[postgis-devel] chunked GeomUnion commit

[Bill Binko]

I added an HTML export at:
http://www.mapshine.com/Perf2.html

On Tue, 28 Jun 2005, Bill Binko wrote:

> 
> strk,
> 
> I have run some more of the test (finally -- sorry about the delay).
> 
> I hope I have run some that will be useful to you.. I have not had time to 
> run all of them.
> 
> I have spreadsheets (in OOCalc and exported XLS formats) available here:
> 
> http://www.mapshine.com/Perf2.sxc
> http://www.mapshine.com/Perf2.xls
> 
> Sorry, I don't have Excel here for a pretty export: I will do so when I 
> have more data filled in.
> 
> I put some notes on the first page of the spreadsheet.  However, a couple 
> of important ones are here:
> 
> 1) I'm using CVS HEAD for this.  Is that what you wanted?  I had to
> rebuild postgis to pick up the libgeos.so.3, but it seems to work fine.
> 
> 2) I see no difference with the #define set to 1 or 0 for the 
> short-circuiting (including no stderr outputs.)
> 
> 3) GEOS 2.1.1 seems to be considerably faster than CVS HEAD for the GIST
> ordered case.  (See the GIST Compare tab) I have not had time to do the
> non-ordered and BTree cases for the new code (it simply ramps up to fast
> for me to do tonight).
> 
> 4) Are you sure that buffer(collect(p), 0) is equivalent to GeomUnion(p)?  
> If so, it is FAR faster in all respects no matter how the shapes come in, 
> etc.  In fact, the randomly ordered  buffer(collect()) method came in 
> faster than the GIST of all of the other methods (!).  Does 
> Buffer(collect()) leave holes where GeomUnion() does?  Or is it a solid 
> outline?
> 
> Anyway, I look forward to feedback.
> 
> Bill
> 
> 
> On Mon, 27 Jun 2005 strk at refractions.net wrote:
> 
> > I've committed the chunked implementation of unite_garray
> > in the head branch.
> > 
> > This one is the version that doesn't require dump/reload
> > so will still get full geometry set in input, but will
> > chunk it before passing to GEOS for processing.
> > 
> > I don't feel comfortable breaking the scripts interface
> > so far. Please make your tests with this setup.
> > 
> > You can fine-tune chunk size changing the MAXGEOMSPOINTS
> > #define around line 267
> > 
> > --strk;
> > 
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> > 
> > 
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