diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 11b7815586bcdae37f7315e40e547857bb898e5f..74a0e8c11cdfe70584ec99a4d1061acc0c1eeac3 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -334,6 +334,7 @@ typedef struct STscObj {
   struct SSqlStream *streamList;
   void*              pDnodeConn;
   pthread_mutex_t    mutex;
+  T_REF_DECLARE();
 } STscObj;
 
 typedef struct SSqlObj {
@@ -503,7 +504,7 @@ static FORCE_INLINE void tscGetResultColumnChr(SSqlRes* pRes, SFieldInfo* pField
   }
 }
 
-extern SCacheObj*    tscCacheHandle;
+extern SCacheObj*    tscMetaCache;
 extern SCacheObj*    tscObjCache;
 extern void *    tscTmr;
 extern void *    tscQhandle;
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index 5e9aa1b1f80689fd7a52fd476dbf75d2f0a70811..09610575f619be3f02059b6e6ca1ba2c56edcb62 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -51,6 +51,11 @@ void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const
   pSql->fp        = fp;
   pSql->fetchFp   = fp;
 
+  uint64_t handle = (uint64_t) pSql;
+  pSql->self = taosCachePut(tscObjCache, &handle, sizeof(uint64_t), &pSql, sizeof(uint64_t), 2*3600*1000);
+
+  T_REF_INC(pSql->pTscObj);
+
   pSql->sqlstr = calloc(1, sqlLen + 1);
   if (pSql->sqlstr == NULL) {
     tscError("%p failed to malloc sql string buffer", pSql);
@@ -64,9 +69,6 @@ void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const
   tscDebugL("%p SQL: %s", pSql, pSql->sqlstr);
   pCmd->curSql = pSql->sqlstr;
 
-  uint64_t handle = (uint64_t) pSql;
-  pSql->self = taosCachePut(tscObjCache, &handle, sizeof(uint64_t), &pSql, sizeof(uint64_t), 2*3600*1000);
-
   int32_t code = tsParseSql(pSql, true);
   if (code == TSDB_CODE_TSC_ACTION_IN_PROGRESS) return;
   
diff --git a/src/client/src/tscLocal.c b/src/client/src/tscLocal.c
index 4b6174e13d08116bf245e8ed870659428a07735a..50f82ae662840a80b717cc99934640626a679d1f 100644
--- a/src/client/src/tscLocal.c
+++ b/src/client/src/tscLocal.c
@@ -429,7 +429,7 @@ int tscProcessLocalCmd(SSqlObj *pSql) {
     pRes->qhandle = 0x1;
     pRes->numOfRows = 0;
   } else if (pCmd->command == TSDB_SQL_RESET_CACHE) {
-    taosCacheEmpty(tscCacheHandle);
+    taosCacheEmpty(tscMetaCache);
     pRes->code = TSDB_CODE_SUCCESS;
   } else if (pCmd->command == TSDB_SQL_SERV_VERSION) {
     pRes->code = tscProcessServerVer(pSql);
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index de00827c3a8b6853b9bcdbf60f71f2d2f5805de9..e8f1a2d758ef72c95506e0d8673a8f5bb950bcc1 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -1181,13 +1181,14 @@ static int32_t handleArithmeticExpr(SSqlCmd* pCmd, int32_t clauseIndex, int32_t
       } END_TRY
 
     len = tbufTell(&bw);
-    char* c = tbufGetData(&bw, true);
+    char* c = tbufGetData(&bw, false);
 
     // set the serialized binary string as the parameter of arithmetic expression
     addExprParams(pExpr, c, TSDB_DATA_TYPE_BINARY, (int32_t)len, index.tableIndex);
 
     insertResultField(pQueryInfo, exprIndex, &columnList, sizeof(double), TSDB_DATA_TYPE_DOUBLE, pExpr->aliasName, pExpr);
 
+    tbufCloseWriter(&bw);
     taosArrayDestroy(colList);
     tExprTreeDestroy(&pNode, NULL);
   } else {
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index 26fe19d8be5d84b2b3430bc53bbc2cdcf50f7e32..1b6a77bdc737980e2cb7eccc777a9ebe82f78b69 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -373,17 +373,17 @@ void tscProcessMsgFromServer(SRpcMsg *rpcMsg, SRpcEpSet *pEpSet) {
     rpcMsg->code = (*tscProcessMsgRsp[pCmd->command])(pSql);
   }
 
-  bool shouldFree = tscShouldBeFreed(pSql);;
+  bool shouldFree = tscShouldBeFreed(pSql);
   if (rpcMsg->code != TSDB_CODE_TSC_ACTION_IN_PROGRESS) {
     rpcMsg->code = (pRes->code == TSDB_CODE_SUCCESS) ? (int32_t)pRes->numOfRows : pRes->code;
     (*pSql->fp)(pSql->param, pSql, rpcMsg->code);
   }
 
   void** p1 = p;
-  taosCacheRelease(tscObjCache, (void**) &p, false);
+  taosCacheRelease(tscObjCache, (void**) &p1, false);
 
-  if (shouldFree) {
-    taosCacheRelease(tscObjCache, (void **)&p1, true);
+  if (shouldFree) { // in case of table-meta/vgrouplist query, automatically free it
+    taosCacheRelease(tscObjCache, (void **)&p, true);
     tscDebug("%p sqlObj is automatically freed", pSql);
   }
 
@@ -1718,7 +1718,7 @@ int tscProcessTableMetaRsp(SSqlObj *pSql) {
   STableMetaInfo *pTableMetaInfo = tscGetTableMetaInfoFromCmd(&pSql->cmd, 0, 0);
   assert(pTableMetaInfo->pTableMeta == NULL);
 
-  pTableMetaInfo->pTableMeta = (STableMeta *) taosCachePut(tscCacheHandle, pTableMetaInfo->name,
+  pTableMetaInfo->pTableMeta = (STableMeta *) taosCachePut(tscMetaCache, pTableMetaInfo->name,
       strlen(pTableMetaInfo->name), pTableMeta, size, tsTableMetaKeepTimer * 1000);
   
   // todo handle out of memory case
@@ -1830,7 +1830,7 @@ int tscProcessMultiMeterMetaRsp(SSqlObj *pSql) {
     //    int32_t size = (int32_t)(rsp - ((char *)pMeta));  // Consistent with STableMeta in cache
     //
     //    pMeta->index = 0;
-    //    (void)taosCachePut(tscCacheHandle, pMeta->tableId, (char *)pMeta, size, tsTableMetaKeepTimer);
+    //    (void)taosCachePut(tscMetaCache, pMeta->tableId, (char *)pMeta, size, tsTableMetaKeepTimer);
     //  }
   }
   
@@ -1917,12 +1917,14 @@ int tscProcessShowRsp(SSqlObj *pSql) {
   key[0] = pCmd->msgType + 'a';
   strcpy(key + 1, "showlist");
 
-  taosCacheRelease(tscCacheHandle, (void *)&(pTableMetaInfo->pTableMeta), false);
-  
+  if (pTableMetaInfo->pTableMeta != NULL) {
+    taosCacheRelease(tscMetaCache, (void *)&(pTableMetaInfo->pTableMeta), false);
+  }
+
   size_t size = 0;
   STableMeta* pTableMeta = tscCreateTableMetaFromMsg(pMetaMsg, &size);
   
-  pTableMetaInfo->pTableMeta = taosCachePut(tscCacheHandle, key, strlen(key), (char *)pTableMeta, size,
+  pTableMetaInfo->pTableMeta = taosCachePut(tscMetaCache, key, strlen(key), (char *)pTableMeta, size,
       tsTableMetaKeepTimer * 1000);
   SSchema *pTableSchema = tscGetTableSchema(pTableMetaInfo->pTableMeta);
 
@@ -1981,6 +1983,8 @@ static void createHBObj(STscObj* pObj) {
   pSql->pTscObj = pObj;
   pSql->signature = pSql;
   pObj->pHb = pSql;
+  T_REF_INC(pObj);
+
   tscAddSubqueryInfo(&pObj->pHb->cmd);
 
   tscDebug("%p HB is allocated, pObj:%p", pObj->pHb, pObj);
@@ -2025,14 +2029,14 @@ int tscProcessUseDbRsp(SSqlObj *pSql) {
 
 int tscProcessDropDbRsp(SSqlObj *pSql) {
   pSql->pTscObj->db[0] = 0;
-  taosCacheEmpty(tscCacheHandle);
+  taosCacheEmpty(tscMetaCache);
   return 0;
 }
 
 int tscProcessDropTableRsp(SSqlObj *pSql) {
   STableMetaInfo *pTableMetaInfo = tscGetTableMetaInfoFromCmd(&pSql->cmd, 0, 0);
 
-  STableMeta *pTableMeta = taosCacheAcquireByKey(tscCacheHandle, pTableMetaInfo->name, strlen(pTableMetaInfo->name));
+  STableMeta *pTableMeta = taosCacheAcquireByKey(tscMetaCache, pTableMetaInfo->name, strlen(pTableMetaInfo->name));
   if (pTableMeta == NULL) { /* not in cache, abort */
     return 0;
   }
@@ -2045,10 +2049,10 @@ int tscProcessDropTableRsp(SSqlObj *pSql) {
    * instead.
    */
   tscDebug("%p force release table meta after drop table:%s", pSql, pTableMetaInfo->name);
-  taosCacheRelease(tscCacheHandle, (void **)&pTableMeta, true);
+  taosCacheRelease(tscMetaCache, (void **)&pTableMeta, true);
 
   if (pTableMetaInfo->pTableMeta) {
-    taosCacheRelease(tscCacheHandle, (void **)&(pTableMetaInfo->pTableMeta), true);
+    taosCacheRelease(tscMetaCache, (void **)&(pTableMetaInfo->pTableMeta), true);
   }
 
   return 0;
@@ -2057,21 +2061,21 @@ int tscProcessDropTableRsp(SSqlObj *pSql) {
 int tscProcessAlterTableMsgRsp(SSqlObj *pSql) {
   STableMetaInfo *pTableMetaInfo = tscGetTableMetaInfoFromCmd(&pSql->cmd, 0, 0);
 
-  STableMeta *pTableMeta = taosCacheAcquireByKey(tscCacheHandle, pTableMetaInfo->name, strlen(pTableMetaInfo->name));
+  STableMeta *pTableMeta = taosCacheAcquireByKey(tscMetaCache, pTableMetaInfo->name, strlen(pTableMetaInfo->name));
   if (pTableMeta == NULL) { /* not in cache, abort */
     return 0;
   }
 
   tscDebug("%p force release metermeta in cache after alter-table: %s", pSql, pTableMetaInfo->name);
-  taosCacheRelease(tscCacheHandle, (void **)&pTableMeta, true);
+  taosCacheRelease(tscMetaCache, (void **)&pTableMeta, true);
 
   if (pTableMetaInfo->pTableMeta) {
     bool isSuperTable = UTIL_TABLE_IS_SUPER_TABLE(pTableMetaInfo);
-    taosCacheRelease(tscCacheHandle, (void **)&(pTableMetaInfo->pTableMeta), true);
+    taosCacheRelease(tscMetaCache, (void **)&(pTableMetaInfo->pTableMeta), true);
 
     if (isSuperTable) {  // if it is a super table, reset whole query cache
       tscDebug("%p reset query cache since table:%s is stable", pSql, pTableMetaInfo->name);
-      taosCacheEmpty(tscCacheHandle);
+      taosCacheEmpty(tscMetaCache);
     }
   }
 
@@ -2156,6 +2160,12 @@ static int32_t getTableMetaFromMgmt(SSqlObj *pSql, STableMetaInfo *pTableMetaInf
   pNew->signature = pNew;
   pNew->cmd.command = TSDB_SQL_META;
 
+  T_REF_INC(pNew->pTscObj);
+
+  // TODO add test case on x86 platform
+  uint64_t adr = (uint64_t) pNew;
+  pNew->self = taosCachePut(tscObjCache, &adr, sizeof(uint64_t), &pNew, sizeof(uint64_t), 2*60*1000);
+
   tscAddSubqueryInfo(&pNew->cmd);
 
   SQueryInfo *pNewQueryInfo = tscGetQueryInfoDetailSafely(&pNew->cmd, 0);
@@ -2179,10 +2189,6 @@ static int32_t getTableMetaFromMgmt(SSqlObj *pSql, STableMetaInfo *pTableMetaInf
   pNew->fp = tscTableMetaCallBack;
   pNew->param = pSql;
 
-  // TODO add test case on x86 platform
-  uint64_t adr = (uint64_t) pNew;
-  pNew->self = taosCachePut(tscObjCache, &adr, sizeof(uint64_t), &pNew, sizeof(uint64_t), 2*60*1000);
-
   int32_t code = tscProcessSql(pNew);
   if (code == TSDB_CODE_SUCCESS) {
     code = TSDB_CODE_TSC_ACTION_IN_PROGRESS;  // notify upper application that current process need to be terminated
@@ -2196,10 +2202,10 @@ int32_t tscGetTableMeta(SSqlObj *pSql, STableMetaInfo *pTableMetaInfo) {
 
   // If this STableMetaInfo owns a table meta, release it first
   if (pTableMetaInfo->pTableMeta != NULL) {
-    taosCacheRelease(tscCacheHandle, (void **)&(pTableMetaInfo->pTableMeta), false);
+    taosCacheRelease(tscMetaCache, (void **)&(pTableMetaInfo->pTableMeta), false);
   }
   
-  pTableMetaInfo->pTableMeta = (STableMeta *)taosCacheAcquireByKey(tscCacheHandle, pTableMetaInfo->name, strlen(pTableMetaInfo->name));
+  pTableMetaInfo->pTableMeta = (STableMeta *)taosCacheAcquireByKey(tscMetaCache, pTableMetaInfo->name, strlen(pTableMetaInfo->name));
   if (pTableMetaInfo->pTableMeta != NULL) {
     STableComInfo tinfo = tscGetTableInfo(pTableMetaInfo->pTableMeta);
     tscDebug("%p retrieve table Meta from cache, the number of columns:%d, numOfTags:%d, %p", pSql, tinfo.numOfColumns,
@@ -2234,7 +2240,7 @@ int tscRenewTableMeta(SSqlObj *pSql, int32_t tableIndex) {
              tscGetNumOfTags(pTableMeta), tscGetNumOfColumns(pTableMeta), pTableMeta->id.uid, pTableMeta);
   }
 
-  taosCacheRelease(tscCacheHandle, (void **)&(pTableMetaInfo->pTableMeta), true);
+  taosCacheRelease(tscMetaCache, (void **)&(pTableMetaInfo->pTableMeta), true);
   return getTableMetaFromMgmt(pSql, pTableMetaInfo);
 }
 
@@ -2264,7 +2270,8 @@ int tscGetSTableVgroupInfo(SSqlObj *pSql, int32_t clauseIndex) {
   pNew->signature = pNew;
 
   pNew->cmd.command = TSDB_SQL_STABLEVGROUP;
-  
+
+  // TODO TEST IT
   SQueryInfo *pNewQueryInfo = tscGetQueryInfoDetailSafely(&pNew->cmd, 0);
   if (pNewQueryInfo == NULL) {
     tscFreeSqlObj(pNew);
@@ -2274,7 +2281,7 @@ int tscGetSTableVgroupInfo(SSqlObj *pSql, int32_t clauseIndex) {
   SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, clauseIndex);
   for (int32_t i = 0; i < pQueryInfo->numOfTables; ++i) {
     STableMetaInfo *pMInfo = tscGetMetaInfo(pQueryInfo, i);
-    STableMeta *pTableMeta = taosCacheAcquireByData(tscCacheHandle, pMInfo->pTableMeta);
+    STableMeta *pTableMeta = taosCacheAcquireByData(tscMetaCache, pMInfo->pTableMeta);
     tscAddTableMetaInfo(pNewQueryInfo, pMInfo->name, pTableMeta, NULL, pMInfo->tagColList);
   }
 
@@ -2284,6 +2291,7 @@ int tscGetSTableVgroupInfo(SSqlObj *pSql, int32_t clauseIndex) {
   }
 
   pNewQueryInfo->numOfTables = pQueryInfo->numOfTables;
+  T_REF_INC(pNew->pTscObj);
 
   uint64_t p = (uint64_t) pNew;
   pNew->self = taosCachePut(tscObjCache, &p, sizeof(uint64_t), &pNew, sizeof(uint64_t), 2 * 600 * 1000);
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index 58859e944cc7e367da9ed924d8755d15b9a8c2bb..025f0a2b142486eb9cccde32cba6ec8dba2edadd 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -102,6 +102,7 @@ SSqlObj *taosConnectImpl(const char *ip, const char *user, const char *pass, con
 
   pObj->signature = pObj;
   pObj->pDnodeConn = pDnodeConn;
+  T_REF_INIT_VAL(pObj, 1);
 
   tstrncpy(pObj->user, user, sizeof(pObj->user));
   secretEncryptLen = MIN(secretEncryptLen, sizeof(pObj->pass));
@@ -155,6 +156,8 @@ SSqlObj *taosConnectImpl(const char *ip, const char *user, const char *pass, con
     *taos = pObj;
   }
 
+  T_REF_INC(pSql->pTscObj);
+
   uint64_t key = (uint64_t) pSql;
   pSql->self = taosCachePut(tscObjCache, &key, sizeof(uint64_t), &pSql, sizeof(uint64_t), 2*3600*1000);
   tsInsertHeadSize = sizeof(SMsgDesc) + sizeof(SSubmitMsg);
@@ -261,6 +264,31 @@ void taos_close(TAOS *taos) {
     tscFreeSqlObj(pObj->pHb);
   }
 
+  // free all sqlObjs created by using this connect before free the STscObj
+  while(1) {
+    pthread_mutex_lock(&pObj->mutex);
+    void* p = pObj->sqlList;
+    pthread_mutex_unlock(&pObj->mutex);
+
+    if (p == NULL) {
+      break;
+    }
+
+    tscDebug("%p waiting for sqlObj to be freed, %p", pObj, p);
+    taosMsleep(100);
+
+    // todo fix me!! two threads call taos_free_result will cause problem.
+    tscDebug("%p free :%p", pObj, p);
+    taos_free_result(p);
+  }
+
+  int32_t ref = T_REF_DEC(pObj);
+  assert(ref >= 0);
+
+  if (ref > 0) {
+    return;
+  }
+
   tscCloseTscObj(pObj);
 }
 
@@ -537,7 +565,7 @@ int taos_select_db(TAOS *taos, const char *db) {
 }
 
 // send free message to vnode to free qhandle and corresponding resources in vnode
-static bool tscKillQueryInDnode(SSqlObj* pSql) {
+static UNUSED_FUNC bool tscKillQueryInDnode(SSqlObj* pSql) {
   SSqlCmd* pCmd = &pSql->cmd;
   SSqlRes* pRes = &pSql->res;
 
@@ -561,7 +589,7 @@ static bool tscKillQueryInDnode(SSqlObj* pSql) {
        cmd == TSDB_SQL_FETCH)) {
     pQueryInfo->type = TSDB_QUERY_TYPE_FREE_RESOURCE;
     pCmd->command = (pCmd->command > TSDB_SQL_MGMT) ? TSDB_SQL_RETRIEVE : TSDB_SQL_FETCH;
-    tscDebug("%p send msg to dnode to free qhandle ASAP before free sqlObj, command:%s, ", pSql, sqlCmd[pCmd->command]);
+    tscDebug("%p send msg to dnode to free qhandle ASAP before free sqlObj, command:%s", pSql, sqlCmd[pCmd->command]);
 
     tscProcessSql(pSql);
     return false;
@@ -577,45 +605,15 @@ void taos_free_result(TAOS_RES *res) {
     return;
   }
 
-  assert(pSql->self != 0 && *pSql->self == pSql);
+//  assert(pSql->self != 0 && *pSql->self == pSql);
 
   bool freeNow = tscKillQueryInDnode(pSql);
   if (freeNow) {
     tscDebug("%p free sqlObj in cache", pSql);
-    taosCacheRelease(tscObjCache, (void**) &pSql->self, true);
-  }
-}
-
-//static void doFreeResult(TAOS_RES *res) {
-//  SSqlObj *pSql = (SSqlObj *)res;
-//
-//  if (pSql == NULL || pSql->signature != pSql) {
-//    tscDebug("%p sqlObj has been freed", pSql);
-//    return;
-//  }
-//
-//  // The semaphore can not be changed while freeing async sub query objects.
-//  SSqlRes *pRes = &pSql->res;
-//  if (pRes == NULL || pRes->qhandle == 0) {
-//    tscFreeSqlObj(pSql);
-//    tscDebug("%p SqlObj is freed by app, qhandle is null", pSql);
-//    return;
-//  }
-//
-//  // set freeFlag to 1 in retrieve message if there are un-retrieved results data in node
-//  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
-//  if (pQueryInfo == NULL) {
-//    tscFreeSqlObj(pSql);
-//    tscDebug("%p SqlObj is freed by app", pSql);
-//    return;
-//  }
-//
-//  pQueryInfo->type = TSDB_QUERY_TYPE_FREE_RESOURCE;
-//  if (!tscKillQueryInDnode(pSql)) {
-//    tscFreeSqlObj(pSql);
-//    tscDebug("%p sqlObj is freed by app", pSql);
-//  }
-//}
+    SSqlObj** p = pSql->self;
+    taosCacheRelease(tscObjCache, (void**) &p, true);
+  }
+}
 
 int taos_errno(TAOS_RES *tres) {
   SSqlObj *pSql = (SSqlObj *) tres;
diff --git a/src/client/src/tscStream.c b/src/client/src/tscStream.c
index 79e00110932682d60cd6f4fe561fc4eb41cc18f1..71ba76dc6cb558453a92aa5c2d0df0905fa0a43a 100644
--- a/src/client/src/tscStream.c
+++ b/src/client/src/tscStream.c
@@ -167,7 +167,7 @@ static void tscProcessStreamQueryCallback(void *param, TAOS_RES *tres, int numOf
              retryDelay);
 
     STableMetaInfo* pTableMetaInfo = tscGetTableMetaInfoFromCmd(&pStream->pSql->cmd, 0, 0);
-    taosCacheRelease(tscCacheHandle, (void**)&(pTableMetaInfo->pTableMeta), true);
+    taosCacheRelease(tscMetaCache, (void**)&(pTableMetaInfo->pTableMeta), true);
     taosTFree(pTableMetaInfo->vgroupList);
   
     tscSetRetryTimer(pStream, pStream->pSql, retryDelay);
@@ -275,7 +275,7 @@ static void tscProcessStreamRetrieveResult(void *param, TAOS_RES *res, int numOf
 
     // release the metric/meter meta information reference, so data in cache can be updated
 
-    taosCacheRelease(tscCacheHandle, (void**)&(pTableMetaInfo->pTableMeta), false);
+    taosCacheRelease(tscMetaCache, (void**)&(pTableMetaInfo->pTableMeta), false);
     tscFreeSqlResult(pSql);
     taosTFree(pSql->pSubs);
     pSql->numOfSubs = 0;
diff --git a/src/client/src/tscSystem.c b/src/client/src/tscSystem.c
index 2c7fcf05c9fa586247b78a71a9715b93453f414d..82ce1d36791e2a5e79177ea1405bf90145f2776d 100644
--- a/src/client/src/tscSystem.c
+++ b/src/client/src/tscSystem.c
@@ -30,7 +30,7 @@
 #include "tlocale.h"
 
 // global, not configurable
-SCacheObj*  tscCacheHandle;
+SCacheObj*  tscMetaCache;
 SCacheObj*  tscObjCache;
 void *  tscTmr;
 void *  tscQhandle;
@@ -145,9 +145,9 @@ void taos_init_imp(void) {
   refreshTime = refreshTime > 10 ? 10 : refreshTime;
   refreshTime = refreshTime < 10 ? 10 : refreshTime;
 
-  if (tscCacheHandle == NULL) {
-    tscCacheHandle = taosCacheInit(TSDB_DATA_TYPE_BINARY, refreshTime, false, NULL, "tableMeta");
-    tscObjCache = taosCacheInit(TSDB_DATA_TYPE_BIGINT, refreshTime, false, tscFreeSqlObjInCache, "sqlObjHandle");
+  if (tscMetaCache == NULL) {
+    tscMetaCache = taosCacheInit(TSDB_DATA_TYPE_BINARY, refreshTime, false, NULL, "tableMeta");
+    tscObjCache = taosCacheInit(TSDB_DATA_TYPE_BIGINT, refreshTime/2, false, tscFreeSqlObjInCache, "sqlObj");
   }
 
   tscDebug("client is initialized successfully");
@@ -156,9 +156,9 @@ void taos_init_imp(void) {
 void taos_init() { pthread_once(&tscinit, taos_init_imp); }
 
 void taos_cleanup() {
-  if (tscCacheHandle != NULL) {
-    taosCacheCleanup(tscCacheHandle);
-    tscCacheHandle = NULL;
+  if (tscMetaCache != NULL) {
+    taosCacheCleanup(tscMetaCache);
+    tscMetaCache = NULL;
 
     taosCacheCleanup(tscObjCache);
     tscObjCache = NULL;
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index 7d4369816a9fcc604adb9427796550fbccf9db2b..7f2c1716a6f8f2a1457d3deaed30740d286a86be 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -344,8 +344,6 @@ void tscPartiallyFreeSqlObj(SSqlObj* pSql) {
   }
 
   SSqlCmd* pCmd = &pSql->cmd;
-  STscObj* pObj = pSql->pTscObj;
-
   int32_t cmd = pCmd->command;
   if (cmd < TSDB_SQL_INSERT || cmd == TSDB_SQL_RETRIEVE_LOCALMERGE || cmd == TSDB_SQL_RETRIEVE_EMPTY_RESULT ||
       cmd == TSDB_SQL_TABLE_JOIN_RETRIEVE) {
@@ -353,11 +351,11 @@ void tscPartiallyFreeSqlObj(SSqlObj* pSql) {
   }
   
   // pSql->sqlstr will be used by tscBuildQueryStreamDesc
-  if (pObj->signature == pObj) {
+//  if (pObj->signature == pObj) {
     //pthread_mutex_lock(&pObj->mutex);
     taosTFree(pSql->sqlstr);
     //pthread_mutex_unlock(&pObj->mutex);
-  }
+//  }
   
   tscFreeSqlResult(pSql);
   
@@ -384,42 +382,61 @@ static void tscFreeSubobj(SSqlObj* pSql) {
   pSql->numOfSubs = 0;
 }
 
+//static UNUSED_FUNC bool tscKillQueryInDnode(SSqlObj* pSql) {
+//  SSqlCmd* pCmd = &pSql->cmd;
+//  SSqlRes* pRes = &pSql->res;
+//
+//  if (pRes == NULL || pRes->qhandle == 0) {
+//    return true;
+//  }
+//
+//  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+//  if ((pQueryInfo == NULL) || tscIsTwoStageSTableQuery(pQueryInfo, 0)) {
+//    return true;
+//  }
+//
+//  STableMetaInfo *pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
+//  tscRemoveFromSqlList(pSql);
+//
+//  int32_t cmd = pCmd->command;
+//  if (pRes->code == TSDB_CODE_SUCCESS && pRes->completed == false && pSql->pStream == NULL && (pTableMetaInfo->pTableMeta != NULL) &&
+//      (cmd == TSDB_SQL_SELECT ||
+//       cmd == TSDB_SQL_SHOW ||
+//       cmd == TSDB_SQL_RETRIEVE ||
+//       cmd == TSDB_SQL_FETCH)) {
+//    pQueryInfo->type = TSDB_QUERY_TYPE_FREE_RESOURCE;
+//    pCmd->command = (pCmd->command > TSDB_SQL_MGMT) ? TSDB_SQL_RETRIEVE : TSDB_SQL_FETCH;
+//    tscDebug("%p send msg to dnode to free qhandle ASAP before free sqlObj, command:%s, ", pSql, sqlCmd[pCmd->command]);
+//
+//    tscProcessSql(pSql);
+//    return false;
+//  }
+//
+//  return true;
+//}
+
+/**
+ * The free operation will cause the pSql to be removed from hash table and free it in
+ * the function of processmsgfromserver is impossible in this case, since it will fail
+ * to retrieve pSqlObj in hashtable.
+ *
+ * @param pSql
+ */
 void tscFreeSqlObjInCache(void *pSql) {
   assert(pSql != NULL);
-  SSqlObj** p = (SSqlObj**) pSql;
+  SSqlObj** p = (SSqlObj**)pSql;
 
+  assert((*p)->self != 0 && (*p)->self == (p));
   tscFreeSqlObj(*p);
 }
 
-static UNUSED_FUNC bool tscKillQueryInDnode(SSqlObj* pSql) {
-  SSqlCmd* pCmd = &pSql->cmd;
-  SSqlRes* pRes = &pSql->res;
-
-  SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
-  STableMetaInfo *pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
-
-  if (tscIsTwoStageSTableQuery(pQueryInfo, 0)) {
-    return false;
-  }
-
-  int32_t cmd = pCmd->command;
-  if (pRes->code == TSDB_CODE_SUCCESS && pRes->completed == false && pSql->pStream == NULL && (pTableMetaInfo->pTableMeta != NULL) &&
-      (cmd == TSDB_SQL_SELECT || cmd == TSDB_SQL_SHOW || cmd == TSDB_SQL_RETRIEVE || cmd == TSDB_SQL_FETCH)) {
-    pCmd->command = (pCmd->command > TSDB_SQL_MGMT) ? TSDB_SQL_RETRIEVE : TSDB_SQL_FETCH;
-    tscDebug("%p send msg to dnode to free qhandle ASAP, command:%s, ", pSql, sqlCmd[pCmd->command]);
-    tscProcessSql(pSql);
-    return true;
-  }
-
-  return false;
-}
-
 void tscFreeSqlObj(SSqlObj* pSql) {
   if (pSql == NULL || pSql->signature != pSql) {
     return;
   }
 
   tscDebug("%p start to free sqlObj", pSql);
+  STscObj* pTscObj = pSql->pTscObj;
 
   tscFreeSubobj(pSql);
   tscPartiallyFreeSqlObj(pSql);
@@ -438,6 +455,13 @@ void tscFreeSqlObj(SSqlObj* pSql) {
 
   free(pSql);
   tscDebug("%p free sqlObj completed", pSql);
+
+  int32_t ref = T_REF_DEC(pTscObj);
+  assert(ref >= 0);
+
+  if (ref == 0) {
+    tscCloseTscObj(pTscObj);
+  }
 }
 
 void tscDestroyDataBlock(STableDataBlocks* pDataBlock) {
@@ -450,7 +474,7 @@ void tscDestroyDataBlock(STableDataBlocks* pDataBlock) {
 
   // free the refcount for metermeta
   if (pDataBlock->pTableMeta != NULL) {
-    taosCacheRelease(tscCacheHandle, (void**)&(pDataBlock->pTableMeta), false);
+    taosCacheRelease(tscMetaCache, (void**)&(pDataBlock->pTableMeta), false);
   }
 
   taosTFree(pDataBlock);
@@ -509,10 +533,10 @@ int32_t tscCopyDataBlockToPayload(SSqlObj* pSql, STableDataBlocks* pDataBlock) {
     tstrncpy(pTableMetaInfo->name, pDataBlock->tableId, sizeof(pTableMetaInfo->name));
 
     if (pTableMetaInfo->pTableMeta != NULL) {
-      taosCacheRelease(tscCacheHandle, (void**)&(pTableMetaInfo->pTableMeta), false);
+      taosCacheRelease(tscMetaCache, (void**)&(pTableMetaInfo->pTableMeta), false);
     }
 
-    pTableMetaInfo->pTableMeta = taosCacheTransfer(tscCacheHandle, (void**)&pDataBlock->pTableMeta);
+    pTableMetaInfo->pTableMeta = taosCacheTransfer(tscMetaCache, (void**)&pDataBlock->pTableMeta);
   } else {
     assert(strncmp(pTableMetaInfo->name, pDataBlock->tableId, tListLen(pDataBlock->tableId)) == 0);
   }
@@ -583,7 +607,7 @@ int32_t tscCreateDataBlock(size_t initialSize, int32_t rowSize, int32_t startOff
    * due to operation such as drop database. So here we add the reference count directly instead of invoke
    * taosGetDataFromCache, which may return NULL value.
    */
-  dataBuf->pTableMeta = taosCacheAcquireByData(tscCacheHandle, pTableMeta);
+  dataBuf->pTableMeta = taosCacheAcquireByData(tscMetaCache, pTableMeta);
   assert(initialSize > 0 && pTableMeta != NULL && dataBuf->pTableMeta != NULL);
 
   *dataBlocks = dataBuf;
@@ -777,28 +801,10 @@ int32_t tscMergeTableDataBlocks(SSqlObj* pSql, SArray* pTableDataBlockList) {
 // TODO: all subqueries should be freed correctly before close this connection.
 void tscCloseTscObj(STscObj* pObj) {
   assert(pObj != NULL);
-  
+
   pObj->signature = NULL;
   taosTmrStopA(&(pObj->pTimer));
 
-  // wait for all sqlObjs created according to this connect closed
-  while(1) {
-    pthread_mutex_lock(&pObj->mutex);
-    void* p = pObj->sqlList;
-    pthread_mutex_unlock(&pObj->mutex);
-
-    if (p == NULL) {
-      break;
-    }
-
-    tscDebug("%p waiting for sqlObj to be freed, %p", pObj, p);
-    taosMsleep(100);
-
-    // todo fix me!! two threads call taos_free_result will cause problem.
-    tscDebug("%p free :%p", pObj, p);
-    taos_free_result(p);
-  }
-
   if (pObj->pDnodeConn != NULL) {
     rpcClose(pObj->pDnodeConn);
     pObj->pDnodeConn = NULL;
@@ -1743,7 +1749,7 @@ void tscClearTableMetaInfo(STableMetaInfo* pTableMetaInfo, bool removeFromCache)
   }
 
   if (pTableMetaInfo->pTableMeta != NULL) {
-    taosCacheRelease(tscCacheHandle, (void**)&(pTableMetaInfo->pTableMeta), removeFromCache);
+    taosCacheRelease(tscMetaCache, (void**)&(pTableMetaInfo->pTableMeta), removeFromCache);
   }
 
   taosTFree(pTableMetaInfo->vgroupList);
@@ -1769,6 +1775,8 @@ SSqlObj* createSimpleSubObj(SSqlObj* pSql, void (*fp)(), void* param, int32_t cm
   }
 
   pNew->pTscObj = pSql->pTscObj;
+  T_REF_INC(pNew->pTscObj);
+
   pNew->signature = pNew;
 
   SSqlCmd* pCmd = &pNew->cmd;
@@ -1800,6 +1808,8 @@ SSqlObj* createSimpleSubObj(SSqlObj* pSql, void (*fp)(), void* param, int32_t cm
 
   tscAddTableMetaInfo(pQueryInfo, pMasterTableMetaInfo->name, NULL, NULL, NULL);
 
+  T_REF_INC(pNew->pTscObj);
+
   uint64_t p = (uint64_t) pNew;
   pNew->self = taosCachePut(tscObjCache, &p, sizeof(uint64_t), &pNew, sizeof(uint64_t), 2 * 600 * 1000);
   return pNew;
@@ -1890,6 +1900,7 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
 
   pNew->pTscObj = pSql->pTscObj;
   pNew->signature = pNew;
+  T_REF_INC(pNew->pTscObj);
 
   pNew->sqlstr = strdup(pSql->sqlstr);
   if (pNew->sqlstr == NULL) {
@@ -1994,14 +2005,14 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
   STableMetaInfo* pFinalInfo = NULL;
 
   if (pPrevSql == NULL) {
-    STableMeta* pTableMeta = taosCacheAcquireByData(tscCacheHandle, pTableMetaInfo->pTableMeta);  // get by name may failed due to the cache cleanup
+    STableMeta* pTableMeta = taosCacheAcquireByData(tscMetaCache, pTableMetaInfo->pTableMeta);  // get by name may failed due to the cache cleanup
     assert(pTableMeta != NULL);
 
     pFinalInfo = tscAddTableMetaInfo(pNewQueryInfo, name, pTableMeta, pTableMetaInfo->vgroupList, pTableMetaInfo->tagColList);
   } else {  // transfer the ownership of pTableMeta to the newly create sql object.
     STableMetaInfo* pPrevInfo = tscGetTableMetaInfoFromCmd(&pPrevSql->cmd, pPrevSql->cmd.clauseIndex, 0);
 
-    STableMeta*  pPrevTableMeta = taosCacheTransfer(tscCacheHandle, (void**)&pPrevInfo->pTableMeta);
+    STableMeta*  pPrevTableMeta = taosCacheTransfer(tscMetaCache, (void**)&pPrevInfo->pTableMeta);
     
     SVgroupsInfo* pVgroupsInfo = pPrevInfo->vgroupList;
     pFinalInfo = tscAddTableMetaInfo(pNewQueryInfo, name, pPrevTableMeta, pVgroupsInfo, pTableMetaInfo->tagColList);
@@ -2041,6 +2052,8 @@ SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void
     tscDebug("%p new sub insertion: %p, vnodeIdx:%d", pSql, pNew, pTableMetaInfo->vgroupIndex);
   }
 
+  T_REF_INC(pNew->pTscObj);
+
   uint64_t p = (uint64_t) pNew;
   pNew->self = taosCachePut(tscObjCache, &p, sizeof(uint64_t), &pNew, sizeof(uint64_t), 2 * 600 * 10);
   return pNew;
@@ -2154,6 +2167,7 @@ int32_t tscSQLSyntaxErrMsg(char* msg, const char* additionalInfo,  const char* s
   return TSDB_CODE_TSC_SQL_SYNTAX_ERROR;
   
 }
+
 int32_t tscInvalidSQLErrMsg(char* msg, const char* additionalInfo, const char* sql) {
   const char* msgFormat1 = "invalid SQL: %s";
   const char* msgFormat2 = "invalid SQL: \'%s\' (%s)";
diff --git a/src/util/src/tcache.c b/src/util/src/tcache.c
index 7fda057483c2ad700083700b5f4b523089610114..4d737ebe66f1e82614d4eb71c1d93129949c5c4e 100644
--- a/src/util/src/tcache.c
+++ b/src/util/src/tcache.c
@@ -71,7 +71,7 @@ static SCacheDataNode *taosCreateCacheNode(const char *key, size_t keyLen, const
  * @param pCacheObj    Cache object
  * @param pNode   Cache slot object
  */
-static void taosAddToTrash(SCacheObj *pCacheObj, SCacheDataNode *pNode);
+static void taosAddToTrashcan(SCacheObj *pCacheObj, SCacheDataNode *pNode);
 
 /**
  * remove nodes in trash with refCount == 0 in cache
@@ -80,7 +80,7 @@ static void taosAddToTrash(SCacheObj *pCacheObj, SCacheDataNode *pNode);
  * @param force   force model, if true, remove data in trash without check refcount.
  *                may cause corruption. So, forece model only applys before cache is closed
  */
-static void taosTrashCanEmpty(SCacheObj *pCacheObj, bool force);
+static void taosTrashcanEmpty(SCacheObj *pCacheObj, bool force);
 
 /**
  * release node
@@ -222,7 +222,7 @@ void *taosCachePut(SCacheObj *pCacheObj, const void *key, size_t keyLen, const v
 
           taosTFree(p);
         } else {
-          taosAddToTrash(pCacheObj, p);
+          taosAddToTrashcan(pCacheObj, p);
           uDebug("cache:%s, key:%p, %p exist in cache, updated old:%p", pCacheObj->name, key, pNode1->data, p->data);
         }
       }
@@ -322,11 +322,11 @@ void *taosCacheTransfer(SCacheObj *pCacheObj, void **data) {
 }
 
 void taosCacheRelease(SCacheObj *pCacheObj, void **data, bool _remove) {
-  if (taosHashGetSize(pCacheObj->pHashTable) + pCacheObj->numOfElemsInTrash == 0) {
+  if (pCacheObj == NULL || taosHashGetSize(pCacheObj->pHashTable) + pCacheObj->numOfElemsInTrash == 0) {
     return;
   }
 
-  if (pCacheObj == NULL || (*data) == NULL) {
+  if ((*data) == NULL) {
     uError("cache:%s, NULL data to release", pCacheObj->name);
     return;
   }
@@ -399,19 +399,19 @@ void taosCacheRelease(SCacheObj *pCacheObj, void **data, bool _remove) {
               "others already", pCacheObj->name, pNode->key, p->data, T_REF_VAL_GET(p), pNode->data);
 
           assert(p->pTNodeHeader == NULL);
-          taosAddToTrash(pCacheObj, p);
+          taosAddToTrashcan(pCacheObj, p);
         } else {
           uDebug("cache:%s, key:%p, %p successfully removed from hash table, refcnt:%d", pCacheObj->name, pNode->key,
                  pNode->data, ref);
           if (ref > 0) {
             assert(pNode->pTNodeHeader == NULL);
 
-            taosAddToTrash(pCacheObj, pNode);
+            taosAddToTrashcan(pCacheObj, pNode);
           } else {  // ref == 0
             atomic_sub_fetch_64(&pCacheObj->totalSize, pNode->size);
 
             int32_t size = (int32_t)taosHashGetSize(pCacheObj->pHashTable);
-            uDebug("cache:%s, key:%p, %p is destroyed from cache, size:%dbytes, num:%d size:%" PRId64 "bytes",
+            uDebug("cache:%s, key:%p, %p is destroyed from cache, size:%dbytes, totalNum:%d size:%" PRId64 "bytes",
                    pCacheObj->name, pNode->key, pNode->data, pNode->size, size, pCacheObj->totalSize);
 
             if (pCacheObj->freeFp) {
@@ -432,6 +432,26 @@ void taosCacheRelease(SCacheObj *pCacheObj, void **data, bool _remove) {
     char* key = pNode->key;
     char* p = pNode->data;
 
+//    int32_t ref = T_REF_VAL_GET(pNode);
+//
+//    if (ref == 1 && inTrashcan) {
+//      // If it is the last ref, remove it from trashcan linked-list first, and then destroy it.Otherwise, it may be
+//      // destroyed by refresh worker if decrease ref count before removing it from linked-list.
+//      assert(pNode->pTNodeHeader->pData == pNode);
+//
+//      __cache_wr_lock(pCacheObj);
+//      doRemoveElemInTrashcan(pCacheObj, pNode->pTNodeHeader);
+//      __cache_unlock(pCacheObj);
+//
+//      ref = T_REF_DEC(pNode);
+//      assert(ref == 0);
+//
+//      doDestroyTrashcanElem(pCacheObj, pNode->pTNodeHeader);
+//    } else {
+//      ref = T_REF_DEC(pNode);
+//      assert(ref >= 0);
+//    }
+
     int32_t ref = T_REF_DEC(pNode);
     uDebug("cache:%s, key:%p, %p released, refcnt:%d, data in trashcan:%d", pCacheObj->name, key, p, ref, inTrashcan);
   }
@@ -452,7 +472,7 @@ static bool travHashTableEmptyFn(void* param, void* data) {
   if (T_REF_VAL_GET(pNode) == 0) {
     taosCacheReleaseNode(pCacheObj, pNode);
   } else { // do add to trashcan
-    taosAddToTrash(pCacheObj, pNode);
+    taosAddToTrashcan(pCacheObj, pNode);
   }
 
   // this node should be remove from hash table
@@ -463,7 +483,7 @@ void taosCacheEmpty(SCacheObj *pCacheObj) {
   SHashTravSupp sup = {.pCacheObj = pCacheObj, .fp = NULL, .time = taosGetTimestampMs()};
 
   taosHashCondTraverse(pCacheObj->pHashTable, travHashTableEmptyFn, &sup);
-  taosTrashCanEmpty(pCacheObj, false);
+  taosTrashcanEmpty(pCacheObj, false);
 }
 
 void taosCacheCleanup(SCacheObj *pCacheObj) {
@@ -503,7 +523,7 @@ SCacheDataNode *taosCreateCacheNode(const char *key, size_t keyLen, const char *
   return pNewNode;
 }
 
-void taosAddToTrash(SCacheObj *pCacheObj, SCacheDataNode *pNode) {
+void taosAddToTrashcan(SCacheObj *pCacheObj, SCacheDataNode *pNode) {
   if (pNode->inTrashcan) { /* node is already in trash */
     assert(pNode->pTNodeHeader != NULL && pNode->pTNodeHeader->pData == pNode);
     return;
@@ -525,11 +545,11 @@ void taosAddToTrash(SCacheObj *pCacheObj, SCacheDataNode *pNode) {
   pCacheObj->numOfElemsInTrash++;
   __cache_unlock(pCacheObj);
 
-  uDebug("cache:%s key:%p, %p move to trash, numOfElem in trash:%d", pCacheObj->name, pNode->key, pNode->data,
+  uDebug("cache:%s key:%p, %p move to trashcan, numOfElem in trashcan:%d", pCacheObj->name, pNode->key, pNode->data,
       pCacheObj->numOfElemsInTrash);
 }
 
-void taosTrashCanEmpty(SCacheObj *pCacheObj, bool force) {
+void taosTrashcanEmpty(SCacheObj *pCacheObj, bool force) {
   __cache_wr_lock(pCacheObj);
 
   if (pCacheObj->numOfElemsInTrash == 0) {
@@ -573,7 +593,7 @@ void doCleanupDataCache(SCacheObj *pCacheObj) {
 
   // todo memory leak if there are object with refcount greater than 0 in hash table?
   taosHashCleanup(pCacheObj->pHashTable);
-  taosTrashCanEmpty(pCacheObj, true);
+  taosTrashcanEmpty(pCacheObj, true);
 
   __cache_lock_destroy(pCacheObj);
   
@@ -648,7 +668,7 @@ void* taosCacheTimedRefresh(void *handle) {
       doCacheRefresh(pCacheObj, now, NULL);
     }
 
-    taosTrashCanEmpty(pCacheObj, false);
+    taosTrashcanEmpty(pCacheObj, false);
   }
 
   return NULL;