diff --git a/include/libs/function/function.h b/include/libs/function/function.h
index 25b0cbc6b7..9fa89f0415 100644
--- a/include/libs/function/function.h
+++ b/include/libs/function/function.h
@@ -110,11 +110,11 @@ typedef struct SFileBlockInfo {
 #define FUNCTION_COV          38
 
 typedef struct SResultRowEntryInfo {
-  int8_t   hasResult:6;       // result generated, not NULL value
+//  int8_t   hasResult:6;       // result generated, not NULL value
   bool     initialized:1;     // output buffer has been initialized
   bool     complete:1;        // query has completed
-  uint8_t  isNullRes:1;       // the result is null
-  uint8_t  numOfRes:7;        // num of output result in current buffer
+  uint8_t  isNullRes:6;       // the result is null
+  uint8_t  numOfRes;        // num of output result in current buffer
 } SResultRowEntryInfo;
 
 // determine the real data need to calculated the result
@@ -157,7 +157,6 @@ typedef struct SResultDataInfo {
 
 #define GET_RES_INFO(ctx)        ((ctx)->resultInfo)
 #define GET_ROWCELL_INTERBUF(_c) ((void*) ((char*)(_c) + sizeof(SResultRowEntryInfo)))
-#define DATA_SET_FLAG ','        // to denote the output area has data, not null value
 
 typedef struct SInputColumnInfoData {
   int32_t           totalRows;      // total rows in current columnar data
diff --git a/source/libs/executor/src/executorimpl.c b/source/libs/executor/src/executorimpl.c
index 02133ca94f..16a94defc2 100644
--- a/source/libs/executor/src/executorimpl.c
+++ b/source/libs/executor/src/executorimpl.c
@@ -1008,7 +1008,6 @@ void doApplyFunctions(SqlFunctionCtx* pCtx, STimeWindow* pWin, SColumnInfoData*
       SScalarParam tw = {.numOfRows = 5, .columnData = pTimeWindowData};
       pCtx[k].sfp.process(&tw, 1, &out);
       pEntryInfo->numOfRes = 1;
-      pEntryInfo->hasResult = ',';
       continue;
     }
 
@@ -3281,7 +3280,8 @@ void doFilter(const SNode* pFilterNode, SSDataBlock* pBlock) {
   }
 
   SFilterInfo* filter = NULL;
-  int32_t      code = filterInitFromNode((SNode*)pFilterNode, &filter, 0);
+
+  int32_t code = filterInitFromNode((SNode*)pFilterNode, &filter, 0);
 
   SFilterColumnParam param1 = {.numOfCols = pBlock->info.numOfCols, .pDataBlock = pBlock->pDataBlock};
   code = filterSetDataFromSlotId(filter, &param1);
@@ -3292,6 +3292,7 @@ void doFilter(const SNode* pFilterNode, SSDataBlock* pBlock) {
   SSDataBlock* px = createOneDataBlock(pBlock);
   blockDataEnsureCapacity(px, pBlock->info.rows);
 
+  // todo extract method
   int32_t numOfRow = 0;
   for (int32_t i = 0; i < pBlock->info.numOfCols; ++i) {
     SColumnInfoData* pDst = taosArrayGet(px->pDataBlock, i);
@@ -3303,7 +3304,11 @@ void doFilter(const SNode* pFilterNode, SSDataBlock* pBlock) {
         continue;
       }
 
-      colDataAppend(pDst, numOfRow, colDataGetData(pSrc, j), false);
+      if (colDataIsNull_s(pSrc, j)) {
+        colDataAppendNULL(pDst, numOfRow);
+      } else {
+        colDataAppend(pDst, numOfRow, colDataGetData(pSrc, j), false);
+      }
       numOfRow += 1;
     }
 
@@ -3521,7 +3526,7 @@ static int32_t doCopyToSDataBlock(SDiskbasedBuf* pBuf, SGroupResInfo* pGroupResI
       SResultRowEntryInfo* pEntryInfo = getResultCell(pRow, j, rowCellOffset);
 
       char* in = GET_ROWCELL_INTERBUF(pEntryInfo);
-      colDataAppend(pColInfoData, nrows, in, pEntryInfo->numOfRes == 0);
+      colDataAppend(pColInfoData, nrows, in, pEntryInfo->isNullRes);
     }
 
     releaseBufPage(pBuf, page);
diff --git a/source/libs/executor/src/groupoperator.c b/source/libs/executor/src/groupoperator.c
index d0cedba0d0..a33a240328 100644
--- a/source/libs/executor/src/groupoperator.c
+++ b/source/libs/executor/src/groupoperator.c
@@ -106,7 +106,7 @@ static bool groupKeyCompare(SGroupbyOperatorInfo* pInfo, SSDataBlock* pBlock, in
   return true;
 }
 
-static void recordGroupKeys(SGroupbyOperatorInfo* pInfo, SSDataBlock* pBlock, int32_t rowIndex, int32_t numOfGroupCols) {
+static void recordNewGroupKeys(SGroupbyOperatorInfo* pInfo, SSDataBlock* pBlock, int32_t rowIndex, int32_t numOfGroupCols) {
   SColumnDataAgg* pColAgg = NULL;
 
   for (int32_t i = 0; i < numOfGroupCols; ++i) {
@@ -131,7 +131,7 @@ static void recordGroupKeys(SGroupbyOperatorInfo* pInfo, SSDataBlock* pBlock, in
   }
 }
 
-static int32_t generatedHashKey(void* pKey, int32_t* length, SArray* pGroupColVals) {
+static int32_t buildGroupValKey(void* pKey, int32_t* length, SArray* pGroupColVals) {
   ASSERT(pKey != NULL);
   size_t numOfGroupCols = taosArrayGetSize(pGroupColVals);
 
@@ -170,11 +170,12 @@ static void doAssignGroupKeys(SqlFunctionCtx* pCtx, int32_t numOfOutput, int32_t
         char* dest = GET_ROWCELL_INTERBUF(pEntryInfo);
         char* data = colDataGetData(pColInfoData, rowIndex);
 
-        // set result exists, todo refactor
         memcpy(dest, data, pColInfoData->info.bytes);
-        pEntryInfo->hasResult = DATA_SET_FLAG;
-        pEntryInfo->numOfRes = 1;
+      } else { // it is a NULL value
+        pEntryInfo->isNullRes = 1;
       }
+
+      pEntryInfo->numOfRes = 1;
     }
   }
 }
@@ -197,7 +198,7 @@ static void doHashGroupbyAgg(SOperatorInfo* pOperator, SSDataBlock* pBlock) {
   for (int32_t j = 0; j < pBlock->info.rows; ++j) {
     // Compare with the previous row of this column, and do not set the output buffer again if they are identical.
     if (!pInfo->isInit) {
-      recordGroupKeys(pInfo, pBlock, j, numOfGroupCols);
+      recordNewGroupKeys(pInfo, pBlock, j, numOfGroupCols);
       pInfo->isInit = true;
       num++;
       continue;
@@ -209,13 +210,14 @@ static void doHashGroupbyAgg(SOperatorInfo* pOperator, SSDataBlock* pBlock) {
       continue;
     }
 
+    // The first row of a new block does not belongs to the previous existed group
     if (!equal && j == 0) {
       num++;
-      recordGroupKeys(pInfo, pBlock, j, numOfGroupCols);
+      recordNewGroupKeys(pInfo, pBlock, j, numOfGroupCols);
       continue;
     }
 
-    /*int32_t ret = */ generatedHashKey(pInfo->keyBuf, &len, pInfo->pGroupColVals);
+    /*int32_t ret = */ buildGroupValKey(pInfo->keyBuf, &len, pInfo->pGroupColVals);
     int32_t ret = setGroupResultOutputBuf_rv(&(pInfo->binfo), pOperator->numOfOutput, pInfo->keyBuf, TSDB_DATA_TYPE_VARCHAR, len, 0, pInfo->aggSup.pResultBuf, pTaskInfo, &pInfo->aggSup);
     if (ret != TSDB_CODE_SUCCESS) {  // null data, too many state code
       longjmp(pTaskInfo->env, TSDB_CODE_QRY_APP_ERROR);
@@ -226,12 +228,12 @@ static void doHashGroupbyAgg(SOperatorInfo* pOperator, SSDataBlock* pBlock) {
 
     // assign the group keys or user input constant values if required
     doAssignGroupKeys(pCtx, pOperator->numOfOutput, pBlock->info.rows, rowIndex);
-    recordGroupKeys(pInfo, pBlock, j, numOfGroupCols);
+    recordNewGroupKeys(pInfo, pBlock, j, numOfGroupCols);
     num = 1;
   }
 
   if (num > 0) {
-    /*int32_t ret = */ generatedHashKey(pInfo->keyBuf, &len, pInfo->pGroupColVals);
+    /*int32_t ret = */ buildGroupValKey(pInfo->keyBuf, &len, pInfo->pGroupColVals);
     int32_t ret =
         setGroupResultOutputBuf_rv(&(pInfo->binfo), pOperator->numOfOutput, pInfo->keyBuf, TSDB_DATA_TYPE_VARCHAR, len,
                                    0, pInfo->aggSup.pResultBuf, pTaskInfo, &pInfo->aggSup);
@@ -294,8 +296,7 @@ static SSDataBlock* hashGroupbyAggregate(SOperatorInfo* pOperator, bool* newgrou
   initGroupResInfo(&pInfo->groupResInfo, &pInfo->binfo.resultRowInfo);
 
   while(1) {
-    toSDatablock(&pInfo->groupResInfo, pInfo->aggSup.pResultBuf, pRes, pInfo->binfo.capacity,
-                 pInfo->binfo.rowCellInfoOffset);
+    toSDatablock(&pInfo->groupResInfo, pInfo->aggSup.pResultBuf, pRes, pInfo->binfo.capacity, pInfo->binfo.rowCellInfoOffset);
     doFilter(pInfo->pCondition, pRes);
 
     bool hasRemain = hasRemainDataInCurrentGroup(&pInfo->groupResInfo);
diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index fb6abe3c5d..6d8eb2c8b0 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -25,7 +25,6 @@
       break;                            \
     }                                   \
     (_info)->numOfRes = (res);          \
-    (_info)->hasResult = DATA_SET_FLAG; \
   } while (0)
 
 typedef struct SSumRes {
@@ -715,7 +714,6 @@ int32_t percentileFunction(SqlFunctionCtx *pCtx) {
   }
 
   SET_VAL(pResInfo, notNullElems, 1);
-  pResInfo->hasResult = DATA_SET_FLAG;
 }
 
 // TODO set the correct parameter.
@@ -775,9 +773,7 @@ int32_t firstFunction(SqlFunctionCtx *pCtx) {
 //      DO_UPDATE_TAG_COLUMNS(pCtx, k);
 //    }
 
-    pResInfo->hasResult = DATA_SET_FLAG;
     pResInfo->complete = true;
-
     numOfElems++;
     break;
   }
@@ -815,8 +811,6 @@ int32_t lastFunction(SqlFunctionCtx *pCtx) {
 
 //      TSKEY ts = pCtx->ptsList ? GET_TS_DATA(pCtx, i) : 0;
 //      DO_UPDATE_TAG_COLUMNS(pCtx, ts);
-
-      pResInfo->hasResult = DATA_SET_FLAG;
       pResInfo->complete = true;  // set query completed on this column
       numOfElems++;
       break;
@@ -830,10 +824,8 @@ int32_t lastFunction(SqlFunctionCtx *pCtx) {
       char* data = colDataGetData(pInputCol, i);
       TSKEY ts = pCtx->ptsList ? GET_TS_DATA(pCtx, i) : 0;
 
-      if (pResInfo->hasResult != DATA_SET_FLAG || (*(TSKEY*)buf) < ts) {
-        pResInfo->hasResult = DATA_SET_FLAG;
+      if (pResInfo->numOfRes == 0 || (*(TSKEY*)buf) < ts) {
         memcpy(buf, data, pCtx->inputBytes);
-
         *(TSKEY*)buf = ts;
 //        DO_UPDATE_TAG_COLUMNS(pCtx, ts);
       }
diff --git a/source/libs/function/src/taggfunction.c b/source/libs/function/src/taggfunction.c
index 789bfb61ee..60566d00d8 100644
--- a/source/libs/function/src/taggfunction.c
+++ b/source/libs/function/src/taggfunction.c
@@ -208,7 +208,7 @@ int32_t getNumOfResult(SqlFunctionCtx* pCtx, int32_t num, SSDataBlock* pResBlock
     SColumnInfoData* pCol = taosArrayGet(pResBlock->pDataBlock, i);
 
     SResultRowEntryInfo *pResInfo = GET_RES_INFO(&pCtx[i]);
-    if (!pResInfo->hasResult) {
+    if (pResInfo->numOfRes == 0) {
       for(int32_t j = 0; j < pResInfo->numOfRes; ++j) {
         colDataAppend(pCol, j, NULL, true);  // TODO add set null data api
       }