fix: reset interpolation buffer after last valid row for interval + fill(next)

source/libs/executor/src/tfill.c

@@ -247,7 +247,7 @@ 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, SRowVal* pRowVal) {
+static void copyCurrentRowIntoBuf(SFillInfo* pFillInfo, int32_t rowIndex, SRowVal* pRowVal, bool reset) {
   SColumnInfoData* pTsCol = taosArrayGet(pFillInfo->pSrcBlock->pDataBlock, pFillInfo->srcTsSlotId);
   pRowVal->key = ((int64_t*)pTsCol->pData)[rowIndex];
 
@@ -268,7 +268,7 @@ static void copyCurrentRowIntoBuf(SFillInfo* pFillInfo, int32_t rowIndex, SRowVa
       bool  isNull = colDataIsNull_s(pSrcCol, rowIndex);
       char* p = colDataGetData(pSrcCol, rowIndex);
 
-      saveColData(pRowVal->pRowVal, i, p, isNull);
+      saveColData(pRowVal->pRowVal, i, p, reset ? true : isNull);
     } else {
       ASSERT(0);
     }
@@ -293,10 +293,10 @@ static int32_t fillResultImpl(SFillInfo* pFillInfo, SSDataBlock* pBlock, int32_t
     // set the next value for interpolation
     if (pFillInfo->currentKey < ts && ascFill) {
       SRowVal* pRVal = pFillInfo->type == TSDB_FILL_NEXT ? &pFillInfo->next : &pFillInfo->prev;
-      copyCurrentRowIntoBuf(pFillInfo, pFillInfo->index, pRVal);
+      copyCurrentRowIntoBuf(pFillInfo, pFillInfo->index, pRVal, false);
     } else if (pFillInfo->currentKey > ts && !ascFill) {
       SRowVal* pRVal = pFillInfo->type == TSDB_FILL_NEXT ? &pFillInfo->prev : &pFillInfo->next;
-      copyCurrentRowIntoBuf(pFillInfo, pFillInfo->index, pRVal);
+      copyCurrentRowIntoBuf(pFillInfo, pFillInfo->index, pRVal, false);
     }
 
     if (((pFillInfo->currentKey < ts && ascFill) || (pFillInfo->currentKey > ts && !ascFill)) &&
@@ -316,9 +316,14 @@ static int32_t fillResultImpl(SFillInfo* pFillInfo, SSDataBlock* pBlock, int32_t
       ASSERT(pFillInfo->currentKey == ts);
       int32_t index = pBlock->info.rows;
 
-      if (pFillInfo->type == TSDB_FILL_NEXT && (pFillInfo->index + 1) < pFillInfo->numOfRows) {
+      if (pFillInfo->type == TSDB_FILL_NEXT) {
         int32_t nextRowIndex = pFillInfo->index + 1;
-        copyCurrentRowIntoBuf(pFillInfo, nextRowIndex, &pFillInfo->next);
+        if ((pFillInfo->index + 1) < pFillInfo->numOfRows) {
+          copyCurrentRowIntoBuf(pFillInfo, nextRowIndex, &pFillInfo->next, false);
+        } else {
+          // reset to null after last row
+          copyCurrentRowIntoBuf(pFillInfo, nextRowIndex, &pFillInfo->next, true);
+        }
       }
 
       // copy rows to dst buffer