Re: [SQL] sql performance and cache

On Tue, 14 Oct 2003, Wei Weng wrote:

> 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)?

Not really, Postgresql's design makes it a bit of a non-winner.