diff --git a/documentation20/webdocs/markdowndocs/TAOS SQL-ch.md b/documentation20/webdocs/markdowndocs/TAOS SQL-ch.md
index e0acaee137eb8f4d65e95ae97be7bbc8988cb122..66d17c6aa686a7ed07ff1b865000f7b4a43f3834 100644
--- a/documentation20/webdocs/markdowndocs/TAOS SQL-ch.md	
+++ b/documentation20/webdocs/markdowndocs/TAOS SQL-ch.md	
@@ -98,12 +98,12 @@ TDengine缺省的时间戳是毫秒精度，但通过修改配置参数enableMic
     KEEP参数是指修改数据文件保存的天数，缺省值为3650，取值范围[days, 365000]，必须大于或等于days参数值。
 
     ```mysql
-    ALTER DATABASE db_name QUORUM 365;
+    ALTER DATABASE db_name QUORUM 2;
     ```
     QUORUM参数是指数据写入成功所需要的确认数。取值范围[1, 3]。对于异步复制，quorum设为1，具有master角色的虚拟节点自己确认即可。对于同步复制，需要至少大于等于2。原则上，Quorum >=1 并且 Quorum <= replica(副本数)，这个参数在启动一个同步模块实例时需要提供。
 
     ```mysql
-    ALTER DATABASE db_name BLOCKS 365;
+    ALTER DATABASE db_name BLOCKS 100;
     ```
     BLOCKS参数是每个VNODE (TSDB) 中有多少cache大小的内存块，因此一个VNODE的用的内存大小粗略为（cache * blocks）。取值范围[3, 1000]。
 
diff --git a/src/client/inc/tscUtil.h b/src/client/inc/tscUtil.h
index 79a792ab65a5327d68f3e75da4ee0610d1f7a6fd..0323434a992ae25b9f3fe54fb596b56e865bdf55 100644
--- a/src/client/inc/tscUtil.h
+++ b/src/client/inc/tscUtil.h
@@ -258,6 +258,8 @@ void tscDoQuery(SSqlObj* pSql);
  */
 SSqlObj* createSimpleSubObj(SSqlObj* pSql, void (*fp)(), void* param, int32_t cmd);
 
+void registerSqlObj(SSqlObj* pSql);
+
 SSqlObj* createSubqueryObj(SSqlObj* pSql, int16_t tableIndex, void (*fp)(), void* param, int32_t cmd, SSqlObj* pPrevSql);
 void     addGroupInfoForSubquery(SSqlObj* pParentObj, SSqlObj* pSql, int32_t subClauseIndex, int32_t tableIndex);
 
diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 55ca02dfb5d67ea150fc0725191fdc570a6c28c8..ea42b0f6a339c241aefd9c16da30a6b98d3ca09b 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -89,7 +89,7 @@ typedef struct STableComInfo {
 
 typedef struct SCMCorVgroupInfo {
   int32_t version;
-  int8_t inUse;
+  int8_t  inUse;
   int8_t  numOfEps;
   SEpAddr epAddr[TSDB_MAX_REPLICA];
 } SCMCorVgroupInfo;
@@ -107,7 +107,7 @@ typedef struct STableMeta {
 } STableMeta;
 
 typedef struct STableMetaInfo {
-  STableMeta *  pTableMeta;      // table meta, cached in client side and acquired by name
+  STableMeta   *pTableMeta;      // table meta, cached in client side and acquired by name
   SVgroupsInfo *vgroupList;
   SArray       *pVgroupTables;   // SArray<SVgroupTableInfo>
   
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index 09610575f619be3f02059b6e6ca1ba2c56edcb62..c5d622e2452d42e6863a294ce83fb850d21c5818 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -51,10 +51,7 @@ 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);
+  registerSqlObj(pSql);
 
   pSql->sqlstr = calloc(1, sqlLen + 1);
   if (pSql->sqlstr == NULL) {
diff --git a/src/client/src/tscPrepare.c b/src/client/src/tscPrepare.c
index c4ca6793ff14a86039738ffce1ffc04dfcc42aec..cdbd8685df55d74836b2bcc768e52bf22b972d72 100644
--- a/src/client/src/tscPrepare.c
+++ b/src/client/src/tscPrepare.c
@@ -545,10 +545,8 @@ int taos_stmt_prepare(TAOS_STMT* stmt, const char* sql, unsigned long length) {
     
     pSql->cmd.numOfParams = 0;
     pSql->cmd.batchSize   = 0;
-    
-    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);
+
+    registerSqlObj(pSql);
 
     int32_t code = tsParseSql(pSql, true);
     if (code == TSDB_CODE_TSC_ACTION_IN_PROGRESS) {
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index b9d4cc13d1692a9cb349ea348ca6596e3053c71f..f690d13164bb82749ec7ce9f6229376bfb3f61ac 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -820,20 +820,20 @@ int32_t tscSetTableFullName(STableMetaInfo* pTableMetaInfo, SStrToken* pzTableNa
   if (hasSpecifyDB(pzTableName)) {
     // db has been specified in sql string so we ignore current db path
     code = setObjFullName(pTableMetaInfo->name, getAccountId(pSql), NULL, pzTableName, NULL);
-    if (code != 0) {
+    if (code != TSDB_CODE_SUCCESS) {
       invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
     }
   } else {  // get current DB name first, then set it into path
     SStrToken t = {0};
     getCurrentDBName(pSql, &t);
     if (t.n == 0) {
-      invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg2);
-    }
-
-    code = setObjFullName(pTableMetaInfo->name, NULL, &t, pzTableName, NULL);
-    if (code != 0) {
-      invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
-    }
+      code = invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg2);
+    } else {
+      code = setObjFullName(pTableMetaInfo->name, NULL, &t, pzTableName, NULL);
+      if (code != TSDB_CODE_SUCCESS) {
+        code = invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
+      }
+    } 
   }
 
   if (code != TSDB_CODE_SUCCESS) {
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index 8eaa406bce95a4831a80366e62b34efea0cc2a5a..3cbb0d936e23bb5e90773f1cb2b0e32159de938c 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -128,6 +128,7 @@ static void tscUpdateVgroupInfo(SSqlObj *pObj, SRpcEpSet *pEpSet) {
   tscDebug("after: EndPoint in use: %d", pVgroupInfo->inUse);
   taosCorEndWrite(&pVgroupInfo->version);
 }
+
 void tscPrintMgmtEp() {
   SRpcEpSet dump;
   tscDumpMgmtEpSet(&dump);
@@ -745,7 +746,6 @@ int tscBuildQueryMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
     SSqlExpr *pExpr = tscSqlExprGet(pQueryInfo, i);
 
     if (!tscValidateColumnId(pTableMetaInfo, pExpr->colInfo.colId, pExpr->numOfParams)) {
-      /* column id is not valid according to the cached table meta, the table meta is expired */
       tscError("%p table schema is not matched with parsed sql", pSql);
       return TSDB_CODE_TSC_INVALID_SQL;
     }
@@ -1987,15 +1987,11 @@ static void createHBObj(STscObj* pObj) {
   pSql->param = pObj;
   pSql->pTscObj = pObj;
   pSql->signature = pSql;
-  pObj->pHb = pSql;
-
-  tscAddSubqueryInfo(&pObj->pHb->cmd);
 
-  int64_t ad = (int64_t) pSql;
-  pSql->self = taosCachePut(tscObjCache, &ad, sizeof(int64_t), &pSql, sizeof(int64_t), 2 * 60 * 1000);
-  T_REF_INC(pObj);
+  registerSqlObj(pSql);
+  tscDebug("%p HB is allocated, pObj:%p", pSql, pObj);
 
-  tscDebug("%p HB is allocated, pObj:%p", pObj->pHb, pObj);
+  pObj->pHb = pSql;
 }
 
 int tscProcessConnectRsp(SSqlObj *pSql) {
@@ -2170,11 +2166,7 @@ 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);
+  registerSqlObj(pNew);
 
   tscAddSubqueryInfo(&pNew->cmd);
 
@@ -2301,10 +2293,8 @@ int tscGetSTableVgroupInfo(SSqlObj *pSql, int32_t clauseIndex) {
   }
 
   pNewQueryInfo->numOfTables = pQueryInfo->numOfTables;
-  T_REF_INC(pNew->pTscObj);
+  registerSqlObj(pNew);
 
-  uint64_t p = (uint64_t) pNew;
-  pNew->self = taosCachePut(tscObjCache, &p, sizeof(uint64_t), &pNew, sizeof(uint64_t), 2 * 600 * 1000);
   tscDebug("%p new sqlObj:%p to get vgroupInfo, numOfTables:%d", pSql, pNew, pNewQueryInfo->numOfTables);
 
   pNew->fp = tscTableMetaCallBack;
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index e1a07fdcfe7f9ff2e24ae9f6469bad181dd0786f..430a762321718eb78f6271e43086390ea1f2439b 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -156,10 +156,7 @@ 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);
+  registerSqlObj(pSql);
   tsInsertHeadSize = sizeof(SMsgDesc) + sizeof(SSubmitMsg);
 
   return pSql;
@@ -270,7 +267,7 @@ void taos_close(TAOS *taos) {
       pHb->pRpcCtx = NULL;
     }
 
-    tscDebug("%p, HB is freed", pHb);
+    tscDebug("%p HB is freed", pHb);
     taos_free_result(pHb);
   }
 
@@ -789,14 +786,17 @@ int taos_validate_sql(TAOS *taos, const char *sql) {
   }
 
   SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+
   pSql->pTscObj = taos;
   pSql->signature = pSql;
+
   SSqlRes *pRes = &pSql->res;
   SSqlCmd *pCmd = &pSql->cmd;
   
   pRes->numOfTotal = 0;
   pRes->numOfClauseTotal = 0;
 
+
   tscDebug("%p Valid SQL: %s pObj:%p", pSql, sql, pObj);
 
   int32_t sqlLen = (int32_t)strlen(sql);
@@ -832,11 +832,12 @@ int taos_validate_sql(TAOS *taos, const char *sql) {
     tsem_wait(&pSql->rspSem);
     code = pSql->res.code;
   }
+
   if (code != TSDB_CODE_SUCCESS) {
     tscDebug("%p Valid SQL result:%d, %s pObj:%p", pSql, code, taos_errstr(taos), pObj);
   }
-  taos_free_result(pSql);
 
+  taos_free_result(pSql);
   return code;
 }
 
@@ -935,34 +936,32 @@ int taos_load_table_info(TAOS *taos, const char *tableNameList) {
   SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
   pSql->pTscObj = taos;
   pSql->signature = pSql;
+
   SSqlRes *pRes = &pSql->res;
 
+  pRes->code = 0;
   pRes->numOfTotal = 0;  // the number of getting table meta from server
   pRes->numOfClauseTotal = 0;
 
-  pRes->code = 0;
-
   assert(pSql->fp == NULL);
   tscDebug("%p tableNameList: %s pObj:%p", pSql, tableNameList, pObj);
 
   int32_t tblListLen = (int32_t)strlen(tableNameList);
   if (tblListLen > MAX_TABLE_NAME_LENGTH) {
     tscError("%p tableNameList too long, length:%d, maximum allowed:%d", pSql, tblListLen, MAX_TABLE_NAME_LENGTH);
-    pRes->code = TSDB_CODE_TSC_INVALID_SQL;
-    taosTFree(pSql);
-    return pRes->code;
+    tscFreeSqlObj(pSql);
+    return TSDB_CODE_TSC_INVALID_SQL;
   }
 
   char *str = calloc(1, tblListLen + 1);
   if (str == NULL) {
-    pRes->code = TSDB_CODE_TSC_OUT_OF_MEMORY;
     tscError("%p failed to malloc sql string buffer", pSql);
-    taosTFree(pSql);
-    return pRes->code;
+    tscFreeSqlObj(pSql);
+    return TSDB_CODE_TSC_OUT_OF_MEMORY;
   }
 
   strtolower(str, tableNameList);
-  pRes->code = (uint8_t)tscParseTblNameList(pSql, str, tblListLen);
+  int32_t code = (uint8_t) tscParseTblNameList(pSql, str, tblListLen);
 
   /*
    * set the qhandle to 0 before return in order to erase the qhandle value assigned in the previous successful query.
@@ -972,17 +971,17 @@ int taos_load_table_info(TAOS *taos, const char *tableNameList) {
   pRes->qhandle = 0;
   free(str);
 
-  if (pRes->code != TSDB_CODE_SUCCESS) {
+  if (code != TSDB_CODE_SUCCESS) {
     tscFreeSqlObj(pSql);
-    return pRes->code;
+    return code;
   }
 
   tscDoQuery(pSql);
 
-  tscDebug("%p load multi metermeta result:%d %s pObj:%p", pSql, pRes->code, taos_errstr(taos), pObj);
-  if (pRes->code != TSDB_CODE_SUCCESS) {
-    tscPartiallyFreeSqlObj(pSql);
+  tscDebug("%p load multi table meta result:%d %s pObj:%p", pSql, pRes->code, taos_errstr(taos), pObj);
+  if ((code = pRes->code) != TSDB_CODE_SUCCESS) {
+    tscFreeSqlObj(pSql);
   }
 
-  return pRes->code;
+  return code;
 }
diff --git a/src/client/src/tscStream.c b/src/client/src/tscStream.c
index 35cd09a0336dbb3580d4025aed363fc65acaf4b7..81b8cf7359a93764551cc4765efebc19be4d62ad 100644
--- a/src/client/src/tscStream.c
+++ b/src/client/src/tscStream.c
@@ -510,9 +510,7 @@ static void tscCreateStream(void *param, TAOS_RES *res, int code) {
     return;
   }
 
-  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);
+  registerSqlObj(pSql);
 
   SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
   STableMetaInfo* pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
diff --git a/src/client/src/tscSub.c b/src/client/src/tscSub.c
index 760c5f5a514af8f90ce3e6461dfff019a766c682..2c81bd7c7ce25535dfffe9c1fd6f8a0197fb900b 100644
--- a/src/client/src/tscSub.c
+++ b/src/client/src/tscSub.c
@@ -105,6 +105,7 @@ static SSub* tscCreateSubscription(STscObj* pObj, const char* topic, const char*
     code = TAOS_SYSTEM_ERROR(errno);
     goto fail;
   }
+
   tstrncpy(pSub->topic, topic, sizeof(pSub->topic));
   pSub->progress = taosArrayInit(32, sizeof(SSubscriptionProgress));
   if (pSub->progress == NULL) {
@@ -119,6 +120,7 @@ static SSub* tscCreateSubscription(STscObj* pObj, const char* topic, const char*
     code = TSDB_CODE_TSC_OUT_OF_MEMORY;
     goto fail;
   }
+
   pSql->signature = pSql;
   pSql->pTscObj = pObj;
   pSql->pSubscription = pSub;
@@ -142,6 +144,7 @@ static SSub* tscCreateSubscription(STscObj* pObj, const char* topic, const char*
     code = TSDB_CODE_TSC_OUT_OF_MEMORY;
     goto fail;
   }
+
   strtolower(pSql->sqlstr, pSql->sqlstr);
   pRes->qhandle = 0;
   pRes->numOfRows = 1;
@@ -152,15 +155,14 @@ static SSub* tscCreateSubscription(STscObj* pObj, const char* topic, const char*
     goto fail;
   }
 
-  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);
+  registerSqlObj(pSql);
 
   code = tsParseSql(pSql, false);
   if (code == TSDB_CODE_TSC_ACTION_IN_PROGRESS) {
     tsem_wait(&pSub->sem);
     code = pSql->res.code;
   }
+
   if (code != TSDB_CODE_SUCCESS) {
     line = __LINE__;
     goto fail;
@@ -182,8 +184,10 @@ fail:
     } else {
       tscFreeSqlObj(pSql);
     }
+
     pSql = NULL;
   }
+
   if (pSub != NULL) {
     taosArrayDestroy(pSub->progress);
     tsem_destroy(&pSub->sem);
diff --git a/src/client/src/tscSystem.c b/src/client/src/tscSystem.c
index 82ce1d36791e2a5e79177ea1405bf90145f2776d..620fe13a9fd37c44b9fa9d25183d5134304a08c3 100644
--- a/src/client/src/tscSystem.c
+++ b/src/client/src/tscSystem.c
@@ -122,11 +122,8 @@ void taos_init_imp(void) {
   tscInitMsgsFp();
   int queueSize = tsMaxConnections*2;
 
-  if (tscEmbedded == 0) {
-    tscNumOfThreads = (int)(tsNumOfCores * tsNumOfThreadsPerCore / 2.0);
-  } else {
-    tscNumOfThreads = (int)(tsNumOfCores * tsNumOfThreadsPerCore / 4.0);
-  }
+  double factor = (tscEmbedded == 0)? 2.0:4.0;
+  tscNumOfThreads = (int)(tsNumOfCores * tsNumOfThreadsPerCore / factor);
 
   if (tscNumOfThreads < 2) tscNumOfThreads = 2;
 
@@ -140,11 +137,8 @@ void taos_init_imp(void) {
   if(0 == tscEmbedded){
     taosTmrReset(tscCheckDiskUsage, 10, NULL, tscTmr, &tscCheckDiskUsageTmr);      
   }
-  
-  int64_t refreshTime = tsTableMetaKeepTimer;
-  refreshTime = refreshTime > 10 ? 10 : refreshTime;
-  refreshTime = refreshTime < 10 ? 10 : refreshTime;
 
+  int64_t refreshTime = 10; // 10 seconds by default
   if (tscMetaCache == NULL) {
     tscMetaCache = taosCacheInit(TSDB_DATA_TYPE_BINARY, refreshTime, false, NULL, "tableMeta");
     tscObjCache = taosCacheInit(TSDB_DATA_TYPE_BIGINT, refreshTime/2, false, tscFreeSqlObjInCache, "sqlObj");
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index 23f412ddd1de1b7ae0f35b702337a9173f984959..33362409cf1fe35384e38fab75282c24707dbb01 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -391,10 +391,21 @@ static UNUSED_FUNC void tscFreeSubobj(SSqlObj* pSql) {
  */
 void tscFreeSqlObjInCache(void *pSql) {
   assert(pSql != NULL);
+
   SSqlObj** p = (SSqlObj**)pSql;
+  STscObj* pTscObj = (*p)->pTscObj;
 
   assert((*p)->self != 0 && (*p)->self == (p));
   tscFreeSqlObj(*p);
+
+  int32_t ref = T_REF_DEC(pTscObj);
+  assert(ref >= 0);
+
+  tscDebug("%p free sqlObj completed, tscObj:%p ref:%d", *p, pTscObj, ref);
+  if (ref == 0) {
+    tscDebug("%p all sqlObj freed, free tscObj:%p", *p, pTscObj);
+    tscCloseTscObj(pTscObj);
+  }
 }
 
 void tscFreeSqlObj(SSqlObj* pSql) {
@@ -403,7 +414,6 @@ void tscFreeSqlObj(SSqlObj* pSql) {
   }
 
   tscDebug("%p start to free sqlObj", pSql);
-  STscObj* pTscObj = pSql->pTscObj;
 
   tscFreeSubobj(pSql);
   tscPartiallyFreeSqlObj(pSql);
@@ -421,14 +431,6 @@ void tscFreeSqlObj(SSqlObj* pSql) {
   tsem_destroy(&pSql->rspSem);
 
   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) {
@@ -1780,6 +1782,16 @@ void tscResetForNextRetrieve(SSqlRes* pRes) {
   pRes->numOfRows = 0;
 }
 
+void registerSqlObj(SSqlObj* pSql) {
+  int32_t DEFAULT_LIFE_TIME = 2 * 600 * 1000;  // 1200 sec
+
+  int32_t ref = T_REF_INC(pSql->pTscObj);
+  tscDebug("%p add to tscObj:%p, ref:%d", pSql, pSql->pTscObj, ref);
+
+  uint64_t p = (uint64_t) pSql;
+  pSql->self = taosCachePut(tscObjCache, &p, sizeof(uint64_t), &p, sizeof(uint64_t), DEFAULT_LIFE_TIME);
+}
+
 SSqlObj* createSimpleSubObj(SSqlObj* pSql, void (*fp)(), void* param, int32_t cmd) {
   SSqlObj* pNew = (SSqlObj*)calloc(1, sizeof(SSqlObj));
   if (pNew == NULL) {
@@ -1808,8 +1820,7 @@ SSqlObj* createSimpleSubObj(SSqlObj* pSql, void (*fp)(), void* param, int32_t cm
   pNew->sqlstr = strdup(pSql->sqlstr);
   if (pNew->sqlstr == NULL) {
     tscError("%p new subquery failed", pSql);
-
-    free(pNew);
+    tscFreeSqlObj(pNew);
     return NULL;
   }
 
@@ -1820,9 +1831,7 @@ 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);
+  registerSqlObj(pNew);
   return pNew;
 }
 
@@ -1912,7 +1921,6 @@ 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) {
@@ -2061,10 +2069,7 @@ 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);
+  registerSqlObj(pNew);
   return pNew;
 
 _error:
diff --git a/src/util/inc/tskiplist.h b/src/util/inc/tskiplist.h
index 4ba620dce03c51cd49faeb0ed113d64fe2d24959..a14a8565617bc08eefc989168a93f523f2e6caff 100644
--- a/src/util/inc/tskiplist.h
+++ b/src/util/inc/tskiplist.h
@@ -136,6 +136,7 @@ typedef struct SSkipListIterator {
   SSkipListNode *cur;
   int32_t        step;          // the number of nodes that have been checked already
   int32_t        order;         // order of the iterator
+  SSkipListNode *next;          // next points to the true qualified node in skip list
 } SSkipListIterator;
 
 /**
diff --git a/src/util/src/tcache.c b/src/util/src/tcache.c
index 49b9996cf4fcb813f3c0db00697277a5352e9116..2637699adb1c6b7508418fe10e189ff37a969b2a 100644
--- a/src/util/src/tcache.c
+++ b/src/util/src/tcache.c
@@ -97,7 +97,7 @@ static FORCE_INLINE void taosCacheReleaseNode(SCacheObj *pCacheObj, SCacheDataNo
   int32_t size = (int32_t)taosHashGetSize(pCacheObj->pHashTable);
   assert(size > 0);
 
-  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 - 1, pCacheObj->totalSize);
 
   if (pCacheObj->freeFp) {
diff --git a/src/util/src/tskiplist.c b/src/util/src/tskiplist.c
index 303c2440bf9b59282b8347604d58d3368dd312c0..bacdaef6c8da1e42218331aaa34d25aa40ab5dc4 100644
--- a/src/util/src/tskiplist.c
+++ b/src/util/src/tskiplist.c
@@ -79,9 +79,12 @@ static SSkipListIterator* doCreateSkipListIterator(SSkipList *pSkipList, int32_t
 
 // when order is TSDB_ORDER_ASC, return the last node with key less than val
 // when order is TSDB_ORDER_DESC, return the first node with key large than val
-static SSkipListNode* getPriorNode(SSkipList* pSkipList, const char* val, int32_t order) {
+static SSkipListNode* getPriorNode(SSkipList* pSkipList, const char* val, int32_t order, SSkipListNode** pCur) {
   __compar_fn_t comparFn = pSkipList->comparFn;
   SSkipListNode *pNode = NULL;
+  if (pCur != NULL) {
+    *pCur = NULL;
+  }
 
   if (order == TSDB_ORDER_ASC) {
     pNode = pSkipList->pHead;
@@ -93,6 +96,9 @@ static SSkipListNode* getPriorNode(SSkipList* pSkipList, const char* val, int32_
           pNode = p;
           p = SL_GET_FORWARD_POINTER(p, i);
         } else {
+          if (pCur != NULL) {
+            *pCur = p;
+          }
           break;
         }
       }
@@ -107,6 +113,9 @@ static SSkipListNode* getPriorNode(SSkipList* pSkipList, const char* val, int32_
           pNode = p;
           p = SL_GET_BACKWARD_POINTER(p, i);
         } else {
+          if (pCur != NULL) {
+            *pCur = p;
+          }
           break;
         }
       }
@@ -295,7 +304,7 @@ SArray* tSkipListGet(SSkipList *pSkipList, SSkipListKey key) {
     pthread_rwlock_wrlock(pSkipList->lock);
   }
 
-  SSkipListNode* pNode = getPriorNode(pSkipList, key, TSDB_ORDER_ASC);
+  SSkipListNode* pNode = getPriorNode(pSkipList, key, TSDB_ORDER_ASC, NULL);
   while (1) {
     SSkipListNode *p = SL_GET_FORWARD_POINTER(pNode, 0);
     if (p == pSkipList->pTail) {
@@ -452,7 +461,7 @@ uint32_t tSkipListRemove(SSkipList *pSkipList, SSkipListKey key) {
     pthread_rwlock_wrlock(pSkipList->lock);
   }
 
-  SSkipListNode* pNode = getPriorNode(pSkipList, key, TSDB_ORDER_ASC);
+  SSkipListNode* pNode = getPriorNode(pSkipList, key, TSDB_ORDER_ASC, NULL);
   while (1) {
     SSkipListNode *p = SL_GET_FORWARD_POINTER(pNode, 0);
     if (p == pSkipList->pTail) {
@@ -545,7 +554,7 @@ SSkipListIterator *tSkipListCreateIterFromVal(SSkipList* pSkipList, const char*
     pthread_rwlock_rdlock(pSkipList->lock);
   }
 
-  iter->cur = getPriorNode(pSkipList, val, order);
+  iter->cur = getPriorNode(pSkipList, val, order, &iter->next);
 
   if (pSkipList->lock) {
     pthread_rwlock_unlock(pSkipList->lock);
@@ -567,8 +576,22 @@ bool tSkipListIterNext(SSkipListIterator *iter) {
   
   if (iter->order == TSDB_ORDER_ASC) {  // ascending order iterate
     iter->cur = SL_GET_FORWARD_POINTER(iter->cur, 0);
+
+    // a new node is inserted into between iter->cur and iter->next, ignore it
+    if (iter->cur != iter->next && (iter->next != NULL)) {
+      iter->cur = iter->next;
+    }
+
+    iter->next = SL_GET_FORWARD_POINTER(iter->cur, 0);
   } else { // descending order iterate
     iter->cur = SL_GET_BACKWARD_POINTER(iter->cur, 0);
+
+    // a new node is inserted into between iter->cur and iter->next, ignore it
+    if (iter->cur != iter->next && (iter->next != NULL)) {
+      iter->cur = iter->next;
+    }
+
+    iter->next = SL_GET_BACKWARD_POINTER(iter->cur, 0);
   }
   
   if (pSkipList->lock) {
@@ -715,9 +738,11 @@ SSkipListIterator* doCreateSkipListIterator(SSkipList *pSkipList, int32_t order)
   iter->order = order;
   if(order == TSDB_ORDER_ASC) {
     iter->cur = pSkipList->pHead;
+    iter->next = SL_GET_FORWARD_POINTER(iter->cur, 0);
   } else {
     iter->cur = pSkipList->pTail;
+    iter->next = SL_GET_BACKWARD_POINTER(iter->cur, 0);
   }
-  
+
   return iter;
 }
\ No newline at end of file
diff --git a/tests/pytest/client/alterDatabase.py b/tests/pytest/client/alterDatabase.py
new file mode 100644
index 0000000000000000000000000000000000000000..fa397d16c57625d53f6f1b2772afa99ade314e1a
--- /dev/null
+++ b/tests/pytest/client/alterDatabase.py
@@ -0,0 +1,55 @@
+###################################################################
+#           Copyright (c) 2016 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+from util.log import *
+from util.cases import *
+from util.sql import *
+
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor(), logSql)
+
+    def run(self):
+        tdSql.prepare()
+
+        tdSql.query('select database()')
+        tdSql.checkData(0, 0, "db")        
+        
+        tdSql.execute("alter database db comp 2")
+        tdSql.query("show databases")
+        tdSql.checkData(0, 14, 2)
+
+        tdSql.execute("alter database db keep 365")
+        tdSql.query("show databases")
+        tdSql.checkData(0, 7, "3650,3650,365")
+
+        tdSql.execute("alter database db quorum 2")
+        tdSql.query("show databases")
+        tdSql.checkData(0, 5, 2)
+
+        tdSql.execute("alter database db blocks 100")
+        tdSql.query("show databases")
+        tdSql.checkData(0, 9, 100)
+
+
+
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())
\ No newline at end of file
diff --git a/tests/pytest/fulltest.sh b/tests/pytest/fulltest.sh
index 597102a0f0b356f921d284ceaace4d99c6850f24..b679942054c000050271fcb96328d18adea60b42 100755
--- a/tests/pytest/fulltest.sh
+++ b/tests/pytest/fulltest.sh
@@ -17,6 +17,7 @@ python3 ./test.py -f insert/nchar-unicode.py
 python3 ./test.py -f insert/multi.py
 python3 ./test.py -f insert/randomNullCommit.py
 python3 insert/retentionpolicy.py
+python3 ./test.py -f insert/alterTableAndInsert.py
 
 python3 ./test.py -f table/column_name.py
 python3 ./test.py -f table/column_num.py
@@ -163,6 +164,7 @@ python3 ./test.py -f alter/alter_table_crash.py
 # client
 python3 ./test.py -f client/client.py
 python3 ./test.py -f client/version.py
+python3 ./test.py -f client/alterDatabase.py
 
 # Misc
 python3 testCompress.py
diff --git a/tests/pytest/insert/alterTableAndInsert.py b/tests/pytest/insert/alterTableAndInsert.py
new file mode 100644
index 0000000000000000000000000000000000000000..a0447704f3cfa594f3bda01cb0dd14b2e795bb5f
--- /dev/null
+++ b/tests/pytest/insert/alterTableAndInsert.py
@@ -0,0 +1,40 @@
+###################################################################
+#           Copyright (c) 2016 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+from util.log import *
+from util.cases import *
+from util.sql import *
+
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor(), logSql)
+
+    def run(self):
+        tdSql.prepare()
+
+        tdSql.execute("create table cars(ts timestamp, speed int) tags(id int)")
+        tdSql.execute("create table car0 using cars tags(0)")
+        tdSql.execute("insert into car0 values(now, 1)")
+        tdSql.execute("alter table cars add column c2 int")
+        tdSql.execute("insert into car0(ts, 'speed') values(now, 2)")
+        tdSql.checkAffectedRows(1)
+
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())
diff --git a/tests/pytest/insert/restful.py b/tests/pytest/insert/restful.py
new file mode 100644
index 0000000000000000000000000000000000000000..bf9bde99f0f97276e9a00aaa3290258274da988b
--- /dev/null
+++ b/tests/pytest/insert/restful.py
@@ -0,0 +1,60 @@
+###################################################################
+#           Copyright (c) 2016 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+import requests, json
+import threading
+import string
+import random
+
+class RestfulInsert:
+    def init(self):
+        self.header = {'Authorization': 'Basic cm9vdDp0YW9zZGF0YQ=='}
+        self.url = "http://127.0.0.1:6041/rest/sql"
+        self.ts = 1104508800000
+        self.numOfThreads = 50
+
+    def get_random_string(self, length):
+        letters = string.ascii_lowercase
+        result_str = ''.join(random.choice(letters) for i in range(length))
+        return result_str
+
+    def insertData(self, threadID):
+        print("thread %d started" % threadID)
+        data = "create table test.tb%d(ts timestamp, name nchar(20))" % threadID
+        requests.post(self.url, data, headers = self.header)              
+        name = self.get_random_string(10)
+        start = self.ts
+        while True:
+            start += 1
+            data = "insert into test.tb%d values(%d, '%s')" % (threadID, start, name)
+            requests.post(self.url, data, headers = self.header)
+
+    def run(self):
+        data = "drop database if exists test"
+        requests.post(self.url, data, headers = self.header)
+        data = "create database test keep 7300"
+        requests.post(self.url, data, headers = self.header)
+
+        threads = []        
+        for i in range(self.numOfThreads):
+            thread = threading.Thread(target=self.insertData, args=(i,))
+            thread.start()
+            threads.append(thread)            
+        
+        for i in range(self.numOfThreads):
+            threads[i].join()
+
+ri = RestfulInsert()
+ri.init()
+ri.run()
\ No newline at end of file
diff --git a/tests/pytest/insert/retentionpolicy.py b/tests/pytest/insert/retentionpolicy.py
index c50de31cc468b6a2d48c226dae24bc3d1fe4f033..c69060b5aec16b8d58aa2742e24c44d1ebe543ab 100644
--- a/tests/pytest/insert/retentionpolicy.py
+++ b/tests/pytest/insert/retentionpolicy.py
@@ -43,7 +43,8 @@ class TDTestRetetion:
         else:
             caller = inspect.getframeinfo(inspect.stack()[1][0])
             args = (caller.filename, caller.lineno, sql, self.queryRows, expectRows)
-            os.system("timedatectl set-ntp true")
+            os.system("sudo timedatectl set-ntp true")
+            time.sleep(40)
             tdLog.exit("%s(%d) failed: sql:%s, queryRows:%d != expect:%d" % args)
 
     def run(self):
@@ -53,7 +54,7 @@ class TDTestRetetion:
         tdSql.execute('use test;')
         tdSql.execute('create table test(ts timestamp,i int);')
 
-        cmd = 'insert into test values(now-2d,11)(now-1d,11)(now,11)(now+1d,11);'
+        cmd = 'insert into test values(now-2d,1)(now-1d,2)(now,3)(now+1d,4);'
         tdLog.info(cmd)
         tdSql.execute(cmd)
         tdSql.query('select * from test')
@@ -61,46 +62,55 @@ class TDTestRetetion:
 
         tdLog.info("=============== step2")
         tdDnodes.stop(1)
-        os.system("timedatectl set-ntp false")
-        os.system("date -s $(date -d \"${DATE} 2 days\" \"+%Y%m%d\")")
+        os.system("sudo timedatectl set-ntp false")
+        os.system("sudo date -s $(date -d \"${DATE} 2 days\" \"+%Y%m%d\")")
         tdDnodes.start(1)
-        cmd = 'insert into test values(now,11);'
+        cmd = 'insert into test values(now,5);'
+        tdDnodes.stop(1)
+        tdDnodes.start(1)
+        
         tdLog.info(cmd)
         tdSql.execute(cmd)
-        queryRows=tdSql.query('select * from test')
-        if queryRows==4:
-            tdSql.checkRows(4)
+        self.queryRows=tdSql.query('select * from test')
+        if self.queryRows==4:
+            self.checkRows(4,cmd)
             return 0
         else:
-            tdSql.checkRows(5)
-
+            self.checkRows(5,cmd)
         tdLog.info("=============== step3")
         tdDnodes.stop(1)
-        os.system("date -s $(date -d \"${DATE} 2 days\" \"+%Y%m%d\")")
+        os.system("sudo date -s $(date -d \"${DATE} 2 days\" \"+%Y%m%d\")")
         tdDnodes.start(1)
-        cmd = 'insert into test values(now-1d,11);'
         tdLog.info(cmd)
         tdSql.execute(cmd)
-        queryRows=tdSql.query('select * from test')
-        tdSql.checkRows(6)
+        self.queryRows=tdSql.query('select * from test')
+        if self.queryRows==4:
+            self.checkRows(4,cmd)
+            return 0
+        cmd = 'insert into test values(now-1d,6);'
+        tdLog.info(cmd)
+        tdSql.execute(cmd)
+        self.queryRows=tdSql.query('select * from test')
+        self.checkRows(6,cmd)
         tdLog.info("=============== step4")
         tdDnodes.stop(1)
         tdDnodes.start(1)
-        cmd = 'insert into test values(now,11);'
+        cmd = 'insert into test values(now,7);'
         tdLog.info(cmd)
         tdSql.execute(cmd)
-        tdSql.query('select * from test')
-        tdSql.checkRows(7)
+        self.queryRows=tdSql.query('select * from test')
+        self.checkRows(7,cmd)
 
         tdLog.info("=============== step5")
         tdDnodes.stop(1)
         tdDnodes.start(1)
         cmd='select * from test where ts > now-1d'
-        queryRows=tdSql.query('select * from test where ts > now-1d')
+        self.queryRows=tdSql.query('select * from test where ts > now-1d')
         self.checkRows(1,cmd)
 
     def stop(self):
-        os.system("timedatectl set-ntp true")
+        os.system("sudo timedatectl set-ntp true")
+        time.sleep(40)
         tdSql.close()
         tdLog.success("%s successfully executed" % __file__)
 
diff --git a/tests/pytest/query/queryNormal.py b/tests/pytest/query/queryNormal.py
index 208ac54ecd5192aec7880c49637794c1fa8e17b8..13393117d642ec1fbdf839d59429428ffee79a27 100644
--- a/tests/pytest/query/queryNormal.py
+++ b/tests/pytest/query/queryNormal.py
@@ -35,7 +35,8 @@ class TDTestCase:
         tdSql.execute(
             "insert into tb2 using stb1 tags(2,'tb2', '表2') values ('2020-04-18 15:00:02.000', 3, 2.1), ('2020-04-18 15:00:03.000', 4, 2.2)")
 
-        # inner join --- bug
+        tdSql.error("select * from tb 1")
+        
         tdSql.query("select * from tb1 a, tb2 b where a.ts = b.ts")
         tdSql.checkRows(0)