[postgis-users] Why PostGIS ST_Intersection much slower than ArcGIS Intersect ?

[Paul Ramsey]

For information: ST_Intersects used to be slow, and the caching system
and "prepared intersects" development made it 10-20x faster. A similar
approach to intersection would yield similar results.

On Thu, Nov 29, 2012 at 10:36 AM, Paul Ramsey <pramsey at opengeo.org> wrote:
> It's normal, assuming that some of your geometries are quite large. If
> someone wants to fund a "prepared intersection" development task I'm
> sure we could make it 10x-40x faster.
>
> P.
>
> On Thu, Nov 29, 2012 at 10:04 AM, Étienne Desgagné
> <etienne.desgagne at roche.ca> wrote:
>> It take millisecond to me to when using ST_Intersects on a spatial join.
>> What take much longer is when using ST_Intersection in the SELECT clause to
>> effectively “clip” a layer with the other one…
>>
>>
>>
>> My computer run under Windows 7 64bits with dual core 2.70GHZ and 8 Go RAM.
>>
>>
>>
>> Is there anything I can do to check if it’s normal behavior on this platform
>> or if something may be wrong on my installation?
>>
>>
>>
>> Thanks
>>
>>
>>
>> Etienne
>>
>>
>>
>> De : postgis-users-bounces at lists.osgeo.org
>> [mailto:postgis-users-bounces at lists.osgeo.org] De la part de Jeff Lake
>> Envoyé : 29 novembre 2012 09:15
>> À : postgis-users at lists.osgeo.org
>> Objet : Re: [postgis-users] Why PostGIS ST_Intersection much slower than
>> ArcGIS Intersect ?
>>
>>
>>
>> Must have something to do with windows and or memory ..
>> I use ST_Intersects daily on a Linux Server (PostGIS 2.0, PG 9.1.6) with a
>> quad core Xeon and 16gb memory
>> it takes milliseconds on much larger layers ..
>>
>> Jeff Lake
>> MichiganWxSystem
>> AllisonHouse
>> GRLevelXStuff
>>
>> On 11/28/2012 16:22, Étienne Desgagné wrote:
>>
>> Hello,
>>
>>     I don't want to denigrate PostGIS in any way and I know that my
>> comparison may be wrong but I'm trying to understand why a basic
>> ST_Intersection of two relatively small layers (< 1000 polygons) take about
>> 1m40 sec in PostGIS(2.0 on PG 9.2 on Windows) while applying the ArcGIS
>> Intersect on same layers and machine take about 2 sec?
>>
>> I'm aware of some PostgreSQL tuning settings but even applying basic tuning
>> recommendation for PostGIS I'm facing the same problem...
>>
>>
>> My two layers also have a spatial index.
>>
>>
>> Is it normal behavior? Any suggestion for reaching better performance?
>>
>> Note that I'm also using ST_Intersects on the join to filter only
>> intersecting features...
>>
>> Thanks a lot
>>
>> Etienne
>>
>>
>>
>>
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