From cca327190d3f7ea844617cf5ff60051ec7a97f74 Mon Sep 17 00:00:00 2001
From: Haojun Liao <hjliao@taosdata.com>
Date: Tue, 31 May 2022 17:46:35 +0800
Subject: [PATCH] fix(query): restore some remove attributes.

---
 source/libs/function/src/builtinsimpl.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index c6c707a91c..6f7ace45b3 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -226,6 +226,7 @@ typedef struct SUniqueInfo {
   int32_t   numOfPoints;
   uint8_t   colType;
   int16_t   colBytes;
+  bool      hasNull; //null is not hashable, handle separately
   SHashObj  *pHash;
   char      pItems[];
 } SUniqueInfo;
@@ -3878,10 +3879,11 @@ static void doUniqueAdd(SUniqueInfo* pInfo, char *data, TSKEY ts, bool isNull) {
   if (isNull == true) {
     int32_t size = sizeof(SUniqueItem) + pInfo->colBytes;
     SUniqueItem *pItem = (SUniqueItem *)(pInfo->pItems + pInfo->numOfPoints * size);
-    if (pItem->isNull == false) {
+    if (pInfo->hasNull == false && pItem->isNull == false) {
       pItem->timestamp = ts;
       pItem->isNull = true;
       pInfo->numOfPoints++;
+      pInfo->hasNull = true;
     } else if (pItem->timestamp > ts && pItem->isNull == true) {
       pItem->timestamp = ts;
     }
-- 
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