From 63a917581d8a10dcfdcbfd1c0dd2ed74e34d0c6e Mon Sep 17 00:00:00 2001
From: Ganlin Zhao <ganlinzhao@hotmail.com>
Date: Mon, 20 Jun 2022 16:11:42 +0800
Subject: [PATCH] fix(query): select last(*) from super table returns 0 if all
 columns are NULL.

TD-16561
---
 source/libs/function/src/builtinsimpl.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index c72d7b5106..7440df062f 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -2563,9 +2563,6 @@ int32_t lastFunction(SqlFunctionCtx* pCtx) {
 }
 
 static void firstLastTransferInfo(SFirstLastRes* pInput, SFirstLastRes* pOutput, bool isFirst) {
-  if (!pInput->hasResult) {
-    return;
-  }
   pOutput->bytes = pInput->bytes;
   TSKEY* tsIn = (TSKEY*)(pInput->buf + pInput->bytes);
   TSKEY* tsOut = (TSKEY*)(pOutput->buf + pInput->bytes);
@@ -2599,7 +2596,9 @@ static int32_t firstLastFunctionMergeImpl(SqlFunctionCtx* pCtx, bool isFirstQuer
 
   firstLastTransferInfo(pInputInfo, pInfo, isFirstQuery);
 
-  SET_VAL(GET_RES_INFO(pCtx), 1, 1);
+  int32_t numOfElems = pInputInfo->hasResult ? 1 : 0;
+
+  SET_VAL(GET_RES_INFO(pCtx), numOfElems, 1);
 
   return TSDB_CODE_SUCCESS;
 }
@@ -2624,6 +2623,7 @@ int32_t firstLastFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
 int32_t firstLastPartialFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
   SResultRowEntryInfo* pEntryInfo = GET_RES_INFO(pCtx);
   SFirstLastRes*       pRes = GET_ROWCELL_INTERBUF(GET_RES_INFO(pCtx));
+
   int32_t              resultBytes = getFirstLastInfoSize(pRes->bytes);
   char*                res = taosMemoryCalloc(resultBytes + VARSTR_HEADER_SIZE, sizeof(char));
 
-- 
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