From ab5cce806c8b9d7406381917512f1de21186efed Mon Sep 17 00:00:00 2001
From: Xiaoyu Wang <xiaoyuwang@taosdata.com>
Date: Tue, 7 Mar 2023 16:25:46 +0800
Subject: [PATCH] fix: fix: after the last_row cache is created, modify the
 schema and query again, resulting in taosd crash

---
 source/dnode/vnode/src/tsdb/tsdbCacheRead.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/source/dnode/vnode/src/tsdb/tsdbCacheRead.c b/source/dnode/vnode/src/tsdb/tsdbCacheRead.c
index 0ee42366de..5528b6313c 100644
--- a/source/dnode/vnode/src/tsdb/tsdbCacheRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbCacheRead.c
@@ -80,7 +80,12 @@ static int32_t saveOneRow(SArray* pRow, SSDataBlock* pBlock, SCacheRowsReader* p
         SLastCol* pColVal = (SLastCol*)taosArrayGet(pRow, 0);
         colDataSetVal(pColInfoData, numOfRows, (const char*)&pColVal->ts, false);
       } else {
-        int32_t   slotId = slotIds[i];
+        int32_t slotId = slotIds[i];
+        // add check for null value, caused by the modification of table schema (new column added).
+        if (slotId >= taosArrayGetSize(pRow)) {
+          colDataSetNULL(pColInfoData, numOfRows);
+          continue;
+        }
         SLastCol* pColVal = (SLastCol*)taosArrayGet(pRow, slotId);
         SColVal*  pVal = &pColVal->colVal;