From 5295955b72f995fd6ab192066cb3cdca54b4a17e Mon Sep 17 00:00:00 2001
From: hjxilinx <hjxilinx@163.com>
Date: Mon, 6 Jan 2020 10:49:14 +0800
Subject: [PATCH] add the union support in sql parser: refactor some codes.
 #1032. [TBASE-1140]

---
 src/client/inc/tscUtil.h           |   9 +-
 src/client/inc/tsclient.h          |   2 +-
 src/client/src/tscAsync.c          |  11 +-
 src/client/src/tscJoinProcess.c    |  10 +-
 src/client/src/tscParseInsert.c    |  18 +-
 src/client/src/tscPrepare.c        |   5 +-
 src/client/src/tscSQLParser.c      |  44 +++--
 src/client/src/tscSecondaryMerge.c |   8 +-
 src/client/src/tscServer.c         |  69 +++++---
 src/client/src/tscSql.c            | 258 +++++++++++++++++++----------
 src/client/src/tscUtil.c           | 133 ++++++++-------
 11 files changed, 346 insertions(+), 221 deletions(-)

diff --git a/src/client/inc/tscUtil.h b/src/client/inc/tscUtil.h
index 3190fd7057..fd0973f319 100644
--- a/src/client/inc/tscUtil.h
+++ b/src/client/inc/tscUtil.h
@@ -97,10 +97,10 @@ SMeterSidExtInfo* tscGetMeterSidInfo(SVnodeSidList* pSidList, int32_t idx);
  */
 bool tscIsPointInterpQuery(SQueryInfo* pQueryInfo);
 bool tscIsTWAQuery(SQueryInfo* pQueryInfo);
-bool tscProjectionQueryOnSTable(SSqlCmd* pCmd, int32_t subClauseIndex);
+bool tscProjectionQueryOnSTable(SQueryInfo *pQueryInfo, int32_t tableIndex);
 bool tscProjectionQueryOnTable(SQueryInfo* pQueryInfo);
 
-bool tscIsTwoStageMergeMetricQuery(SSqlCmd* pCmd);
+bool tscIsTwoStageMergeMetricQuery(SQueryInfo* pQueryInfo, int32_t tableIndex);
 bool tscQueryOnMetric(SSqlCmd* pCmd);
 bool tscQueryMetricTags(SQueryInfo* pQueryInfo);
 bool tscIsSelectivityWithTagQuery(SSqlCmd* pCmd);
@@ -126,7 +126,7 @@ void tscFieldInfoSetValue(SFieldInfo* pFieldInfo, int32_t index, int8_t type, co
 void tscFieldInfoUpdateVisible(SFieldInfo* pFieldInfo, int32_t index, bool visible);
 
 void tscFieldInfoCalOffset(SQueryInfo* pQueryInfo);
-void tscFieldInfoUpdateOffset(SQueryInfo* pQueryInfo);
+void tscFieldInfoUpdateOffsetForInterResult(SQueryInfo* pQueryInfo);
 void tscFieldInfoCopy(SFieldInfo* src, SFieldInfo* dst, const int32_t* indexList, int32_t size);
 void tscFieldInfoCopyAll(SFieldInfo* dst, SFieldInfo* src);
 
@@ -135,6 +135,7 @@ int16_t     tscFieldInfoGetOffset(SQueryInfo* pQueryInfo, int32_t index);
 int32_t     tscGetResRowLength(SQueryInfo* pQueryInfo);
 void        tscClearFieldInfo(SFieldInfo* pFieldInfo);
 int32_t tscNumOfFields(SQueryInfo* pQueryInfo);
+int32_t tscFieldInfoCompare(SFieldInfo* pFieldInfo1, SFieldInfo* pFieldInfo2);
 
 void addExprParams(SSqlExpr* pExpr, char* argument, int32_t type, int32_t bytes, int16_t tableIndex);
 
@@ -163,7 +164,7 @@ int32_t tscValidateName(SSQLToken* pToken);
 
 void tscIncStreamExecutionCount(void* pStream);
 
-bool tscValidateColumnId(SSqlCmd* pCmd, int32_t colId);
+bool tscValidateColumnId(SMeterMetaInfo* pMeterMetaInfo, int32_t colId);
 
 // get starter position of metric query condition (query on tags) in SSqlCmd.payload
 SCond* tsGetMetricQueryCondPos(STagCond* pCond, uint64_t tableIndex);
diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 2de9819d92..a3e1e624c1 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -253,9 +253,9 @@ typedef struct {
   union {
     int32_t count;
     int32_t numOfTablesInSubmit;
-    int32_t clauseIndex;    // index of multiple subclause query
   };
 
+  int32_t      clauseIndex;    // index of multiple subclause query
   short        numOfCols;
   uint32_t     allocSize;
   char *       payload;
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index 22613386a5..8b0edaf9fe 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -121,7 +121,7 @@ static void tscProcessAsyncFetchRowsProxy(void *param, TAOS_RES *tres, int numOf
   SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
   
   // sequentially retrieve data from remain vnodes first, query vnode specified by vnodeIdx
-  if (numOfRows == 0 && tscProjectionQueryOnSTable(pCmd, 0)) {
+  if (numOfRows == 0 && tscProjectionQueryOnSTable(pQueryInfo, 0)) {
     // vnode is denoted by vnodeIdx, continue to query vnode specified by vnodeIdx
     SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
     assert(pMeterMetaInfo->vnodeIndex >= 0);
@@ -133,7 +133,6 @@ static void tscProcessAsyncFetchRowsProxy(void *param, TAOS_RES *tres, int numOf
     }
 
     /* update the limit value according to current retrieval results */
-    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
     pQueryInfo->limit.limit = pCmd->globalLimit - pRes->numOfTotal;
     pQueryInfo->limit.offset = pRes->offset;
 
@@ -269,14 +268,14 @@ void tscProcessAsyncRetrieve(void *param, TAOS_RES *tres, int numOfRows) {
   SSqlRes *pRes = &pSql->res;
   SSqlCmd *pCmd = &pSql->cmd;
 
-  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   if (numOfRows == 0) {
     // sequentially retrieve data from remain vnodes.
-    if (tscProjectionQueryOnSTable(pCmd, 0)) {
+    if (tscProjectionQueryOnSTable(pQueryInfo, 0)) {
       /*
        * vnode is denoted by vnodeIdx, continue to query vnode specified by vnodeIdx till all vnode have been retrieved
        */
-      SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+      SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
       assert(pMeterMetaInfo->vnodeIndex >= 0);
 
       /* reach the maximum number of output rows, abort */
@@ -527,7 +526,7 @@ void tscMeterMetaCallBack(void *param, TAOS_RES *res, int code) {
     }
 
   } else {  // stream computing
-    SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+    SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
     code = tscGetMeterMeta(pSql, pMeterMetaInfo);
     pRes->code = code;
 
diff --git a/src/client/src/tscJoinProcess.c b/src/client/src/tscJoinProcess.c
index 4e0ce14a6c..1f26e2a0e5 100644
--- a/src/client/src/tscJoinProcess.c
+++ b/src/client/src/tscJoinProcess.c
@@ -438,7 +438,7 @@ 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(&pParentSql->cmd, 0)) {
+      if (tscProjectionQueryOnSTable(pQueryInfo, 0)) {
         SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
         assert(pQueryInfo->numOfTables == 1);
 
@@ -494,9 +494,7 @@ static void joinRetrieveCallback(void* param, TAOS_RES* tres, int numOfRows) {
       pSql->res.numOfTotal += pSql->res.numOfRows;
     }
   
-    SSqlCmd* pCmd = &pSql->cmd;
-  
-    if (tscProjectionQueryOnSTable(pCmd, 0) && numOfRows == 0) {
+    if (tscProjectionQueryOnSTable(pQueryInfo, 0) && numOfRows == 0) {
       SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
       assert(pQueryInfo->numOfTables == 1);
 
@@ -541,7 +539,7 @@ void tscFetchDatablockFromSubquery(SSqlObj* pSql) {
   
     SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
   
-    if (tscProjectionQueryOnSTable(&pSql->cmd, 0)) {
+    if (tscProjectionQueryOnSTable(pQueryInfo, 0)) {
       if (pRes->row >= pRes->numOfRows && pMeterMetaInfo->vnodeIndex < pMeterMetaInfo->pMetricMeta->numOfVnodes &&
           (!tscHasReachLimitation(pSql->pSubs[i]))) {
         numOfFetch++;
@@ -709,7 +707,7 @@ void tscJoinQueryCallback(void* param, TAOS_RES* tres, int code) {
          * if the query is a continue query (vnodeIndex > 0 for projection query) for next vnode, do the retrieval of
          * data instead of returning to its invoker
          */
-        if (pMeterMetaInfo->vnodeIndex > 0 && tscProjectionQueryOnSTable(&pSql->cmd, 0)) {
+        if (pMeterMetaInfo->vnodeIndex > 0 && tscProjectionQueryOnSTable(pQueryInfo, 0)) {
           assert(pMeterMetaInfo->vnodeIndex < pMeterMetaInfo->pMetricMeta->numOfVnodes);
           pSupporter->pState->numOfCompleted = 0;  // reset the record value
 
diff --git a/src/client/src/tscParseInsert.c b/src/client/src/tscParseInsert.c
index 7af27aa386..f67319bc43 100644
--- a/src/client/src/tscParseInsert.c
+++ b/src/client/src/tscParseInsert.c
@@ -655,7 +655,7 @@ void sortRemoveDuplicates(STableDataBlocks *dataBuf) {
 static int32_t doParseInsertStatement(SSqlObj *pSql, void *pTableHashList, char **str, SParsedDataColInfo *spd,
                                       int32_t *totalNum) {
   SSqlCmd *       pCmd = &pSql->cmd;
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   SMeterMeta *    pMeterMeta = pMeterMetaInfo->pMeterMeta;
 
   STableDataBlocks *dataBuf = NULL;
@@ -1143,7 +1143,7 @@ int doParseInsertSql(SSqlObj *pSql, char *str) {
       strcpy(pDataBlock->filename, fname);
     } else if (sToken.type == TK_LP) {
       /* insert into tablename(col1, col2,..., coln) values(v1, v2,... vn); */
-      SMeterMeta *pMeterMeta = tscGetMeterMetaInfo(pCmd, 0, 0)->pMeterMeta;
+      SMeterMeta *pMeterMeta = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0)->pMeterMeta;
       SSchema *   pSchema = tsGetSchema(pMeterMeta);
 
       if (validateDataSource(pCmd, DATA_FROM_SQL_STRING, sToken.z) != TSDB_CODE_SUCCESS) {
@@ -1275,7 +1275,7 @@ int tsParseInsertSql(SSqlObj *pSql) {
   pCmd->command = TSDB_SQL_INSERT;
 
   SQueryInfo *pQueryInfo = NULL;
-  tscGetQueryInfoDetailSafely(pCmd, 0, &pQueryInfo);
+  tscGetQueryInfoDetailSafely(pCmd, pCmd->clauseIndex, &pQueryInfo);
 
   if (sToken.type == TK_INSERT) {
     TSDB_QUERY_SET_TYPE(pQueryInfo->type, TSDB_QUERY_TYPE_INSERT);
@@ -1343,7 +1343,8 @@ static int doPackSendDataBlock(SSqlObj *pSql, int32_t numOfRows, STableDataBlock
   int32_t  code = TSDB_CODE_SUCCESS;
   SSqlCmd *pCmd = &pSql->cmd;
 
-  SMeterMeta *pMeterMeta = tscGetMeterMetaInfo(pCmd, 0, 0)->pMeterMeta;
+  assert(pCmd->numOfClause == 1);
+  SMeterMeta *pMeterMeta = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0)->pMeterMeta;
 
   SShellSubmitBlock *pBlocks = (SShellSubmitBlock *)(pTableDataBlocks->pData);
   tsSetBlockInfo(pBlocks, pMeterMeta, numOfRows);
@@ -1375,8 +1376,11 @@ static int tscInsertDataFromFile(SSqlObj *pSql, FILE *fp, char *tmpTokenBuf) {
   int             numOfRows = 0;
   int32_t         code = 0;
   int             nrows = 0;
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   SMeterMeta *    pMeterMeta = pMeterMetaInfo->pMeterMeta;
+  assert(pCmd->numOfClause == 1);
+  
   int32_t         rowSize = pMeterMeta->rowSize;
 
   pCmd->pDataBlocks = tscCreateBlockArrayList();
@@ -1465,7 +1469,9 @@ void tscProcessMultiVnodesInsert(SSqlObj *pSql) {
   }
 
   STableDataBlocks *pDataBlock = NULL;
-  SMeterMetaInfo *  pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *  pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
+  assert(pCmd->numOfClause == 1);
+  
   int32_t           code = TSDB_CODE_SUCCESS;
 
   /* the first block has been sent to server in processSQL function */
diff --git a/src/client/src/tscPrepare.c b/src/client/src/tscPrepare.c
index 51c43fd3f7..744ffd5b2b 100644
--- a/src/client/src/tscPrepare.c
+++ b/src/client/src/tscPrepare.c
@@ -408,7 +408,7 @@ static int insertStmtReset(STscStmt* pStmt) {
   }
   pCmd->batchSize = 0;
   
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   pMeterMetaInfo->vnodeIndex = 0;
   return TSDB_CODE_SUCCESS;
 }
@@ -422,7 +422,8 @@ static int insertStmtExecute(STscStmt* stmt) {
     ++pCmd->batchSize;
   }
 
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
+  assert(pCmd->numOfClause == 1);
   
   if (pCmd->pDataBlocks->nSize > 0) {
     // merge according to vgid
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index f6ef076b27..49d2678ea5 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -101,7 +101,7 @@ static bool validateOneTags(SSqlCmd* pCmd, TAOS_FIELD* pTagField);
 static bool hasTimestampForPointInterpQuery(SQueryInfo* pQueryInfo);
 static void updateTagColumnIndex(SQueryInfo* pQueryInfo, int32_t tableIndex);
 
-static int32_t parseLimitClause(SQueryInfo* pQueryInfo, SQuerySQL* pQuerySql, SSqlObj* pSql);
+static int32_t parseLimitClause(SQueryInfo* pQueryInfo, int32_t index, SQuerySQL* pQuerySql, SSqlObj* pSql);
 static int32_t parseCreateDBOptions(SSqlCmd* pCmd, SCreateDBInfo* pCreateDbSql);
 static int32_t getColumnIndexByNameEx(SSQLToken* pToken, SQueryInfo* pQueryInfo, SColumnIndex* pIndex);
 static int32_t getTableIndexByName(SSQLToken* pToken, SQueryInfo* pQueryInfo, SColumnIndex* pIndex);
@@ -205,7 +205,7 @@ int32_t tscToSQLCmd(SSqlObj* pSql, struct SSqlInfo* pInfo) {
     return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), pInfo->pzErrMsg);
   }
 
-  int32_t code = tscGetQueryInfoDetailSafely(pCmd, 0, &pQueryInfo);
+  int32_t code = tscGetQueryInfoDetailSafely(pCmd, pCmd->clauseIndex, &pQueryInfo);
 
   assert(pQueryInfo->numOfTables == 0);
   SMeterMetaInfo* pMeterMetaInfo = tscAddEmptyMeterMetaInfo(pQueryInfo);
@@ -502,7 +502,8 @@ int32_t tscToSQLCmd(SSqlObj* pSql, struct SSqlInfo* pInfo) {
 
     case TSDB_SQL_SELECT: {
       assert(pCmd->numOfClause == 1);
-
+      const char* msg1 = "columns in select caluse not identical";
+      
       for (int32_t i = pCmd->numOfClause; i < pInfo->subclauseInfo.numOfClause; ++i) {
         SQueryInfo* pqi = NULL;
         if ((code = tscGetQueryInfoDetailSafely(pCmd, i, &pqi)) != TSDB_CODE_SUCCESS) {
@@ -526,6 +527,17 @@ int32_t tscToSQLCmd(SSqlObj* pSql, struct SSqlInfo* pInfo) {
       // if there is only one element, the limit of clause is the limit of global result.
       if (pCmd->numOfClause == 1) {
         pCmd->globalLimit = pQueryInfo1->clauseLimit;
+      } else { // check the output fields information, column name and column type
+        pCmd->globalLimit = -1;
+        
+        for(int32_t i = 1; i < pCmd->numOfClause; ++i) {
+          SQueryInfo* pQueryInfo2 = tscGetQueryInfoDetail(pCmd, i);
+          
+          int32_t ret = tscFieldInfoCompare(&pQueryInfo1->fieldsInfo, &pQueryInfo2->fieldsInfo);
+          if (ret != 0) {
+            return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
+          }
+        }
       }
 
       return TSDB_CODE_SUCCESS;  // do not build query message here
@@ -852,7 +864,9 @@ bool validateOneTags(SSqlCmd* pCmd, TAOS_FIELD* pTagField) {
   const char* msg5 = "invalid binary/nchar tag length";
   const char* msg6 = "invalid data type in tags";
 
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  assert(pCmd->numOfClause == 1);
+  
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   SMeterMeta*     pMeterMeta = pMeterMetaInfo->pMeterMeta;
 
   // no more than 6 tags
@@ -921,7 +935,8 @@ bool validateOneColumn(SSqlCmd* pCmd, TAOS_FIELD* pColField) {
   const char* msg5 = "invalid column name";
   const char* msg6 = "invalid column length";
 
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  assert(pCmd->numOfClause == 1);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   SMeterMeta*     pMeterMeta = pMeterMetaInfo->pMeterMeta;
 
   // no more max columns
@@ -1975,8 +1990,9 @@ int32_t changeFunctionID(int32_t optr, int16_t* functionId) {
 
 int32_t setShowInfo(SSqlObj* pSql, struct SSqlInfo* pInfo) {
   SSqlCmd*        pCmd = &pSql->cmd;
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
-
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
+  assert(pCmd->numOfClause == 1);
+  
   pCmd->command = TSDB_SQL_SHOW;
 
   const char* msg1 = "invalid name";
@@ -2125,7 +2141,7 @@ int32_t tscTansformSQLFunctionForSTableQuery(SQueryInfo* pQueryInfo) {
     }
   }
 
-  tscFieldInfoUpdateOffset(pQueryInfo);
+  tscFieldInfoUpdateOffsetForInterResult(pQueryInfo);
   return TSDB_CODE_SUCCESS;
 }
 
@@ -2370,7 +2386,7 @@ int32_t parseGroupbyClause(SQueryInfo* pQueryInfo, tVariantList* pList, SSqlCmd*
 
 void setColumnOffsetValueInResultset(SQueryInfo* pQueryInfo) {
   if (QUERY_IS_STABLE_QUERY(pQueryInfo->type)) {
-    tscFieldInfoUpdateOffset(pQueryInfo);
+    tscFieldInfoUpdateOffsetForInterResult(pQueryInfo);
   } else {
     tscFieldInfoCalOffset(pQueryInfo);
   }
@@ -4410,7 +4426,7 @@ bool hasTimestampForPointInterpQuery(SQueryInfo* pQueryInfo) {
   return (pQueryInfo->stime == pQueryInfo->etime) && (pQueryInfo->stime != 0);
 }
 
-int32_t parseLimitClause(SQueryInfo* pQueryInfo, SQuerySQL* pQuerySql, SSqlObj* pSql) {
+int32_t parseLimitClause(SQueryInfo* pQueryInfo, int32_t clauseIndex, SQuerySQL* pQuerySql, SSqlObj* pSql) {
   SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
 
   const char* msg0 = "soffset/offset can not be less than 0";
@@ -4443,7 +4459,7 @@ int32_t parseLimitClause(SQueryInfo* pQueryInfo, SQuerySQL* pQuerySql, SSqlObj*
     if (queryOnTags == true) {  // local handle the metric tag query
       pQueryInfo->command = TSDB_SQL_RETRIEVE_TAGS;
     } else {
-      if (tscProjectionQueryOnSTable(&pSql->cmd, 0) &&
+      if (tscProjectionQueryOnSTable(pQueryInfo, 0) &&
           (pQueryInfo->slimit.limit > 0 || pQueryInfo->slimit.offset > 0)) {
         return invalidSqlErrMsg(pQueryInfo->msg, msg3);
       }
@@ -4461,7 +4477,7 @@ int32_t parseLimitClause(SQueryInfo* pQueryInfo, SQuerySQL* pQuerySql, SSqlObj*
      * And then launching multiple async-queries against all qualified virtual nodes, during the first-stage
      * query operation.
      */
-    int32_t code = tscGetMetricMeta(pSql, 0);
+    int32_t code = tscGetMetricMeta(pSql, clauseIndex);
     if (code != TSDB_CODE_SUCCESS) {
       return code;
     }
@@ -4983,7 +4999,7 @@ int32_t doFunctionsCompatibleCheck(SSqlCmd* pCmd, SQueryInfo* pQueryInfo) {
     }
 
     // projection query on metric does not compatible with "group by" syntax
-    if (tscProjectionQueryOnSTable(pCmd, 0)) {
+    if (tscProjectionQueryOnSTable(pQueryInfo, 0)) {
       return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg3);
     }
 
@@ -5564,7 +5580,7 @@ int32_t doCheckForQuery(SSqlObj* pSql, SQuerySQL* pQuerySql, int32_t index) {
   pQueryInfo->limit = pQuerySql->limit;
 
   // temporarily save the original limitation value
-  if ((code = parseLimitClause(pQueryInfo, pQuerySql, pSql)) != TSDB_CODE_SUCCESS) {
+  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 ebf1a7a8b7..e9a63b028b 100644
--- a/src/client/src/tscSecondaryMerge.c
+++ b/src/client/src/tscSecondaryMerge.c
@@ -311,7 +311,7 @@ void tscCreateLocalReducer(tExtMemBuffer **pMemBuffer, int32_t numOfBuffer, tOrd
   pRes->pLocalReducer = pReducer;
   pRes->numOfGroups = 0;
 
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   int16_t prec = pMeterMetaInfo->pMeterMeta->precision;
 
   int64_t stime = (pQueryInfo->stime < pQueryInfo->etime) ? pQueryInfo->stime : pQueryInfo->etime;
@@ -582,7 +582,7 @@ int32_t tscLocalReducerEnvCreate(SSqlObj *pSql, tExtMemBuffer ***pMemBuffer, tOr
   tColModel *pModel = NULL;
   *pFinalModel = NULL;
 
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
 
   (*pMemBuffer) = (tExtMemBuffer **)malloc(POINTER_BYTES * pMeterMetaInfo->pMetricMeta->numOfVnodes);
@@ -871,7 +871,7 @@ static void doInterpolateResult(SSqlObj *pSql, SLocalReducer *pLocalReducer, boo
     functions[i] = tscSqlExprGet(pQueryInfo, i)->functionId;
   }
 
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   int8_t precision = pMeterMetaInfo->pMeterMeta->precision;
 
   while (1) {
@@ -1212,7 +1212,7 @@ static void resetEnvForNewResultset(SSqlRes *pRes, SSqlCmd *pCmd, SLocalReducer
   
   pQueryInfo->limit.offset = pLocalReducer->offset;
 
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   int16_t precision = pMeterMetaInfo->pMeterMeta->precision;
 
   // for group result interpolation, do not return if not data is generated
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index 358c7d4692..ee66599f0f 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -129,6 +129,11 @@ void tscProcessActivityTimer(void *handle, void *tmrId) {
 
     pSql->fp = tscProcessHeartBeatRsp;
     pSql->cmd.command = TSDB_SQL_HB;
+    
+    SQueryInfo *pQueryInfo = NULL;
+    tscGetQueryInfoDetailSafely(&pSql->cmd, 0, &pQueryInfo);
+    pQueryInfo->command = TSDB_SQL_HB;
+    
     if (TSDB_CODE_SUCCESS != tscAllocPayload(&(pSql->cmd), TSDB_DEFAULT_PAYLOAD_SIZE)) {
       tfree(pSql);
       return;
@@ -223,7 +228,7 @@ void tscGetConnToVnode(SSqlObj *pSql, uint8_t *pCode) {
   pSql->thandle = NULL;
 
   SSqlCmd *       pCmd = &pSql->cmd;
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
 
   if (UTIL_METER_IS_SUPERTABLE(pMeterMetaInfo)) {  // multiple vnode query
     SVnodeSidList *vnodeList = tscGetVnodeSidList(pMeterMetaInfo->pMetricMeta, pMeterMetaInfo->vnodeIndex);
@@ -423,7 +428,7 @@ void *tscProcessMsgFromServer(char *msg, void *ahandle, void *thandle) {
     return ahandle;
   }
 
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   if (msg == NULL) {
     tscTrace("%p no response from ip:0x%x", pSql, pSql->ip);
 
@@ -783,6 +788,9 @@ int tscProcessSql(SSqlObj *pSql) {
     }
 
     type = pQueryInfo->type;
+  
+    // for hearbeat, numOfTables == 0;
+    assert((pQueryInfo->numOfTables == 0 && pQueryInfo->command == TSDB_SQL_HB) || pQueryInfo->numOfTables > 0);
   }
 
   tscTrace("%p SQL cmd:%d will be processed, name:%s, type:%d", pSql, pCmd->command, name, type);
@@ -796,6 +804,7 @@ int tscProcessSql(SSqlObj *pSql) {
 
     if (pMeterMetaInfo == NULL) {  // the pMeterMetaInfo cannot be NULL
       pSql->res.code = TSDB_CODE_OTHERS;
+      assert(0);
       return pSql->res.code;
     }
 
@@ -862,7 +871,7 @@ int tscProcessSql(SSqlObj *pSql) {
     }
   }
 
-  if (tscIsTwoStageMergeMetricQuery(pCmd)) {
+  if (tscIsTwoStageMergeMetricQuery(pQueryInfo, 0)) {
     /*
      * (ref. line: 964)
      * Before this function returns from tscLaunchMetricSubQueries and continues, pSql may have been released at user
@@ -932,7 +941,7 @@ int tscLaunchMetricSubQueries(SSqlObj *pSql) {
 
   const uint32_t nBufferSize = (1 << 16);  // 64KB
 
-  SQueryInfo *    pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo *    pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
   SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
   int32_t         numOfSubQueries = pMeterMetaInfo->pMetricMeta->numOfVnodes;
   assert(numOfSubQueries > 0);
@@ -1308,7 +1317,10 @@ void tscRetrieveFromVnodeCallBack(void *param, TAOS_RES *tres, int numOfRows) {
 }
 
 void tscKillMetricQuery(SSqlObj *pSql) {
-  if (!tscIsTwoStageMergeMetricQuery(&pSql->cmd)) {
+  SSqlCmd* pCmd = &pSql->cmd;
+  
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
+  if (!tscIsTwoStageMergeMetricQuery(pQueryInfo, 0)) {
     return;
   }
 
@@ -1351,14 +1363,17 @@ void tscKillMetricQuery(SSqlObj *pSql) {
 static void tscRetrieveDataRes(void *param, TAOS_RES *tres, int retCode);
 
 static SSqlObj *tscCreateSqlObjForSubquery(SSqlObj *pSql, SRetrieveSupport *trsupport, SSqlObj *prevSqlObj) {
-  SSqlObj *pNew = createSubqueryObj(pSql, 0, tscRetrieveDataRes, trsupport, prevSqlObj);
+  const int32_t table_index = 0;
+  
+  SSqlObj *pNew = createSubqueryObj(pSql, table_index, tscRetrieveDataRes, trsupport, prevSqlObj);
   if (pNew != NULL) {  // the sub query of two-stage super table query
     SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pNew->cmd, 0);
     pQueryInfo->type |= TSDB_QUERY_TYPE_STABLE_SUBQUERY;
-    assert(pQueryInfo->numOfTables == 1);
+    
+    assert(pQueryInfo->numOfTables == 1 && pNew->cmd.numOfClause == 1);
 
     // launch subquery for each vnode, so the subquery index equals to the vnodeIndex.
-    SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
+    SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, table_index);
     pMeterMetaInfo->vnodeIndex = trsupport->subqueryIndex;
 
     pSql->pSubs[trsupport->subqueryIndex] = pNew;
@@ -1471,7 +1486,7 @@ int tscBuildRetrieveMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
 void tscUpdateVnodeInSubmitMsg(SSqlObj *pSql, char *buf) {
   SShellSubmitMsg *pShellMsg;
   char *           pMsg;
-  SMeterMetaInfo * pMeterMetaInfo = tscGetMeterMetaInfo(&pSql->cmd, 0, 0);
+  SMeterMetaInfo * pMeterMetaInfo = tscGetMeterMetaInfo(&pSql->cmd, pSql->cmd.clauseIndex, 0);
 
   SMeterMeta *pMeterMeta = pMeterMetaInfo->pMeterMeta;
 
@@ -1506,13 +1521,13 @@ int tscBuildSubmitMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   pSql->cmd.msgType = TSDB_MSG_TYPE_SUBMIT;
   tscTrace("%p update submit msg vnode:%s:%d", pSql, taosIpStr(pMeterMeta->vpeerDesc[pMeterMeta->index].ip),
            htons(pShellMsg->vnode));
-
-  return msgLen;
+  
+  return TSDB_CODE_SUCCESS;
 }
 
 void tscUpdateVnodeInQueryMsg(SSqlObj *pSql, char *buf) {
   SSqlCmd *       pCmd = &pSql->cmd;
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
 
   char *          pStart = buf + tsRpcHeadSize;
   SQueryMeterMsg *pQueryMsg = (SQueryMeterMsg *)pStart;
@@ -1561,7 +1576,7 @@ static int32_t tscEstimateQueryMsgSize(SSqlCmd *pCmd, int32_t clauseIndex) {
 }
 
 static char *doSerializeTableInfo(SSqlObj *pSql, int32_t numOfMeters, int32_t vnodeId, char *pMsg) {
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(&pSql->cmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(&pSql->cmd, pSql->cmd.clauseIndex, 0);
 
   SMeterMeta * pMeterMeta = pMeterMetaInfo->pMeterMeta;
   SMetricMeta *pMetricMeta = pMeterMetaInfo->pMetricMeta;
@@ -1611,8 +1626,8 @@ int tscBuildQueryMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   }
 
   SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
-
   SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
+  
   char *          pStart = pCmd->payload + tsRpcHeadSize;
 
   SMeterMeta * pMeterMeta = pMeterMetaInfo->pMeterMeta;
@@ -1772,7 +1787,7 @@ int tscBuildQueryMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
       hasArithmeticFunction = true;
     }
 
-    if (!tscValidateColumnId(pCmd, pExpr->colInfo.colId)) {
+    if (!tscValidateColumnId(pMeterMetaInfo, pExpr->colInfo.colId)) {
       /* column id is not valid according to the cached metermeta, the meter meta is expired */
       tscError("%p table schema is not matched with parsed sql", pSql);
       return -1;
@@ -1913,7 +1928,9 @@ int32_t tscBuildCreateDbMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   pMsg = doBuildMsgHeader(pSql, &pStart);
   pCreateDbMsg = (SCreateDbMsg *)pMsg;
 
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  assert(pCmd->numOfClause == 1);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
+  
   strncpy(pCreateDbMsg->db, pMeterMetaInfo->name, tListLen(pCreateDbMsg->db));
   pMsg += sizeof(SCreateDbMsg);
 
@@ -2063,7 +2080,7 @@ int32_t tscBuildDropDbMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   pMsg = doBuildMsgHeader(pSql, &pStart);
   pDropDbMsg = (SDropDbMsg *)pMsg;
 
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   strncpy(pDropDbMsg->db, pMeterMetaInfo->name, tListLen(pDropDbMsg->db));
   pDropDbMsg->ignoreNotExists = pInfo->pDCLInfo->existsCheck ? 1 : 0;
 
@@ -2085,7 +2102,7 @@ int32_t tscBuildDropTableMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   pMsg = doBuildMsgHeader(pSql, &pStart);
   pDropTableMsg = (SDropTableMsg *)pMsg;
 
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   strcpy(pDropTableMsg->meterId, pMeterMetaInfo->name);
 
   pDropTableMsg->igNotExists = pInfo->pDCLInfo->existsCheck ? 1 : 0;
@@ -2103,7 +2120,7 @@ int32_t tscBuildDropDnodeMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   char *         pMsg, *pStart;
 
   SSqlCmd *       pCmd = &pSql->cmd;
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
 
   pMsg = doBuildMsgHeader(pSql, &pStart);
   pDrop = (SDropDnodeMsg *)pMsg;
@@ -2128,7 +2145,7 @@ int32_t tscBuildDropAcctMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   pMsg = doBuildMsgHeader(pSql, &pStart);
   pDropMsg = (SDropUserMsg *)pMsg;
 
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   strcpy(pDropMsg->user, pMeterMetaInfo->name);
 
   pMsg += sizeof(SDropUserMsg);
@@ -2148,7 +2165,7 @@ int32_t tscBuildUseDbMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   pMsg = doBuildMsgHeader(pSql, &pStart);
   pUseDbMsg = (SUseDbMsg *)pMsg;
 
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   strcpy(pUseDbMsg->db, pMeterMetaInfo->name);
 
   pMsg += sizeof(SUseDbMsg);
@@ -2178,7 +2195,7 @@ int32_t tscBuildShowMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
 
   SMgmtHead *pMgmt = (SMgmtHead *)pMsg;
 
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
   size_t          nameLen = strlen(pMeterMetaInfo->name);
 
   if (nameLen > 0) {
@@ -2414,7 +2431,7 @@ int tscAlterDbMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
 
   SSqlCmd *       pCmd = &pSql->cmd;
   STscObj *       pObj = pSql->pTscObj;
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
 
   pStart = pCmd->payload + tsRpcHeadSize;
   pMsg = pStart;
@@ -2532,7 +2549,7 @@ static int tscLocalResultCommonBuilder(SSqlObj *pSql, int32_t numOfRes) {
 
 int tscProcessDescribeTableRsp(SSqlObj *pSql) {
   SSqlCmd *       pCmd = &pSql->cmd;
-  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
 
   int32_t numOfRes = pMeterMetaInfo->pMeterMeta->numOfColumns + pMeterMetaInfo->pMeterMeta->numOfTags;
 
@@ -2772,7 +2789,7 @@ int tscBuildMetricMetaMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   pMsg += sizeof(int16_t);
 
   for (int32_t i = 0; i < pQueryInfo->numOfTables; ++i) {
-    pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, i);
+    pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, i);
     uint64_t uid = pMeterMetaInfo->pMeterMeta->uid;
 
     offset = pMsg - (char *)pMetaMsg;
@@ -3431,7 +3448,7 @@ int tscProcessRetrieveRspFromVnode(SSqlObj *pSql) {
    * If the query result is exhausted, or current query is to free resource at server side,
    * the connection will be recycled.
    */
-  if ((pRes->numOfRows == 0 && !(tscProjectionQueryOnSTable(pCmd, 0) && pRes->offset > 0)) ||
+  if ((pRes->numOfRows == 0 && !(tscProjectionQueryOnSTable(pQueryInfo, 0) && pRes->offset > 0)) ||
       ((pQueryInfo->type & TSDB_QUERY_TYPE_FREE_RESOURCE) == TSDB_QUERY_TYPE_FREE_RESOURCE)) {
     tscTrace("%p no result or free resource, recycle connection", pSql);
     taosAddConnIntoCache(tscConnCache, pSql->thandle, pSql->ip, pSql->vnode, pObj->user);
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index 6aa6cfaf5a..2175d017ad 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -13,6 +13,7 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "hash.h"
 #include "os.h"
 #include "tcache.h"
 #include "tlog.h"
@@ -28,7 +29,6 @@
 #include "tsocket.h"
 #include "ttimer.h"
 #include "tutil.h"
-#include "hash.h"
 
 TAOS *taos_connect_imp(const char *ip, const char *user, const char *pass, const char *db, uint16_t port,
                        void (*fp)(void *, TAOS_RES *, int), void *param, void **taos) {
@@ -205,7 +205,7 @@ int taos_query_imp(STscObj *pObj, SSqlObj *pSql) {
     taosCleanUpHashTable(pSql->pTableHashList);
     pSql->pTableHashList = NULL;
   }
-  
+
   tscTrace("%p SQL: %s pObj:%p", pSql, pSql->sqlstr, pObj);
 
   pRes->code = (uint8_t)tsParseSql(pSql, false);
@@ -293,11 +293,11 @@ int taos_num_fields(TAOS_RES *res) {
   SSqlObj *pSql = (SSqlObj *)res;
   if (pSql == NULL || pSql->signature != pSql) return 0;
 
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
   if (pQueryInfo == NULL) {
     return 0;
   }
-  
+
   SFieldInfo *pFieldsInfo = &pQueryInfo->fieldsInfo;
   return (pFieldsInfo->numOfOutputCols - pFieldsInfo->numOfHiddenCols);
 }
@@ -319,8 +319,8 @@ int taos_affected_rows(TAOS *taos) {
 TAOS_FIELD *taos_fetch_fields(TAOS_RES *res) {
   SSqlObj *pSql = (SSqlObj *)res;
   if (pSql == NULL || pSql->signature != pSql) return 0;
-  
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
+
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
   return pQueryInfo->fieldsInfo.pFields;
 }
 
@@ -370,7 +370,7 @@ int taos_fetch_block_impl(TAOS_RES *res, TAOS_ROW *rows) {
     pRes->numOfTotal += pRes->numOfRows;
   }
 
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
   for (int i = 0; i < pQueryInfo->fieldsInfo.numOfOutputCols; ++i) {
     pRes->tsrow[i] = TSC_GET_RESPTR_BASE(pRes, pQueryInfo, i, pQueryInfo->order) +
                      pRes->bytes[i] * (1 - pQueryInfo->order.order) * (pRes->numOfRows - 1);
@@ -384,9 +384,9 @@ int taos_fetch_block_impl(TAOS_RES *res, TAOS_ROW *rows) {
 static void **doSetResultRowData(SSqlObj *pSql) {
   SSqlCmd *pCmd = &pSql->cmd;
   SSqlRes *pRes = &pSql->res;
-  
+
   SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
-  
+
   int32_t num = 0;
   for (int i = 0; i < pQueryInfo->fieldsInfo.numOfOutputCols; ++i) {
     pRes->tsrow[i] = TSC_GET_RESPTR_BASE(pRes, pQueryInfo, i, pQueryInfo->order) + pRes->bytes[i] * pRes->row;
@@ -439,16 +439,17 @@ static bool tscHashRemainDataInSubqueryResultSet(SSqlObj *pSql) {
   bool     hasData = true;
   SSqlCmd *pCmd = &pSql->cmd;
 
-  if (tscProjectionQueryOnSTable(pCmd, 0)) {
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
+  if (tscProjectionQueryOnSTable(pQueryInfo, 0)) {
     bool allSubqueryExhausted = true;
 
     for (int32_t i = 0; i < pSql->numOfSubs; ++i) {
       SSqlRes *pRes1 = &pSql->pSubs[i]->res;
       SSqlCmd *pCmd1 = &pSql->pSubs[i]->cmd;
 
-      SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd1, 0);
-      SMeterMetaInfo *pMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
-  
+      SQueryInfo *    pQueryInfo1 = tscGetQueryInfoDetail(pCmd1, pCmd1->clauseIndex);
+      SMeterMetaInfo *pMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo1, 0);
+
       assert(pQueryInfo->numOfTables == 1);
 
       /*
@@ -465,12 +466,12 @@ static bool tscHashRemainDataInSubqueryResultSet(SSqlObj *pSql) {
     hasData = !allSubqueryExhausted;
   } else {  // otherwise, in case inner join, if any subquery exhausted, query completed.
     for (int32_t i = 0; i < pSql->numOfSubs; ++i) {
-      SSqlRes *pRes1 = &pSql->pSubs[i]->res;
-      SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->pSubs[i]->cmd, 0);
-      
+      SSqlRes *   pRes1 = &pSql->pSubs[i]->res;
+      SQueryInfo *pQueryInfo1 = tscGetQueryInfoDetail(&pSql->pSubs[i]->cmd, 0);
+
       if ((pRes1->row >= pRes1->numOfRows && tscHasReachLimitation(pSql->pSubs[i]) &&
-           tscProjectionQueryOnTable(pQueryInfo)) || (pRes1->numOfRows == 0)) {
-        
+           tscProjectionQueryOnTable(pQueryInfo1)) ||
+          (pRes1->numOfRows == 0)) {
         hasData = false;
         break;
       }
@@ -501,9 +502,9 @@ static void **tscJoinResultsetFromBuf(SSqlObj *pSql) {
       free(pState);
       return NULL;
     }
-  
-    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
-  
+
+    SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
+
     if (pRes->tsrow == NULL) {
       pRes->tsrow = malloc(POINTER_BYTES * pQueryInfo->exprsInfo.numOfExprs);
     }
@@ -578,9 +579,82 @@ TAOS_ROW taos_fetch_row_impl(TAOS_RES *res) {
       pCmd->command = (pCmd->command > TSDB_SQL_MGMT) ? TSDB_SQL_RETRIEVE : TSDB_SQL_FETCH;
     }
 
-    tscProcessSql(pSql);
-    if (pRes->numOfRows == 0) {
-      return NULL;
+    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);
+      }
     }
 
     /*
@@ -590,6 +664,10 @@ TAOS_ROW taos_fetch_row_impl(TAOS_RES *res) {
     if (pCmd->command != TSDB_SQL_RETRIEVE_METRIC) {
       pRes->numOfTotal += pRes->numOfRows;
     }
+
+    if (pRes->numOfRows == 0) {
+      return NULL;
+    }
   }
 
   return getOneRowFromBuf(pSql);
@@ -597,8 +675,8 @@ 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;
+//  SSqlCmd *pCmd = &pSql->cmd;
+//  SSqlRes *pRes = &pSql->res;
 
   if (pSql == NULL || pSql->signature != pSql) {
     globalCode = TSDB_CODE_DISCONNECTED;
@@ -607,63 +685,64 @@ TAOS_ROW taos_fetch_row(TAOS_RES *res) {
 
   // projection query on metric, pipeline retrieve data from vnode list, instead of two-stage merge
   TAOS_ROW rows = taos_fetch_row_impl(res);
-  
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
-  while (rows == NULL && tscProjectionQueryOnSTable(pCmd, 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);
-    tscProcessSql(pSql);
-    
-    rows = taos_fetch_row_impl(res);
-  }
+  //  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);
+  //  }
 
   return rows;
 }
 
 int taos_fetch_block(TAOS_RES *res, TAOS_ROW *rows) {
   SSqlObj *pSql = (SSqlObj *)res;
-  SSqlCmd *pCmd = &pSql->cmd;
   SSqlRes *pRes = &pSql->res;
 
   int nRows = 0;
@@ -677,9 +756,9 @@ int taos_fetch_block(TAOS_RES *res, TAOS_ROW *rows) {
   // projection query on metric, pipeline retrieve data from vnode list,
   // instead of two-stage mergevnodeProcessMsgFromShell free qhandle
   nRows = taos_fetch_block_impl(res, rows);
-  
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
-  while (*rows == NULL && tscProjectionQueryOnSTable(pCmd, 0)) {
+
+  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;
@@ -746,7 +825,7 @@ void taos_free_result(TAOS_RES *res) {
   }
 
   // set freeFlag to 1 in retrieve message if there are un-retrieved results
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
   pQueryInfo->type = TSDB_QUERY_TYPE_FREE_RESOURCE;
 
   SMeterMetaInfo *pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
@@ -863,12 +942,15 @@ void taos_stop_query(TAOS_RES *res) {
   if (res == NULL) return;
 
   SSqlObj *pSql = (SSqlObj *)res;
+  SSqlCmd *pCmd = &pSql->cmd;
+
   if (pSql->signature != pSql) return;
   tscTrace("%p start to cancel query", res);
 
   pSql->res.code = TSDB_CODE_QUERY_CANCELLED;
 
-  if (tscIsTwoStageMergeMetricQuery(&pSql->cmd)) {
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
+  if (tscIsTwoStageMergeMetricQuery(pQueryInfo, 0)) {
     tscKillMetricQuery(pSql);
     return;
   }
@@ -915,15 +997,13 @@ int taos_print_row(char *str, TAOS_ROW row, TAOS_FIELD *fields, int num_fields)
         float fv = 0;
         fv = GET_FLOAT_VAL(row[i]);
         len += sprintf(str + len, "%f ", fv);
-      }
-        break;
+      } break;
 
-      case TSDB_DATA_TYPE_DOUBLE:{
+      case TSDB_DATA_TYPE_DOUBLE: {
         double dv = 0;
         dv = GET_DOUBLE_VAL(row[i]);
         len += sprintf(str + len, "%lf ", dv);
-      }
-        break;
+      } break;
 
       case TSDB_DATA_TYPE_BINARY:
       case TSDB_DATA_TYPE_NCHAR: {
@@ -1011,9 +1091,9 @@ static int tscParseTblNameList(SSqlObj *pSql, const char *tblNameList, int32_t t
   int   code = TSDB_CODE_INVALID_METER_ID;
   char *str = (char *)tblNameList;
 
-  SQueryInfo* pQueryInfo = NULL;
-  tscGetQueryInfoDetailSafely(pCmd, 0, &pQueryInfo);
-  
+  SQueryInfo *pQueryInfo = NULL;
+  tscGetQueryInfoDetailSafely(pCmd, pCmd->clauseIndex, &pQueryInfo);
+
   SMeterMetaInfo *pMeterMetaInfo = tscAddEmptyMeterMetaInfo(pQueryInfo);
 
   if ((code = tscAllocPayload(pCmd, tblListLen + 16)) != TSDB_CODE_SUCCESS) {
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index ea08901d6b..c456324de5 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -208,47 +208,38 @@ SMeterSidExtInfo* tscGetMeterSidInfo(SVnodeSidList* pSidList, int32_t idx) {
   return (SMeterSidExtInfo*)(pSidList->pSidExtInfoList[idx] + (char*)pSidList);
 }
 
-bool tscIsTwoStageMergeMetricQuery(SSqlCmd* pCmd) {
-  assert(pCmd != NULL);
-
-  int32_t     subClauseIndex = 0;
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, subClauseIndex);
+bool tscIsTwoStageMergeMetricQuery(SQueryInfo* pQueryInfo, int32_t tableIndex) {
   if (pQueryInfo == NULL) {
     return false;
   }
-
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
+  
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, tableIndex);
   if (pMeterMetaInfo == NULL || pMeterMetaInfo->pMetricMeta == NULL) {
     return false;
   }
 
   // for projection query, iterate all qualified vnodes sequentially
-  if (tscProjectionQueryOnSTable(pCmd, subClauseIndex)) {
+  if (tscProjectionQueryOnSTable(pQueryInfo, tableIndex)) {
     return false;
   }
 
   if (((pQueryInfo->type & TSDB_QUERY_TYPE_STABLE_SUBQUERY) != TSDB_QUERY_TYPE_STABLE_SUBQUERY) &&
-      pCmd->command == TSDB_SQL_SELECT) {
+      pQueryInfo->command == TSDB_SQL_SELECT) {
     return UTIL_METER_IS_SUPERTABLE(pMeterMetaInfo);
   }
 
   return false;
 }
 
-bool tscProjectionQueryOnSTable(SSqlCmd* pCmd, int32_t subClauseIndex) {
-  assert(pCmd != NULL);
-
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, subClauseIndex);
-  assert(pQueryInfo->numOfTables > 0);
-  
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, 0);
+bool tscProjectionQueryOnSTable(SQueryInfo *pQueryInfo, int32_t tableIndex) {
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfoFromQueryInfo(pQueryInfo, tableIndex);
 
   /*
    * In following cases, return false for project query on metric
    * 1. failed to get metermeta from server; 2. not a metric; 3. limit 0; 4. show query, instead of a select query
    */
   if (pMeterMetaInfo == NULL || !UTIL_METER_IS_SUPERTABLE(pMeterMetaInfo) ||
-      pCmd->command == TSDB_SQL_RETRIEVE_EMPTY_RESULT || pQueryInfo->exprsInfo.numOfExprs == 0) {
+      pQueryInfo->command == TSDB_SQL_RETRIEVE_EMPTY_RESULT || pQueryInfo->exprsInfo.numOfExprs == 0) {
     return false;
   }
 
@@ -538,14 +529,16 @@ int32_t tscCopyDataBlockToPayload(SSqlObj* pSql, STableDataBlocks* pDataBlock) {
   assert(pDataBlock->pMeterMeta != NULL);
 
   pCmd->numOfTablesInSubmit = pDataBlock->numOfMeters;
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+  
+  assert(pCmd->numOfClause == 1);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, 0);
 
   // set the correct metermeta object, the metermeta has been locked in pDataBlocks, so it must be in the cache
   if (pMeterMetaInfo->pMeterMeta != pDataBlock->pMeterMeta) {
     strcpy(pMeterMetaInfo->name, pDataBlock->meterId);
     taosRemoveDataFromCache(tscCacheHandle, (void**)&(pMeterMetaInfo->pMeterMeta), false);
-  
-    pMeterMetaInfo->pMeterMeta = taosTransferDataInCache(tscCacheHandle, (void**) &pDataBlock->pMeterMeta);
+
+    pMeterMetaInfo->pMeterMeta = taosTransferDataInCache(tscCacheHandle, (void**)&pDataBlock->pMeterMeta);
   } else {
     assert(strncmp(pMeterMetaInfo->name, pDataBlock->meterId, tListLen(pDataBlock->meterId)) == 0);
   }
@@ -654,9 +647,9 @@ int32_t tscMergeTableDataBlocks(SSqlObj* pSql, SDataBlockList* pTableDataBlockLi
     STableDataBlocks* pOneTableBlock = pTableDataBlockList->pData[i];
 
     STableDataBlocks* dataBuf = NULL;
-    int32_t           ret = tscGetDataBlockFromList(pVnodeDataBlockHashList, pVnodeDataBlockList, pOneTableBlock->vgid,
-                                          TSDB_PAYLOAD_SIZE, tsInsertHeadSize, 0, pOneTableBlock->meterId,
-                                          pOneTableBlock->pMeterMeta, &dataBuf);
+    int32_t           ret =
+        tscGetDataBlockFromList(pVnodeDataBlockHashList, pVnodeDataBlockList, pOneTableBlock->vgid, TSDB_PAYLOAD_SIZE,
+                                tsInsertHeadSize, 0, pOneTableBlock->meterId, pOneTableBlock->pMeterMeta, &dataBuf);
     if (ret != TSDB_CODE_SUCCESS) {
       tscError("%p failed to prepare the data block buffer for merging table data, code:%d", pSql, ret);
       taosCleanUpHashTable(pVnodeDataBlockHashList);
@@ -859,7 +852,7 @@ void tscFieldInfoCalOffset(SQueryInfo* pQueryInfo) {
   }
 }
 
-void tscFieldInfoUpdateOffset(SQueryInfo* pQueryInfo) {
+void tscFieldInfoUpdateOffsetForInterResult(SQueryInfo* pQueryInfo) {
   SFieldInfo* pFieldInfo = &pQueryInfo->fieldsInfo;
   if (pFieldInfo->numOfOutputCols == 0) {
     return;
@@ -922,6 +915,26 @@ int16_t tscFieldInfoGetOffset(SQueryInfo* pQueryInfo, int32_t index) {
   return pQueryInfo->fieldsInfo.pOffset[index];
 }
 
+int32_t tscFieldInfoCompare(SFieldInfo* pFieldInfo1, SFieldInfo* pFieldInfo2) {
+  assert(pFieldInfo1 != NULL && pFieldInfo2 != NULL);
+  
+  if (pFieldInfo1->numOfOutputCols != pFieldInfo2->numOfOutputCols) {
+    return pFieldInfo1->numOfOutputCols - pFieldInfo2->numOfOutputCols;
+  }
+
+  for (int32_t i = 0; i < pFieldInfo1->numOfOutputCols; ++i) {
+    TAOS_FIELD* pField1 = &pFieldInfo1->pFields[i];
+    TAOS_FIELD* pField2 = &pFieldInfo2->pFields[i];
+
+    if (pField1->type != pField2->type || pField1->bytes != pField2->bytes ||
+        strcasecmp(pField1->name, pField2->name) != 0) {
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
 int32_t tscGetResRowLength(SQueryInfo* pQueryInfo) {
   SFieldInfo* pFieldInfo = &pQueryInfo->fieldsInfo;
   if (pFieldInfo->numOfOutputCols <= 0) {
@@ -1394,8 +1407,7 @@ void tscIncStreamExecutionCount(void* pStream) {
   ps->num += 1;
 }
 
-bool tscValidateColumnId(SSqlCmd* pCmd, int32_t colId) {
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, 0);
+bool tscValidateColumnId(SMeterMetaInfo* pMeterMetaInfo, int32_t colId) {
   if (pMeterMetaInfo->pMeterMeta == NULL) {
     return false;
   }
@@ -1592,7 +1604,7 @@ SMeterMetaInfo* tscGetMeterMetaInfoFromQueryInfo(SQueryInfo* pQueryInfo, int32_t
 
 SQueryInfo* tscGetQueryInfoDetail(SSqlCmd* pCmd, int32_t subClauseIndex) {
   assert(pCmd != NULL && subClauseIndex >= 0 && subClauseIndex < TSDB_MAX_UNION_CLAUSE);
-  
+
   if (pCmd->pQueryInfo == NULL || subClauseIndex >= pCmd->numOfClause) {
     return NULL;
   }
@@ -1600,19 +1612,19 @@ SQueryInfo* tscGetQueryInfoDetail(SSqlCmd* pCmd, int32_t subClauseIndex) {
   return pCmd->pQueryInfo[subClauseIndex];
 }
 
-int32_t tscGetQueryInfoDetailSafely(SSqlCmd *pCmd, int32_t subClauseIndex, SQueryInfo** pQueryInfo) {
+int32_t tscGetQueryInfoDetailSafely(SSqlCmd* pCmd, int32_t subClauseIndex, SQueryInfo** pQueryInfo) {
   int32_t ret = TSDB_CODE_SUCCESS;
-  
+
   *pQueryInfo = tscGetQueryInfoDetail(pCmd, subClauseIndex);
-  
+
   while ((*pQueryInfo) == NULL) {
     if ((ret = tscAddSubqueryInfo(pCmd)) != TSDB_CODE_SUCCESS) {
       return ret;
     }
-    
+
     (*pQueryInfo) = tscGetQueryInfoDetail(pCmd, subClauseIndex);
   }
-  
+
   return TSDB_CODE_SUCCESS;
 }
 
@@ -1654,20 +1666,20 @@ int32_t tscAddSubqueryInfo(SSqlCmd* pCmd) {
 static void doClearSubqueryInfo(SQueryInfo* pQueryInfo) {
   tscTagCondRelease(&pQueryInfo->tagCond);
   tscClearFieldInfo(&pQueryInfo->fieldsInfo);
-  
+
   tfree(pQueryInfo->exprsInfo.pExprs);
   memset(&pQueryInfo->exprsInfo, 0, sizeof(pQueryInfo->exprsInfo));
-  
+
   tscColumnBaseInfoDestroy(&pQueryInfo->colList);
   memset(&pQueryInfo->colList, 0, sizeof(pQueryInfo->colList));
-  
+
   pQueryInfo->tsBuf = tsBufDestory(pQueryInfo->tsBuf);
-  
+
   tfree(pQueryInfo->defaultVal);
 }
 
 void tscClearSubqueryInfo(SSqlCmd* pCmd) {
-  for(int32_t i = 0; i < pCmd->numOfClause; ++i) {
+  for (int32_t i = 0; i < pCmd->numOfClause; ++i) {
     SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, i);
     doClearSubqueryInfo(pQueryInfo);
   }
@@ -1679,27 +1691,21 @@ void tscFreeSubqueryInfo(SSqlCmd* pCmd) {
   }
 
   for (int32_t i = 0; i < pCmd->numOfClause; ++i) {
-    char *addr = (char *) pCmd - offsetof(SSqlObj, cmd);
-    
-    SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, i);
-  
+    char* addr = (char*)pCmd - offsetof(SSqlObj, cmd);
+
+    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, i);
+
     doClearSubqueryInfo(pQueryInfo);
-    tscRemoveAllMeterMetaInfo(pQueryInfo, (const char *) addr, false);
+    tscRemoveAllMeterMetaInfo(pQueryInfo, (const char*)addr, false);
     tfree(pQueryInfo);
   }
-  
+
   pCmd->numOfClause = 0;
   tfree(pCmd->pQueryInfo);
 }
 
 SMeterMetaInfo* tscAddMeterMetaInfo(SQueryInfo* pQueryInfo, const char* name, SMeterMeta* pMeterMeta,
                                     SMetricMeta* pMetricMeta, int16_t numOfTags, int16_t* tags) {
-//  while (pCmd->numOfClause <= subClauseIndex) {
-//    tscAddSubqueryInfo(pCmd);
-//  }
-
-//  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
-
   void* pAlloc = realloc(pQueryInfo->pMeterInfo, (pQueryInfo->numOfTables + 1) * POINTER_BYTES);
   if (pAlloc == NULL) {
     return NULL;
@@ -1777,7 +1783,7 @@ void tscResetForNextRetrieve(SSqlRes* pRes) {
 
 SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void* param, SSqlObj* pPrevSql) {
   SSqlCmd*        pCmd = &pSql->cmd;
-  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, 0, tableIndex);
+  SMeterMetaInfo* pMeterMetaInfo = tscGetMeterMetaInfo(pCmd, pCmd->clauseIndex, tableIndex);
 
   SSqlObj* pNew = (SSqlObj*)calloc(1, sizeof(SSqlObj));
   if (pNew == NULL) {
@@ -1804,6 +1810,7 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
 
   pNew->cmd.pQueryInfo = NULL;
   pNew->cmd.numOfClause = 0;
+  pNew->cmd.clauseIndex = 0;
 
   if (tscAddSubqueryInfo(&pNew->cmd) != TSDB_CODE_SUCCESS) {
     tscFreeSqlObj(pNew);
@@ -1811,25 +1818,25 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
   }
 
   SQueryInfo* pNewQueryInfo = tscGetQueryInfoDetail(&pNew->cmd, 0);
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, pCmd->clauseIndex);
 
   memcpy(pNewQueryInfo, pQueryInfo, sizeof(SQueryInfo));
 
   memset(&pNewQueryInfo->colList, 0, sizeof(pNewQueryInfo->colList));
   memset(&pNewQueryInfo->fieldsInfo, 0, sizeof(SFieldInfo));
-  
+
   pNewQueryInfo->pMeterInfo = NULL;
   pNewQueryInfo->defaultVal = NULL;
   pNewQueryInfo->numOfTables = 0;
   pNewQueryInfo->tsBuf = NULL;
 
   tscTagCondCopy(&pNewQueryInfo->tagCond, &pQueryInfo->tagCond);
-  
+
   if (pQueryInfo->interpoType != TSDB_INTERPO_NONE) {
     pNewQueryInfo->defaultVal = malloc(pQueryInfo->fieldsInfo.numOfOutputCols * sizeof(int64_t));
     memcpy(pNewQueryInfo->defaultVal, pQueryInfo->defaultVal, pQueryInfo->fieldsInfo.numOfOutputCols * sizeof(int64_t));
   }
-  
+
   if (tscAllocPayload(&pNew->cmd, TSDB_DEFAULT_PAYLOAD_SIZE) != TSDB_CODE_SUCCESS) {
     tscError("%p new subquery failed, tableIndex:%d, vnodeIndex:%d", pSql, tableIndex, pMeterMetaInfo->vnodeIndex);
     tscFreeSqlObj(pNew);
@@ -1840,7 +1847,7 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
 
   // set the correct query type
   if (pPrevSql != NULL) {
-    SQueryInfo* pPrevQueryInfo = tscGetQueryInfoDetail(&pPrevSql->cmd, 0);
+    SQueryInfo* pPrevQueryInfo = tscGetQueryInfoDetail(&pPrevSql->cmd, pPrevSql->cmd.clauseIndex);
     pNewQueryInfo->type = pPrevQueryInfo->type;
   } else {
     pNewQueryInfo->type |= TSDB_QUERY_TYPE_SUBQUERY;  // it must be the subquery
@@ -1863,14 +1870,14 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
     tscFieldInfoCopy(&pQueryInfo->fieldsInfo, &pNewQueryInfo->fieldsInfo, indexList, numOfOutputCols);
     free(indexList);
 
-    tscFieldInfoUpdateOffset(pNewQueryInfo);
+    tscFieldInfoUpdateOffsetForInterResult(pNewQueryInfo);
   }
 
   pNew->fp = fp;
   pNew->param = param;
 
   char key[TSDB_MAX_TAGS_LEN + 1] = {0};
-  tscGetMetricMetaCacheKey(pCmd, 0, key, uid);
+  tscGetMetricMetaCacheKey(pCmd, pCmd->clauseIndex, key, uid);
 
 #ifdef _DEBUG_VIEW
   printf("the metricmeta key is:%s\n", key);
@@ -1886,12 +1893,12 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
 
     pFinalInfo = tscAddMeterMetaInfo(pNewQueryInfo, name, pMeterMeta, pMetricMeta, pMeterMetaInfo->numOfTags,
                                      pMeterMetaInfo->tagColumnIndex);
-  } else { // transfer the ownership of pMeterMeta/pMetricMeta to the newly create sql object.
-    SMeterMetaInfo* pPrevInfo = tscGetMeterMetaInfo(&pPrevSql->cmd, 0, 0);
-    
-    SMeterMeta* pPrevMeterMeta = taosTransferDataInCache(tscCacheHandle, (void**) &pPrevInfo->pMeterMeta);
-    SMetricMeta* pPrevMetricMeta = taosTransferDataInCache(tscCacheHandle, (void**) &pPrevInfo->pMetricMeta);
-    
+  } else {  // transfer the ownership of pMeterMeta/pMetricMeta to the newly create sql object.
+    SMeterMetaInfo* pPrevInfo = tscGetMeterMetaInfo(&pPrevSql->cmd, pPrevSql->cmd.clauseIndex, 0);
+
+    SMeterMeta*  pPrevMeterMeta = taosTransferDataInCache(tscCacheHandle, (void**)&pPrevInfo->pMeterMeta);
+    SMetricMeta* pPrevMetricMeta = taosTransferDataInCache(tscCacheHandle, (void**)&pPrevInfo->pMetricMeta);
+
     pFinalInfo = tscAddMeterMetaInfo(pNewQueryInfo, name, pPrevMeterMeta, pPrevMetricMeta, pMeterMetaInfo->numOfTags,
                                      pMeterMetaInfo->tagColumnIndex);
   }
-- 
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