7478d9f730ffa3a73bd8ea9970cc554 100644
--- a/src/util/src/tref.c
+++ b/src/util/src/tref.c
@@ -195,7 +195,6 @@ int taosRemoveRef(int rsetId, int64_t rid)
   return taosDecRefCount(rsetId, rid, 1);
 }
 
-// if rid is 0, return the first p in hash list, otherwise, return the next after current rid
 void *taosAcquireRef(int rsetId, int64_t rid)
 {
   int       hash;