Am 30.04.2011 17:45, schrieb Ferenc Kovacs: > On Sat, Apr 30, 2011 at 5:39 PM, Rasmus Lerdorf <ras...@lerdorf.com> wrote: >> Do you realize why we did this in the first place? The common versions of >> MySQL in use out there are not very clever when it comes to the native >> prepared statement handling. First, there is no prepared statement cache, so >> there is no benefit to doing them natively, but worse, when you use a native >> prepared statement you completely miss the query result cache. As a result >> emulated prepared statements are either the same speed or faster than the >> native ones. Changing this default would result in a performance hit for >> most people. It should be better documented, but that is the only problem I >> see here. >> > I disable query_cache on my machines, because it can cause performance and > stability issues. > http://www.mysqlperformanceblog.com/2011/04/10/should-we-give-a-mysqlquery-cache-a-second-chance/
i guess you must have some really strange things in your applications > which can take a lot of time if you have millions of queries cache for given > table makes me sure you do something wrong and not know the SQL_NO:_CACHE hints for disable caching of queries from them you know that they can not benefit or with really small results with the wehre-statemant on the primary key where the cache is not faster as the normal query and I/O does not matter because the result size _______________________ we are using mysql-query-cache on all servers with some hundret domains since years and as long the whole generate time of a dynamic page is done between 0.008 and 0.011 seconds there is no performance issue disable the query cache would degrade the whole box 10 years back and even on a dbmail-mailserver with innodb-backend the qc improve performance dramatically [--] Reads / Writes: 68% / 32% [--] Total buffers: 2.4G global + 3.2M per thread (200 max threads) [OK] Maximum possible memory usage: 3.0G (37% of installed RAM) [OK] Slow queries: 0% (3/27M) [OK] Highest usage of available connections: 17% (35/200) [OK] Key buffer size / total MyISAM indexes: 256.0M/106.8M [OK] Key buffer hit rate: 99.9% (109M cached / 126K reads) [OK] Query cache efficiency: 89.6% (20M cached / 23M selects) [OK] Query cache prunes per day: 0 [OK] Sorts requiring temporary tables: 0% (924 temp sorts / 210K sorts)
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