diff --git a/include/common/tdatablock.h b/include/common/tdatablock.h
index 4208d856485d095a1d955de9eef2366c643eefba..e1d3b016113e6a117f81d2ceaf2034da38e7879c 100644
--- a/include/common/tdatablock.h
+++ b/include/common/tdatablock.h
@@ -41,9 +41,9 @@ typedef struct SBlockOrderInfo {
     BMCharPos(bm_, r_) |= (1u << (7u - BitPos(r_))); \
   } while (0)
 
-#define colDataClearNull_f(bm_, r_)                  \
-  do {                                                \
-    BMCharPos(bm_, r_) &= ~(1u << (7u - BitPos(r_))); \
+#define colDataClearNull_f(bm_, r_)                             \
+  do {                                                          \
+    BMCharPos(bm_, r_) &= ((char)(~(1u << (7u - BitPos(r_))))); \
   } while (0)
 
 #define colDataIsNull_var(pColumnInfoData, row)  (pColumnInfoData->varmeta.offset[row] == -1)
diff --git a/source/common/src/tdatablock.c b/source/common/src/tdatablock.c
index c300c3e6f0eb81059c611b5cb05ecb1d2991ff4b..e9be89a68bfd108a3aa900b3cb8f81af1fe5ed6e 100644
--- a/source/common/src/tdatablock.c
+++ b/source/common/src/tdatablock.c
@@ -1679,15 +1679,15 @@ static void colDataKeepFirstNRows(SColumnInfoData* pColInfoData, size_t n, size_
     pColInfoData->varmeta.length = colDataMoveVarData(pColInfoData, 0, n);
     memset(&pColInfoData->varmeta.offset[n], 0, total - n);
   } else {  // reset the bitmap value
-    int32_t stopIndex = BitmapLen(n) * 8;
-    for(int32_t i = n + 1; i < stopIndex; ++i) {
+    /*int32_t stopIndex = BitmapLen(n) * 8;
+    for(int32_t i = n; i < stopIndex; ++i) {
       colDataClearNull_f(pColInfoData->nullbitmap, i);
     }
 
     int32_t remain = BitmapLen(total) - BitmapLen(n);
     if (remain > 0) {
-      memset(pColInfoData->nullbitmap, 0, remain);
-    }
+      memset(pColInfoData->nullbitmap+BitmapLen(n), 0, remain);
+    }*/
   }
 }
 
diff --git a/source/libs/executor/src/tfill.c b/source/libs/executor/src/tfill.c
index 42b1d058b544a28414e11ffb486f5a5c7fefb2a3..4c8967744e0ac0f0df5116d5f0f47bf0dc7b376e 100644
--- a/source/libs/executor/src/tfill.c
+++ b/source/libs/executor/src/tfill.c
@@ -60,8 +60,18 @@ static void setNullRow(SSDataBlock* pBlock, SFillInfo* pFillInfo, int32_t rowInd
     if (pCol->notFillCol) {
       bool filled = fillIfWindowPseudoColumn(pFillInfo, pCol, pDstColInfo, rowIndex);
       if (!filled) {
-        SArray*     p = FILL_IS_ASC_FILL(pFillInfo) ? pFillInfo->prev.pRowVal : pFillInfo->next.pRowVal;
-        SGroupKeys* pKey = taosArrayGet(p, i);
+        SRowVal* p = NULL;
+        if (FILL_IS_ASC_FILL(pFillInfo)) {
+          if (pFillInfo->prev.key != 0) {
+            p = &pFillInfo->prev;  // prev has been set value
+          } else { // otherwise, use the value in the next row
+            p = &pFillInfo->next;
+          }
+        } else {
+          p = &pFillInfo->next;
+        }
+
+        SGroupKeys* pKey = taosArrayGet(p->pRowVal, i);
         doSetVal(pDstColInfo, rowIndex, pKey);
       }
     } else {
@@ -261,7 +271,10 @@ static void initBeforeAfterDataBuf(SFillInfo* pFillInfo) {
 
 static void saveColData(SArray* rowBuf, int32_t columnIndex, const char* src, bool isNull);
 
-static void copyCurrentRowIntoBuf(SFillInfo* pFillInfo, int32_t rowIndex, SArray* pRow) {
+static void copyCurrentRowIntoBuf(SFillInfo* pFillInfo, int32_t rowIndex, SRowVal* pRowVal) {
+  SColumnInfoData* pTsCol = taosArrayGet(pFillInfo->pSrcBlock->pDataBlock, pFillInfo->srcTsSlotId);
+  pRowVal->key = ((int64_t*)pTsCol->pData)[rowIndex];
+
   for (int32_t i = 0; i < pFillInfo->numOfCols; ++i) {
     int32_t type = pFillInfo->pFillCol[i].pExpr->pExpr->nodeType;
     if (type == QUERY_NODE_COLUMN || type == QUERY_NODE_OPERATOR || type == QUERY_NODE_FUNCTION) {
@@ -272,7 +285,7 @@ static void copyCurrentRowIntoBuf(SFillInfo* pFillInfo, int32_t rowIndex, SArray
       bool  isNull = colDataIsNull_s(pSrcCol, rowIndex);
       char* p = colDataGetData(pSrcCol, rowIndex);
 
-      saveColData(pRow, i, p, isNull);
+      saveColData(pRowVal->pRowVal, i, p, isNull);
     } else {
       ASSERT(0);
     }
@@ -296,7 +309,7 @@ static int32_t fillResultImpl(SFillInfo* pFillInfo, SSDataBlock* pBlock, int32_t
 
     // set the next value for interpolation
     if ((pFillInfo->currentKey < ts && ascFill) || (pFillInfo->currentKey > ts && !ascFill)) {
-      copyCurrentRowIntoBuf(pFillInfo, pFillInfo->index, pFillInfo->next.pRowVal);
+      copyCurrentRowIntoBuf(pFillInfo, pFillInfo->index, &pFillInfo->next);
     }
 
     if (((pFillInfo->currentKey < ts && ascFill) || (pFillInfo->currentKey > ts && !ascFill)) &&
@@ -318,7 +331,7 @@ static int32_t fillResultImpl(SFillInfo* pFillInfo, SSDataBlock* pBlock, int32_t
 
       if (pFillInfo->type == TSDB_FILL_NEXT && (pFillInfo->index + 1) < pFillInfo->numOfRows) {
         int32_t nextRowIndex = pFillInfo->index + 1;
-        copyCurrentRowIntoBuf(pFillInfo, nextRowIndex, pFillInfo->next.pRowVal);
+        copyCurrentRowIntoBuf(pFillInfo, nextRowIndex, &pFillInfo->next);
       }
 
       // copy rows to dst buffer
@@ -334,6 +347,9 @@ static int32_t fillResultImpl(SFillInfo* pFillInfo, SSDataBlock* pBlock, int32_t
         if (!colDataIsNull_s(pSrc, pFillInfo->index)) {
           colDataAppend(pDst, index, src, false);
           saveColData(pFillInfo->prev.pRowVal, i, src, false);
+          if (pFillInfo->srcTsSlotId == dstSlotId) {
+            pFillInfo->prev.key = *(int64_t*)src;
+          }
         } else {  // the value is null
           if (pDst->info.type == TSDB_DATA_TYPE_TIMESTAMP) {
             colDataAppend(pDst, index, (const char*)&pFillInfo->currentKey, false);
diff --git a/tests/script/tsim/parser/lastrow_query.sim b/tests/script/tsim/parser/lastrow_query.sim
index 5f557fd7bd6d2d23dbf356e8443a3744167eafdb..9ca9d407b8c28f81b15bffe61d95f302beb4d74b 100644
--- a/tests/script/tsim/parser/lastrow_query.sim
+++ b/tests/script/tsim/parser/lastrow_query.sim
@@ -70,10 +70,10 @@ sql select _wstart, t1,t1,count(*),t1,t1 from lr_stb0 where ts>'2018-09-24 00:00
 if $row != 2 then
   return -1
 endi
-if $data01 != NULL then
+if $data01 != 8 then
   return -1
 endi
-if $data02 != NULL then
+if $data02 != 8 then
   return -1
 endi
 if  $data03 != NULL then
diff --git a/tests/script/tsim/valgrind/checkUdf.sim b/tests/script/tsim/valgrind/checkUdf.sim
index 594d649714bf6524d807d996c6f8fa86fcf967d6..caf316bd868a057cd8a161817c85d8664a9db82e 100644
--- a/tests/script/tsim/valgrind/checkUdf.sim
+++ b/tests/script/tsim/valgrind/checkUdf.sim
@@ -121,12 +121,13 @@ if $data01 != 152.420471066 then
   return -1
 endi
 
-sql select udf2(f2) from udf.t2 group by 1-udf1(f1);
+sql select udf2(f2) from udf.t2 group by 1-udf1(f1) order by 1-udf1(f1)
 print $rows , $data00 , $data10
 if $rows != 2 then
   return -1
 endi
 if $data00 != 2.000000000 then
+  print expect 2.000000000 , actual: $data00
   return -1
 endi
 if $data10 != 12.083045974 then