Hi Rick,
Thanks for the advise. I have now set my query-cache to zero.
(I take your point about query cache too large. I understand that a
smaller cache size, and the use of the SQL_NO_CACHE and SQL_CACHE
directives can be used to control which queries are cached. Therefore
trying to get the advantage without the disadvantage. But this is a lot
of work to change every query we ever run!)
I am working on reproducing the error, but so far it appears to be random.
Ben
On 2012-10-09 18:44, Rick James wrote:
As for the crash, I don't know. Instead, I recommend either shrinking the size
(if you use a big QC) or turning it off. This would make the issue go away.
ANY modification to a particular table leads to ALL entries in the Query cache
being purged. For that reason, we (Yahoo) almost never use the QC on any of
our many servers.
Please provide
SHOW GLOBAL VARIABLES LIKE 'query%';
SHOW GLOBAL STATUS LIKE 'Qc%';
Because of inefficiencies in 'pruning', having a query_cache_size bigger than
50M may actually degrade performance.
In you have a reproducible test case, submit to bugs.mysql.com .
-----Original Message-----
From: Ben Clewett [mailto:b...@clewett.org.uk]
Sent: Tuesday, October 09, 2012 4:47 AM
To: mysql@lists.mysql.com
Subject: Query Cache Crashing
Hi MySql,
Since upgrading to 5.5.27 (5.5.27-ndb-7.2.8-cluster-gpl-log to be
exact) I have experienced problems with the query cache. I am
wondering if I am the only one?
Twice I have had a core-dump (show at end of mail) on two separate
servers running this version.
Now I had a complete lock, where 'SHOW PROCESSLIST' showed this for
every connection:
"Waiting for query cache lock"
This resulted in connections building until the limit was hit. I could
only cure this with a 'kill -9' on the mysqld process.
Are any other users experiencing this? Do any users know of a fix?
Thanks!
Ben Clewett.
Thread pointer: 0x7f6ea014cf90
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 410220e8 thread_stack 0x40000
/usr/sbin/mysqld(my_print_stacktrace+0x35)[0x81c7f5]
/usr/sbin/mysqld(handle_fatal_signal+0x403)[0x6e9383]
/lib64/libpthread.so.0[0x7f6f491b2b30]
/usr/sbin/mysqld(_ZN11Query_cache12unlink_tableEP23Query_cache_block_ta
ble+0x1b)[0x5bd1ab]
/usr/sbin/mysqld(_ZN11Query_cache19free_query_internalEP17Query_cache_b
lock+0x7a)[0x5bdb5a]
/usr/sbin/mysqld(_ZN11Query_cache27invalidate_query_block_listEP3THDP23
Query_cache_block_table+0x7e)[0x5be8ee]
/usr/sbin/mysqld(_ZN11Query_cache12insert_tableEjPcP23Query_cache_block
_tablejhPFcP3THDS0_jPyEy+0x91)[0x5bf7e1]
/usr/sbin/mysqld(_ZN11Query_cache25register_tables_from_listEP10TABLE_L
ISTjP23Query_cache_block_table+0x176)[0x5bfa76]
/usr/sbin/mysqld(_ZN11Query_cache19register_all_tablesEP17Query_cache_b
lockP10TABLE_LISTj+0x15)[0x5bfbb5]
/usr/sbin/mysqld(_ZN11Query_cache11store_queryEP3THDP10TABLE_LIST+0x39e
)[0x5bff5e]
/usr/sbin/mysqld[0x5eb02d]
/usr/sbin/mysqld(_Z21mysql_execute_commandP3THD+0x269b)[0x5f0aeb]
/usr/sbin/mysqld(_Z11mysql_parseP3THDPcjP12Parser_state+0x18a)[0x5f2cba
]
/usr/sbin/mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0x13
21)[0x5f4861]
/usr/sbin/mysqld(_Z24do_handle_one_connectionP3THD+0x167)[0x68d807]
/usr/sbin/mysqld(handle_one_connection+0x54)[0x68d874]
/lib64/libpthread.so.0[0x7f6f491ab040]
/lib64/libc.so.6(clone+0x6d)[0x7f6f4847c08d]
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