Mysql crashes by some strange queries

Question

I have some strange log entries in my debug where I see that the mysql crashes:

Apr 13 08:51:16 cronjob1 mysqld[22953]: Attempting backtrace. You can use the following information to find out Apr 13 08:51:16 cronjob1 mysqld[22953]: where mysqld died. If you see no messages after this, something went Apr 13 08:51:16 cronjob1 mysqld[22953]: terribly wrong... Apr 13 08:51:16 cronjob1 mysqld[22953]: Cannot determine thread, fp=0x8543090, backtrace may not be correct. Apr 13 08:51:16 cronjob1 mysqld[22953]: Bogus stack limit or frame pointer, fp=0x8543090, stack_bottom=0x44b70000, thread_stack=262144, aborting backtrace. Apr 13 08:51:16 cronjob1 mysqld[22953]: Trying to get some variables. Apr 13 08:51:16 cronjob1 mysqld[22953]: Some pointers may be invalid and cause the dump to abort... Apr 13 08:51:16 cronjob1 mysqld[22953]: thd->query at 0x80ea1c0 = (SELECT city_id, name, count_character Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 FROM base.cities Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 WHERE country_id = 176 Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011#011AND name = "kierownik działu" Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 LIMIT 1) UNION ALL (SELECT city_id, name, count_character Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 FROM base.cities Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 WHERE country_id = 176 Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011#011AND name = "kierownik jakości" Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 LIMIT 1) UNION ALL (SELECT city_id, name, count_character Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 FROM base.cities Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 WHERE country_id = 176 Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011#011AND name = "kierownik łódzkie" Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 LIMIT 1) UNION ALL (SELECT city_id, name, count_character Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 FROM base.cities Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 WHERE country_id = 176 Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011#011AND name = "działu jakości" Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 LIMIT 1) UNION ALL (SELECT city_id, name, count_character Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 FROM base.cities Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 WHERE country_id = 176 Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011#011AND name = "działu łódzkie" Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 LIMIT 1) UNION ALL (SELECT city_id, name, count_character Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 FROM base.cities Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 WHERE country_id = 176 Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011#011AND name = "jakości łódzkie" Apr 13 08:51:16 cronjob1 mysqld[22953]: #011#011#011#011#011 LIMIT 1) UNION ALL (SELECT city_id, na Apr 13 08:51:16 cronjob1 mysqld[22953]: thd->thread_id=20686 Apr 13 08:51:16 cronjob1 mysqld[22953]: The manual page at http://www.mysql.com/doc/en/Crashing.html contains Apr 13 08:51:16 cronjob1 mysqld[22953]: information that should help you find out what is causing the crash. Apr 13 08:51:16 cronjob1 mysqld_safe[31297]: Number of processes running now: 0 Apr 13 08:51:16 cronjob1 mysqld_safe[31299]: restarted 

The problem here is I don't know where this one #011#011#011#011#011# is coming from. I am using mysql_real_escape_string() for the query.

Answer 1

@Ignacio says stop using kill -9. Here is why:

MyISAM tables maintain the count of open file handles to the MyISAM table. If mysqld just up and dies without a shutdown process, that count stays as is. To remove its footprint you can do one of two things:

For example, if the MyISAM table is mydb.mytable

Option 1

While mysqld is shutdown,

cd /var/lib/mysql/mydb myisamchk -r mytable.MYD 

myisamchk documentation

Option 2

With mysqld running, do

CHECK TABLE tblname; REPAIR TABLE tblname; 

Answer 2

This seems to be an encoding problem. There may be a symbol in the query string that cannot get interpreted by the connections charset. Try using a distinct charset for the connection or set a proper default in mysql.conf (my.conf). Print or log the query string before you fire it, to get an idea what the string after the mysql_real_escape_string() function looks like.