From e45023f3e98c869c1e6dc1525b573552ad03281f Mon Sep 17 00:00:00 2001
From: Haojun Liao <hjliao@taosdata.com>
Date: Wed, 30 Nov 2022 12:23:08 +0800
Subject: [PATCH] fix(query): add an null ptr checking before copying memory.

---
 source/dnode/vnode/src/tsdb/tsdbRead.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index 4ba311212a..26c9ce6810 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -775,7 +775,10 @@ static void doCopyColVal(SColumnInfoData* pColInfoData, int32_t rowIndex, int32_
     } else {
       varDataSetLen(pSup->buildBuf[colIndex], pColVal->value.nData);
       ASSERT(pColVal->value.nData <= pColInfoData->info.bytes);
-      memcpy(varDataVal(pSup->buildBuf[colIndex]), pColVal->value.pData, pColVal->value.nData);
+      if (pColVal->value.nData > 0) {  // pData may be null, if nData is 0
+        memcpy(varDataVal(pSup->buildBuf[colIndex]), pColVal->value.pData, pColVal->value.nData);
+      }
+
       colDataAppend(pColInfoData, rowIndex, pSup->buildBuf[colIndex], false);
     }
   } else {