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

Étienne Desgagné etienne.desgagne at roche.ca
Thu Nov 29 08:04:57 PST 2012

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?






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 <http://www.michiganwxsystem.com> 
AllisonHouse <http://www.allisonhouse.com> 
GRLevelXStuff <http://www.grlevelxstuff.com> 

On 11/28/2012 16:22, Étienne Desgagné wrote:


    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 


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