From 2c0c13053acad7ebbf8405f9be004dffaa5e462c Mon Sep 17 00:00:00 2001
From: wjHuang <huangwenjun1997@gmail.com>
Date: Tue, 29 Nov 2022 22:12:00 +0800
Subject: [PATCH] session: workaround for upgrade from the old master version
 (#39451)

close pingcap/tidb#39450
---
 session/session.go | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/session/session.go b/session/session.go
index bdaf8abf3f6ef..437c663999b83 100644
--- a/session/session.go
+++ b/session/session.go
@@ -2898,11 +2898,17 @@ func InitMDLVariable(store kv.Storage) error {
 		if err != nil {
 			return err
 		}
+		if isNull {
+			// Workaround for version: nightly-2022-11-07 to nightly-2022-11-17.
+			enable = true
+			logutil.BgLogger().Warn("metadata lock is null")
+			err = t.SetMetadataLock(true)
+			if err != nil {
+				return err
+			}
+		}
 		return nil
 	})
-	if isNull {
-		return errors.New("metadata lock is null")
-	}
 	variable.EnableMDL.Store(enable)
 	return err
 }