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

[Ron Mayer]

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?).

   Ron