Invalidating query cache entries key mysql
You have 0 out of 12312036 that take longer than 10.000000 sec.去slave从库上查看运行状态，果然Seconds_Behind_Master: 28810，而且提示Slave_SQL_Running_State: System lock而且这个是变化的，有的时候提示Slave_SQL_Running_State: invalidating query cache entries (table)，而且Seconds_Behind_Master: 29086 不停的增长着： show slave status\G*************************** 1.It is the Query #3 that eventually produces the error "", presumably because it is the first one to timeout.When My SQL locks up, I execute SHOW PROCESSLIST command and I see the following queries: N User Time Status SQL query 1 system user XX update INSERT INTO `db A`.`table A` (...) VALUES (...) 2 ????When the query cache size is zero, all query cache functionallity should be skipped.Since query_cache_size is protected from any changes by the barrier in Query_cache::resize() we can safely add a test at the begining of the invalidate* functions to avoid having mutexes locked when the query cache is ment to be disabled.It looks like some sort of dead lock, but I cannot understand why.It should be safe to follow these recommendations To find out more information on how each of these runtime variables effects performance visit: info about My SQL's Enterprise Monitoring and Advisory Service SLOW QUERIES The slow query log is NOT enabled.
#At file:///export/home/thek/bzr/mysql-5.1-bug38551/ 2735 Kristofer Pettersson 2008-09-08 Bug#38551 query cache can still consume [very little] cpu time even when it is off.Each item has a unique identifier that is used to query the data, making it a prime candidate for auto cache invalidation.Auto cache invalidation can also be useful where point selects are prevalent but cannot be cached using the TTL-based method.Once the cache rules are created and grouped, Scale Arc will add cache objects created by the select calls with the metadata value extracted from the column location.When the application modifies data with the update or insert queries, Scale Arc will extract the metadata values from the column location.