| Bug #29878 | Garbage data generation when executing SESSION_USER() on a slave. | ||
|---|---|---|---|
| Submitted: | 18 Jul 2007 20:40 | Modified: | 6 Aug 2007 19:20 |
| Reporter: | Dave Costantino | ||
| Status: | Closed | ||
| Category: | Server: Replication | Severity: | S2 (Serious) |
| Version: | 5.0.30, 5.0 BK, 5.1 BK | OS: | Any |
| Assigned to: | Alexey Botchkov | Target Version: | |
[19 Jul 2007 0:25]
Sveta Smirnova
Thank you for the report. Verified as described. Version 4.1 returns different result: select * from test_rep; id data 1
[25 Jul 2007 13:58]
Bugs System
A patch for this bug has been committed. After review, it may be pushed to the relevant source trees for release in the next version. You can access the patch from: http://lists.mysql.com/commits/31540 ChangeSet@1.2476, 2007-07-25 15:56:55+05:00, holyfoot@mysql.com +5 -0 Bug #29878 Garbage data generation when executing SESSION_USER() on a slave. Item_func_user doesn't calculate anything in it's val_str() method, just returns saved str_value. Though Item::save_in_field method can destroy str_value, relying on val_str() return. As a result we get the garbage stored in field. We cannot use Item::save_in_field implementation for Item_func_user, reimplement it in simpler way.
[27 Jul 2007 15:16]
Alexander Barkov
ok to push
[27 Jul 2007 16:43]
Bugs System
A patch for this bug has been committed. After review, it may be pushed to the relevant source trees for release in the next version. You can access the patch from: http://lists.mysql.com/commits/31710 ChangeSet@1.2476, 2007-07-27 18:42:25+05:00, holyfoot@mysql.com +5 -0 Bug #29878 Garbage data generation when executing SESSION_USER() on a slave. Item_func_user doesn't calculate anything in it's val_str() method, just returns saved str_value. Though Item::save_in_field method can destroy str_value, relying on val_str() return. As a result we get the garbage stored in field. We cannot use Item::save_in_field implementation for Item_func_user, reimplement it in simpler way.
[2 Aug 2007 21:11]
Bugs System
Pushed into 5.1.21-beta
[2 Aug 2007 21:14]
Bugs System
Pushed into 5.0.48
[6 Aug 2007 19:20]
Paul DuBois
Noted in 5.0.48, 5.1.21 changelogs. SESSION_USER() returned garbage data (rather than the correct value of the empty string) when executed by a slave SQL thread.
Description: The SESSION_USER() function generates junk data when executed on a slave server when MySQL is configured for replication. While it may not be possible to execute this function identically on the slave, it should not produce garbage. How to repeat: Configure 2 MySQL servers in a master/slave configuration. Create a table on the master: CREATE TABLE `test_rep` ( `id` int(11) NOT NULL auto_increment, `data` varchar(100) default NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM; On the master, execute an INSERT: insert into test_rep(data) values (session_user()); Verify the data is correct with 'select'. On the master, you will see valid data: mysql> select * from test_rep; +----+----------------------+ | id | data | +----+----------------------+ | 1 | root@127.0.0.1 | +----+----------------------+ 1 row in set (0.02 sec) Execute the same select on the slave, and you will see garbage for the data field: mysql> select * from test_rep; +----+------------------------------------------------------------------------------------------------------+ | id | data | +----+------------------------------------------------------------------------------------------------------+ | 1 | (iO [ jO hfO ??W hfO ?R? ?r?36??+ | +----+------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec) Suggested fix: If the master SESSION_USER cannot be determined from the execution context on the slave, have it generate an empty string or other sensible value.