[postgis-devel] Re: [postgis-users] Index scan performance difference between 0.8 and rc1; (fwd)

[strk at refractions.net]

On Wed, Feb 02, 2005 at 10:16:40AM -0800, Ron Mayer wrote:
> On Tue, 1 Feb 2005 strk at refractions.net wrote:
> > On Mon, Jan 31, 2005 at 03:53:20PM -0800, Ron Mayer wrote:
> > > ...the performance changes a lot if I use find_srid() or "-1" when
> > > defining my BOX3D; even though my srid is -1.
> >
> > Mmm.. this is interesting.
> > I've tested a sample query three times, with find_srid defined as
> > VOLATILE, STABLE, IMMUTABLE. Here are the results:
> >
> >    VOLATILE: Total runtime: 1096.708 ms
> >      STABLE: Total runtime: 42.457 ms
> >   IMMUTABLE: Total runtime: 18.457 ms
> 
> Thanks!  Making find_srid IMMUTABLE solved my performance problem.
> 
> Now small queries are just as fast as they were in 0.8, and
> large queries are considerably faster (probably due to more
> compact geometry on disk?).

Yes, and smaller index keys.
--strk;

> 
>    Ron
> 
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