[postgis-users] performace question

[Paul Ramsey]

OK, so the operation is spending all its time in GEOS, running the
Touches test. You have a since 2848-vertex linestring and 6361
candidate features. And you get back 285 touches. Fortunately, because
you are testing against a linestring, you have an alternative test,
since the interaction of a polygon boundary and linestring interior
counts as an intersection.

SELECT count(obce.gid) FROM obce,cr WHERE ST_Intersects(obce.the_geom,
cr.the_geom);

I found this to run 10 times as fast, because it can use the prepared
geometry optimization. It still returns 285 resultants.

Paul


On Wed, Apr 1, 2009 at 11:06 AM, Martin Landa <landa.martin at gmail.com> wrote:
> Hi,
>
> 2009/4/1 Paul Ramsey <pramsey at opengeo.org>:
>> Can you share your data with me? I'm interested to profile and see
>> where the bottleneck actually is.
>
> data are available at
>
> http://josef.fsv.cvut.cz/~landa/postgis/obce_cr.sql.gz
>
> before import define also local SRS
>
> INSERT INTO spatial_ref_sys VALUES (102067, 'local', 102067,
> 'PROJCS["Krovak",GEOGCS["bessel",DATUM["unknown",
> SPHEROID["Bessel_1841",6377397.155,299.1528128],
> TOWGS84[570.8,85.7,462.8,4.998,1.587,5.261,3.56]],
> PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]],
> PROJECTION["Krovak"],PARAMETER["latitude_of_center",0],
> PARAMETER["longitude_of_center",0],PARAMETER["azimuth",0],
> PARAMETER["pseudo_standard_parallel_1",0],PARAMETER["scale_factor",1],
> PARAMETER["false_easting",0],PARAMETER["false_northing",0],UNIT["meter",1]]',
> '+proj=krovak +a=6377397.155 +rf=299.1528128 +no_defs
> +towgs84=570.8,85.7,462.8,4.998,1.587,5.261,3.56 +to_meter=1.0');
>
> Thanks in advance, Martin
>
> --
> Martin Landa <landa.martin gmail.com> * http://gama.fsv.cvut.cz/~landa
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