Re: [SQL] sql performance and cache
От | Wei Weng |
---|---|
Тема | Re: [SQL] sql performance and cache |
Дата | |
Msg-id | Pine.LNX.4.56.0310141247370.7836@localhost.localdomain обсуждение исходный текст |
Ответ на | Re: sql performance and cache (Christopher Kings-Lynne <chriskl@familyhealth.com.au>) |
Список | pgsql-performance |
On Sat, 11 Oct 2003, Christopher Kings-Lynne wrote: > > > I have two very similar queries which I need to execute. They both have > > exactly the same from / where conditions. When I execute the first, it takes > > about 16 seconds. The second is executed almost immediately after, it takes > > 13 seconds. In short, I'd like to know why the query result isn't being > > cached and any ideas on how to improve the execution. > > <snip> > > > OK - so I could execute the query once, and get the maximum size of the > > array and the result set in one. I know what I am doing is less than optimal > > but I had expected the query results to be cached. So the second execution > > would be very quick. So why aren't they ? I have increased my cache size - > > shared_buffers is 2000 and I have doubled the default max_fsm... settings > > (although I am not sure what they do). sort_mem is 8192. > > PostgreSQL does not have, and has never had a query cache - so nothing > you do is going to make that second query faster. > > Perhaps you are confusing it with the MySQL query cache? > > Chris > Is there plan on developing one (query cache)? Thanks Wei
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