diff --git a/src/client/inc/tscSecondaryMerge.h b/src/client/inc/tscSecondaryMerge.h
index 0c6472f6b367857edbdc92a08e0bc8a263572ee1..bcfe14fcb79e79b6d3965dfd5970421819f27b23 100644
--- a/src/client/inc/tscSecondaryMerge.h
+++ b/src/client/inc/tscSecondaryMerge.h
@@ -120,7 +120,7 @@ void tscCreateLocalReducer(tExtMemBuffer **pMemBuffer, int32_t numOfBuffer, tOrd
 
 void tscDestroyLocalReducer(SSqlObj *pSql);
 
-int32_t tscLocalDoReduce(SSqlObj *pSql);
+int32_t tscDoLocalreduce(SSqlObj *pSql);
 
 #ifdef __cplusplus
 }
diff --git a/src/client/inc/tscUtil.h b/src/client/inc/tscUtil.h
index fd0973f319166a9eba73bb89df607f7d121efa9e..aa05c782cc35b59ffcc82bbf0078d1116db392b6 100644
--- a/src/client/inc/tscUtil.h
+++ b/src/client/inc/tscUtil.h
@@ -187,7 +187,7 @@ SMeterMetaInfo* tscGetMeterMetaInfoFromQueryInfo(SQueryInfo *pQueryInfo, int32_t
 SQueryInfo *tscGetQueryInfoDetail(SSqlCmd* pCmd, int32_t subClauseIndex);
 int32_t tscGetQueryInfoDetailSafely(SSqlCmd *pCmd, int32_t subClauseIndex, SQueryInfo** pQueryInfo);
 
-SMeterMetaInfo* tscGetMeterMetaInfoByUid(SQueryInfo* pQueryInfo, int32_t subClauseIndex, uint64_t uid, int32_t* index);
+SMeterMetaInfo* tscGetMeterMetaInfoByUid(SQueryInfo* pQueryInfo, uint64_t uid, int32_t* index);
 void            tscClearMeterMetaInfo(SMeterMetaInfo* pMeterMetaInfo, bool removeFromCache);
 
 SMeterMetaInfo* tscAddMeterMetaInfo(SQueryInfo* pQueryInfo, const char* name, SMeterMeta* pMeterMeta, SMetricMeta* pMetricMeta,
@@ -197,7 +197,7 @@ int32_t tscAddSubqueryInfo(SSqlCmd *pCmd);
 void tscFreeSubqueryInfo(SSqlCmd* pCmd);
 void tscClearSubqueryInfo(SSqlCmd* pCmd);
 
-void tscGetMetricMetaCacheKey(SSqlCmd* pCmd, int32_t subClauseIndex, char* keyStr, uint64_t uid);
+void tscGetMetricMetaCacheKey(SQueryInfo* pQueryInfo, char* keyStr, uint64_t uid);
 int  tscGetMetricMeta(SSqlObj* pSql, int32_t clauseIndex);
 int  tscGetMeterMeta(SSqlObj* pSql, SMeterMetaInfo* pMeterMetaInfo);
 int  tscGetMeterMetaEx(SSqlObj* pSql, SMeterMetaInfo* pMeterMetaInfo, bool createIfNotExists);
diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 773924c1105f6fd70b9c86bb03e35f5b29aa9eaf..823fd359cc7af8aa2cd899eeea7e6c1d25651eae 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -273,8 +273,10 @@ struct STSBuf;
 
 typedef struct {
   uint8_t               code;
-  int                   numOfRows;   // num of results in current retrieved
-  int                   numOfTotal;  // num of total results
+  int64_t               numOfRows;   // num of results in current retrieved
+  int64_t               numOfTotal;  // num of total results
+  int64_t               numOfTotalInCurrentClause;  // num of total result in current subclause
+  
   char *                pRsp;
   int                   rspType;
   int                   rspLen;
@@ -431,7 +433,7 @@ void tscProcessMultiVnodesInsertFromFile(SSqlObj *pSql);
 void tscKillMetricQuery(SSqlObj *pSql);
 void tscInitResObjForLocalQuery(SSqlObj *pObj, int32_t numOfRes, int32_t rowLen);
 bool tscIsUpdateQuery(STscObj *pObj);
-bool tscHasReachLimitation(SSqlObj *pSql);
+bool tscHasReachLimitation(SQueryInfo* pQueryInfo, SSqlRes* pRes);
 
 char *tscGetErrorMsgPayload(SSqlCmd *pCmd);
 
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index 8b0edaf9fe735b5d25307967b2f7c06905a54c1b..0e22214147af8c7595c08fe86b1e3db2828a7740 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -118,7 +118,7 @@ static void tscProcessAsyncFetchRowsProxy(void *param, TAOS_RES *tres, int numOf
   SSqlRes *pRes = &pSql->res;
   SSqlCmd *pCmd = &pSql->cmd;
 
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   // sequentially retrieve data from remain vnodes first, query vnode specified by vnodeIdx
   if (numOfRows == 0 && tscProjectionQueryOnSTable(pQueryInfo, 0)) {
@@ -285,7 +285,7 @@ void tscProcessAsyncRetrieve(void *param, TAOS_RES *tres, int numOfRows) {
       }
 
       /* update the limit value according to current retrieval results */
-      SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+      SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
       pQueryInfo->limit.limit = pCmd->globalLimit - pRes->numOfTotal;
 
       if ((++pMeterMetaInfo->vnodeIndex) <= pMeterMetaInfo->pMetricMeta->numOfVnodes) {
@@ -312,9 +312,8 @@ void tscProcessFetchRow(SSchedMsg *pMsg) {
   SSqlObj *pSql = (SSqlObj *)pMsg->ahandle;
   SSqlRes *pRes = &pSql->res;
   SSqlCmd *pCmd = &pSql->cmd;
-  assert(0);
   
-  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   assert(pCmd->numOfCols == pQueryInfo->fieldsInfo.numOfOutputCols);
 
   for (int i = 0; i < pCmd->numOfCols; ++i)
@@ -497,7 +496,7 @@ void tscMeterMetaCallBack(void *param, TAOS_RES *res, int code) {
 
   if (pSql->pStream == NULL) {
     // check if it is a sub-query of metric query first, if true, enter another routine
-    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
+    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
     if ((pQueryInfo->type & TSDB_QUERY_TYPE_STABLE_SUBQUERY) == TSDB_QUERY_TYPE_STABLE_SUBQUERY) {
       SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
@@ -552,7 +551,7 @@ void tscMeterMetaCallBack(void *param, TAOS_RES *res, int code) {
      * transfer the sql function for metric query before get meter/metric meta,
      * since in callback functions, only tscProcessSql(pStream->pSql) is executed!
      */
-    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
     
     tscTansformSQLFunctionForSTableQuery(pQueryInfo);
     tscIncStreamExecutionCount(pSql->pStream);
diff --git a/src/client/src/tscJoinProcess.c b/src/client/src/tscJoinProcess.c
index bd9a782d8cd052f53b57b85a75ceb3bcf3bf44b8..3000be213a335b8683e6e7a31cea3579df5bad28 100644
--- a/src/client/src/tscJoinProcess.c
+++ b/src/client/src/tscJoinProcess.c
@@ -441,7 +441,10 @@ static void joinRetrieveCallback(void* param, TAOS_RES* tres, int numOfRows) {
 
       taos_fetch_rows_a(tres, joinRetrieveCallback, param);
     } else if (numOfRows == 0) {  // no data from this vnode anymore
-      if (tscProjectionQueryOnSTable(pQueryInfo, 0)) {
+      SQueryInfo* pParentQueryInfo = tscGetQueryInfoDetail(&pParentSql->cmd, pParentSql->cmd.clauseIndex);
+      
+      //todo refactor
+      if (tscProjectionQueryOnSTable(pParentQueryInfo, 0)) {
         SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
         assert(pQueryInfo->numOfTables == 1);
 
@@ -548,11 +551,11 @@ void tscFetchDatablockFromSubquery(SSqlObj* pSql) {
   
     if (tscProjectionQueryOnSTable(pQueryInfo, 0)) {
       if (pRes->row >= pRes->numOfRows && pMeterMetaInfo->vnodeIndex < pMeterMetaInfo->pMetricMeta->numOfVnodes &&
-          (!tscHasReachLimitation(pSql->pSubs[i]))) {
+          (!tscHasReachLimitation(pQueryInfo, pRes))) {
         numOfFetch++;
       }
     } else {
-      if (pRes->row >= pRes->numOfRows && (!tscHasReachLimitation(pSql->pSubs[i]))) {
+      if (pRes->row >= pRes->numOfRows && (!tscHasReachLimitation(pQueryInfo, pRes))) {
         numOfFetch++;
       }
     }
diff --git a/src/client/src/tscPrepare.c b/src/client/src/tscPrepare.c
index 744ffd5b2bdc6dbf1c9db900b90cc97525d70d03..4ab63c18e9ad339664b1771bead46aedcb0c9d48 100644
--- a/src/client/src/tscPrepare.c
+++ b/src/client/src/tscPrepare.c
@@ -448,6 +448,8 @@ static int insertStmtExecute(STscStmt* stmt) {
   SSqlRes *pRes = &pSql->res;
   pRes->numOfRows = 0;
   pRes->numOfTotal = 0;
+  pRes->numOfTotalInCurrentClause = 0;
+  
   pRes->qhandle = 0;
   pSql->thandle = NULL;
 
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index 49d2678ea5deab6d8fe1a0b043bf6205d7b33678..7b92ad5fcf6345e459a96384cb073e64e8666737 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -520,7 +520,7 @@ int32_t tscToSQLCmd(SSqlObj* pSql, struct SSqlInfo* pInfo) {
         }
       }
       
-      // set the command/globallimit parameters from the first subclause to the sqlcmd object
+      // set the command/global limit parameters from the first subclause to the sqlcmd object
       SQueryInfo* pQueryInfo1 = tscGetQueryInfoDetail(pCmd, 0);
       pCmd->command = pQueryInfo1->command;
   
@@ -5576,10 +5576,6 @@ int32_t doCheckForQuery(SSqlObj* pSql, SQuerySQL* pQuerySql, int32_t index) {
     }
   }
 
-  // handle the limit offset value, validate the limit
-  pQueryInfo->limit = pQuerySql->limit;
-
-  // temporarily save the original limitation value
   if ((code = parseLimitClause(pQueryInfo, index, pQuerySql, pSql)) != TSDB_CODE_SUCCESS) {
     return code;
   }
diff --git a/src/client/src/tscSecondaryMerge.c b/src/client/src/tscSecondaryMerge.c
index e9a63b028b957e5604ad4c22ecdf636aa0c5d4ef..e7a4941fc179e43019219b6dc2db22cf68e7cacf 100644
--- a/src/client/src/tscSecondaryMerge.c
+++ b/src/client/src/tscSecondaryMerge.c
@@ -58,7 +58,7 @@ static void tscInitSqlContext(SSqlCmd *pCmd, SSqlRes *pRes, SLocalReducer *pRedu
    * the fields and offset attributes in pCmd and pModel may be different due to
    * merge requirement. So, the final result in pRes structure is formatted in accordance with the pCmd object.
    */
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   for (int32_t i = 0; i < pQueryInfo->fieldsInfo.numOfOutputCols; ++i) {
     SQLFunctionCtx *pCtx = &pReducer->pCtx[i];
 
@@ -215,7 +215,7 @@ void tscCreateLocalReducer(tExtMemBuffer **pMemBuffer, int32_t numOfBuffer, tOrd
 #ifdef _DEBUG_VIEW
       printf("load data page into mem for build loser tree: %ld rows\n", pDS->filePage.numOfElems);
       SSrcColumnInfo colInfo[256] = {0};
-      SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+      SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
 
       tscGetSrcColumnInfo(colInfo, pQueryInfo);
 
@@ -241,7 +241,7 @@ void tscCreateLocalReducer(tExtMemBuffer **pMemBuffer, int32_t numOfBuffer, tOrd
   param->pLocalData = pReducer->pLocalDataSrc;
   param->pDesc = pReducer->pDesc;
   param->numOfElems = pReducer->pLocalDataSrc[0]->pMemBuffer->numOfElemsPerPage;
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   param->groupOrderType = pQueryInfo->groupbyExpr.orderType;
 
@@ -434,7 +434,7 @@ void tscDestroyLocalReducer(SSqlObj *pSql) {
   }
 
   SSqlCmd *pCmd = &pSql->cmd;
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   // there is no more result, so we release all allocated resource
   SLocalReducer *pLocalReducer = (SLocalReducer*)atomic_exchange_ptr(&pRes->pLocalReducer, NULL);
@@ -500,7 +500,7 @@ void tscDestroyLocalReducer(SSqlObj *pSql) {
 
 static int32_t createOrderDescriptor(tOrderDescriptor **pOrderDesc, SSqlCmd *pCmd, tColModel *pModel) {
   int32_t numOfGroupByCols = 0;
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   if (pQueryInfo->groupbyExpr.numOfGroupCols > 0) {
     numOfGroupByCols = pQueryInfo->groupbyExpr.numOfGroupCols;
@@ -541,7 +541,7 @@ static int32_t createOrderDescriptor(tOrderDescriptor **pOrderDesc, SSqlCmd *pCm
 }
 
 bool isSameGroup(SSqlCmd *pCmd, SLocalReducer *pReducer, char *pPrev, tFilePage *tmpBuffer) {
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   int16_t functionId = tscSqlExprGet(pQueryInfo, 0)->functionId;
 
@@ -787,7 +787,7 @@ static void doInterpolateResult(SSqlObj *pSql, SLocalReducer *pLocalReducer, boo
   SSqlCmd *  pCmd = &pSql->cmd;
   SSqlRes *  pRes = &pSql->res;
   tFilePage *pFinalDataPage = pLocalReducer->pResultBuf;
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   if (pRes->pLocalReducer != pLocalReducer) {
     /*
@@ -802,7 +802,7 @@ static void doInterpolateResult(SSqlObj *pSql, SLocalReducer *pLocalReducer, boo
     // no interval query, no interpolation
     pRes->data = pLocalReducer->pFinalRes;
     pRes->numOfRows = pFinalDataPage->numOfElems;
-    pRes->numOfTotal += pRes->numOfRows;
+    pRes->numOfTotalInCurrentClause += pRes->numOfRows;
 
     if (pQueryInfo->limit.offset > 0) {
       if (pQueryInfo->limit.offset < pRes->numOfRows) {
@@ -813,23 +813,23 @@ static void doInterpolateResult(SSqlObj *pSql, SLocalReducer *pLocalReducer, boo
         tColModelCompact(pLocalReducer->resColModel, pFinalDataPage, prevSize);
 
         pRes->numOfRows -= pQueryInfo->limit.offset;
-        pRes->numOfTotal -= pQueryInfo->limit.offset;
+        pRes->numOfTotalInCurrentClause -= pQueryInfo->limit.offset;
         pQueryInfo->limit.offset = 0;
       } else {
         pQueryInfo->limit.offset -= pRes->numOfRows;
         pRes->numOfRows = 0;
-        pRes->numOfTotal = 0;
+        pRes->numOfTotalInCurrentClause = 0;
       }
     }
 
-    if (pQueryInfo->limit.limit >= 0 && pRes->numOfTotal > pQueryInfo->limit.limit) {
+    if (pQueryInfo->limit.limit >= 0 && pRes->numOfTotalInCurrentClause > pQueryInfo->limit.limit) {
       /* impose the limitation of output rows on the final result */
       int32_t prevSize = pFinalDataPage->numOfElems;
-      int32_t overFlow = pRes->numOfTotal - pQueryInfo->limit.limit;
+      int32_t overFlow = pRes->numOfTotalInCurrentClause - pQueryInfo->limit.limit;
 
       assert(overFlow < pRes->numOfRows);
 
-      pRes->numOfTotal = pQueryInfo->limit.limit;
+      pRes->numOfTotalInCurrentClause = pQueryInfo->limit.limit;
       pRes->numOfRows -= overFlow;
       pFinalDataPage->numOfElems -= overFlow;
 
@@ -898,7 +898,7 @@ static void doInterpolateResult(SSqlObj *pSql, SLocalReducer *pLocalReducer, boo
 
       pRes->data = pLocalReducer->pFinalRes;
       pRes->numOfRows = newRows;
-      pRes->numOfTotal += newRows;
+      pRes->numOfTotalInCurrentClause += newRows;
 
       pQueryInfo->limit.offset = 0;
       break;
@@ -924,13 +924,13 @@ static void doInterpolateResult(SSqlObj *pSql, SLocalReducer *pLocalReducer, boo
   }
 
   if (pRes->numOfRows > 0) {
-    if (pQueryInfo->limit.limit >= 0 && pRes->numOfTotal > pQueryInfo->limit.limit) {
-      int32_t overFlow = pRes->numOfTotal - pQueryInfo->limit.limit;
+    if (pQueryInfo->limit.limit >= 0 && pRes->numOfTotalInCurrentClause > pQueryInfo->limit.limit) {
+      int32_t overFlow = pRes->numOfTotalInCurrentClause - pQueryInfo->limit.limit;
       pRes->numOfRows -= overFlow;
 
       assert(pRes->numOfRows >= 0);
 
-      pRes->numOfTotal = pQueryInfo->limit.limit;
+      pRes->numOfTotalInCurrentClause = pQueryInfo->limit.limit;
       pFinalDataPage->numOfElems -= overFlow;
 
       /* set remain data to be discarded, and reset the interpolation information */
@@ -974,7 +974,7 @@ static void savePreviousRow(SLocalReducer *pLocalReducer, tFilePage *tmpBuffer)
 
 static void doExecuteSecondaryMerge(SSqlCmd* pCmd, SLocalReducer *pLocalReducer, bool needInit) {
   // the tag columns need to be set before all functions execution
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   for(int32_t j = 0; j < pQueryInfo->fieldsInfo.numOfOutputCols; ++j) {
     SSqlExpr *      pExpr = tscSqlExprGet(pQueryInfo, j);
@@ -1129,7 +1129,7 @@ static bool saveGroupResultInfo(SSqlObj *pSql) {
   SSqlCmd *pCmd = &pSql->cmd;
   SSqlRes *pRes = &pSql->res;
 
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   pRes->numOfGroups += 1;
 
   // the output group is limited by the slimit clause
@@ -1139,7 +1139,7 @@ static bool saveGroupResultInfo(SSqlObj *pSql) {
 
   //    pRes->pGroupRec = realloc(pRes->pGroupRec, pRes->numOfGroups*sizeof(SResRec));
   //    pRes->pGroupRec[pRes->numOfGroups-1].numOfRows = pRes->numOfRows;
-  //    pRes->pGroupRec[pRes->numOfGroups-1].numOfTotal = pRes->numOfTotal;
+  //    pRes->pGroupRec[pRes->numOfGroups-1].numOfTotalInCurrentClause = pRes->numOfTotalInCurrentClause;
 
   return false;
 }
@@ -1155,7 +1155,7 @@ bool doGenerateFinalResults(SSqlObj *pSql, SLocalReducer *pLocalReducer, bool no
   SSqlCmd *  pCmd = &pSql->cmd;
   SSqlRes *  pRes = &pSql->res;
   
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   tFilePage *pResBuf = pLocalReducer->pResultBuf;
   tColModel *pModel = pLocalReducer->resColModel;
 
@@ -1207,8 +1207,9 @@ void resetOutputBuf(SQueryInfo* pQueryInfo, SLocalReducer *pLocalReducer) {  //
 static void resetEnvForNewResultset(SSqlRes *pRes, SSqlCmd *pCmd, SLocalReducer *pLocalReducer) {
   // In handling data in other groups, we need to reset the interpolation information for a new group data
   pRes->numOfRows = 0;
-  pRes->numOfTotal = 0;
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  pRes->numOfTotalInCurrentClause = 0;
+  
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   pQueryInfo->limit.offset = pLocalReducer->offset;
 
@@ -1233,7 +1234,7 @@ static bool doInterpolationForCurrentGroup(SSqlObj *pSql) {
   SSqlCmd *pCmd = &pSql->cmd;
   SSqlRes *pRes = &pSql->res;
 
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   SLocalReducer *     pLocalReducer = pRes->pLocalReducer;
   SInterpolationInfo *pInterpoInfo = &pLocalReducer->interpolationInfo;
 
@@ -1269,7 +1270,7 @@ static bool doHandleLastRemainData(SSqlObj *pSql) {
 
   bool prevGroupCompleted = (!pLocalReducer->discard) && pLocalReducer->hasUnprocessedRow;
 
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
   int8_t precision = pMeterMetaInfo->pMeterMeta->precision;
 
@@ -1313,7 +1314,7 @@ static void doMergeWithPrevRows(SSqlObj *pSql, int32_t numOfRes) {
   SSqlRes *      pRes = &pSql->res;
   
   SLocalReducer *pLocalReducer = pRes->pLocalReducer;
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   for (int32_t k = 0; k < pQueryInfo->fieldsInfo.numOfOutputCols; ++k) {
     SSqlExpr *pExpr = tscSqlExprGet(pQueryInfo, k);
@@ -1330,26 +1331,21 @@ static void doMergeWithPrevRows(SSqlObj *pSql, int32_t numOfRes) {
   doExecuteSecondaryMerge(pCmd, pLocalReducer, true);
 }
 
-int32_t tscLocalDoReduce(SSqlObj *pSql) {
+int32_t tscDoLocalreduce(SSqlObj *pSql) {
   SSqlCmd *pCmd = &pSql->cmd;
   SSqlRes *pRes = &pSql->res;
-
+  
+  tscResetForNextRetrieve(pRes);
+  
   if (pSql->signature != pSql || pRes == NULL || pRes->pLocalReducer == NULL) {  // all data has been processed
     tscTrace("%s call the drop local reducer", __FUNCTION__);
 
     tscDestroyLocalReducer(pSql);
-    if (pRes) {
-      pRes->numOfRows = 0;
-      pRes->row = 0;
-    }
     return 0;
   }
-
-  pRes->row = 0;
-  pRes->numOfRows = 0;
-
+  
   SLocalReducer *pLocalReducer = pRes->pLocalReducer;
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   
   // set the data merge in progress
   int32_t prevStatus =
@@ -1397,7 +1393,7 @@ int32_t tscLocalDoReduce(SSqlObj *pSql) {
 #if defined(_DEBUG_VIEW)
     printf("chosen row:\t");
     SSrcColumnInfo colInfo[256] = {0};
-    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
 
     tscGetSrcColumnInfo(colInfo, pQueryInfo);
 
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index ee66599f0f5c4b520fa93dddcee38751172959f1..a125fd1ed6407f9d22507bdf6ac424f0ca299287 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -652,18 +652,18 @@ void *tscProcessMsgFromServer(char *msg, void *ahandle, void *thandle) {
 }
 
 static SSqlObj *tscCreateSqlObjForSubquery(SSqlObj *pSql, SRetrieveSupport *trsupport, SSqlObj *prevSqlObj);
-static int      tscLaunchMetricSubQueries(SSqlObj *pSql);
+static int      tscLaunchSTableSubqueries(SSqlObj *pSql);
 
 // todo merge with callback
 int32_t tscLaunchJoinSubquery(SSqlObj *pSql, int16_t tableIndex, SJoinSubquerySupporter *pSupporter) {
   SSqlCmd *   pCmd = &pSql->cmd;
-  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
 
   pSql->res.qhandle = 0x1;
   pSql->res.numOfRows = 0;
 
   if (pSql->pSubs == NULL) {
-    pSql->pSubs = malloc(POINTER_BYTES * pSupporter->pState->numOfTotal);
+    pSql->pSubs = calloc(pSupporter->pState->numOfTotal, POINTER_BYTES);
     if (pSql->pSubs == NULL) {
       return TSDB_CODE_CLI_OUT_OF_MEMORY;
     }
@@ -874,7 +874,7 @@ int tscProcessSql(SSqlObj *pSql) {
   if (tscIsTwoStageMergeMetricQuery(pQueryInfo, 0)) {
     /*
      * (ref. line: 964)
-     * Before this function returns from tscLaunchMetricSubQueries and continues, pSql may have been released at user
+     * Before this function returns from tscLaunchSTableSubqueries and continues, pSql may have been released at user
      * program context after retrieving all data from vnodes. User function is called at tscRetrieveFromVnodeCallBack.
      *
      * when pSql being released, pSql->fp == NULL, it may pass the check of pSql->fp == NULL,
@@ -882,7 +882,7 @@ int tscProcessSql(SSqlObj *pSql) {
      */
     void *fp = pSql->fp;
 
-    if (tscLaunchMetricSubQueries(pSql) != TSDB_CODE_SUCCESS) {
+    if (tscLaunchSTableSubqueries(pSql) != TSDB_CODE_SUCCESS) {
       return pRes->code;
     }
 
@@ -923,7 +923,7 @@ static void doCleanupSubqueries(SSqlObj *pSql, int32_t numOfSubs, SSubqueryState
   free(pState);
 }
 
-int tscLaunchMetricSubQueries(SSqlObj *pSql) {
+int tscLaunchSTableSubqueries(SSqlObj *pSql) {
   SSqlRes *pRes = &pSql->res;
   SSqlCmd *pCmd = &pSql->cmd;
 
@@ -1217,7 +1217,7 @@ void tscRetrieveFromVnodeCallBack(void *param, TAOS_RES *tres, int numOfRows) {
 #ifdef _DEBUG_VIEW
     printf("received data from vnode: %d rows\n", pRes->numOfRows);
     SSrcColumnInfo colInfo[256] = {0};
-    SQueryInfo *   pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+    SQueryInfo *   pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
 
     tscGetSrcColumnInfo(colInfo, pQueryInfo);
     tColModelDisplayEx(pDesc->pSchema, pRes->data, pRes->numOfRows, pRes->numOfRows, colInfo);
@@ -2575,8 +2575,8 @@ int tscProcessRetrieveMetricRsp(SSqlObj *pSql) {
   SSqlRes *pRes = &pSql->res;
   SSqlCmd *pCmd = &pSql->cmd;
 
-  pRes->code = tscLocalDoReduce(pSql);
-  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  pRes->code = tscDoLocalreduce(pSql);
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
 
   if (pRes->code == TSDB_CODE_SUCCESS && pRes->numOfRows > 0) {
     tscSetResultPointer(pQueryInfo, pRes);
@@ -3223,7 +3223,7 @@ int tscProcessMetricMetaRsp(SSqlObj *pSql) {
     char name[TSDB_MAX_TAGS_LEN + 1] = {0};
 
     SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, i);
-    tscGetMetricMetaCacheKey(&pSql->cmd, 0, name, pMeterMetaInfo->pMeterMeta->uid);
+    tscGetMetricMetaCacheKey(pQueryInfo, name, pMeterMetaInfo->pMeterMeta->uid);
 
 #ifdef _DEBUG_VIEW
     printf("generate the metric key:%s, index:%d\n", name, i);
@@ -3646,7 +3646,7 @@ int tscGetMetricMeta(SSqlObj *pSql, int32_t clauseIndex) {
     char tagstr[TSDB_MAX_TAGS_LEN + 1] = {0};
 
     SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, i);
-    tscGetMetricMetaCacheKey(pCmd, clauseIndex, tagstr, pMeterMetaInfo->pMeterMeta->uid);
+    tscGetMetricMetaCacheKey(pQueryInfo, tagstr, pMeterMetaInfo->pMeterMeta->uid);
 
     taosRemoveDataFromCache(tscCacheHandle, (void **)&(pMeterMetaInfo->pMetricMeta), false);
 
@@ -3712,7 +3712,7 @@ int tscGetMetricMeta(SSqlObj *pSql, int32_t clauseIndex) {
         char tagstr[TSDB_MAX_TAGS_LEN] = {0};
     
         SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, i);
-        tscGetMetricMetaCacheKey(pCmd, 0, tagstr, pMeterMetaInfo->pMeterMeta->uid);
+        tscGetMetricMetaCacheKey(pQueryInfo, tagstr, pMeterMetaInfo->pMeterMeta->uid);
 
 #ifdef _DEBUG_VIEW
         printf("create metric key:%s, index:%d\n", tagstr, i);
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index 2cfe0f949fed63ffaa3f5cf2aba5754d5bdbcef1..0ce3d39d756b5a50a294fdddb56b076380535c3a 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -200,6 +200,8 @@ int taos_query_imp(STscObj *pObj, SSqlObj *pSql) {
 
   pRes->numOfRows = 1;
   pRes->numOfTotal = 0;
+  pRes->numOfTotalInCurrentClause = 0;
+  
   pSql->asyncTblPos = NULL;
   if (NULL != pSql->pTableHashList) {
     taosCleanUpHashTable(pSql->pTableHashList);
@@ -367,7 +369,7 @@ int taos_fetch_block_impl(TAOS_RES *res, TAOS_ROW *rows) {
 
   // secondary merge has handle this situation
   if (pCmd->command != TSDB_SQL_RETRIEVE_METRIC) {
-    pRes->numOfTotal += pRes->numOfRows;
+    pRes->numOfTotalInCurrentClause += pRes->numOfRows;
   }
 
   SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
@@ -457,7 +459,7 @@ static bool tscHashRemainDataInSubqueryResultSet(SSqlObj *pSql) {
        * available, go on
        */
       if (pMetaInfo->vnodeIndex < pMetaInfo->pMetricMeta->numOfVnodes && pRes1->row < pRes1->numOfRows &&
-          (!tscHasReachLimitation(pSql->pSubs[i]))) {
+          (!tscHasReachLimitation(pQueryInfo1, pRes1))) {
         allSubqueryExhausted = false;
         break;
       }
@@ -469,7 +471,7 @@ static bool tscHashRemainDataInSubqueryResultSet(SSqlObj *pSql) {
       SSqlRes *   pRes1 = &pSql->pSubs[i]->res;
       SQueryInfo *pQueryInfo1 = tscGetQueryInfoDetail(&pSql->pSubs[i]->cmd, 0);
 
-      if ((pRes1->row >= pRes1->numOfRows && tscHasReachLimitation(pSql->pSubs[i]) &&
+      if ((pRes1->row >= pRes1->numOfRows && tscHasReachLimitation(pQueryInfo1, pRes1) &&
            tscProjectionQueryOnTable(pQueryInfo1)) ||
           (pRes1->numOfRows == 0)) {
         hasData = false;
@@ -552,6 +554,94 @@ static void **tscJoinResultsetFromBuf(SSqlObj *pSql) {
   return pRes->tsrow;
 }
 
+/**
+ *  If current vnode query does not return results anymore (pRes->numOfRows == 0), try the next vnode if exists,
+ *  in case of multi-vnode super table projection query and the result does not reach the limitation.
+ */
+static bool hasMoreVnodesToTry(SSqlObj *pSql) {
+  SSqlCmd *pCmd = &pSql->cmd;
+  SSqlRes *pRes = &pSql->res;
+  
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
+  
+  return pRes->numOfRows == 0 && tscProjectionQueryOnSTable(pQueryInfo, 0) && !tscHasReachLimitation(pQueryInfo, pRes);
+}
+
+static void tscTryQueryNextVnode(SSqlObj *pSql) {
+  SSqlCmd *pCmd = &pSql->cmd;
+  SSqlRes *pRes = &pSql->res;
+
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
+
+  /*
+   * no result returned from the current virtual node anymore, try the next vnode if exists
+   * if case of: multi-vnode super table projection query
+   */
+  assert(pRes->numOfRows == 0 && tscProjectionQueryOnSTable(pQueryInfo, 0) && !tscHasReachLimitation(pQueryInfo, pRes));
+  
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
+  int32_t         totalVnode = pMeterMetaInfo->pMetricMeta->numOfVnodes;
+
+  while (++pMeterMetaInfo->vnodeIndex < totalVnode) {
+    tscTrace("%p current vnode:%d exhausted, try next:%d. total vnode:%d. current numOfRes:%d", pSql,
+             pMeterMetaInfo->vnodeIndex - 1, pMeterMetaInfo->vnodeIndex, totalVnode, pRes->numOfTotalInCurrentClause);
+
+    /*
+     * update the limit and offset value for the query on the next vnode,
+     * according to current retrieval results
+     *
+     * NOTE:
+     * if the pRes->offset is larger than 0, the start returned position has not reached yet.
+     * Therefore, the pRes->numOfRows, as well as pRes->numOfTotalInCurrentClause, must be 0.
+     * The pRes->offset value will be updated by virtual node, during query execution.
+     */
+    if (pQueryInfo->clauseLimit >= 0) {
+      pQueryInfo->limit.limit = pQueryInfo->clauseLimit - pRes->numOfTotalInCurrentClause;
+    }
+
+    pQueryInfo->limit.offset = pRes->offset;
+
+    assert((pRes->offset >= 0 && pRes->numOfRows == 0) || (pRes->offset == 0 && pRes->numOfRows >= 0));
+    tscTrace("%p new query to next vnode, vnode index:%d, limit:%" PRId64 ", offset:%" PRId64 ", glimit:%" PRId64, pSql,
+             pMeterMetaInfo->vnodeIndex, pQueryInfo->limit.limit, pQueryInfo->limit.offset, pQueryInfo->clauseLimit);
+
+    /*
+     * For project query with super table join, the numOfSub is equalled to the number of all subqueries.
+     * Therefore, we need to reset the value of numOfSubs to be 0.
+     *
+     * For super table join with projection query, if anyone of the subquery is exhausted, the query completed.
+     */
+    pSql->numOfSubs = 0;
+
+    pCmd->command = TSDB_SQL_SELECT;
+    assert(pSql->fp == NULL);
+
+    int32_t ret = tscProcessSql(pSql);  // todo check for failure
+    if (ret != TSDB_CODE_SUCCESS) {
+      pSql->res.code = ret;
+      return;
+    }
+
+    // retrieve data
+    assert(pCmd->command == TSDB_SQL_SELECT);
+    pCmd->command = TSDB_SQL_FETCH;
+
+    if ((ret = tscProcessSql(pSql)) != TSDB_CODE_SUCCESS) {
+      pSql->res.code = ret;
+      return;
+    }
+
+    // if the result from current virtual node are empty, try next if exists. otherwise, return the results.
+    if (pRes->numOfRows > 0) {
+      break;
+    }
+  }
+
+  if (pRes->numOfRows == 0) {
+    tscTrace("%p all vnodes exhausted, prj query completed. total res:%d", pSql, totalVnode, pRes->numOfTotal);
+  }
+}
+
 TAOS_ROW taos_fetch_row_impl(TAOS_RES *res) {
   SSqlObj *pSql = (SSqlObj *)res;
   SSqlCmd *pCmd = &pSql->cmd;
@@ -572,7 +662,13 @@ TAOS_ROW taos_fetch_row_impl(TAOS_RES *res) {
       return NULL;
     }
 
-  } else if (pRes->row >= pRes->numOfRows) {  // not a join query
+  } else if (pRes->row >= pRes->numOfRows) {
+    /**
+     * NOT a join query
+     *
+     * If the data block of current result set have been consumed already, try fetch next result
+     * data block from virtual node.
+     */
     tscResetForNextRetrieve(pRes);
 
     if (pCmd->command < TSDB_SQL_LOCAL) {
@@ -580,89 +676,17 @@ TAOS_ROW taos_fetch_row_impl(TAOS_RES *res) {
     }
 
     tscProcessSql(pSql);  // retrieve data from virtual node
-    
-    SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
-  
-    /*
-     * no result returned from the current virtual node anymore, try the next vnode if exists
-     * if case of: multi-vnode super table projection query
-     */
-    if (pRes->numOfRows == 0 && tscProjectionQueryOnSTable(pQueryInfo, 0)) {
-      SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
-      int32_t         totalVnode = pMeterMetaInfo->pMetricMeta->numOfVnodes;
-
-      while (++pMeterMetaInfo->vnodeIndex < totalVnode) {
-        tscTrace("%p current vnode:%d exhausted, try next:%d. total vnode:%d. current numOfRes:%d", pSql,
-                 pMeterMetaInfo->vnodeIndex - 1, pMeterMetaInfo->vnodeIndex, totalVnode, pRes->numOfTotal);
-
-        // reach the maximum number of output rows, abort
-        if (tscHasReachLimitation(pSql)) {
-          return NULL;
-        }
-
-        /*
-         * update the limit and offset value for the query on the next vnode,
-         * according to current retrieval results
-         *
-         * NOTE:
-         * if the pRes->offset is larger than 0, the start returned position has not reached yet.
-         * Therefore, the pRes->numOfRows, as well as pRes->numOfTotal, must be 0.
-         * The pRes->offset value will be updated by virtual node, during query execution.
-         */
-        if (pQueryInfo->clauseLimit >= 0) {
-          pQueryInfo->limit.limit = pQueryInfo->clauseLimit - pRes->numOfTotal;
-        }
-        
-        pQueryInfo->limit.offset = pRes->offset;
-
-        assert((pRes->offset >= 0 && pRes->numOfRows == 0) || (pRes->offset == 0 && pRes->numOfRows >= 0));
-        tscTrace("%p new query to next vnode, vnode index:%d, limit:%" PRId64 ", offset:%" PRId64 ", glimit:%" PRId64,
-                 pSql, pMeterMetaInfo->vnodeIndex, pQueryInfo->limit.limit, pQueryInfo->limit.offset,
-                 pQueryInfo->clauseLimit);
-        
-        /*
-         * For project query with super table join, the numOfSub is equalled to the number of all subqueries.
-         * Therefore, we need to reset the value of numOfSubs to be 0.
-         *
-         * For super table join with projection query, if anyone of the subquery is exhausted, the query completed.
-         */
-        pSql->numOfSubs = 0;
-
-        pCmd->command = TSDB_SQL_SELECT;
-        assert(pSql->fp == NULL);
-
-        int32_t ret = tscProcessSql(pSql);  // todo check for failure
-        if (ret != TSDB_CODE_SUCCESS) {
-          pSql->res.code = ret;
-          return NULL;
-        }
-        
-        // retrieve data
-        assert(pCmd->command == TSDB_SQL_SELECT);
-        pCmd->command = TSDB_SQL_FETCH;
-
-        if ((ret = tscProcessSql(pSql)) != TSDB_CODE_SUCCESS) {
-          pSql->res.code = ret;
-          return NULL;
-        }
-  
-        // if the result from current virtual node are empty, try next if exists. otherwise, return the results.
-        if (pRes->numOfRows > 0) {
-          break;
-        }
-      }
 
-      if (pRes->numOfRows == 0) {
-        tscTrace("%p all vnodes exhausted, prj query completed. total res:%d", pSql, totalVnode, pRes->numOfTotal);
-      }
+    if (hasMoreVnodesToTry(pSql)) {
+      tscTryQueryNextVnode(pSql);
     }
 
     /*
      * local reducer has handle this case,
-     * so no need to add the pRes->numOfRows for metric retrieve
+     * so no need to add the pRes->numOfRows for super table query
      */
     if (pCmd->command != TSDB_SQL_RETRIEVE_METRIC) {
-      pRes->numOfTotal += pRes->numOfRows;
+      pRes->numOfTotalInCurrentClause += pRes->numOfRows;
     }
 
     if (pRes->numOfRows == 0) {
@@ -675,73 +699,43 @@ TAOS_ROW taos_fetch_row_impl(TAOS_RES *res) {
 
 TAOS_ROW taos_fetch_row(TAOS_RES *res) {
   SSqlObj *pSql = (SSqlObj *)res;
-
+  SSqlCmd *pCmd = &pSql->cmd;
+  SSqlRes *pRes = &pSql->res;
+  
   if (pSql == NULL || pSql->signature != pSql) {
     globalCode = TSDB_CODE_DISCONNECTED;
     return NULL;
   }
 
-  // projection query on metric, pipeline retrieve data from vnode list, instead of two-stage merge
+  /*
+   * 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);
+  
+  pRes->numOfTotal += pRes->numOfTotalInCurrentClause;
+  pRes->numOfTotalInCurrentClause = 0;
+  
+  // current subclause is completed, try the next subclause
+  while (rows == NULL && pCmd->clauseIndex < pCmd->numOfClause - 1) {
+    pSql->cmd.command = TSDB_SQL_SELECT;
+    pCmd->clauseIndex++;
+
+    assert(pSql->fp == NULL);
+
+    tscTrace("%p try data in the next subclause:%d, total subclause:%d", pSql, pCmd->clauseIndex, pCmd->numOfClause);
+    tscProcessSql(pSql);
 
-  //  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
-  //  while (rows == NULL && tscProjectionQueryOnSTable(pQueryInfo, 0)) {
-  //    SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
-  //
-  //    // reach the maximum number of output rows, abort
-  //    if (tscHasReachLimitation(pSql)) {
-  //      return NULL;
-  //    }
-  //
-  //    /*
-  //     * update the limit and offset value according to current retrieval results
-  //     * Note: if pRes->offset > 0, pRes->numOfRows = 0, pRes->numOfTotal = 0;
-  //     */
-  //    pQueryInfo->limit.limit = pCmd->globalLimit - pRes->numOfTotal;
-  //    pQueryInfo->limit.offset = pRes->offset;
-  //
-  //    assert((pRes->offset >= 0 && pRes->numOfRows == 0) || (pRes->offset == 0 && pRes->numOfRows >= 0));
-  //
-  //    /*
-  //     * For project query with super table join, the numOfSub is equalled to the number of all subqueries, so
-  //     * we need to reset the value of numOfSubs to be 0.
-  //     *
-  //     * For super table join with projection query, if anyone of the subquery is exhausted, the query completed.
-  //     */
-  //    pSql->numOfSubs = 0;
-  //
-  //    if ((++pMeterMetaInfo->vnodeIndex) < pMeterMetaInfo->pMetricMeta->numOfVnodes) {
-  //      pCmd->command = TSDB_SQL_SELECT;
-  //      assert(pSql->fp == NULL);
-  //      tscProcessSql(pSql);
-  //      rows = taos_fetch_row_impl(res);
-  //    }
-  //
-  //    // check!!!
-  //    if (rows != NULL || pMeterMetaInfo->vnodeIndex >= pMeterMetaInfo->pMetricMeta->numOfVnodes) {
-  //      break;
-  //    }
-  //  }
-  //
-  //  // current subclause is completed, try the next subclause
-  //  if (rows == NULL && pCmd->clauseIndex < pCmd->numOfClause - 1) {
-  //    pSql->cmd.command = TSDB_SQL_SELECT;
-  //    pCmd->clauseIndex++;
-  //
-  //    assert(pSql->fp == NULL);
-  //
-  //    tscTrace("%p start next subclause:%d, total subclause:%d", pSql, pCmd->clauseIndex, pCmd->numOfClause);
-  //    tscProcessSql(pSql);
-  //
-  //    rows = taos_fetch_row_impl(res);
-  //  }
+    // if the rows is not NULL, return immediately
+    rows = taos_fetch_row_impl(res);
+  }
 
   return rows;
 }
 
 int taos_fetch_block(TAOS_RES *res, TAOS_ROW *rows) {
   SSqlObj *pSql = (SSqlObj *)res;
-  SSqlRes *pRes = &pSql->res;
+  SSqlCmd *pCmd = &pSql->cmd;
 
   int nRows = 0;
 
@@ -755,32 +749,19 @@ int taos_fetch_block(TAOS_RES *res, TAOS_ROW *rows) {
   // instead of two-stage mergevnodeProcessMsgFromShell free qhandle
   nRows = taos_fetch_block_impl(res, rows);
 
-  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, pSql->cmd.clauseIndex);
-  while (*rows == NULL && tscProjectionQueryOnSTable(pQueryInfo, 0)) {
-    /* reach the maximum number of output rows, abort */
-    if (tscHasReachLimitation(pSql)) {
-      return 0;
-    }
-
-    SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
-
-    /* update the limit value according to current retrieval results */
-    pQueryInfo->limit.limit = pSql->cmd.globalLimit - pRes->numOfTotal;
-    pQueryInfo->limit.offset = pRes->offset;
-
-    if ((++pMeterMetaInfo->vnodeIndex) < pMeterMetaInfo->pMetricMeta->numOfVnodes) {
-      pSql->cmd.command = TSDB_SQL_SELECT;
-      assert(pSql->fp == NULL);
-      tscProcessSql(pSql);
-      nRows = taos_fetch_block_impl(res, rows);
-    }
-
-    // check!!!
-    if (*rows != NULL || pMeterMetaInfo->vnodeIndex >= pMeterMetaInfo->pMetricMeta->numOfVnodes) {
-      break;
-    }
+  // current subclause is completed, try the next subclause
+  while (rows == NULL && pCmd->clauseIndex < pCmd->numOfClause - 1) {
+    pSql->cmd.command = TSDB_SQL_SELECT;
+    pCmd->clauseIndex++;
+    
+    assert(pSql->fp == NULL);
+    
+    tscTrace("%p try data in the next subclause:%d, total subclause:%d", pSql, pCmd->clauseIndex, pCmd->numOfClause);
+    tscProcessSql(pSql);
+  
+    nRows = taos_fetch_block_impl(res, rows);
   }
-
+  
   return nRows;
 }
 
@@ -1042,7 +1023,8 @@ int taos_validate_sql(TAOS *taos, const char *sql) {
 
   pRes->numOfRows = 1;
   pRes->numOfTotal = 0;
-
+  pRes->numOfTotalInCurrentClause = 0;
+  
   tscTrace("%p Valid SQL: %s pObj:%p", pSql, sql, pObj);
 
   int32_t sqlLen = strlen(sql);
@@ -1172,6 +1154,8 @@ int taos_load_table_info(TAOS *taos, const char *tableNameList) {
   SSqlRes *pRes = &pSql->res;
 
   pRes->numOfTotal = 0;  // the number of getting table meta from server
+  pRes->numOfTotalInCurrentClause = 0;
+  
   pRes->code = 0;
 
   assert(pSql->fp == NULL);
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index c456324de5f5674097a9ccda5767bf6d1ca828f7..7b1a71d0ce8cf61d6d007508b53dadef93e634c4 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -37,12 +37,9 @@
  * fullmetername + '.' + '(nil)' + '.' + '(nil)' + relation + '.' + [tagId1,
  * tagId2,...] + '.' + group_orderType
  */
-void tscGetMetricMetaCacheKey(SSqlCmd* pCmd, int32_t subClauseIndex, char* str, uint64_t uid) {
+void tscGetMetricMetaCacheKey(SQueryInfo* pQueryInfo, char* str, uint64_t uid) {
   int32_t index = -1;
-
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
-
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoByUid(pQueryInfo, subClauseIndex, uid, &index);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoByUid(pQueryInfo, uid, &index);
 
   int32_t len = 0;
   char    tagIdBuf[128] = {0};
@@ -395,7 +392,8 @@ void tscFreeSqlObjPartial(SSqlObj* pSql) {
   pRes->row = 0;
   pRes->numOfRows = 0;
   pRes->numOfTotal = 0;
-
+  pRes->numOfTotalInCurrentClause = 0;
+  
   pRes->numOfGroups = 0;
   tfree(pRes->pGroupRec);
 
@@ -1591,13 +1589,14 @@ SMeterMetaInfo* tscGetMeterMetaInfo(SSqlCmd* pCmd, int32_t clauseIndex, int32_t
 }
 
 SMeterMetaInfo* tscGetMeterMetaInfoFromQueryInfo(SQueryInfo* pQueryInfo, int32_t tableIndex) {
+  assert(pQueryInfo != NULL);
+  
   if (pQueryInfo->pMeterInfo == NULL) {
     assert(pQueryInfo->numOfTables == 0);
     return NULL;
   }
 
-  assert(pQueryInfo != NULL && tableIndex >= 0 && tableIndex <= pQueryInfo->numOfTables &&
-         pQueryInfo->pMeterInfo != NULL);
+  assert(tableIndex >= 0 && tableIndex <= pQueryInfo->numOfTables && pQueryInfo->pMeterInfo != NULL);
 
   return pQueryInfo->pMeterInfo[tableIndex];
 }
@@ -1628,7 +1627,7 @@ int32_t tscGetQueryInfoDetailSafely(SSqlCmd* pCmd, int32_t subClauseIndex, SQuer
   return TSDB_CODE_SUCCESS;
 }
 
-SMeterMetaInfo* tscGetMeterMetaInfoByUid(SQueryInfo* pQueryInfo, int32_t subClauseIndex, uint64_t uid, int32_t* index) {
+SMeterMetaInfo* tscGetMeterMetaInfoByUid(SQueryInfo* pQueryInfo, uint64_t uid, int32_t* index) {
   int32_t k = -1;
 
   for (int32_t i = 0; i < pQueryInfo->numOfTables; ++i) {
@@ -1642,6 +1641,7 @@ SMeterMetaInfo* tscGetMeterMetaInfoByUid(SQueryInfo* pQueryInfo, int32_t subClau
     *index = k;
   }
 
+  assert(k != -1);
   return tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, k);
 }
 
@@ -1777,6 +1777,10 @@ void tscClearMeterMetaInfo(SMeterMetaInfo* pMeterMetaInfo, bool removeFromCache)
 }
 
 void tscResetForNextRetrieve(SSqlRes* pRes) {
+  if (pRes == NULL) {
+    return;
+  }
+  
   pRes->row = 0;
   pRes->numOfRows = 0;
 }
@@ -1877,7 +1881,7 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
   pNew->param = param;
 
   char key[TSDB_MAX_TAGS_LEN + 1] = {0};
-  tscGetMetricMetaCacheKey(pCmd, pCmd->clauseIndex, key, uid);
+  tscGetMetricMetaCacheKey(pQueryInfo, key, uid);
 
 #ifdef _DEBUG_VIEW
   printf("the metricmeta key is:%s\n", key);
@@ -1980,13 +1984,9 @@ int32_t tscInvalidSQLErrMsg(char* msg, const char* additionalInfo, const char* s
   return TSDB_CODE_INVALID_SQL;
 }
 
-bool tscHasReachLimitation(SSqlObj* pSql) {
-  assert(pSql != NULL && pSql->cmd.globalLimit != 0);
-
-  SSqlCmd* pCmd = &pSql->cmd;
-  SSqlRes* pRes = &pSql->res;
-
-  return (pCmd->globalLimit > 0 && pRes->numOfTotal >= pCmd->globalLimit);
+bool tscHasReachLimitation(SQueryInfo* pQueryInfo, SSqlRes* pRes) {
+  assert(pQueryInfo != NULL && pQueryInfo->clauseLimit != 0);
+  return (pQueryInfo->clauseLimit > 0 && pRes->numOfTotalInCurrentClause >= pQueryInfo->clauseLimit);
 }
 
 char* tscGetErrorMsgPayload(SSqlCmd* pCmd) { return pCmd->payload; }