[postgis-users] Optimization - point density calculation

[Paul Ramsey]

Functional indexes do work, but you have to be very careful to match
your SQL invocation to the index you build... it can be fiddly, which
is why I just start by recommending transforming the data :)

P

On Wed, May 28, 2008 at 6:04 AM, Markus Schaber <schabi at logix-tt.com> wrote:
> Hi, Paul,
>
> "Paul Ramsey" <pramsey at cleverelephant.ca> wrote:
>
>> (a) The ST_Transform() function is making your spatial index
>> un-usable, because your spatial index is against the raw coordinates
>> of your data.
>> [...]
>> So, first transform your data to your working projection.
>
> You could also try to create a functional index on the transformed
> geometries. In theory it should work, but I did never test it myself.
>
>
> Regards,
> Markus
>
> --
> Markus Schaber | Logical Tracking&Tracing International AG
> Dipl. Inf.     | Software Development GIS
>
> Fight against software patents in Europe! www.ffii.org
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