MySQL Bugs: #115706: use database doesn't work

Bug #115706	use database doesn't work
Submitted:	28 Jul 2024 8:39	Modified:	10 Mar 19:28
Reporter:	csg sz	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Command-line Clients	Severity:	S3 (Non-critical)
Version:	8.4	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	regression, use database doesn't work

Description:
I started by executing the following statement in session 1：
mysql> use test;
mysql> begin;
mysql> select * from t22;

Then execute the following statement in session 2：
mysql> drop table t22;   ------It'll hang here.

Finally, execute the following statement in session 3：
mysql -uroot -p
mysql> use test; ------It'll hang here.I think it's a bug.I can't get into the database.

How to repeat:
I started by executing the following statement in session 1：
mysql> use test;
mysql> begin;
mysql> select * from t22;

Then execute the following statement in session 2：
mysql> drop table t22;   ------It'll hang here.

Finally, execute the following statement in session 3：
mysql -uroot -p
mysql> use test; ------It'll hang here.I think it's a bug.I can't get into the database.

Hi Mr. sz,

Thank you for your bug report.

However, we can not repeat it with out official binary for 8.4.2.

Yes, of course, drop table was blocked. It is expected behaviour. That is how MDL work.

But , using test schema went without any problems.

Can't repeat.

HI Mr. sz,

Actually, 8.4.2 has this bug, which 8.4.1 did not have !!!!

Thank you for your test case !!!!!

Verified as reported.

This bug affects latest 8.4 and 9.0.

It does not affect latest 8.0, which is 8.0.39.

Posted by developer:
 
Added the following entry to the MySQL 9.4.0 and 8.4.5 changlogs:

"If one client session had a uncommitted transaction that caused a DROP TABLE statement in another client session to be blocked, a third client session hung when trying to issue a USE DATABASE statement."

Posted by developer:
 
Move the changelog entry from the 9.4.0 to the 9.3.0 changelog.