[postgis-users] "Erase" and "Intersect" performance questions - PostGIS way slower than ArcGIS

[Sheara Cohen]

Hey Chris - Thanks for your response.

 

With regard to ST_Difference, what I was trying to accomplish is a
"deletion" or  "clipping out" of rivers and lakes from a parcel file.
Both are vector files. Based on your description, it sounds like I'm
using the wrong query. Do you know which one I should be using?

 

And with regard to both the ST_Intersection and ST_Difference... yes, I
am using vector files with HUGE, complex polygons that spread over very
large areas (hundreds of miles). I can dice these in ArcGIS or something
like that before throwing the files over the fence into Postgres. But
I'm still confused by the fact that similar operations run so quickly on
the exact same files in ArcGIS. I feel like there is something I'm
totally missing about how to set up these queries correctly in PostGIS.

 

If you or anyone have any last thoughts, I'd be really interested.

 

Thanks again,

 

~ Sheara

 

Sheara Cohen
Planner

C A L T H O R P E  A S S O C I A T E S
2095 ROSE STREET, SUITE 201, BERKELEY, CALIFORNIA, 94709 USA
510 809-1165 (direct) | 510-548-6800 x35 (main) | 510 548-6848 (fax)
sheara at calthorpe.com <mailto:sheara at calthorpe.com>  | www.calthorpe.com

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20110825/da6cbb32/attachment.html>