From a52e0027cf6508a562a4ed04ba30c90763c46fe4 Mon Sep 17 00:00:00 2001
From: Ganlin Zhao <ganlinzhao@hotmail.com>
Date: Wed, 18 May 2022 16:03:59 +0800
Subject: [PATCH] enh(query): support count(NULL) = 0

---
 source/libs/function/src/builtinsimpl.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index d8d7a2f62e..77126225bf 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -330,8 +330,18 @@ static FORCE_INLINE int32_t getNumofElem(SqlFunctionCtx* pCtx) {
 int32_t countFunction(SqlFunctionCtx* pCtx) {
   int32_t numOfElem = getNumofElem(pCtx);
   SResultRowEntryInfo* pResInfo = GET_RES_INFO(pCtx);
-  char*                buf = GET_ROWCELL_INTERBUF(pResInfo);
-  *((int64_t*)buf) += numOfElem;
+
+  SInputColumnInfoData* pInput = &pCtx->input;
+  int32_t type   = pInput->pData[0]->info.type;
+
+  char* buf = GET_ROWCELL_INTERBUF(pResInfo);
+  if (IS_NULL_TYPE(type)) {
+    //select count(NULL) returns 0
+    numOfElem = 1;
+    *((int64_t*)buf) = 0;
+  } else {
+    *((int64_t*)buf) += numOfElem;
+  }
 
   SET_VAL(pResInfo, numOfElem, 1);
   return TSDB_CODE_SUCCESS;
-- 
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