diff --git a/source/libs/function/src/builtins.c b/source/libs/function/src/builtins.c
index 282b527b31..51f30aca21 100644
--- a/source/libs/function/src/builtins.c
+++ b/source/libs/function/src/builtins.c
@@ -884,7 +884,7 @@ const SBuiltinFuncDefinition funcMgtBuiltins[] = {
     .getEnvFunc   = getTailFuncEnv,
     .initFunc     = tailFunctionSetup,
     .processFunc  = tailFunction,
-    .finalizeFunc = NULL
+    .finalizeFunc = tailFinalize
   },
   {
     .name = "abs",
diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index 02382cc228..7081a65dd0 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -164,10 +164,10 @@ typedef struct SSampleInfo {
   int64_t *timestamp;
 } SSampleInfo;
 
-typedef struct STailUnit {
+typedef struct STailItem {
   int64_t timestamp;
   char    data[];
-} STailUnit;
+} STailItem;
 
 typedef struct STailInfo {
   int32_t   numOfPoints;
@@ -175,7 +175,7 @@ typedef struct STailInfo {
   int32_t   offset;
   uint8_t   colType;
   int16_t   colBytes;
-  STailUnit **pRes;
+  STailItem **pItems;
 } STailInfo;
 
 #define SET_VAL(_info, numOfElem, res) \
@@ -3164,7 +3164,7 @@ bool getTailFuncEnv(SFunctionNode* pFunc, SFuncExecEnv* pEnv) {
   SColumnNode* pCol = (SColumnNode*)nodesListGetNode(pFunc->pParameterList, 0);
   SValueNode*  pVal = (SValueNode*)nodesListGetNode(pFunc->pParameterList, 1);
   int32_t numOfPoints = pVal->datum.i;
-  pEnv->calcMemSize = sizeof(STailInfo) + numOfPoints * (POINTER_BYTES + sizeof(STailUnit) + pCol->node.resType.bytes);
+  pEnv->calcMemSize = sizeof(STailInfo) + numOfPoints * (POINTER_BYTES + sizeof(STailItem) + pCol->node.resType.bytes);
   return true;
 }
 
@@ -3184,36 +3184,37 @@ bool tailFunctionSetup(SqlFunctionCtx *pCtx, SResultRowEntryInfo *pResultInfo) {
     return false;
   }
 
-  pInfo->pRes = (STailUnit **)((char *)pInfo + sizeof(STailInfo));
-  char *pUnit = (char *)pInfo->pRes + pInfo->numOfPoints * POINTER_BYTES;
+  pInfo->pItems = (STailItem **)((char *)pInfo + sizeof(STailInfo));
+  char *pItem = (char *)pInfo->pItems + pInfo->numOfPoints * POINTER_BYTES;
 
-  size_t unitSize = sizeof(STailUnit) + pInfo->colBytes;
+  size_t unitSize = sizeof(STailItem) + pInfo->colBytes;
   for (int32_t i = 0; i < pInfo->numOfPoints; ++i) {
-    pInfo->pRes[i] = (STailUnit *)(pUnit + i * unitSize);
+    pInfo->pItems[i] = (STailItem *)(pItem + i * unitSize);
   }
 
   return true;
 }
 
-static void tailAssignResult(STailUnit* pUnit, char *data, int32_t colBytes, TSKEY ts) {
-  pUnit->timestamp = ts;
-  memcpy(pUnit->data, data, colBytes);
+static void tailAssignResult(STailItem* pItem, char *data, int32_t colBytes, TSKEY ts) {
+  pItem->timestamp = ts;
+  memcpy(pItem->data, data, colBytes);
 }
 
 static int32_t tailCompFn(const void *p1, const void *p2, const void *param) {
-  STailUnit *d1 = *(STailUnit **)p1;
-  STailUnit *d2 = *(STailUnit **)p2;
+  STailItem *d1 = *(STailItem **)p1;
+  STailItem *d2 = *(STailItem **)p2;
   return compareInt64Val(&d1->timestamp, &d2->timestamp);
 }
 
 static void doTailAdd(STailInfo* pInfo, char *data, TSKEY ts) {
-  STailUnit **pList = pInfo->pRes;
+  STailItem **pList = pInfo->pItems;
   if (pInfo->numAdded < pInfo->numOfPoints) {
     tailAssignResult(pList[pInfo->numAdded], data, pInfo->colBytes, ts);
-    taosheapsort((void *)pList, sizeof(STailUnit **), pInfo->numAdded + 1, NULL, tailCompFn, 0);
+    taosheapsort((void *)pList, sizeof(STailItem **), pInfo->numAdded + 1, NULL, tailCompFn, 0);
+    pInfo->numAdded++;
   } else if (pList[0]->timestamp < ts) {
     tailAssignResult(pList[0], data, pInfo->colBytes, ts);
-    taosheapadjust((void *)pList, sizeof(STailUnit **), 0, pInfo->numOfPoints - 1, NULL, tailCompFn, NULL, 0);
+    taosheapadjust((void *)pList, sizeof(STailItem **), 0, pInfo->numOfPoints - 1, NULL, tailCompFn, NULL, 0);
   }
 }
 
@@ -3231,7 +3232,7 @@ int32_t tailFunction(SqlFunctionCtx* pCtx) {
   int32_t startOffset = pCtx->offset;
   for (int32_t i = pInput->startRowIndex; i < pInput->numOfRows + pInput->startRowIndex; i += 1) {
     if (colDataIsNull_f(pInputCol->nullbitmap, i)) {
-      //colDataAppendNULL(pOutput, i);
+      colDataAppendNULL(pOutput, i);
       continue;
     }
 
@@ -3239,5 +3240,34 @@ int32_t tailFunction(SqlFunctionCtx* pCtx) {
     doTailAdd(pInfo, data, tsList[i]);
   }
 
+  for (int32_t i = 0; i < pInfo->numOfPoints; ++i) {
+    int32_t pos = startOffset + i;
+    STailItem *pItem = pInfo->pItems[i];
+    colDataAppend(pOutput, pos, pItem->data, false);
+  }
+
   return pInfo->numOfPoints;
 }
+
+int32_t tailFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
+  SResultRowEntryInfo* pEntryInfo = GET_RES_INFO(pCtx);
+  STailInfo*                pInfo = GET_ROWCELL_INTERBUF(pEntryInfo);
+  pEntryInfo->complete = true;
+
+  int32_t type = pCtx->input.pData[0]->info.type;
+  int32_t slotId = pCtx->pExpr->base.resSchema.slotId;
+
+  SColumnInfoData* pCol = taosArrayGet(pBlock->pDataBlock, slotId);
+
+  // todo assign the tag value and the corresponding row data
+  int32_t currentRow = pBlock->info.rows;
+  for (int32_t i = 0; i < pEntryInfo->numOfRes; ++i) {
+    STailItem *pItem = pInfo->pItems[i];
+    colDataAppend(pCol, currentRow, pItem->data, false);
+
+    //setSelectivityValue(pCtx, pBlock, &pInfo->pItems[i].tuplePos, currentRow);
+    currentRow += 1;
+  }
+
+  return pEntryInfo->numOfRes;
+}