diff --git a/src/client/inc/tscUtil.h b/src/client/inc/tscUtil.h
index c16945bbcf35ac5247ecbb505aaf667870fc9d09..d46c32d73d823d52c739fc01d1d11c0a59f27168 100644
--- a/src/client/inc/tscUtil.h
+++ b/src/client/inc/tscUtil.h
@@ -196,14 +196,14 @@ STableMetaInfo* tscGetMetaInfo(SQueryInfo *pQueryInfo, int32_t tableIndex);
 SQueryInfo *tscGetQueryInfoDetail(SSqlCmd* pCmd, int32_t subClauseIndex);
 int32_t tscGetQueryInfoDetailSafely(SSqlCmd *pCmd, int32_t subClauseIndex, SQueryInfo** pQueryInfo);
 
-void tscClearMeterMetaInfo(STableMetaInfo* pTableMetaInfo, bool removeFromCache);
+void tscClearTableMetaInfo(STableMetaInfo* pTableMetaInfo, bool removeFromCache);
 
 STableMetaInfo* tscAddTableMetaInfo(SQueryInfo* pQueryInfo, const char* name, STableMeta* pTableMeta,
     SVgroupsInfo* vgroupList, SArray* pTagCols);
 
 STableMetaInfo* tscAddEmptyMetaInfo(SQueryInfo *pQueryInfo);
 int32_t tscAddSubqueryInfo(SSqlCmd *pCmd);
-void tscFreeSubqueryInfo(SSqlCmd* pCmd);
+void tscFreeQueryInfo(SSqlCmd* pCmd);
 void tscClearSubqueryInfo(SSqlCmd* pCmd);
 
 int  tscGetSTableVgroupInfo(SSqlObj* pSql, int32_t clauseIndex);
diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 9cc6bcb364b76b8156a95cefb34afb27d41a599f..d6fb9279c7f1fd634795967d63829163689e1ed1 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -298,6 +298,7 @@ typedef struct STscObj {
   char               sversion[TSDB_VERSION_LEN];
   char               writeAuth : 1;
   char               superAuth : 1;
+  void*              pMgmtConn;
   struct SSqlObj *   pSql;
   struct SSqlObj *   pHb;
   struct SSqlObj *   sqlList;
@@ -359,7 +360,7 @@ typedef struct SSqlStream {
   struct SSqlStream *prev, *next;
 } SSqlStream;
 
-int32_t tscInitRpc(const char *user, const char *secret);
+int32_t tscInitRpc(const char *user, const char *secret, void** pMgmtConn);
 void    tscInitMsgsFp();
 
 int tsParseSql(SSqlObj *pSql, bool multiVnodeInsertion);
@@ -427,9 +428,7 @@ int32_t tscToSQLCmd(SSqlObj *pSql, struct SSqlInfo *pInfo);
 char *  tscGetResultColumnChr(SSqlRes *pRes, SQueryInfo *pQueryInfo, int32_t column);
 
 extern void *    pVnodeConn;
-extern void *    pTscMgmtConn;
 extern void *    tscCacheHandle;
-extern int       slaveIndex;
 extern void *    tscTmr;
 extern void *    tscQhandle;
 extern int       tscKeepConn[];
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index 99d20de48bcf8b02590b5030a4432f5d83076998..b954db0734be2ffa14a01955fc50e1573bc33ee5 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -46,7 +46,7 @@ void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const
   pSql->signature = pSql;
   pSql->param = param;
   pSql->pTscObj = pObj;
-  pSql->maxRetry = 1;
+  pSql->maxRetry = TSDB_REPLICA_MAX_NUM;
   pSql->fp = fp;
   
   if (TSDB_CODE_SUCCESS != tscAllocPayload(pCmd, TSDB_DEFAULT_PAYLOAD_SIZE)) {
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index 588e45c0b142213adc40d9981a442069f296faef..59e2f147e1b62a6ff507cfc404902f26cc4d498b 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -733,7 +733,7 @@ int32_t tscSetTableId(STableMetaInfo* pTableMetaInfo, SSQLToken* pzTableName, SS
    */
   if (size > 0) {
     if (strncasecmp(oldName, pTableMetaInfo->name, tListLen(pTableMetaInfo->name)) != 0) {
-      tscClearMeterMetaInfo(pTableMetaInfo, false);
+      tscClearTableMetaInfo(pTableMetaInfo, false);
     }
   } else {
     assert(pTableMetaInfo->pTableMeta == NULL);
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index 5ae8f2402bf0dfdaddd73afcfd4bfbd77c6f7949..c36102034b1e4c20f281bde0145e98499dfa9f98 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -188,6 +188,7 @@ void tscProcessActivityTimer(void *handle, void *tmrId) {
 }
 
 int tscSendMsgToServer(SSqlObj *pSql) {
+  STscObj* pObj = pSql->pTscObj;
   SSqlCmd* pCmd = &pSql->cmd;
   
   char *pMsg = rpcMallocCont(pCmd->payloadLen);
@@ -221,7 +222,7 @@ int tscSendMsgToServer(SSqlObj *pSql) {
         .handle  = pSql,
         .code   = 0
     };
-    rpcSendRequest(pTscMgmtConn, &pSql->ipList, &rpcMsg);
+    rpcSendRequest(pObj->pMgmtConn, &pSql->ipList, &rpcMsg);
   }
 
   return TSDB_CODE_SUCCESS;
@@ -2597,7 +2598,7 @@ int tscGetSTableVgroupInfo(SSqlObj *pSql, int32_t clauseIndex) {
 
 //  if (pSql->fp != NULL && pSql->pStream == NULL) {
 //    pCmd->pDataBlocks = tscDestroyBlockArrayList(pCmd->pDataBlocks);
-//    tscFreeSubqueryInfo(pCmd);
+//    tscFreeQueryInfo(pCmd);
 //  }
 
   tscTrace("%p allocate new pSqlObj:%p to get stable vgroupInfo", pSql, pNew);
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index f70beab16625eb9c80e74b921bf6b66987ca0e62..4320e8f81b39d521bba29750d709e60709d33a4b 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -66,7 +66,8 @@ STscObj *taosConnectImpl(const char *ip, const char *user, const char *pass, con
     return NULL;
   }
 
-  if (tscInitRpc(user, pass) != 0) {
+  void* pMgmtConn = NULL;
+  if (tscInitRpc(user, pass, &pMgmtConn) != 0) {
     terrno = TSDB_CODE_NETWORK_UNAVAIL;
     return NULL;
   }
@@ -118,6 +119,7 @@ STscObj *taosConnectImpl(const char *ip, const char *user, const char *pass, con
     strtolower(pObj->db, tmp);
   }
 
+  pObj->pMgmtConn = pMgmtConn;
   pthread_mutex_init(&pObj->mutex, NULL);
 
   SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
diff --git a/src/client/src/tscStream.c b/src/client/src/tscStream.c
index 9f7d4887d131d7bec873f409188b188f96e16245..d69068172937692ac95dd6ca64717b00e236321b 100644
--- a/src/client/src/tscStream.c
+++ b/src/client/src/tscStream.c
@@ -147,7 +147,7 @@ static void tscProcessStreamQueryCallback(void *param, TAOS_RES *tres, int numOf
              retryDelay);
 
     STableMetaInfo* pTableMetaInfo = tscGetTableMetaInfoFromCmd(&pStream->pSql->cmd, 0, 0);
-    tscClearMeterMetaInfo(pTableMetaInfo, true);
+    tscClearTableMetaInfo(pTableMetaInfo, true);
   
     tscSetRetryTimer(pStream, pStream->pSql, retryDelay);
     return;
@@ -177,7 +177,7 @@ static void tscProcessStreamRetrieveResult(void *param, TAOS_RES *res, int numOf
   if (pSql == NULL || numOfRows < 0) {
     int64_t retryDelayTime = tscGetRetryDelayTime(pStream->slidingTime, pStream->precision);
     tscError("%p stream:%p, retrieve data failed, code:%d, retry in %" PRId64 "ms", pSql, pStream, numOfRows, retryDelayTime);
-    tscClearMeterMetaInfo(pTableMetaInfo, true);
+    tscClearTableMetaInfo(pTableMetaInfo, true);
   
     tscSetRetryTimer(pStream, pStream->pSql, retryDelayTime);
     return;
@@ -259,7 +259,7 @@ static void tscProcessStreamRetrieveResult(void *param, TAOS_RES *res, int numOf
              pStream->numOfRes);
 
     // release the metric/meter meta information reference, so data in cache can be updated
-    tscClearMeterMetaInfo(pTableMetaInfo, false);
+    tscClearTableMetaInfo(pTableMetaInfo, false);
     tscSetNextLaunchTimer(pStream, pSql);
   }
 }
diff --git a/src/client/src/tscSystem.c b/src/client/src/tscSystem.c
index 6713f84f9922ed81763562ff1f48ad5b0a74c551..6966a58c45d3a6645c4f2920c45ef961ac8e4d50 100644
--- a/src/client/src/tscSystem.c
+++ b/src/client/src/tscSystem.c
@@ -33,9 +33,6 @@
 
 // global, not configurable
 void *  pVnodeConn;
-void *  pVMeterConn;
-void *  pTscMgmtConn;
-void *  pSlaveConn;
 void *  tscCacheHandle;
 int     slaveIndex;
 void *  tscTmr;
@@ -55,7 +52,7 @@ void tscCheckDiskUsage(void *para, void *unused) {
   taosTmrReset(tscCheckDiskUsage, 1000, NULL, tscTmr, &tscCheckDiskUsageTmr);
 }
 
-int32_t tscInitRpc(const char *user, const char *secret) {
+int32_t tscInitRpc(const char *user, const char *secret, void** pMgmtConn) {
   SRpcInit rpcInit;
   char secretEncrypt[32] = {0};
   taosEncryptPass((uint8_t *)secret, strlen(secret), secretEncrypt);
@@ -83,13 +80,13 @@ int32_t tscInitRpc(const char *user, const char *secret) {
   }
 
   // not stop service, switch users
-  if (strcmp(tsLastUser, user) != 0 && pTscMgmtConn != NULL) {
+  if (strcmp(tsLastUser, user) != 0 && *pMgmtConn != NULL) {
     tscTrace("switch user from %s to %s", user, tsLastUser);
-    rpcClose(pTscMgmtConn);
-    pTscMgmtConn = NULL;
+    rpcClose(*pMgmtConn);
+    *pMgmtConn = NULL;
   }
 
-  if (pTscMgmtConn == NULL) {
+  if (*pMgmtConn == NULL) {
     memset(&rpcInit, 0, sizeof(rpcInit));
     rpcInit.localIp = tsLocalIp;
     rpcInit.localPort = 0;
@@ -104,8 +101,8 @@ int32_t tscInitRpc(const char *user, const char *secret) {
     rpcInit.secret = secretEncrypt;
     strcpy(tsLastUser, user);
 
-    pTscMgmtConn = rpcOpen(&rpcInit);
-    if (pTscMgmtConn == NULL) {
+    *pMgmtConn = rpcOpen(&rpcInit);
+    if (*pMgmtConn == NULL) {
       tscError("failed to init connection to mgmt");
       return -1;
     }
@@ -219,11 +216,6 @@ void taos_cleanup() {
     pVnodeConn = NULL;
   }
   
-  if (pTscMgmtConn != NULL) {
-    rpcClose(pTscMgmtConn);
-    pTscMgmtConn = NULL;
-  }
-  
   taosTmrCleanUp(tscTmr);
 }
 
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index abdab2d9a162faf544dfbf7daa958b657aaa446f..e9ff558b92e45342c615ef8904a9236f913969ce 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -337,7 +337,7 @@ void tscResetSqlCmdObj(SSqlCmd* pCmd) {
   pCmd->pTableList= NULL;
   
   pCmd->pDataBlocks = tscDestroyBlockArrayList(pCmd->pDataBlocks);
-  tscFreeSubqueryInfo(pCmd);
+  tscFreeQueryInfo(pCmd);
 }
 
 /*
@@ -761,6 +761,8 @@ void tscCloseTscObj(STscObj* pObj) {
   tscFreeSqlObj(pSql);
 
   sem_destroy(&pSql->rspSem);
+  rpcClose(pObj->pMgmtConn);
+  
   pthread_mutex_destroy(&pObj->mutex);
   
   tscTrace("%p DB connection is closed", pObj);
@@ -1459,7 +1461,7 @@ bool tscShouldFreeHeatBeat(SSqlObj* pHb) {
 
 void tscCleanSqlCmd(SSqlCmd* pCmd) {
   pCmd->pDataBlocks = tscDestroyBlockArrayList(pCmd->pDataBlocks);
-  tscFreeSubqueryInfo(pCmd);
+  tscFreeQueryInfo(pCmd);
 
   uint32_t allocSize = pCmd->allocSize;
   char*    allocPtr = pCmd->payload;
@@ -1601,7 +1603,7 @@ int32_t tscAddSubqueryInfo(SSqlCmd* pCmd) {
   return TSDB_CODE_SUCCESS;
 }
 
-static void doClearSubqueryInfo(SQueryInfo* pQueryInfo) {
+static void freeQueryInfoImpl(SQueryInfo* pQueryInfo) {
   tscTagCondRelease(&pQueryInfo->tagCond);
   tscFieldInfoClear(&pQueryInfo->fieldsInfo);
 
@@ -1611,6 +1613,11 @@ static void doClearSubqueryInfo(SQueryInfo* pQueryInfo) {
   tscColumnListDestroy(pQueryInfo->colList);
   memset(&pQueryInfo->colList, 0, sizeof(pQueryInfo->colList));
 
+  if (pQueryInfo->groupbyExpr.columnInfo != NULL) {
+    taosArrayDestroy(pQueryInfo->groupbyExpr.columnInfo);
+    pQueryInfo->groupbyExpr.columnInfo = NULL;
+  }
+  
   pQueryInfo->tsBuf = tsBufDestory(pQueryInfo->tsBuf);
 
   tfree(pQueryInfo->defaultVal);
@@ -1619,11 +1626,11 @@ static void doClearSubqueryInfo(SQueryInfo* pQueryInfo) {
 void tscClearSubqueryInfo(SSqlCmd* pCmd) {
   for (int32_t i = 0; i < pCmd->numOfClause; ++i) {
     SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, i);
-    doClearSubqueryInfo(pQueryInfo);
+    freeQueryInfoImpl(pQueryInfo);
   }
 }
 
-void tscFreeSubqueryInfo(SSqlCmd* pCmd) {
+void tscFreeQueryInfo(SSqlCmd* pCmd) {
   if (pCmd == NULL || pCmd->numOfClause == 0) {
     return;
   }
@@ -1632,7 +1639,7 @@ void tscFreeSubqueryInfo(SSqlCmd* pCmd) {
     char* addr = (char*)pCmd - offsetof(SSqlObj, cmd);
     SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, i);
 
-    doClearSubqueryInfo(pQueryInfo);
+    freeQueryInfoImpl(pQueryInfo);
     tscClearAllTableMetaInfo(pQueryInfo, (const char*)addr, false);
     tfree(pQueryInfo);
   }
@@ -1691,7 +1698,7 @@ void doRemoveTableMetaInfo(SQueryInfo* pQueryInfo, int32_t index, bool removeFro
 
   STableMetaInfo* pTableMetaInfo = tscGetMetaInfo(pQueryInfo, index);
 
-  tscClearMeterMetaInfo(pTableMetaInfo, removeFromCache);
+  tscClearTableMetaInfo(pTableMetaInfo, removeFromCache);
   free(pTableMetaInfo);
 
   int32_t after = pQueryInfo->numOfTables - index - 1;
@@ -1713,13 +1720,18 @@ void tscClearAllTableMetaInfo(SQueryInfo* pQueryInfo, const char* address, bool
   tfree(pQueryInfo->pTableMetaInfo);
 }
 
-void tscClearMeterMetaInfo(STableMetaInfo* pTableMetaInfo, bool removeFromCache) {
+void tscClearTableMetaInfo(STableMetaInfo* pTableMetaInfo, bool removeFromCache) {
   if (pTableMetaInfo == NULL) {
     return;
   }
 
   taosCacheRelease(tscCacheHandle, (void**)&(pTableMetaInfo->pTableMeta), removeFromCache);
   tfree(pTableMetaInfo->vgroupList);
+  
+  if (pTableMetaInfo->tagColList != NULL) {
+    taosArrayDestroy(pTableMetaInfo->tagColList);
+    pTableMetaInfo->tagColList = NULL;
+  }
 }
 
 void tscResetForNextRetrieve(SSqlRes* pRes) {
diff --git a/tests/examples/c/demo.c b/tests/examples/c/demo.c
index 984730002436f870e70cf9cc0f23f48b178257eb..e5a70740f112f44428c3a75d96c0bba3927d8731 100644
--- a/tests/examples/c/demo.c
+++ b/tests/examples/c/demo.c
@@ -75,7 +75,7 @@ int main(int argc, char *argv[]) {
   
   doQuery(taos, "create database if not exists test");
   doQuery(taos, "use test");
-  doQuery(taos, "insert into tm99 values('2020-01-01 1:1:1', 99);");
+  doQuery(taos, "select count(*),k,sum(k) from m1 group by k");
 //  doQuery(taos, "create table if not exists tm0 (ts timestamp, k int);");
 //  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:1', 1);");
 //  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:2', 2);");
@@ -86,7 +86,7 @@ int main(int argc, char *argv[]) {
 //  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:7', 7);");
 //  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:8', 8);");
 //  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:9', 9);");
-  doQuery(taos, "select sum(k),count(*) from m1 group by a");
+//  doQuery(taos, "select sum(k),count(*) from m1 group by a");
   
   taos_close(taos);
   return 0;