diff --git a/src/query/src/qAggMain.c b/src/query/src/qAggMain.c
index 3e1ebbd1ff756fb29306e465f29d41dd74051f26..61f0ac78779a1269f95296cb93c975b0db63a544 100644
--- a/src/query/src/qAggMain.c
+++ b/src/query/src/qAggMain.c
@@ -5504,20 +5504,35 @@ static bool tail_function_setup(SQLFunctionCtx *pCtx, SResultRowCellInfo* pResIn
 static void tail_function(SQLFunctionCtx *pCtx) {
   STailInfo *pRes = getOutputInfo(pCtx);
 
-  for (int32_t i = 0; i < pCtx->size; ++i) {
-    if (pRes->offset++ < (int32_t)pCtx->param[1].i64){
-      continue;
-    }
-    if (pRes->num >= (int32_t)pCtx->param[0].i64){
-      break;
+  if (pCtx->stableQuery){
+    for (int32_t i = 0; i < pCtx->size; ++i) {
+      char *data = GET_INPUT_DATA(pCtx, i);
+
+      TSKEY ts = (pCtx->ptsList != NULL)? GET_TS_DATA(pCtx, i):0;
+      do_tail_function_add(pRes, (int32_t)(pCtx->param[0].i64 + pCtx->param[1].i64), data, ts,
+                           pCtx->inputBytes, &pCtx->tagInfo, NULL, pCtx->currentStage);
     }
-    char *data = GET_INPUT_DATA(pCtx, i);
+  }else{
+    for (int32_t i = pCtx->size - 1; i >= 0; --i) {
+      if (pRes->offset++ < (int32_t)pCtx->param[1].i64){
+        continue;
+      }
+      if (pRes->num >= (int32_t)pCtx->param[0].i64){    // query complete
+        pCtx->resultInfo->complete = true;
+        for (int32_t j = 0; j < pCtx->tagInfo.numOfTagCols; ++j) {
+          SQLFunctionCtx *ctx = pCtx->tagInfo.pTagCtxList[j];
+          ctx->resultInfo->complete = true;
+        }
+        break;
+      }
+      char *data = GET_INPUT_DATA(pCtx, i);
 
-    TSKEY ts = (pCtx->ptsList != NULL)? GET_TS_DATA(pCtx, i):0;
+      TSKEY ts = (pCtx->ptsList != NULL)? GET_TS_DATA(pCtx, i):0;
 
-    valueTailAssign(pRes->res[pRes->num], pCtx->inputBytes, data, ts, &pCtx->tagInfo, NULL, pCtx->currentStage);
+      valueTailAssign(pRes->res[pRes->num], pCtx->inputBytes, data, ts, &pCtx->tagInfo, NULL, pCtx->currentStage);
 
-    pRes->num++;
+      pRes->num++;
+    }
   }
 
   // treat the result as only one result
@@ -5534,7 +5549,7 @@ static void tail_func_merge(SQLFunctionCtx *pCtx) {
 
   // the intermediate result is binary, we only use the output data type
   for (int32_t i = 0; i < pInput->num; ++i) {
-    do_tail_function_add(pOutput, (int32_t)pCtx->param[0].i64, pInput->res[i]->data, pInput->res[i]->timestamp,
+    do_tail_function_add(pOutput, (int32_t)(pCtx->param[0].i64 + pCtx->param[1].i64), pInput->res[i]->data, pInput->res[i]->timestamp,
                         pCtx->outputBytes, &pCtx->tagInfo, pInput->res[i]->data + pCtx->outputBytes, pCtx->currentStage);
   }
 
@@ -5555,9 +5570,11 @@ static void tail_func_finalizer(SQLFunctionCtx *pCtx) {
 
   int32_t bytes = 0;
   int32_t type = 0;
+  int32_t start = 0;
   if (pCtx->currentStage == MERGE_STAGE) {
     bytes = pCtx->outputBytes;
     type = pCtx->outputType;
+    start = pCtx->param[1].i64;
     assert(pCtx->inputType == TSDB_DATA_TYPE_BINARY);
   } else {
     bytes = pCtx->inputBytes;
@@ -5580,7 +5597,7 @@ static void tail_func_finalizer(SQLFunctionCtx *pCtx) {
     qError("calloc error in tail_func_finalizer: size:%d, num:%d", (int32_t)size, GET_RES_INFO(pCtx)->numOfRes);
     return;
   }
-  for(int32_t start = pCtx->param[1].i64, i = 0; start < pRes->num; start++, i++){
+  for(int32_t i = 0; start < pRes->num; start++, i++){
     memcpy(data + i * size, pRes->res[start], size);
   }
   taosqsort(data, (size_t)GET_RES_INFO(pCtx)->numOfRes, size, &support, sortCompareFn);
diff --git a/src/query/src/qUtil.c b/src/query/src/qUtil.c
index 6aebb32191813ee7bdc79628246e8c2dddba79ee..cc85c421a9a9ee41eae368d0db823a61ee1c9f67 100644
--- a/src/query/src/qUtil.c
+++ b/src/query/src/qUtil.c
@@ -38,10 +38,12 @@ int32_t getRowNumForMultioutput(SQueryAttr* pQueryAttr, bool topBottomQuery, boo
       if (pQueryAttr->pExpr1[i].base.functionId == TSDB_FUNC_TOP ||
           pQueryAttr->pExpr1[i].base.functionId == TSDB_FUNC_BOTTOM ||
           pQueryAttr->pExpr1[i].base.functionId == TSDB_FUNC_SAMPLE ||
-          pQueryAttr->pExpr1[i].base.functionId == TSDB_FUNC_HISTOGRAM ||
-          pQueryAttr->pExpr1[i].base.functionId == TSDB_FUNC_TAIL) {
+          pQueryAttr->pExpr1[i].base.functionId == TSDB_FUNC_HISTOGRAM) {
         return (int32_t)pQueryAttr->pExpr1[i].base.param[0].i64;
       }
+      if (pQueryAttr->pExpr1[i].base.functionId == TSDB_FUNC_TAIL) {
+        return (int32_t)(pQueryAttr->pExpr1[i].base.param[0].i64 + pQueryAttr->pExpr1[i].base.param[1].i64);
+      }
     }
     if (pQueryAttr->uniqueQuery){
       return MAX_UNIQUE_RESULT_ROWS;
diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index abf14520e8c9fc5140200753b5272e1aa0c3b4e1..60c7311d4c0f3d784231fceb8a7e2628a5bd4eda 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -1855,12 +1855,11 @@ static void mergeTwoRowFromMem(STsdbQueryHandle* pQueryHandle, int32_t capacity,
   while(i < numOfCols && (j < numOfColsOfRow1 || k < numOfColsOfRow2)) {
     SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
 
-    pData = (char*)pColInfo->pData + numOfRows * pColInfo->info.bytes;
-//    if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
-//      pData = (char*)pColInfo->pData + numOfRows * pColInfo->info.bytes;
-//    } else {
-//      pData = (char*)pColInfo->pData + (capacity - numOfRows - 1) * pColInfo->info.bytes;
-//    }
+    if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
+      pData = (char*)pColInfo->pData + numOfRows * pColInfo->info.bytes;
+    } else {
+      pData = (char*)pColInfo->pData + (capacity - numOfRows - 1) * pColInfo->info.bytes;
+    }
 
     int32_t colIdOfRow1;
     if(j >= numOfColsOfRow1) {
@@ -1991,12 +1990,11 @@ static void mergeTwoRowFromMem(STsdbQueryHandle* pQueryHandle, int32_t capacity,
   if(forceSetNull) {
     while (i < numOfCols) { // the remain columns are all null data
       SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
-      pData = (char*)pColInfo->pData + numOfRows * pColInfo->info.bytes;
-//      if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
-//        pData = (char*)pColInfo->pData + numOfRows * pColInfo->info.bytes;
-//      } else {
-//        pData = (char*)pColInfo->pData + (capacity - numOfRows - 1) * pColInfo->info.bytes;
-//      }
+      if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
+        pData = (char*)pColInfo->pData + numOfRows * pColInfo->info.bytes;
+      } else {
+        pData = (char*)pColInfo->pData + (capacity - numOfRows - 1) * pColInfo->info.bytes;
+      }
 
       if (pColInfo->info.type == TSDB_DATA_TYPE_BINARY || pColInfo->info.type == TSDB_DATA_TYPE_NCHAR) {
         setVardataNull(pData, pColInfo->info.type);
@@ -2342,7 +2340,7 @@ static void doMergeTwoLevelData(STsdbQueryHandle* pQueryHandle, STableCheckInfo*
     SWAP(cur->win.skey, cur->win.ekey, TSKEY);
   }
 
-  //moveDataToFront(pQueryHandle, numOfRows, numOfCols);
+  moveDataToFront(pQueryHandle, numOfRows, numOfCols);
   updateInfoAfterMerge(pQueryHandle, pCheckInfo, numOfRows, pos);
   doCheckGeneratedBlockRange(pQueryHandle);
 
@@ -2980,14 +2978,14 @@ static int tsdbReadRowsFromCache(STableCheckInfo* pCheckInfo, TSKEY maxKey, int
   assert(numOfRows <= maxRowsToRead);
 
   // if the buffer is not full in case of descending order query, move the data in the front of the buffer
-//  if (!ASCENDING_TRAVERSE(pQueryHandle->order) && numOfRows < maxRowsToRead) {
-//    int32_t emptySize = maxRowsToRead - numOfRows;
-//
-//    for(int32_t i = 0; i < numOfCols; ++i) {
-//      SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
-//      memmove((char*)pColInfo->pData, (char*)pColInfo->pData + emptySize * pColInfo->info.bytes, numOfRows * pColInfo->info.bytes);
-//    }
-//  }
+  if (!ASCENDING_TRAVERSE(pQueryHandle->order) && numOfRows < maxRowsToRead) {
+    int32_t emptySize = maxRowsToRead - numOfRows;
+
+    for(int32_t i = 0; i < numOfCols; ++i) {
+      SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
+      memmove((char*)pColInfo->pData, (char*)pColInfo->pData + emptySize * pColInfo->info.bytes, numOfRows * pColInfo->info.bytes);
+    }
+  }
 
   int64_t elapsedTime = taosGetTimestampUs() - st;
   tsdbDebug("%p build data block from cache completed, elapsed time:%"PRId64" us, numOfRows:%d, numOfCols:%d, 0x%"PRIx64, pQueryHandle,