diff --git a/include/common/tcommon.h b/include/common/tcommon.h
index 1d979c274f..dd55722513 100644
--- a/include/common/tcommon.h
+++ b/include/common/tcommon.h
@@ -115,8 +115,6 @@ void*   tDecodeDataBlocks(const void* buf, SArray** blocks);
 void    colDataDestroy(SColumnInfoData* pColData);
 
 static FORCE_INLINE void blockDestroyInner(SSDataBlock* pBlock) {
-  // WARNING: do not use info.numOfCols,
-  // sometimes info.numOfCols != array size
   int32_t numOfOutput = taosArrayGetSize(pBlock->pDataBlock);
   for (int32_t i = 0; i < numOfOutput; ++i) {
     SColumnInfoData* pColInfoData = (SColumnInfoData*)taosArrayGet(pBlock->pDataBlock, i);
diff --git a/include/libs/executor/executor.h b/include/libs/executor/executor.h
index ad57cbf4e4..e0fce2aa6a 100644
--- a/include/libs/executor/executor.h
+++ b/include/libs/executor/executor.h
@@ -165,15 +165,6 @@ int32_t qGetQualifiedTableIdList(void* pTableList, const char* tagCond, int32_t
  */
 int32_t qUpdateQueriedTableIdList(qTaskInfo_t tinfo, int64_t uid, int32_t type);
 
-/**
- * release the query handle and decrease the reference count in cache
- * @param pMgmt
- * @param pQInfo
- * @param freeHandle
- * @return
- */
-void** qReleaseTask(void* pMgmt, void* pQInfo, bool freeHandle);
-
 void qProcessFetchRsp(void* parent, struct SRpcMsg* pMsg, struct SEpSet* pEpSet);
 
 int32_t qGetExplainExecInfo(qTaskInfo_t tinfo, int32_t *resNum, SExplainExecInfo **pRes);
diff --git a/source/dnode/vnode/src/tsdb/tsdbMemTable.c b/source/dnode/vnode/src/tsdb/tsdbMemTable.c
index 48d32c0dd3..eaa0893f29 100644
--- a/source/dnode/vnode/src/tsdb/tsdbMemTable.c
+++ b/source/dnode/vnode/src/tsdb/tsdbMemTable.c
@@ -249,8 +249,10 @@ int tsdbLoadDataFromCache(STable *pTable, SSkipListIterator *pIter, TSKEY maxKey
             pMergeInfo->keyFirst = TMIN(pMergeInfo->keyFirst, rowKey);
             pMergeInfo->keyLast = TMAX(pMergeInfo->keyLast, rowKey);
             lastKey = rowKey;
-            ++pCols->numOfRows;
-            tsdbAppendTableRowToCols(pTable, pCols, &pSchema, row, false);
+            if (pCols) {
+              ++pCols->numOfRows;
+              tsdbAppendTableRowToCols(pTable, pCols, &pSchema, row, false);
+            }
           } else {
             tsdbAppendTableRowToCols(pTable, pCols, &pSchema, row, true);
           }
@@ -279,7 +281,7 @@ int tsdbLoadDataFromCache(STable *pTable, SSkipListIterator *pIter, TSKEY maxKey
     }
 #endif
   }
-  if (lastKey != TSKEY_INITIAL_VAL) {
+  if (pCols && (lastKey != TSKEY_INITIAL_VAL)) {
     ++pCols->numOfRows;
   }
 
diff --git a/source/dnode/vnode/src/tsdb/tsdbSma.c b/source/dnode/vnode/src/tsdb/tsdbSma.c
index 105bc330d3..856481bc5f 100644
--- a/source/dnode/vnode/src/tsdb/tsdbSma.c
+++ b/source/dnode/vnode/src/tsdb/tsdbSma.c
@@ -1638,7 +1638,7 @@ int32_t tsdbCreateTSma(STsdb *pTsdb, char *pMsg) {
     tsdbWarn("vgId:%d tsma create msg received but deserialize failed since %s", REPO_ID(pTsdb), terrstr(terrno));
     return -1;
   }
-  
+
   tsdbDebug("vgId:%d tsma create msg %s:%" PRIi64 " for table %" PRIi64 " received", REPO_ID(pTsdb),
             vCreateSmaReq.tSma.indexName, vCreateSmaReq.tSma.indexUid, vCreateSmaReq.tSma.tableUid);
 
@@ -2006,6 +2006,12 @@ static FORCE_INLINE int32_t tsdbExecuteRSmaImpl(STsdb *pTsdb, const void *pMsg,
                                                 qTaskInfo_t *taskInfo, STSchema *pTSchema, tb_uid_t suid, tb_uid_t uid,
                                                 int8_t level) {
   SArray *pResult = NULL;
+
+  if (!taskInfo) {
+    tsdbDebug("vgId:%d no qTaskInfo to execute rsma %" PRIi8 " task for suid:%" PRIu64, REPO_ID(pTsdb), level, suid);
+    return TSDB_CODE_SUCCESS;
+  }
+
   tsdbDebug("vgId:%d execute rsma %" PRIi8 " task for qTaskInfo:%p suid:%" PRIu64, REPO_ID(pTsdb), level, taskInfo,
             suid);
 
@@ -2071,10 +2077,18 @@ static int32_t tsdbExecuteRSma(STsdb *pTsdb, const void *pMsg, int32_t inputType
     tsdbDebug("vgId:%d no rsma info for suid:%" PRIu64, REPO_ID(pTsdb), suid);
     return TSDB_CODE_SUCCESS;
   }
+  if (!pRSmaInfo->taskInfo[0]) {
+    tsdbDebug("vgId:%d no rsma qTaskInfo for suid:%" PRIu64, REPO_ID(pTsdb), suid);
+    return TSDB_CODE_SUCCESS;
+  }
 
   if (inputType == STREAM_DATA_TYPE_SUBMIT_BLOCK) {
     // TODO: use the proper schema instead of 0, and cache STSchema in cache
     STSchema *pTSchema = metaGetTbTSchema(pTsdb->pVnode->pMeta, suid, 0);
+    if (!pTSchema) {
+      terrno = TSDB_CODE_TDB_IVD_TB_SCHEMA_VERSION;
+      return TSDB_CODE_FAILED;
+    }
     tsdbExecuteRSmaImpl(pTsdb, pMsg, inputType, pRSmaInfo->taskInfo[0], pTSchema, suid, uid, TSDB_RETENTION_L1);
     tsdbExecuteRSmaImpl(pTsdb, pMsg, inputType, pRSmaInfo->taskInfo[1], pTSchema, suid, uid, TSDB_RETENTION_L2);
     taosMemoryFree(pTSchema);
diff --git a/source/dnode/vnode/src/vnd/vnodeCfg.c b/source/dnode/vnode/src/vnd/vnodeCfg.c
index 7eac0389d2..5e21abb404 100644
--- a/source/dnode/vnode/src/vnd/vnodeCfg.c
+++ b/source/dnode/vnode/src/vnd/vnodeCfg.c
@@ -25,7 +25,7 @@ const SVnodeCfg vnodeCfgDefault = {
     .isHeap = false,
     .isWeak = 0,
     .tsdbCfg = {.precision = TSDB_TIME_PRECISION_MILLI,
-                .update = 0,
+                .update = 1,
                 .compression = 2,
                 .slLevel = 5,
                 .days = 10,
diff --git a/source/libs/executor/inc/executorimpl.h b/source/libs/executor/inc/executorimpl.h
index 9eed76a0fe..3ed65f4a05 100644
--- a/source/libs/executor/inc/executorimpl.h
+++ b/source/libs/executor/inc/executorimpl.h
@@ -225,6 +225,7 @@ typedef struct SExecTaskInfo {
   char*            sql;                  // query sql string
   jmp_buf          env;                  // jump to this position when error happens.
   EOPTR_EXEC_MODEL execModel;            // operator execution model [batch model|stream model]
+  struct SSubplan  *plan;
   struct SOperatorInfo* pRoot;
 } SExecTaskInfo;
 
diff --git a/source/libs/executor/src/executorMain.c b/source/libs/executor/src/executorMain.c
index 7705744694..ba77950912 100644
--- a/source/libs/executor/src/executorMain.c
+++ b/source/libs/executor/src/executorMain.c
@@ -36,21 +36,6 @@ typedef struct STaskMgmt {
   bool            closed;
 } STaskMgmt;
 
-static void taskMgmtKillTaskFn(void* handle, void* param1) {
-  void** fp = (void**)handle;
-  qKillTask(*fp);
-}
-
-static void freeqinfoFn(void *qhandle) {
-  void** handle = qhandle;
-  if (handle == NULL || *handle == NULL) {
-    return;
-  }
-
-  qKillTask(*handle);
-  qDestroyTask(*handle);
-}
-
 int32_t qCreateExecTask(SReadHandle* readHandle, int32_t vgId, uint64_t taskId, SSubplan* pSubplan,
     qTaskInfo_t* pTaskInfo, DataSinkHandle* handle, EOPTR_EXEC_MODEL model) {
   assert(readHandle != NULL && pSubplan != NULL);
diff --git a/source/libs/executor/src/executorimpl.c b/source/libs/executor/src/executorimpl.c
index 6d13a8a42b..c0ea54ce4a 100644
--- a/source/libs/executor/src/executorimpl.c
+++ b/source/libs/executor/src/executorimpl.c
@@ -1225,6 +1225,8 @@ static void* destroySqlFunctionCtx(SqlFunctionCtx* pCtx, int32_t numOfOutput) {
 
     taosVariantDestroy(&pCtx[i].tag);
     taosMemoryFreeClear(pCtx[i].subsidiaries.pCtx);
+    taosMemoryFree(pCtx[i].input.pData);
+    taosMemoryFree(pCtx[i].input.pColumnDataAgg);
   }
 
   taosMemoryFreeClear(pCtx);
@@ -2840,9 +2842,9 @@ void relocateColumnData(SSDataBlock* pBlock, const SArray* pColMatchInfo, SArray
 int32_t setSDataBlockFromFetchRsp(SSDataBlock* pRes, SLoadRemoteDataInfo* pLoadInfo, int32_t numOfRows, char* pData,
                                   int32_t compLen, int32_t numOfOutput, int64_t startTs, uint64_t* total,
                                   SArray* pColList) {
-  blockDataEnsureCapacity(pRes, numOfRows);
-
   if (pColList == NULL) {  // data from other sources
+    blockDataEnsureCapacity(pRes, numOfRows);
+
     int32_t dataLen = *(int32_t*)pData;
     pData += sizeof(int32_t);
 
@@ -2898,20 +2900,23 @@ int32_t setSDataBlockFromFetchRsp(SSDataBlock* pRes, SLoadRemoteDataInfo* pLoadI
       pStart += sizeof(SSysTableSchema);
     }
 
-    SSDataBlock block = {.pDataBlock = taosArrayInit(numOfCols, sizeof(SColumnInfoData)), .info.numOfCols = numOfCols};
+    SSDataBlock* pBlock = taosMemoryCalloc(1, sizeof(SSDataBlock));
+    pBlock->pDataBlock = taosArrayInit(numOfCols, sizeof(SColumnInfoData));
+    pBlock->info.numOfCols = numOfCols;
+
     for (int32_t i = 0; i < numOfCols; ++i) {
       SColumnInfoData idata = {0};
       idata.info.type = pSchema[i].type;
       idata.info.bytes = pSchema[i].bytes;
       idata.info.colId = pSchema[i].colId;
 
-      taosArrayPush(block.pDataBlock, &idata);
+      taosArrayPush(pBlock->pDataBlock, &idata);
       if (IS_VAR_DATA_TYPE(idata.info.type)) {
-        block.info.hasVarCol = true;
+        pBlock->info.hasVarCol = true;
       }
     }
 
-    blockDataEnsureCapacity(&block, numOfRows);
+    blockDataEnsureCapacity(pBlock, numOfRows);
 
     int32_t  dataLen = *(int32_t*)pStart;
     uint64_t groupId = *(uint64_t*)(pStart + sizeof(int32_t));
@@ -2924,7 +2929,7 @@ int32_t setSDataBlockFromFetchRsp(SSDataBlock* pRes, SLoadRemoteDataInfo* pLoadI
       colLen[i] = htonl(colLen[i]);
       ASSERT(colLen[i] >= 0);
 
-      SColumnInfoData* pColInfoData = taosArrayGet(block.pDataBlock, i);
+      SColumnInfoData* pColInfoData = taosArrayGet(pBlock->pDataBlock, i);
       if (IS_VAR_DATA_TYPE(pColInfoData->info.type)) {
         pColInfoData->varmeta.length = colLen[i];
         pColInfoData->varmeta.allocLen = colLen[i];
@@ -2943,7 +2948,10 @@ int32_t setSDataBlockFromFetchRsp(SSDataBlock* pRes, SLoadRemoteDataInfo* pLoadI
     }
 
     // data from mnode
-    relocateColumnData(pRes, pColList, block.pDataBlock);
+    relocateColumnData(pRes, pColList, pBlock->pDataBlock);
+    taosArrayDestroy(pBlock->pDataBlock);
+    taosMemoryFree(pBlock);
+//    blockDataDestroy(pBlock);
   }
 
   pRes->info.rows = numOfRows;
@@ -4184,6 +4192,18 @@ static void destroyOperatorInfo(SOperatorInfo* pOperator) {
     pOperator->numOfDownstream = 0;
   }
 
+  if (pOperator->pExpr != NULL) {
+    for (int32_t i = 0; i < pOperator->numOfExprs; ++i) {
+      SExprInfo* pExprInfo = &pOperator->pExpr[i];
+      if (pExprInfo->pExpr->nodeType == QUERY_NODE_COLUMN) {
+        taosMemoryFree(pExprInfo->base.pParam[0].pCol);
+      }
+      taosMemoryFree(pExprInfo->base.pParam);
+      taosMemoryFree(pExprInfo->pExpr);
+    }
+  }
+
+  taosMemoryFree(pOperator->pExpr);
   taosMemoryFreeClear(pOperator->info);
   taosMemoryFreeClear(pOperator);
 }
@@ -4195,8 +4215,6 @@ int32_t doInitAggInfoSup(SAggSupporter* pAggSup, SqlFunctionCtx* pCtx, int32_t n
   pAggSup->resultRowSize = getResultRowSize(pCtx, numOfOutput);
   pAggSup->keyBuf = taosMemoryCalloc(1, keyBufSize + POINTER_BYTES + sizeof(int64_t));
   pAggSup->pResultRowHashTable = taosHashInit(10, hashFn, true, HASH_NO_LOCK);
-  //  pAggSup->pResultRowListSet = taosHashInit(100, hashFn, false, HASH_NO_LOCK);
-  //  pAggSup->pResultRowArrayList = taosArrayInit(10, sizeof(SResultRowCell));
 
   if (pAggSup->keyBuf == NULL /*|| pAggSup->pResultRowArrayList == NULL || pAggSup->pResultRowListSet == NULL*/ ||
       pAggSup->pResultRowHashTable == NULL) {
@@ -4358,6 +4376,8 @@ void destroySFillOperatorInfo(void* param, int32_t numOfOutput) {
 static void destroyProjectOperatorInfo(void* param, int32_t numOfOutput) {
   SProjectOperatorInfo* pInfo = (SProjectOperatorInfo*)param;
   doDestroyBasicInfo(&pInfo->binfo, numOfOutput);
+  cleanupAggSup(&pInfo->aggSup);
+  taosArrayDestroy(pInfo->pPseudoColInfo);
 }
 
 void destroyExchangeOperatorInfo(void* param, int32_t numOfOutput) {
@@ -5189,6 +5209,7 @@ int32_t createExecTaskInfoImpl(SSubplan* pPlan, SExecTaskInfo** pTaskInfo, SRead
     goto _complete;
   }
 
+  (*pTaskInfo)->plan = pPlan;
   return code;
 
 _complete:
@@ -5287,10 +5308,10 @@ void doDestroyTask(SExecTaskInfo* pTaskInfo) {
   qDebug("%s execTask is freed", GET_TASKID(pTaskInfo));
 
   doDestroyTableQueryInfo(&pTaskInfo->tableqinfoGroupInfo);
+  destroyOperatorInfo(pTaskInfo->pRoot);
   //  taosArrayDestroy(pTaskInfo->summary.queryProfEvents);
   //  taosHashCleanup(pTaskInfo->summary.operatorProfResults);
 
-  destroyOperatorInfo(pTaskInfo->pRoot);
   taosMemoryFreeClear(pTaskInfo->sql);
   taosMemoryFreeClear(pTaskInfo->id.str);
   taosMemoryFreeClear(pTaskInfo);
diff --git a/source/libs/executor/src/scanoperator.c b/source/libs/executor/src/scanoperator.c
index b28a65d1d2..2b94c5fdce 100644
--- a/source/libs/executor/src/scanoperator.c
+++ b/source/libs/executor/src/scanoperator.c
@@ -670,6 +670,8 @@ static void destroySysScanOperator(void* param, int32_t numOfOutput) {
   if (strncasecmp(name, TSDB_INS_TABLE_USER_TABLES, TSDB_TABLE_FNAME_LEN) == 0) {
     metaCloseTbCursor(pInfo->pCur);
   }
+
+  taosArrayDestroy(pInfo->scanCols);
 }
 
 EDealRes getDBNameFromConditionWalker(SNode* pNode, void* pContext) {
@@ -1154,7 +1156,7 @@ SOperatorInfo* createSysTableScanOperatorInfo(void* readHandle, SSDataBlock* pRe
   pOperator->blocking     = false;
   pOperator->status       = OP_NOT_OPENED;
   pOperator->info         = pInfo;
-  pOperator->numOfExprs  = pResBlock->info.numOfCols;
+  pOperator->numOfExprs   = pResBlock->info.numOfCols;
   pOperator->fpSet = createOperatorFpSet(operatorDummyOpenFn, doSysTableScan, NULL, NULL, destroySysScanOperator,
                                          NULL, NULL, NULL);
   pOperator->pTaskInfo = pTaskInfo;
@@ -1248,6 +1250,11 @@ static SSDataBlock* doTagScan(SOperatorInfo* pOperator) {
   SExprInfo*    pExprInfo = &pOperator->pExpr[0];
   SSDataBlock*  pRes = pInfo->pRes;
 
+  if (taosArrayGetSize(pInfo->pTableGroups->pGroupList) == 0) {
+    setTaskStatus(pTaskInfo, TASK_COMPLETED);
+    return NULL;
+  }
+
   SArray* pa = taosArrayGetP(pInfo->pTableGroups->pGroupList, 0);
 
   char        str[512] = {0};
diff --git a/tests/system-test/2-query/Timediff.py b/tests/system-test/2-query/Timediff.py
index 2824fea5a2..ad64d29007 100644
--- a/tests/system-test/2-query/Timediff.py
+++ b/tests/system-test/2-query/Timediff.py
@@ -181,7 +181,16 @@ class TDTestCase:
         tdSql.error("select timediff(10,1,1.5) from stb")
         # tdSql.error("select timediff(10,1,2s) from stb")
         # tdSql.error("select timedifff(10,1,c1) from stb")
-
+        tdSql.error("select timediff(1.5,1.5) from stb_1")
+        tdSql.error("select timediff(1) from stb_1")
+        tdSql.error("select timediff(10,1,1.5) from stb_1")
+        # tdSql.error("select timediff(10,1,2s) from stb_1")
+        # tdSql.error("select timedifff(10,1,c1) from stb_1")
+        tdSql.error("select timediff(1.5,1.5) from ntb")
+        tdSql.error("select timediff(1) from ntb")
+        tdSql.error("select timediff(10,1,1.5) from ntb")
+        # tdSql.error("select timediff(10,1,2s) from ntb")
+        # tdSql.error("select timedifff(10,1,c1) from ntb")
 
 
 
diff --git a/tests/system-test/2-query/diff.py b/tests/system-test/2-query/diff.py
new file mode 100644
index 0000000000..82c450771f
--- /dev/null
+++ b/tests/system-test/2-query/diff.py
@@ -0,0 +1,150 @@
+from util.log import *
+from util.cases import *
+from util.sql import *
+import numpy as np
+
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor())
+
+        self.rowNum = 10
+        self.ts = 1537146000000
+        self.perfix = 'dev'
+        self.tables = 10
+
+    def insertData(self):
+        print("==============step1")
+        tdSql.execute(
+            "create table if not exists st (ts timestamp, col int) tags(dev nchar(50))")
+
+        for i in range(self.tables):
+            tdSql.execute("create table %s%d using st tags(%d)" % (self.perfix, i, i))
+            rows = 15 + i
+            for j in range(rows):
+                tdSql.execute("insert into %s%d values(%d, %d)" %(self.perfix, i, self.ts + i * 20 * 10000 + j * 10000, j))
+
+    def run(self):
+        tdSql.prepare()
+
+        tdSql.execute('''create table stb(ts timestamp, col1 tinyint, col2 smallint, col3 int, col4 bigint, col5 float, col6 double, 
+                    col7 bool, col8 binary(20), col9 nchar(20), col11 tinyint unsigned, col12 smallint unsigned, col13 int unsigned, col14 bigint unsigned) tags(loc nchar(20))''')
+        tdSql.execute("create table stb_1 using stb tags('beijing')")
+        tdSql.execute("insert into stb_1 values(%d, 0, 0, 0, 0, 0.0, 0.0, False, ' ', ' ', 0, 0, 0, 0)" % (self.ts - 1))
+        
+        # diff verifacation 
+        tdSql.query("select diff(col1) from stb_1")
+        tdSql.checkRows(0)
+        
+        tdSql.query("select diff(col2) from stb_1")
+        tdSql.checkRows(0)
+
+        tdSql.query("select diff(col3) from stb_1")
+        tdSql.checkRows(0)
+
+        tdSql.query("select diff(col4) from stb_1")
+        tdSql.checkRows(0)
+
+        tdSql.query("select diff(col5) from stb_1")
+        tdSql.checkRows(0)
+
+        tdSql.query("select diff(col6) from stb_1")
+        tdSql.checkRows(0)
+
+        for i in range(self.rowNum):
+            tdSql.execute("insert into stb_1 values(%d, %d, %d, %d, %d, %f, %f, %d, 'taosdata%d', '涛思数据%d', %d, %d, %d, %d)" 
+                        % (self.ts + i, i + 1, i + 1, i + 1, i + 1, i + 0.1, i + 0.1, i % 2, i + 1, i + 1, i + 1, i + 1, i + 1, i + 1))                                
+        
+        tdSql.error("select diff(ts) from stb")
+        tdSql.error("select diff(ts) from stb_1")
+        tdSql.error("select diff(col1) from stb")
+        tdSql.error("select diff(col2) from stb")
+        tdSql.error("select diff(col3) from stb")
+        tdSql.error("select diff(col4) from stb")
+        tdSql.error("select diff(col5) from stb")
+        tdSql.error("select diff(col6) from stb")
+        tdSql.error("select diff(col7) from stb")     
+        tdSql.error("select diff(col7) from stb_1")               
+        tdSql.error("select diff(col8) from stb") 
+        tdSql.error("select diff(col8) from stb_1")
+        tdSql.error("select diff(col9) from stb")        
+        tdSql.error("select diff(col9) from stb_1")
+        tdSql.error("select diff(col11) from stb_1")
+        tdSql.error("select diff(col12) from stb_1")
+        tdSql.error("select diff(col13) from stb_1")
+        tdSql.error("select diff(col14) from stb_1")
+        tdSql.error("select diff(col11) from stb")
+        tdSql.error("select diff(col12) from stb")
+        tdSql.error("select diff(col13) from stb")
+        tdSql.error("select diff(col14) from stb")
+
+        tdSql.query("select ts,diff(col1),ts from stb_1")
+        tdSql.checkRows(10)
+        tdSql.checkData(0, 0, "2018-09-17 09:00:00.000")
+        tdSql.checkData(0, 1, "2018-09-17 09:00:00.000")
+        tdSql.checkData(0, 3, "2018-09-17 09:00:00.000")
+        tdSql.checkData(9, 0, "2018-09-17 09:00:00.009")
+        tdSql.checkData(9, 1, "2018-09-17 09:00:00.009")
+        tdSql.checkData(9, 3, "2018-09-17 09:00:00.009")
+
+        tdSql.query("select ts,diff(col1),ts from stb group by tbname")
+        tdSql.checkRows(10)
+        tdSql.checkData(0, 0, "2018-09-17 09:00:00.000")
+        tdSql.checkData(0, 1, "2018-09-17 09:00:00.000")
+        tdSql.checkData(0, 3, "2018-09-17 09:00:00.000")
+        tdSql.checkData(9, 0, "2018-09-17 09:00:00.009")
+        tdSql.checkData(9, 1, "2018-09-17 09:00:00.009")
+        tdSql.checkData(9, 3, "2018-09-17 09:00:00.009")
+
+        tdSql.query("select ts,diff(col1),ts from stb_1")
+        tdSql.checkRows(10)
+        tdSql.checkData(0, 0, "2018-09-17 09:00:00.000")
+        tdSql.checkData(0, 1, "2018-09-17 09:00:00.000")
+        tdSql.checkData(0, 3, "2018-09-17 09:00:00.000")
+        tdSql.checkData(9, 0, "2018-09-17 09:00:00.009")
+        tdSql.checkData(9, 1, "2018-09-17 09:00:00.009")
+        tdSql.checkData(9, 3, "2018-09-17 09:00:00.009")
+
+        tdSql.query("select ts,diff(col1),ts from stb group by tbname")
+        tdSql.checkRows(10)
+        tdSql.checkData(0, 0, "2018-09-17 09:00:00.000")
+        tdSql.checkData(0, 1, "2018-09-17 09:00:00.000")
+        tdSql.checkData(0, 3, "2018-09-17 09:00:00.000")
+        tdSql.checkData(9, 0, "2018-09-17 09:00:00.009")
+        tdSql.checkData(9, 1, "2018-09-17 09:00:00.009")
+        tdSql.checkData(9, 3, "2018-09-17 09:00:00.009")
+
+        tdSql.query("select diff(col1) from stb_1")
+        tdSql.checkRows(10)
+
+        tdSql.query("select diff(col2) from stb_1")
+        tdSql.checkRows(10)
+
+        tdSql.query("select diff(col3) from stb_1")
+        tdSql.checkRows(10)
+
+        tdSql.query("select diff(col4) from stb_1")
+        tdSql.checkRows(10)
+
+        tdSql.query("select diff(col5) from stb_1")
+        tdSql.checkRows(10)
+
+        tdSql.query("select diff(col6) from stb_1")
+        tdSql.checkRows(10)
+
+        self.insertData()
+
+        tdSql.query("select diff(col) from st group by tbname")
+        tdSql.checkRows(185)
+
+        tdSql.error("select diff(col) from st group by dev")        
+
+        tdSql.error("select diff(col) from st group by col")
+        
+    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/system-test/2-query/last.py b/tests/system-test/2-query/last.py
index b5c0498e40..b491679c62 100644
--- a/tests/system-test/2-query/last.py
+++ b/tests/system-test/2-query/last.py
@@ -21,12 +21,12 @@ class TDTestCase:
         tdSql.execute("insert into stb_1(ts) values(%d)" % (self.ts - 1))
 
         # last verifacation         
-        # tdSql.query("select last(*) from stb_1")
-        # tdSql.checkRows(1)
-        # tdSql.checkData(0, 1, None)
-        # tdSql.query("select last(*) from db.stb_1")
-        # tdSql.checkRows(1)
-        # tdSql.checkData(0, 1, None)
+        tdSql.query("select last(*) from stb_1")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 1, None)
+        tdSql.query("select last(*) from db.stb_1")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 1, None)
         tdSql.query("select last(col1) from stb_1")
         tdSql.checkRows(0) 
         tdSql.query("select last(col1) from db.stb_1")
@@ -86,12 +86,12 @@ class TDTestCase:
             tdSql.execute("insert into stb_1 values(%d, %d, %d, %d, %d, %f, %f, %d, 'taosdata%d', '涛思数据%d', %d, %d, %d, %d)" 
                         % (self.ts + i, i + 1, i + 1, i + 1, i + 1, i + 0.1, i + 0.1, i % 2, i + 1, i + 1, i + 1, i + 1, i + 1, i + 1))            
 
-        # tdSql.query("select last(*) from stb_1")
-        # tdSql.checkRows(1)
-        # tdSql.checkData(0, 1, 10)
-        # tdSql.query("select last(*) from db.stb_1")
-        # tdSql.checkRows(1)
-        # tdSql.checkData(0, 1, 10)
+        tdSql.query("select last(*) from stb_1")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 1, 10)
+        tdSql.query("select last(*) from db.stb_1")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 1, 10)
         tdSql.query("select last(col1) from stb_1")
         tdSql.checkRows(1)
         tdSql.checkData(0, 0, 10)
@@ -175,12 +175,12 @@ class TDTestCase:
         tdSql.execute('''create table ntb(ts timestamp, col1 tinyint, col2 smallint, col3 int, col4 bigint, col5 float, col6 double, 
                     col7 bool, col8 binary(20), col9 nchar(20), col11 tinyint unsigned, col12 smallint unsigned, col13 int unsigned, col14 bigint unsigned)''')
         tdSql.execute("insert into ntb(ts) values(%d)" % (self.ts - 1))
-        # tdSql.query("select last(*) from ntb")
-        # tdSql.checkRows(1)
-        # tdSql.checkData(0, 1, None)
-        # tdSql.query("select last(*) from db.ntb")
-        # tdSql.checkRows(1)
-        # tdSql.checkData(0, 1, None)
+        tdSql.query("select last(*) from ntb")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 1, None)
+        tdSql.query("select last(*) from db.ntb")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 1, None)
         tdSql.query("select last(col1) from ntb")
         tdSql.checkRows(0) 
         tdSql.query("select last(col1) from db.ntb")
@@ -316,12 +316,12 @@ class TDTestCase:
         tdSql.query("select last(col8) from db.ntb")
         tdSql.checkRows(1)
         tdSql.checkData(0, 0, 'taosdata10')
-        # tdSql.query("select last(col9) from ntb")
-        # tdSql.checkRows(1)
-        # tdSql.checkData(0, 0, '涛思数据10')
-        # tdSql.query("select last(col9) from db.ntb")
-        # tdSql.checkRows(1)
-        # tdSql.checkData(0, 0, '涛思数据10')
+        tdSql.query("select last(col9) from ntb")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 0, '涛思数据10')
+        tdSql.query("select last(col9) from db.ntb")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 0, '涛思数据10')
  
     def stop(self):
         tdSql.close()
diff --git a/tests/system-test/fulltest.sh b/tests/system-test/fulltest.sh
index 22dc59365a..cb9d472116 100755
--- a/tests/system-test/fulltest.sh
+++ b/tests/system-test/fulltest.sh
@@ -23,7 +23,8 @@ python3 ./test.py -f 2-query/last.py
 python3 ./test.py -f 2-query/To_unixtimestamp.py
 python3 ./test.py -f 2-query/timetruncate.py
 
-# python3 ./test.py -f 2-query/Timediff.py
+python3 ./test.py -f 2-query/Timediff.py
+# python3 ./test.py -f 2-query/diff.py
 #python3 ./test.py -f 2-query/cast.py