Bug #11973 SELECT .. INTO var_name; in trigger cause crash on update

Description:
Hi,
 
Using a SELECT .. INTO var_name in a trigger causes the server to crash when updating the table from 2 different sessions.

An ugly work around is to do a FLUSH TABLES if privileges alow it. A better one is to
use a SET var_name .. when possible.

Regards,

Geert

How to repeat:

-- Test case:

drop table if exists csct1;
create table csct1 ( id int not null auto_increment key, username varchar(16), d
 datetime);
insert into csct1 values (),(),(),();
delimiter //;
create trigger csct1_whoupdated before update on csct1
for each row
begin
  declare user varchar(16);
  select substring_index(user(),_utf8'@',1) into user;
  if user IN ('geert') then
      set NEW.username = 'Belgian';
  else
      set NEW.username = 'Unknown';
  end if;
end//
delimiter ;//

Two sessions:
- ses1 logged in as root
- ses2 logged in as clueless user geert

ses1:
mysql> -- Create above tables, data and trigger
mysql> update csct1 set d = now() where id = 1;

ses2:
mysql> update csct1 set d = now() where id = 1;
RROR 2013 (HY000): Lost connection to MySQL server during query

Workaround using FUSH TABLES
-----------------------------------
ses1:
mysql> -- Create above tables, data and trigger
mysql> update csct1 set d = now() where id = 1;
mysql> flush tables;

ses2:
mysql> update csct1 set d = now() where id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0
mysql>

Best workaround I found in this case:
-------------------------------------------------------
In the trigger replacing:
  select substring_index(user(),_utf8'@',1) into user;
With:
  set user = substring_index(user(),_utf8'@',1);

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/internals/28086

Fixed in 5.0.12

Noted in 5.0.12 changelog.