diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index 0a4b7e9f787dbd01685c2913e513250e46136b4a..bb21b43e677c50abf49223ff86bce1d1ac95b5d7 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -2505,6 +2505,7 @@ int32_t addExprAndResultField(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, int32_t col
   const char* msg13 = "parameter list required";
   const char* msg14 = "third parameter algorithm must be 'default' or 't-digest'";
   const char* msg15 = "parameter is out of range [1, 1000]";
+  const char* msg16 = "elapsed duration should be greater than or equal to database precision";
 
   switch (functionId) {
     case TSDB_FUNC_COUNT: {
@@ -2599,19 +2600,21 @@ int32_t addExprAndResultField(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, int32_t col
     case TSDB_FUNC_FLOOR:
     case TSDB_FUNC_ROUND:
     case TSDB_FUNC_STDDEV:
-    case TSDB_FUNC_LEASTSQR: {
+    case TSDB_FUNC_LEASTSQR:
+    case TSDB_FUNC_ELAPSED: {
       // 1. valid the number of parameters
       int32_t numOfParams = (pItem->pNode->Expr.paramList == NULL)? 0: (int32_t) taosArrayGetSize(pItem->pNode->Expr.paramList);
 
       // no parameters or more than one parameter for function
       if (pItem->pNode->Expr.paramList == NULL ||
-          (functionId != TSDB_FUNC_LEASTSQR && functionId != TSDB_FUNC_DERIVATIVE && numOfParams != 1) ||
-          ((functionId == TSDB_FUNC_LEASTSQR || functionId == TSDB_FUNC_DERIVATIVE) && numOfParams != 3)) {
+          (functionId != TSDB_FUNC_LEASTSQR && functionId != TSDB_FUNC_DERIVATIVE && functionId != TSDB_FUNC_ELAPSED && numOfParams != 1) ||
+          ((functionId == TSDB_FUNC_LEASTSQR || functionId == TSDB_FUNC_DERIVATIVE) && numOfParams != 3) ||
+          (functionId == TSDB_FUNC_ELAPSED && numOfParams > 2)) {
         return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg2);
       }
 
       tSqlExprItem* pParamElem = taosArrayGet(pItem->pNode->Expr.paramList, 0);
-      if (pParamElem->pNode->tokenId != TK_ALL && pParamElem->pNode->tokenId != TK_ID) {
+      if ((pParamElem->pNode->tokenId != TK_ALL && pParamElem->pNode->tokenId != TK_ID) || 0 == pParamElem->pNode->columnName.n) {
         return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg2);
       }
 
@@ -2620,6 +2623,11 @@ int32_t addExprAndResultField(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, int32_t col
         return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg3);
       }
 
+      // elapsed only can be applied to primary key
+      if (functionId == TSDB_FUNC_ELAPSED && index.columnIndex != PRIMARYKEY_TIMESTAMP_COL_INDEX) {
+        return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), "elapsed only can be applied to primary key");
+      }
+
       pTableMetaInfo = tscGetMetaInfo(pQueryInfo, index.tableIndex);
       STableComInfo info = tscGetTableInfo(pTableMetaInfo->pTableMeta);
 
@@ -2631,7 +2639,7 @@ int32_t addExprAndResultField(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, int32_t col
       // 2. check if sql function can be applied on this column data type
       SSchema* pSchema = tscGetTableColumnSchema(pTableMetaInfo->pTableMeta, index.columnIndex);
 
-      if (!IS_NUMERIC_TYPE(pSchema->type)) {
+      if (!IS_NUMERIC_TYPE(pSchema->type) && (functionId != TSDB_FUNC_ELAPSED)) {
         return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg1);
       } else if (IS_UNSIGNED_NUMERIC_TYPE(pSchema->type) && (functionId == TSDB_FUNC_DIFF || functionId == TSDB_FUNC_DERIVATIVE)) {
         return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg9);
@@ -2676,11 +2684,11 @@ int32_t addExprAndResultField(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, int32_t col
       } else if (functionId == TSDB_FUNC_IRATE) {
         int64_t prec = info.precision;
         tscExprAddParams(&pExpr->base, (char*)&prec, TSDB_DATA_TYPE_BIGINT, LONG_BYTES);
-      } else if (functionId == TSDB_FUNC_DERIVATIVE) {
+      } else if (functionId == TSDB_FUNC_DERIVATIVE || (functionId == TSDB_FUNC_ELAPSED && 2 == numOfParams)) {
         char val[8] = {0};
 
         int64_t tickPerSec = 0;
-        if (tVariantDump(&pParamElem[1].pNode->value, (char*) &tickPerSec, TSDB_DATA_TYPE_BIGINT, true) < 0) {
+        if ((TSDB_DATA_TYPE_NULL == pParamElem[1].pNode->value.nType) || tVariantDump(&pParamElem[1].pNode->value, (char*) &tickPerSec, TSDB_DATA_TYPE_BIGINT, true) < 0) {
           return TSDB_CODE_TSC_INVALID_OPERATION;
         }
 
@@ -2690,23 +2698,27 @@ int32_t addExprAndResultField(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, int32_t col
           tickPerSec /= TSDB_TICK_PER_SECOND(TSDB_TIME_PRECISION_MILLI);
         }
 
-        if (tickPerSec <= 0 || tickPerSec < TSDB_TICK_PER_SECOND(info.precision)) {
+        if ((tickPerSec < TSDB_TICK_PER_SECOND(info.precision)) && (functionId == TSDB_FUNC_DERIVATIVE)) {
           return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg10);
-        }
+        } else if (tickPerSec <= 0) {
+          return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg16);
+        } 
 
         tscExprAddParams(&pExpr->base, (char*) &tickPerSec, TSDB_DATA_TYPE_BIGINT, LONG_BYTES);
-        memset(val, 0, tListLen(val));
+        if (functionId == TSDB_FUNC_DERIVATIVE) {
+          memset(val, 0, tListLen(val));
 
-        if (tVariantDump(&pParamElem[2].pNode->value, val, TSDB_DATA_TYPE_BIGINT, true) < 0) {
-          return TSDB_CODE_TSC_INVALID_OPERATION;
-        }
+          if (tVariantDump(&pParamElem[2].pNode->value, val, TSDB_DATA_TYPE_BIGINT, true) < 0) {
+            return TSDB_CODE_TSC_INVALID_OPERATION;
+          }
 
-        int64_t v = *(int64_t*) val;
-        if (v != 0 && v != 1) {
-          return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg11);
-        }
+          int64_t v = *(int64_t*) val;
+          if (v != 0 && v != 1) {
+            return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg11);
+          }
 
-        tscExprAddParams(&pExpr->base, val, TSDB_DATA_TYPE_BIGINT, LONG_BYTES);
+          tscExprAddParams(&pExpr->base, val, TSDB_DATA_TYPE_BIGINT, LONG_BYTES);
+        }
       }
 
       SColumnList ids = createColumnList(1, index.tableIndex, index.columnIndex);
@@ -3125,7 +3137,6 @@ int32_t addExprAndResultField(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, int32_t col
 
       return TSDB_CODE_SUCCESS;
     }
-
     default: {
       pUdfInfo = isValidUdf(pQueryInfo->pUdfInfo, pItem->pNode->Expr.operand.z, pItem->pNode->Expr.operand.n);
       if (pUdfInfo == NULL) {
@@ -3496,7 +3507,7 @@ int32_t tscTansformFuncForSTableQuery(SQueryInfo* pQueryInfo) {
     if ((functionId >= TSDB_FUNC_SUM && functionId <= TSDB_FUNC_TWA) ||
         (functionId >= TSDB_FUNC_FIRST_DST && functionId <= TSDB_FUNC_STDDEV_DST) ||
         (functionId >= TSDB_FUNC_RATE && functionId <= TSDB_FUNC_IRATE) ||
-        (functionId == TSDB_FUNC_SAMPLE)) {
+        (functionId == TSDB_FUNC_SAMPLE) || (functionId == TSDB_FUNC_ELAPSED)) {
       if (getResultDataInfo(pSrcSchema->type, pSrcSchema->bytes, functionId, (int32_t)pExpr->base.param[0].i64, &type, &bytes,
                             &interBytes, 0, true, NULL) != TSDB_CODE_SUCCESS) {
         return TSDB_CODE_TSC_INVALID_OPERATION;
@@ -3551,8 +3562,8 @@ void tscRestoreFuncForSTableQuery(SQueryInfo* pQueryInfo) {
 }
 
 bool hasUnsupportFunctionsForSTableQuery(SSqlCmd* pCmd, SQueryInfo* pQueryInfo) {
-  const char* msg1 = "TWA/Diff/Derivative/Irate/CSUM/MAVG/SAMPLE/INTERP are not allowed to apply to super table directly";
-  const char* msg2 = "TWA/Diff/Derivative/Irate/CSUM/MAVG/SAMPLE/INTERP only support group by tbname for super table query";
+  const char* msg1 = "TWA/Diff/Derivative/Irate/CSUM/MAVG/SAMPLE/INTERP/Elapsed are not allowed to apply to super table directly";
+  const char* msg2 = "TWA/Diff/Derivative/Irate/CSUM/MAVG/SAMPLE/INTERP/Elapsed only support group by tbname for super table query";
   const char* msg3 = "functions not support for super table query";
 
   // filter sql function not supported by metric query yet.
@@ -3570,7 +3581,7 @@ bool hasUnsupportFunctionsForSTableQuery(SSqlCmd* pCmd, SQueryInfo* pQueryInfo)
   }
 
   if (tscIsTWAQuery(pQueryInfo) || tscIsDiffDerivLikeQuery(pQueryInfo) || tscIsIrateQuery(pQueryInfo) ||
-      tscQueryContainsFunction(pQueryInfo, TSDB_FUNC_SAMPLE) || tscGetPointInterpQuery(pQueryInfo)) {
+      tscQueryContainsFunction(pQueryInfo, TSDB_FUNC_SAMPLE) || tscGetPointInterpQuery(pQueryInfo) || tscQueryContainsFunction(pQueryInfo, TSDB_FUNC_ELAPSED)) {
     if (pQueryInfo->groupbyExpr.numOfGroupCols == 0) {
       invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg1);
       return true;
@@ -7474,7 +7485,7 @@ int32_t doFunctionsCompatibleCheck(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, char*
   const char* msg3 = "group by/session/state_window not allowed on projection query";
   const char* msg4 = "retrieve tags not compatible with group by or interval query";
   const char* msg5 = "functions can not be mixed up";
-  const char* msg6 = "TWA/Diff/Derivative/Irate/CSum/MAvg only support group by tbname";
+  const char* msg6 = "TWA/Diff/Derivative/Irate/CSum/MAvg/Elapsed only support group by tbname";
 
   // only retrieve tags, group by is not supportted
   if (tscQueryTags(pQueryInfo)) {
@@ -7536,7 +7547,7 @@ int32_t doFunctionsCompatibleCheck(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, char*
       }
 
       if ((!pQueryInfo->stateWindow) && (f == TSDB_FUNC_DIFF || f == TSDB_FUNC_DERIVATIVE || f == TSDB_FUNC_TWA ||
-                                         f == TSDB_FUNC_IRATE || f == TSDB_FUNC_CSUM || f == TSDB_FUNC_MAVG)) {
+                                         f == TSDB_FUNC_IRATE || f == TSDB_FUNC_CSUM || f == TSDB_FUNC_MAVG || f == TSDB_FUNC_ELAPSED)) {
         for (int32_t j = 0; j < pQueryInfo->groupbyExpr.numOfGroupCols; ++j) {
           SColIndex* pColIndex = taosArrayGet(pQueryInfo->groupbyExpr.columnInfo, j);
           if (j == 0) {
@@ -7585,7 +7596,7 @@ int32_t doFunctionsCompatibleCheck(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, char*
 
 
 int32_t validateFunctionFromUpstream(SQueryInfo* pQueryInfo, char* msg) {
-  const char* msg1 = "TWA/Diff/Derivative/Irate are not allowed to apply to super table without group by tbname";
+  const char* msg1 = "TWA/Diff/Derivative/Irate/elapsed are not allowed to apply to super table without group by tbname";
   const char* msg2 = "group by not supported in nested interp query";
   const char* msg3 = "order by not supported in nested interp query";
   const char* msg4 = "first column should be timestamp for interp query";
@@ -7598,7 +7609,7 @@ int32_t validateFunctionFromUpstream(SQueryInfo* pQueryInfo, char* msg) {
     SExprInfo* pExpr = tscExprGet(pQueryInfo, i);
   
     int32_t f = pExpr->base.functionId;
-    if (f == TSDB_FUNC_DERIVATIVE || f == TSDB_FUNC_TWA || f == TSDB_FUNC_IRATE || f == TSDB_FUNC_DIFF) {
+    if (f == TSDB_FUNC_DERIVATIVE || f == TSDB_FUNC_TWA || f == TSDB_FUNC_IRATE || f == TSDB_FUNC_DIFF || f == TSDB_FUNC_ELAPSED) {
       for (int32_t j = 0; j < upNum; ++j) {
         SQueryInfo* pUp = taosArrayGetP(pQueryInfo->pUpstream, j);
         STableMetaInfo  *pTableMetaInfo = tscGetMetaInfo(pUp, 0);
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index 98693c94f1d68c194946fbf8b4c00e92c410c9ea..361f73945533b03017b5e156fff975fa1106925f 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -943,6 +943,7 @@ int tscBuildQueryMsg(SSqlObj *pSql, SSqlInfo *pInfo) {
   pQueryMsg->tsCompQuery      = query.tsCompQuery;
   pQueryMsg->simpleAgg        = query.simpleAgg;
   pQueryMsg->pointInterpQuery = query.pointInterpQuery;
+  pQueryMsg->needTableSeqScan = query.needTableSeqScan;
   pQueryMsg->needReverseScan  = query.needReverseScan;
   pQueryMsg->stateWindow      = query.stateWindow;
   pQueryMsg->numOfTags        = htonl(numOfTags);
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index 94b4b45eda919e704f2551624b120081d903f50b..835b32eaaa198445945aff5ddd72cedc444f8318 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -375,6 +375,10 @@ bool tscIsPointInterpQuery(SQueryInfo* pQueryInfo) {
   return true;
 }
 
+bool tscNeedTableSeqScan(SQueryInfo* pQueryInfo) {
+  return pQueryInfo->stableQuery && (tscQueryContainsFunction(pQueryInfo, TSDB_FUNC_TWA) || tscQueryContainsFunction(pQueryInfo, TSDB_FUNC_ELAPSED));
+}
+
 bool tscGetPointInterpQuery(SQueryInfo* pQueryInfo) {
   size_t size = tscNumOfExprs(pQueryInfo);
   for (int32_t i = 0; i < size; ++i) {
@@ -391,7 +395,6 @@ bool tscGetPointInterpQuery(SQueryInfo* pQueryInfo) {
   return false;
 }
 
-
 bool tsIsArithmeticQueryOnAggResult(SQueryInfo* pQueryInfo) {
   if (tscIsProjectionQuery(pQueryInfo)) {
     return false;
@@ -524,7 +527,7 @@ bool timeWindowInterpoRequired(SQueryInfo *pQueryInfo) {
     }
 
     int32_t functionId = pExpr->base.functionId;
-    if (functionId == TSDB_FUNC_TWA || functionId == TSDB_FUNC_INTERP) {
+    if (functionId == TSDB_FUNC_TWA || functionId == TSDB_FUNC_INTERP || functionId == TSDB_FUNC_ELAPSED) {
       return true;
     }
   }
@@ -5054,6 +5057,7 @@ int32_t tscCreateQueryFromQueryInfo(SQueryInfo* pQueryInfo, SQueryAttr* pQueryAt
   pQueryAttr->groupbyColumn     = (!pQueryInfo->stateWindow) && tscGroupbyColumn(pQueryInfo);
   pQueryAttr->queryBlockDist    = isBlockDistQuery(pQueryInfo);
   pQueryAttr->pointInterpQuery  = tscIsPointInterpQuery(pQueryInfo);
+  pQueryAttr->needTableSeqScan  = tscNeedTableSeqScan(pQueryInfo);
   pQueryAttr->timeWindowInterpo = timeWindowInterpoRequired(pQueryInfo);
   pQueryAttr->distinct          = pQueryInfo->distinct;
   pQueryAttr->sw                = pQueryInfo->sessionWindow;
diff --git a/src/inc/taosmsg.h b/src/inc/taosmsg.h
index 0f291936f5519b1db7f98b098e5f9f82303cd0f5..84491e0a438fdb3b5dd2905acffaf32c76b23c9b 100644
--- a/src/inc/taosmsg.h
+++ b/src/inc/taosmsg.h
@@ -475,6 +475,7 @@ typedef struct {
   bool        tsCompQuery;      // is tscomp query
   bool        simpleAgg;
   bool        pointInterpQuery; // point interpolation query
+  bool        needTableSeqScan; // need scan table by table
   bool        needReverseScan;  // need reverse scan
   bool        stateWindow;       // state window flag 
 
diff --git a/src/query/inc/qAggMain.h b/src/query/inc/qAggMain.h
index c9a022d7a1210b31b81bf3895a9b804a03bd30ae..be0f6aee59de760088c8f10b9d1a5dca79882edd 100644
--- a/src/query/inc/qAggMain.h
+++ b/src/query/inc/qAggMain.h
@@ -79,6 +79,8 @@ extern "C" {
 
 #define TSDB_FUNC_BLKINFO      39
 
+#define TSDB_FUNC_ELAPSED         40
+
 ///////////////////////////////////////////
 // the following functions is not implemented.
 // after implementation, move them before TSDB_FUNC_BLKINFO. also make TSDB_FUNC_BLKINFO the maxium function index
diff --git a/src/query/inc/qExecutor.h b/src/query/inc/qExecutor.h
index fe4fb6c950d4f3e0186668d957900934ba243e5d..0a52a44ed1f7019abc7542fab75cfd098302dbc1 100644
--- a/src/query/inc/qExecutor.h
+++ b/src/query/inc/qExecutor.h
@@ -230,6 +230,7 @@ typedef struct SQueryAttr {
   bool             diffQuery;        // is diff query
   bool             simpleAgg;
   bool             pointInterpQuery; // point interpolation query
+  bool             needTableSeqScan; // need scan table by table
   bool             needReverseScan;  // need reverse scan
   bool             distinct;         // distinct  query or not
   bool             stateWindow;       // window State on sub/normal table
diff --git a/src/query/src/qAggMain.c b/src/query/src/qAggMain.c
index f26b3cda1a56df698db0db1465bd6116726ca0ae..62f0edc8b13c97955fb35c6ae74a9c9abb3b59ea 100644
--- a/src/query/src/qAggMain.c
+++ b/src/query/src/qAggMain.c
@@ -196,6 +196,12 @@ typedef struct  {
   char  *taglists;
 } SSampleFuncInfo;
 
+typedef struct SElapsedInfo {
+  int8_t hasResult;
+  TSKEY min;
+  TSKEY max;
+} SElapsedInfo;
+
 typedef struct {
   bool valueAssigned;
   union {
@@ -371,6 +377,11 @@ int32_t getResultDataInfo(int32_t dataType, int32_t dataBytes, int32_t functionI
       *bytes = sizeof(STwaInfo);
       *interBytes = *bytes;
       return TSDB_CODE_SUCCESS;
+    } else if (functionId == TSDB_FUNC_ELAPSED) {
+      *type = TSDB_DATA_TYPE_BINARY;
+      *bytes = sizeof(SElapsedInfo);
+      *interBytes = *bytes;
+      return TSDB_CODE_SUCCESS;
     }
   }
 
@@ -471,6 +482,10 @@ int32_t getResultDataInfo(int32_t dataType, int32_t dataBytes, int32_t functionI
     *bytes = sizeof(SStddevdstInfo);
     *interBytes = (*bytes);
 
+  } else if (functionId == TSDB_FUNC_ELAPSED) {
+    *type = TSDB_DATA_TYPE_DOUBLE;
+    *bytes = tDataTypes[*type].bytes;
+    *interBytes = sizeof(SElapsedInfo);
   } else {
     return TSDB_CODE_TSC_INVALID_OPERATION;
   }
@@ -480,7 +495,7 @@ int32_t getResultDataInfo(int32_t dataType, int32_t dataBytes, int32_t functionI
 
 // TODO use hash table
 int32_t isValidFunction(const char* name, int32_t len) {
-  for(int32_t i = 0; i <= TSDB_FUNC_BLKINFO; ++i) {
+  for(int32_t i = 0; i <= TSDB_FUNC_ELAPSED; ++i) {
     int32_t nameLen = (int32_t) strlen(aAggs[i].name);
     if (len != nameLen) {
       continue;
@@ -3449,7 +3464,7 @@ static void spread_function(SQLFunctionCtx *pCtx) {
   SSpreadInfo *pInfo = GET_ROWCELL_INTERBUF(pResInfo);
   
   int32_t numOfElems = 0;
-  
+
   // todo : opt with pre-calculated result
   // column missing cause the hasNull to be true
   if (pCtx->preAggVals.isSet) {
@@ -3552,7 +3567,7 @@ void spread_function_finalizer(SQLFunctionCtx *pCtx) {
    * the type of intermediate data is binary
    */
   SResultRowCellInfo *pResInfo = GET_RES_INFO(pCtx);
-  
+
   if (pCtx->currentStage == MERGE_STAGE) {
     assert(pCtx->inputType == TSDB_DATA_TYPE_BINARY);
     
@@ -4922,6 +4937,120 @@ static void sample_func_finalizer(SQLFunctionCtx *pCtx) {
   doFinalizer(pCtx);
 }
 
+static SElapsedInfo * getSElapsedInfo(SQLFunctionCtx *pCtx) {
+  if (pCtx->stableQuery && pCtx->currentStage != MERGE_STAGE) {
+    return (SElapsedInfo *)pCtx->pOutput;
+  } else {
+    return GET_ROWCELL_INTERBUF(GET_RES_INFO(pCtx));
+  }
+}
+
+static bool elapsedSetup(SQLFunctionCtx *pCtx, SResultRowCellInfo* pResInfo) {
+  if (!function_setup(pCtx, pResInfo)) {
+    return false;
+  }
+
+  SElapsedInfo *pInfo = getSElapsedInfo(pCtx);
+  pInfo->min = MAX_TS_KEY;
+  pInfo->max = 0;
+  pInfo->hasResult = 0;
+
+  return true;
+}
+
+static int32_t elapsedRequired(SQLFunctionCtx *pCtx, STimeWindow* w, int32_t colId) {
+  return BLK_DATA_NO_NEEDED;
+}
+
+static void elapsedFunction(SQLFunctionCtx *pCtx) {
+  SElapsedInfo *pInfo = getSElapsedInfo(pCtx);
+  if (pCtx->preAggVals.isSet) {
+    if (pInfo->min == MAX_TS_KEY) {
+      pInfo->min = pCtx->preAggVals.statis.min;
+      pInfo->max = pCtx->preAggVals.statis.max;
+    } else {
+      if (pCtx->order == TSDB_ORDER_ASC) {
+        pInfo->max = pCtx->preAggVals.statis.max;
+      } else {
+        pInfo->min = pCtx->preAggVals.statis.min;
+      }
+    }
+  } else {
+    // 0 == pCtx->size mean this is end interpolation.
+    if (0 == pCtx->size) {
+      if (pCtx->order == TSDB_ORDER_DESC) {
+        if (pCtx->end.key != INT64_MIN) {
+          pInfo->min = pCtx->end.key;
+        }
+      } else {
+        if (pCtx->end.key != INT64_MIN) {
+          pInfo->max = pCtx->end.key + 1;
+        }
+      }
+      goto elapsedOver;
+    }
+
+    int64_t *ptsList = (int64_t *)GET_INPUT_DATA_LIST(pCtx);
+    // pCtx->start.key == INT64_MIN mean this is first window or there is actual start point of current window.
+    // pCtx->end.key == INT64_MIN mean current window does not end in current data block or there is actual end point of current window.
+    if (pCtx->order == TSDB_ORDER_DESC) {
+      if (pCtx->start.key == INT64_MIN) {
+        pInfo->max = (pInfo->max < ptsList[pCtx->size - 1]) ? ptsList[pCtx->size - 1] : pInfo->max;
+      } else {
+        pInfo->max = pCtx->start.key + 1;
+      }
+
+      if (pCtx->end.key != INT64_MIN) {
+        pInfo->min = pCtx->end.key;
+      } else {
+        pInfo->min = ptsList[0];
+      }
+    } else {
+      if (pCtx->start.key == INT64_MIN) {
+        pInfo->min = (pInfo->min > ptsList[0]) ? ptsList[0] : pInfo->min;
+      } else {
+        pInfo->min = pCtx->start.key;
+      }
+
+      if (pCtx->end.key != INT64_MIN) {
+        pInfo->max = pCtx->end.key + 1;
+      } else {
+        pInfo->max = ptsList[pCtx->size - 1];
+      }
+    }
+  }
+
+elapsedOver:
+  SET_VAL(pCtx, pCtx->size, 1);
+  
+  if (pCtx->size > 0) {
+    GET_RES_INFO(pCtx)->hasResult = DATA_SET_FLAG;
+    pInfo->hasResult = DATA_SET_FLAG;
+  }
+}
+
+static void elapsedMerge(SQLFunctionCtx *pCtx) {
+  SElapsedInfo *pInfo = getSElapsedInfo(pCtx);
+  memcpy(pInfo, pCtx->pInput, (size_t)pCtx->inputBytes);
+  GET_RES_INFO(pCtx)->hasResult = pInfo->hasResult;
+}
+
+static void elapsedFinalizer(SQLFunctionCtx *pCtx) {
+  if (GET_RES_INFO(pCtx)->hasResult != DATA_SET_FLAG) {
+    setNull(pCtx->pOutput, pCtx->outputType, pCtx->outputBytes);
+    return;
+  }
+
+  SElapsedInfo *pInfo = GET_ROWCELL_INTERBUF(GET_RES_INFO(pCtx));
+  *(double *)pCtx->pOutput = (double)pInfo->max - (double)pInfo->min;
+  if (pCtx->numOfParams > 0 && pCtx->param[0].i64 > 0) {
+    *(double *)pCtx->pOutput = *(double *)pCtx->pOutput / pCtx->param[0].i64;
+  }
+  GET_RES_INFO(pCtx)->numOfRes = 1;
+
+  doFinalizer(pCtx);
+}
+
 /////////////////////////////////////////////////////////////////////////////////////////////
 /*
  * function compatible list.
@@ -4942,8 +5071,8 @@ int32_t functionCompatList[] = {
     1,          1,        1,         1,       -1,      1,          1,           1,          5,          1,      1,
     // tid_tag, deriv,    ceil,     floor,    round,   csum,       mavg,        sample,
     6,          8,        1,        1,         1,      -1,         -1,          -1,
-    // block_info
-    7
+    // block_info, elapsed
+    7,             1
 };
 
 SAggFunctionInfo aAggs[] = {{
@@ -5426,4 +5555,16 @@ SAggFunctionInfo aAggs[] = {{
                               block_func_merge,
                               dataBlockRequired,
                           },
+                          {
+                              // 40
+                              "elapsed",
+                              TSDB_FUNC_ELAPSED,
+                              TSDB_FUNC_ELAPSED,
+                              TSDB_BASE_FUNC_SO,
+                              elapsedSetup,
+                              elapsedFunction,
+                              elapsedFinalizer,
+                              elapsedMerge,
+                              elapsedRequired,
+                          }
 };
diff --git a/src/query/src/qExecutor.c b/src/query/src/qExecutor.c
index 7e89b3a766f0c9124417c65b83dfe55853b0f094..251e210600198de0ba9aec34d322de6839a621b2 100644
--- a/src/query/src/qExecutor.c
+++ b/src/query/src/qExecutor.c
@@ -933,9 +933,10 @@ void doInvokeUdf(SUdfInfo* pUdfInfo, SQLFunctionCtx *pCtx, int32_t idx, int32_t
 static void doApplyFunctions(SQueryRuntimeEnv* pRuntimeEnv, SQLFunctionCtx* pCtx, STimeWindow* pWin, int32_t offset,
                              int32_t forwardStep, TSKEY* tsCol, int32_t numOfTotal, int32_t numOfOutput) {
   SQueryAttr *pQueryAttr = pRuntimeEnv->pQueryAttr;
-  bool hasAggregates = pCtx[0].preAggVals.isSet;
 
   for (int32_t k = 0; k < numOfOutput; ++k) {
+    bool hasAggregates = pCtx[k].preAggVals.isSet;
+
     pCtx[k].size    = forwardStep;
     pCtx[k].startTs = pWin->skey;
 
@@ -1258,7 +1259,7 @@ void doTimeWindowInterpolation(SOperatorInfo* pOperator, SOptrBasicInfo* pInfo,
 
   for (int32_t k = 0; k < pOperator->numOfOutput; ++k) {
     int32_t functionId = pCtx[k].functionId;
-    if (functionId != TSDB_FUNC_TWA && functionId != TSDB_FUNC_INTERP) {
+    if (functionId != TSDB_FUNC_TWA && functionId != TSDB_FUNC_INTERP && functionId != TSDB_FUNC_ELAPSED) {
       pCtx[k].start.key = INT64_MIN;
       continue;
     }
@@ -1301,7 +1302,7 @@ void doTimeWindowInterpolation(SOperatorInfo* pOperator, SOptrBasicInfo* pInfo,
           pCtx[k].end.ptr = (char *)pColInfo->pData + curRowIndex * pColInfo->info.bytes;
         }
       }
-    } else if (functionId == TSDB_FUNC_TWA) {
+    } else if (functionId == TSDB_FUNC_TWA || functionId == TSDB_FUNC_ELAPSED) {
       assert(curTs != windowKey);
 
       if (prevRowIndex == -1) {
@@ -1468,7 +1469,6 @@ static void hashIntervalAgg(SOperatorInfo* pOperatorInfo, SResultRowInfo* pResul
 
   STimeWindow win = getActiveTimeWindow(pResultRowInfo, ts, pQueryAttr);
   bool masterScan = IS_MASTER_SCAN(pRuntimeEnv);
-
   SResultRow* pResult = NULL;
   int32_t ret = setResultOutputBufByKey(pRuntimeEnv, pResultRowInfo, pSDataBlock->info.tid, &win, masterScan, &pResult, tableGroupId, pInfo->pCtx,
                                         numOfOutput, pInfo->rowCellInfoOffset);
@@ -1491,23 +1491,22 @@ static void hashIntervalAgg(SOperatorInfo* pOperatorInfo, SResultRowInfo* pResul
         continue;
       }
 
-        STimeWindow w = pRes->win;
-        ret = setResultOutputBufByKey(pRuntimeEnv, pResultRowInfo, pSDataBlock->info.tid, &w, masterScan, &pResult,
-                                      tableGroupId, pInfo->pCtx, numOfOutput, pInfo->rowCellInfoOffset);
-        if (ret != TSDB_CODE_SUCCESS) {
-          longjmp(pRuntimeEnv->env, TSDB_CODE_QRY_OUT_OF_MEMORY);
-        }
-
-        assert(!resultRowInterpolated(pResult, RESULT_ROW_END_INTERP));
+      STimeWindow w = pRes->win;
+      ret = setResultOutputBufByKey(pRuntimeEnv, pResultRowInfo, pSDataBlock->info.tid, &w, masterScan, &pResult,
+                                    tableGroupId, pInfo->pCtx, numOfOutput, pInfo->rowCellInfoOffset);
+      if (ret != TSDB_CODE_SUCCESS) {
+        longjmp(pRuntimeEnv->env, TSDB_CODE_QRY_OUT_OF_MEMORY);
+      }
 
-        doTimeWindowInterpolation(pOperatorInfo, pInfo, pSDataBlock->pDataBlock, *(TSKEY*)pRuntimeEnv->prevRow[0], -1,
-                                  tsCols[startPos], startPos, w.ekey, RESULT_ROW_END_INTERP);
+      assert(!resultRowInterpolated(pResult, RESULT_ROW_END_INTERP));
 
-        setResultRowInterpo(pResult, RESULT_ROW_END_INTERP);
-        setNotInterpoWindowKey(pInfo->pCtx, pQueryAttr->numOfOutput, RESULT_ROW_START_INTERP);
+      doTimeWindowInterpolation(pOperatorInfo, pInfo, pSDataBlock->pDataBlock, *(TSKEY*)pRuntimeEnv->prevRow[0], -1,
+                                tsCols[startPos], startPos, QUERY_IS_ASC_QUERY(pQueryAttr) ? w.ekey : w.skey, RESULT_ROW_END_INTERP);
 
-        doApplyFunctions(pRuntimeEnv, pInfo->pCtx, &w, startPos, 0, tsCols, pSDataBlock->info.rows, numOfOutput);
-      }
+      setResultRowInterpo(pResult, RESULT_ROW_END_INTERP);
+      setNotInterpoWindowKey(pInfo->pCtx, pQueryAttr->numOfOutput, RESULT_ROW_START_INTERP);
+      doApplyFunctions(pRuntimeEnv, pInfo->pCtx, &w, startPos, 0, tsCols, pSDataBlock->info.rows, numOfOutput);
+    }
 
     // restore current time window
     ret = setResultOutputBufByKey(pRuntimeEnv, pResultRowInfo, pSDataBlock->info.tid, &win, masterScan, &pResult, tableGroupId, pInfo->pCtx,
@@ -1821,7 +1820,7 @@ void setBlockStatisInfo(SQLFunctionCtx *pCtx, SSDataBlock* pSDataBlock, SColInde
   pCtx->hasNull = hasNull(pColIndex, pStatis);
 
   // set the statistics data for primary time stamp column
-  if (pCtx->functionId == TSDB_FUNC_SPREAD && pColIndex->colId == PRIMARYKEY_TIMESTAMP_COL_INDEX) {
+  if ((pCtx->functionId == TSDB_FUNC_SPREAD || pCtx->functionId == TSDB_FUNC_ELAPSED) && pColIndex->colId == PRIMARYKEY_TIMESTAMP_COL_INDEX) {
     pCtx->preAggVals.isSet  = true;
     pCtx->preAggVals.statis.min = pSDataBlock->info.window.skey;
     pCtx->preAggVals.statis.max = pSDataBlock->info.window.ekey;
@@ -6203,7 +6202,17 @@ group_finished_exit:
   return true;
 }
 
+static void resetInterpolation(SQLFunctionCtx *pCtx, SQueryRuntimeEnv* pRuntimeEnv, int32_t numOfOutput) {
+  if (!pRuntimeEnv->pQueryAttr->timeWindowInterpo) {
+    return;
+  }
 
+  for (int32_t i = 0; i < numOfOutput; ++i) {
+    pCtx[i].start.key = INT64_MIN;
+    pCtx[i].end.key = INT64_MIN;
+  }
+  *(TSKEY *)pRuntimeEnv->prevRow[0] = INT64_MIN;
+}
 
 static void doTimeEveryImpl(SOperatorInfo* pOperator, SQLFunctionCtx *pCtx, SSDataBlock* pBlock, bool newgroup) {
   STimeEveryOperatorInfo* pEveryInfo = (STimeEveryOperatorInfo*) pOperator->info;
@@ -6431,6 +6440,7 @@ static SSDataBlock* doSTableIntervalAgg(void* param, bool* newgroup) {
 
   SOperatorInfo* upstream = pOperator->upstream[0];
 
+  STableId prevId = {0, 0};
   while(1) {
     publishOperatorProfEvent(upstream, QUERY_PROF_BEFORE_OPERATOR_EXEC);
     SSDataBlock* pBlock = upstream->exec(upstream, newgroup);
@@ -6440,6 +6450,12 @@ static SSDataBlock* doSTableIntervalAgg(void* param, bool* newgroup) {
       break;
     }
 
+    if (prevId.tid != pBlock->info.tid || prevId.uid != pBlock->info.uid) {
+      resetInterpolation(pIntervalInfo->pCtx, pRuntimeEnv, pOperator->numOfOutput);
+      prevId.uid = pBlock->info.uid;
+      prevId.tid = pBlock->info.tid;
+    }
+
     // the pDataBlock are always the same one, no need to call this again
     STableQueryInfo* pTableQueryInfo = pRuntimeEnv->current;
 
@@ -8785,6 +8801,7 @@ SQInfo* createQInfoImpl(SQueryTableMsg* pQueryMsg, SGroupbyExpr* pGroupbyExpr, S
   pQueryAttr->tsCompQuery     = pQueryMsg->tsCompQuery;
   pQueryAttr->simpleAgg       = pQueryMsg->simpleAgg;
   pQueryAttr->pointInterpQuery = pQueryMsg->pointInterpQuery;
+  pQueryAttr->needTableSeqScan = pQueryMsg->needTableSeqScan;
   pQueryAttr->needReverseScan  = pQueryMsg->needReverseScan;
   pQueryAttr->stateWindow      = pQueryMsg->stateWindow;
   pQueryAttr->vgId            = vgId;
diff --git a/src/query/src/qPlan.c b/src/query/src/qPlan.c
index 27a22f70832dc9669aa473b03820d84d4736b497..eb3a3f36207d27d610e29bd890a56b2ef411157c 100644
--- a/src/query/src/qPlan.c
+++ b/src/query/src/qPlan.c
@@ -538,7 +538,7 @@ SArray* createTableScanPlan(SQueryAttr* pQueryAttr) {
   } else {
     if (pQueryAttr->queryBlockDist) {
       op = OP_TableBlockInfoScan;
-    } else if (pQueryAttr->tsCompQuery || pQueryAttr->diffQuery) {
+    } else if (pQueryAttr->tsCompQuery || pQueryAttr->diffQuery || pQueryAttr->needTableSeqScan) {
       op = OP_TableSeqScan;
     } else if (pQueryAttr->needReverseScan || pQueryAttr->pointInterpQuery) {
       op = OP_DataBlocksOptScan;
diff --git a/tests/pytest/fulltest.sh b/tests/pytest/fulltest.sh
index 86bd39fa065d99ff66eeb2580ec80f07aa7601e6..3359931d5437a6007973b8522bb7cc7fe66fbc78 100755
--- a/tests/pytest/fulltest.sh
+++ b/tests/pytest/fulltest.sh
@@ -371,6 +371,7 @@ python3 ./test.py  -f functions/function_irate.py
 python3 ./test.py  -f functions/function_ceil.py
 python3 ./test.py  -f functions/function_floor.py
 python3 ./test.py  -f functions/function_round.py
+python3 ./test.py  -f functions/function_elapsed.py
 python3 ./test.py -f functions/function_mavg.py
 python3 ./test.py -f functions/function_csum.py
 
diff --git a/tests/pytest/functions/function_elapsed.py b/tests/pytest/functions/function_elapsed.py
new file mode 100644
index 0000000000000000000000000000000000000000..6bc54bfc1c7fc173bf9447da1a9b0aa4aba3e525
--- /dev/null
+++ b/tests/pytest/functions/function_elapsed.py
@@ -0,0 +1,97 @@
+###################################################################
+#           Copyright (c) 2020 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 taos
+from util.log import *
+from util.cases import *
+from util.sql import *
+from functions.function_elapsed_case import *
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor())
+
+    def genTime(self, no):
+        h = int(no / 60)
+        hs = "%d" %h
+        if h < 10:
+            hs = "0%d" %h
+
+        m = int(no % 60)
+        ms = "%d" %m
+        if m < 10:
+            ms = "0%d" %m
+
+        return hs, ms
+
+    def general(self):
+        # normal table
+        tdSql.execute("create database wxy_db minrows 10 maxrows 200")
+        tdSql.execute("use wxy_db")
+        tdSql.execute("create table t1(ts timestamp, i int, b bigint, f float, d double, bin binary(10), s smallint, t tinyint, bl bool, n nchar(10), ts1 timestamp)")
+        for i in range(1, 1001):
+            hs, ms = self.genTime(i)
+            if i < 500:
+                ret = tdSql.execute("insert into t1(ts, i, b) values (\"2021-11-22 %s:%s:00\", %d, 1)" % (hs, ms, i))
+            else:
+                ret = tdSql.execute("insert into t1(ts, i, b) values (\"2021-11-22 %s:%s:00\", %d, 0)" % (hs, ms, i))
+        tdSql.query("select count(*) from t1")
+        tdSql.checkEqual(int(tdSql.getData(0, 0)), 1000)
+
+        # empty normal table
+        tdSql.execute("create table t2(ts timestamp, i int, b bigint, f float, d double, bin binary(10), s smallint, t tinyint, bl bool, n nchar(10), ts1 timestamp)")
+
+        tdSql.execute("create database wxy_db_ns precision \"ns\"")
+        tdSql.execute("use wxy_db_ns")
+        tdSql.execute("create table t1 (ts timestamp, f float)")
+        tdSql.execute("insert into t1 values('2021-11-18 00:00:00.000000100', 1)"
+                                           "('2021-11-18 00:00:00.000000200', 2)"
+                                           "('2021-11-18 00:00:00.000000300', 3)"
+                                           "('2021-11-18 00:00:00.000000500', 4)")
+
+        # super table
+        tdSql.execute("use wxy_db")
+        tdSql.execute("create stable st1(ts timestamp, i int, b bigint, f float, d double, bin binary(10), s smallint, t tinyint, bl bool, n nchar(10), ts1 timestamp) tags(id int)")
+        tdSql.execute("create table st1s1 using st1 tags(1)")
+        tdSql.execute("create table st1s2 using st1 tags(2)")
+        for i in range(1, 1001):
+            hs, ms = self.genTime(i)
+            if 0 == i % 2:
+                ret = tdSql.execute("insert into st1s1(ts, i) values (\"2021-11-22 %s:%s:00\", %d)" % (hs, ms, i))
+            else:
+                ret = tdSql.execute("insert into st1s2(ts, i) values (\"2021-11-22 %s:%s:00\", %d)" % (hs, ms, i))
+        tdSql.query("select count(*) from st1s1")
+        tdSql.checkEqual(int(tdSql.getData(0, 0)), 500)
+        tdSql.query("select count(*) from st1s2")
+        tdSql.checkEqual(int(tdSql.getData(0, 0)), 500)
+        # empty super table
+        tdSql.execute("create stable st2(ts timestamp, i int, b bigint, f float, d double, bin binary(10), s smallint, t tinyint, bl bool, n nchar(10), ts1 timestamp) tags(id int)")
+        tdSql.execute("create table st2s1 using st1 tags(1)")
+        tdSql.execute("create table st2s2 using st1 tags(2)")
+
+        tdSql.execute("create stable st3(ts timestamp, i int, b bigint, f float, d double, bin binary(10), s smallint, t tinyint, bl bool, n nchar(10), ts1 timestamp) tags(id int)")
+
+    def run(self):
+        tdSql.prepare()
+        self.general()
+        ElapsedCase().run()
+
+
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())
diff --git a/tests/pytest/functions/function_elapsed_case.py b/tests/pytest/functions/function_elapsed_case.py
new file mode 100644
index 0000000000000000000000000000000000000000..56610a9347c3ab90a9addc64dd62a6ed60758abf
--- /dev/null
+++ b/tests/pytest/functions/function_elapsed_case.py
@@ -0,0 +1,374 @@
+###################################################################
+#           Copyright (c) 2020 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 taos
+from util.log import *
+from util.cases import *
+from util.sql import *
+
+class ElapsedCase:
+    def __init__(self, restart = False):
+        self.restart = restart
+
+    def selectTest(self):
+        tdSql.execute("use wxy_db")
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.checkRows(1)
+        tdSql.checkCols(1)
+
+        tdSql.query("select elapsed(ts, 1m) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.checkEqual(int(tdSql.getData(0, 0)), 999)
+
+        tdSql.query("select elapsed(ts), elapsed(ts, 1m), elapsed(ts, 10m) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.checkEqual(int(tdSql.getData(0, 1)), 999)
+        tdSql.checkEqual(int(tdSql.getData(0, 2)), 99)
+
+        tdSql.query("select elapsed(ts), count(*), avg(f), twa(f), irate(f), sum(f), stddev(f), leastsquares(f, 1, 1), "
+                    "min(f), max(f), first(f), last(f), percentile(i, 20), apercentile(i, 30), last_row(i), spread(i) "
+                    "from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.checkRows(1)
+        tdSql.checkCols(16)
+        tdSql.checkEqual(int(tdSql.getData(0, 1)), 1000)
+
+        tdSql.query("select elapsed(ts) + 10, elapsed(ts) - 20, elapsed(ts) * 0, elapsed(ts) / 10, elapsed(ts) / elapsed(ts, 1m) from t1 "
+                    "where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.checkRows(1)
+        tdSql.checkCols(5)
+        tdSql.checkEqual(int(tdSql.getData(0, 2)), 0)
+
+        tdSql.query("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname")
+        tdSql.checkRows(2)
+        tdSql.checkCols(2) # append tbname
+
+        tdSql.query("select elapsed(ts, 10m) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname")
+        tdSql.checkEqual(int(tdSql.getData(0, 0)), 99)
+        tdSql.checkEqual(int(tdSql.getData(1, 0)), 99)
+
+        tdSql.query("select elapsed(ts), elapsed(ts, 10m), elapsed(ts, 100m) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname")
+        tdSql.checkEqual(int(tdSql.getData(0, 1)), 99)
+        tdSql.checkEqual(int(tdSql.getData(0, 2)), 9)
+        # stddev(f), 
+        tdSql.query("select elapsed(ts), count(*), avg(f), twa(f), irate(f), sum(f), min(f), max(f), first(f), last(f), apercentile(i, 30), last_row(i), spread(i) "
+                    "from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname")
+        tdSql.checkRows(2)
+        tdSql.checkCols(14) # append tbname
+        tdSql.checkEqual(int(tdSql.getData(0, 1)), 500)
+
+        tdSql.query("select elapsed(ts) + 10, elapsed(ts) - 20, elapsed(ts) * 0, elapsed(ts) / 10, elapsed(ts) / elapsed(ts, 1m) "
+                    "from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname")
+        tdSql.checkRows(2)
+        tdSql.checkCols(6) # append tbname
+        tdSql.checkEqual(int(tdSql.getData(0, 2)), 0)
+
+        tdSql.query("select elapsed(ts), tbname from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname")
+        tdSql.checkRows(2)
+        tdSql.checkCols(3) # additional append tbname
+
+        tdSql.execute("use wxy_db_ns")
+        tdSql.query("select elapsed(ts, 1b), elapsed(ts, 1u) from t1")
+        tdSql.checkRows(1)
+        tdSql.checkCols(2)
+
+        self.selectIllegalTest()
+
+    # It has little to do with the elapsed function, so just simple test.
+    def whereTest(self):
+        tdSql.execute("use wxy_db")
+
+        tdSql.query("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' and id = 1 group by tbname")
+        tdSql.checkRows(1)
+        tdSql.checkCols(2) # append tbname
+
+    # It has little to do with the elapsed function, so just simple test.
+    def sessionTest(self):
+        tdSql.execute("use wxy_db")
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' session(ts, 10s)")
+        tdSql.checkRows(1000)
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' session(ts, 70s)")
+        tdSql.checkRows(1)
+    
+    # It has little to do with the elapsed function, so just simple test.
+    def stateWindowTest(self):
+        tdSql.execute("use wxy_db")
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' state_window(i)")
+        tdSql.checkRows(1000)
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' state_window(b)")
+        tdSql.checkRows(2)
+    
+    def intervalTest(self):
+        tdSql.execute("use wxy_db")
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(1m)")
+        tdSql.checkRows(1000)
+
+        # The first window has 9 records, and the last window has 1 record.
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(10m)")
+        tdSql.checkRows(101)
+        tdSql.checkEqual(int(tdSql.getData(0, 1)), 9 * 60 * 1000)
+        tdSql.checkEqual(int(tdSql.getData(100, 1)), 0)
+
+        # Skip windows without data.
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(35s)")
+        tdSql.checkRows(1000)
+
+        tdSql.query("select elapsed(ts), count(*), avg(f), twa(f), irate(f), sum(f), stddev(f), leastsquares(f, 1, 1), "
+                    "min(f), max(f), first(f), last(f), percentile(i, 20), apercentile(i, 30), last_row(i), spread(i) "
+                    "from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(20m)")
+        tdSql.checkRows(51) # ceil(1000/50) + 1(last point), window is half-open interval.
+        tdSql.checkCols(17) # front push timestamp
+
+        tdSql.query("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(40s) group by tbname")
+        tdSql.checkRows(1000)
+
+        tdSql.query("select elapsed(ts) + 10, elapsed(ts) - 20, elapsed(ts) * 0, elapsed(ts) / 10, elapsed(ts) / elapsed(ts, 1m) "
+                    "from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(30m) group by tbname")
+        tdSql.checkRows(68) # ceil(1000/30)
+        tdSql.checkCols(7) # front push timestamp and append tbname
+
+    # It has little to do with the elapsed function, so just simple test.
+    def fillTest(self):
+        tdSql.execute("use wxy_db")
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(30s) fill(value, 1000)")
+        tdSql.checkRows(2880) # The range of window conditions is 24 hours.
+        tdSql.checkEqual(int(tdSql.getData(0, 1)), 1000)
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(30s) fill(prev)")
+        tdSql.checkRows(2880) # The range of window conditions is 24 hours.
+        tdSql.checkData(0, 1, None)
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(30s) fill(null)")
+        tdSql.checkRows(2880) # The range of window conditions is 24 hours.
+        tdSql.checkData(0, 1, None)
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(30s) fill(linear)")
+        tdSql.checkRows(2880) # The range of window conditions is 24 hours.
+
+        tdSql.query("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(30s) fill(next)")
+        tdSql.checkRows(2880) # The range of window conditions is 24 hours.
+
+    # Elapsed only support group by tbname. Supported tests have been done in selectTest().
+    def groupbyTest(self):
+        tdSql.execute("use wxy_db")
+
+        tdSql.error("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by i")
+        tdSql.error("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by i")
+
+    def orderbyCheck(self, sql, elapsedCol):
+        resultAsc = tdSql.getResult(sql)
+        resultdesc = tdSql.getResult(sql + " order by ts desc")
+        resultRows = len(resultAsc)
+        for i in range(resultRows):
+            tdSql.checkEqual(resultAsc[i][elapsedCol], resultdesc[resultRows - i - 1][elapsedCol])
+
+    def splitStableResult(self, sql, elapsedCol, tbnameCol):
+        subtable = {}
+        result = tdSql.getResult(sql)
+        for i in range(len(result)):
+            if None == subtable.get(result[i][tbnameCol]):
+                subtable[result[i][tbnameCol]] = [result[i][elapsedCol]]
+            else:
+                subtable[result[i][tbnameCol]].append(result[i][elapsedCol])
+        return subtable
+    
+    def doOrderbyCheck(self, resultAsc, resultdesc):
+        resultRows = len(resultAsc)
+        for i in range(resultRows):
+            tdSql.checkEqual(resultAsc[i], resultdesc[resultRows - i - 1])
+
+    def orderbyForStableCheck(self, sql, elapsedCol, tbnameCol):
+        subtableAsc = self.splitStableResult(sql, elapsedCol, tbnameCol)
+        subtableDesc = self.splitStableResult(sql + " order by ts desc", elapsedCol, tbnameCol)
+        for kv in subtableAsc.items():
+            descValue = subtableDesc.get(kv[0])
+            if None == descValue:
+                tdLog.exit("%s failed: subtable %s not exists" % (sql))
+            else:
+                self.doOrderbyCheck(kv[1], descValue)
+
+    # Orderby clause only changes the output order and has no effect on the calculation results.
+    def orderbyTest(self):
+        tdSql.execute("use wxy_db")
+
+        self.orderbyCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'", 0)
+        self.orderbyCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(40s)", 1)
+        self.orderbyCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(1m)", 1)
+        self.orderbyCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(10m)", 1)
+        self.orderbyCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(150m)", 1)
+        self.orderbyCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(222m)", 1)
+        self.orderbyCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(1000m)", 1)
+
+        self.orderbyForStableCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname", 0, 1)
+        self.orderbyForStableCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(40s) group by tbname", 1, 2)
+        self.orderbyForStableCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(1m) group by tbname", 1, 2)
+        self.orderbyForStableCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(10m) group by tbname", 1, 2)
+        self.orderbyForStableCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(150m) group by tbname", 1, 2)
+        self.orderbyForStableCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(222m) group by tbname", 1, 2)
+        self.orderbyForStableCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(1000m) group by tbname", 1, 2)
+
+    def slimitCheck(self, sql):
+        tdSql.checkEqual(tdSql.query(sql + " slimit 0"), 0)
+        tdSql.checkEqual(tdSql.query(sql + " slimit 1 soffset 0"), tdSql.query(sql + " slimit 0, 1"))
+        tdSql.checkEqual(tdSql.query(sql + " slimit 1, 1"), tdSql.query(sql) / 2)
+        tdSql.checkEqual(tdSql.query(sql + " slimit 10"), tdSql.query(sql))
+
+    # It has little to do with the elapsed function, so just simple test.
+    def slimitTest(self):
+        tdSql.execute("use wxy_db")
+
+        self.slimitCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname")
+        self.slimitCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(40s) group by tbname")
+
+    def limitCheck(self, sql, groupby = 0):
+        rows = tdSql.query(sql)
+        if rows > 0:
+            tdSql.checkEqual(tdSql.query(sql + " limit 0"), 0)
+            if 1 == groupby:
+                tdSql.checkEqual(tdSql.query(sql + " limit 1"), 2)
+                tdSql.checkEqual(tdSql.query(sql + " limit %d offset %d" % (rows / 2, rows / 3)), tdSql.query(sql + " limit %d, %d" % (rows / 3, rows / 2)))
+                tdSql.checkEqual(tdSql.query(sql + " limit %d" % (rows / 2)), rows)
+            else:
+                tdSql.checkEqual(tdSql.query(sql + " limit 1"), 1)
+                tdSql.checkEqual(tdSql.query(sql + " limit %d offset %d" % (rows / 2, rows / 3)), tdSql.query(sql + " limit %d, %d" % (rows / 3, rows / 2)))
+                tdSql.checkEqual(tdSql.query(sql + " limit %d" % (rows + 1)), rows)
+
+    # It has little to do with the elapsed function, so just simple test.
+    def limitTest(self):
+        tdSql.execute("use wxy_db")
+
+        self.limitCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        self.limitCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(40s)")
+
+        self.limitCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname", 1)
+        self.limitCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(40s) group by tbname", 1)
+
+    def fromCheck(self, sqlTemplate, table):
+        tdSql.checkEqual(tdSql.getResult(sqlTemplate % table), tdSql.getResult(sqlTemplate % ("(select * from %s)" % table)))
+        tdSql.query(sqlTemplate % ("(select last(ts) from %s interval(10s))" % table))
+        tdSql.query(sqlTemplate % ("(select elapsed(ts) from %s interval(10s))" % table))
+
+    # It has little to do with the elapsed function, so just simple test.
+    def fromTest(self):
+        tdSql.execute("use wxy_db")
+
+        self.fromCheck("select elapsed(ts) from %s where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'", "t1")
+        self.fromCheck("select elapsed(ts) from %s where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(40s)", "t1")
+        tdSql.query("select * from (select elapsed(ts) from t1 interval(10s)) where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.query("select * from (select elapsed(ts) from t1)")
+        # empty table test
+        tdSql.checkEqual(tdSql.query("select elapsed(ts) from t2"), 0)
+        tdSql.checkEqual(tdSql.query("select elapsed(ts) from st2 group by tbname"), 0)
+        tdSql.checkEqual(tdSql.query("select elapsed(ts) from st3 group by tbname"), 0)
+        # Tags not allowed for table query, so there is no need to test super table.
+        tdSql.error("select elapsed(ts) from (select * from st1)")
+
+    def joinCheck(self, sqlTemplate, rtable):
+        tdSql.checkEqual(tdSql.getResult(sqlTemplate % (rtable, "")), tdSql.getResult(sqlTemplate % ("t1, %s t2" % rtable, "t1.ts = t2.ts and ")))
+
+    # It has little to do with the elapsed function, so just simple test.
+    def joinTest(self):
+        tdSql.execute("use wxy_db")
+
+        # st1s1 is a subset of t1.
+        self.joinCheck("select elapsed(ts) from %s where %s ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'", "st1s1")
+        self.joinCheck("select elapsed(ts) from %s where %s ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(150m)", "st1s1")
+        # join query does not support group by, so there is no need to test super table.
+
+    def unionAllCheck(self, sql1, sql2):
+        rows1 = tdSql.query(sql1)
+        rows2 = tdSql.query(sql2)
+        tdSql.checkEqual(tdSql.query(sql1 + " union all " + sql2), rows1 + rows2)
+
+    # It has little to do with the elapsed function, so just simple test.
+    def unionAllTest(self):
+        tdSql.execute("use wxy_db")
+
+        self.unionAllCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'",
+                           "select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-22 01:00:00'")
+        self.unionAllCheck("select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(40s)",
+                           "select elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(150m)")
+        self.unionAllCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname",
+                           "select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-22 02:00:00' group by tbname")
+        self.unionAllCheck("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(1m) group by tbname",
+                           "select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' interval(222m) group by tbname")
+    
+    # It has little to do with the elapsed function, so just simple test.
+    def continuousQueryTest(self):
+        tdSql.execute("use wxy_db")
+
+        if (self.restart):
+            tdSql.execute("drop table elapsed_t")
+            tdSql.execute("drop table elapsed_st")
+        tdSql.execute("create table elapsed_t as select elapsed(ts) from t1 interval(1m) sliding(30s)")
+        tdSql.execute("create table elapsed_st as select elapsed(ts) from st1 interval(1m) sliding(30s) group by tbname")
+
+    def selectIllegalTest(self):
+        tdSql.execute("use wxy_db")
+        tdSql.error("select elapsed(1) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed('2021-11-18 00:00:10') from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(now) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(i) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(b) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(f) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(d) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(bin) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(s) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(t) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(bl) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(n) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts1) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(*) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts, '1s') from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts, i) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        #tdSql.error("select elapsed(ts, now) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts, ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts + 1) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts, 1b) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts, 1u) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(max(ts)) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select distinct elapsed(ts) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select distinct elapsed(ts) from st1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00' group by tbname")
+        tdSql.error("select elapsed(ts), i from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), ts from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), _c0 from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), top(i, 1) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), bottom(i, 1) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), inerp(i) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), diff(i) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), derivative(i, 1s, 0) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), ceil(i) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), floor(i) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+        tdSql.error("select elapsed(ts), round(i) from t1 where ts > '2021-11-22 00:00:00' and ts < '2021-11-23 00:00:00'")
+
+    def run(self):
+        self.selectTest()
+        self.whereTest()
+        self.sessionTest()
+        self.stateWindowTest()
+        self.intervalTest()
+        self.fillTest()
+        self.groupbyTest()
+        self.orderbyTest()
+        self.slimitTest()
+        self.limitTest()
+        self.fromTest()
+        self.joinTest()
+        self.unionAllTest()
+        self.continuousQueryTest()
diff --git a/tests/pytest/functions/function_elapsed_restart.py b/tests/pytest/functions/function_elapsed_restart.py
new file mode 100644
index 0000000000000000000000000000000000000000..8b492267abdd8ea2d2b2fc27ee2e957e1038f48d
--- /dev/null
+++ b/tests/pytest/functions/function_elapsed_restart.py
@@ -0,0 +1,35 @@
+###################################################################
+#           Copyright (c) 2020 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 taos
+from util.log import *
+from util.cases import *
+from util.sql import *
+from functions.function_elapsed_case import *
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor())
+
+    def run(self):
+        tdSql.prepare()
+        ElapsedCase(True).run()
+
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())