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

[Paul Ramsey]

No thoughts, you're turning up expected results, I'd say. Arc is a
GIS, PostGIS is a database. I'm sure we could get much better
performance on your workload if we added the intersection operation
into the prepared geometry concept, but that would be quite a bit of
work I'm sure.

P.

On Thu, Aug 25, 2011 at 2:56 PM, Sheara Cohen <Sheara at calthorpe.com> wrote:
> 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
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