database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-12-24 11:21:21 +03:00
Code Activity

Patch for Bug#52356: query_cache_debug fails on Linux.

Browse Source 
There were two problems here:
  1. misleading error message
  2. abusing KILL QUERY in the test case

1. The server reported "'DELETE FROM t1' failed: 1689: Wait on a lock was
aborted due to a pending exclusive lock", while the proper error message
should be "'DELETE FROM t1' failed: 1317: Query execution was interrupted".

The problem is that the server has two different flags for
signalling that a query is being killed: THD::killed and
mysys_var::abort. The test case triggers a race: sometimes
mysys_var::abort is set earlier than THD::killed. That leads
to the following situation:

  - thr_lock() checks mysys_var::abort and returns error status,
    since mysys_var::abort is set;

  - the caller (mysql_lock_tables()) gets an error from thr_lock(),
    but THD::killed is not set, so it decides that thr_lock() couldn't
    get a lock due to a pending exclusive lock.

This is a known issue with the server and it's not going to be fixed soon.

5.5 differs from 5.1 here as follows: when thr_lock() returns an error:
  - 5.1 continues trying thr_lock() until success;
  - 5.5 propagates the error

2. The test case uses KILL QUERY is a highly concurent environment.

The fix is to wait for the dying statement to rest in peace before
executing another DELETE FROM t1.
This commit is contained in:
Alexander Nozdrin
2010-04-30 16:12:41 +04:00
parent ae2eafc098
commit c784ee2782
2 changed files with 3 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
mysql-test/t/query_cache_debug.test
View File

@@ -221,6 +221,9 @@ KILL QUERY @thread_id;
SELECT SQL_NO_CACHE id FROM information_schema.processlist WHERE state='wait_in_query_cache_invalidate2' LIMIT 1 INTO @flush_thread_id;
KILL QUERY @flush_thread_id;
LET $wait_condition= SELECT SQL_NO_CACHE COUNT(*) = 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE Id = @flush_thread_id AND Command = 'Sleep';
--source include/wait_condition.inc
--echo **
--echo *************************************************************************
--echo ** No tables should be locked