[postgis-devel] GeomUnion Performance Info

[strk at refractions.net]

On Wed, Jun 22, 2005 at 09:52:17PM -0400, Bill Binko wrote:
> 
> strk,
> 
> I'm going to have to rerun all of the performance graphs if it's going to 
> be a reasonable comparision.  The reason is that the database has simply 
> not stayed static since I ran those.  I have added columns, indexes, etc. 
> and it simply wouldn't be meaningful.
> 
> So, I will get your short-circuit code in there, and run the following 
> tests (with the same data and load):
> 
> 1) Random Sort (clustered)
> 2) GiST Clustered
> 3) BTree clustered (a bit hard, but I can do it)
> 
> And I'll run them both with and without the short-circuit code.  Is there 
> a runtime switch?  If not, I'll recompile gdal with and without (I 
> shouldn't have to rebuild postgis right?).

You only need rebuild GEOS, no runtime switch, just a define
#define SHORTCIRCUIT_PREDICATES 1
on top of source/geom/Geometry.cpp

Also, on line 611 uncomment the 
'//cerr<<"SHORTCIRCUITED-UNION engaged"<<endl;'
line, so you can see how many cases of disjoint bboxes happen with
btree or GiST and report that as well.

> It will take at least tomorrow to do that.  However, I'll aim for being 
> complete before the weekend in case there's development to be done then.

Thank you !
--strk;