[postgis-devel] Which intersection is faster?

[Bborie Park]

Your best bet would be to convert the geometry to an aligned raster
once, cache that raster and then run the intersection test.
Otherwise, things get converted needlessly and repeatedly.

-bborie

On Sat, Mar 23, 2013 at 11:12 AM, Jorge Arévalo
<jorgearevalo at libregis.org> wrote:
> Ok, understood.
>
> The point is I'm trying to make the GDAL PostGIS Raster driver faster, and the main bottleneck is in the intersection between raster columns and user requested window (I construct a polygon from the user's request coords and instersect that polygon with the raster data).
>
> Swapping raster - vector objects was my first (naive) approach. Any (for sure smarter) suggestions are welcome.
>
> --
> Jorge Arevalo
> Freelance developer
>
> http://www.krop.com/jorgearevalo
> http://about.me/jorgeas80
>
> Enviado con Sparrow (http://www.sparrowmailapp.com/?sig)
>
>
> El sábado 23 de marzo de 2013 a las 18:53, Bborie Park escribió:
>
>> There's not too much difference between 2.0 and 2.1. I think the
>> major change is ST_Intersects(raster, geometry) =
>> ST_Intersects(geometry, raster). Basically, if one of the arguments
>> is a geometry, the op is done in geometry space (raster is converted
>> to a set of geometries).
>>
>> -bborie
>>
>> On Sat, Mar 23, 2013 at 10:50 AM, Jorge Arévalo
>> <jorgearevalo at libregis.org (mailto:jorgearevalo at libregis.org)> wrote:
>> > Many thanks for the quick response. I can see is pretty fast. But, what about previous version of PostGIS? Say 2.0. Is there any significant difference between both versions?
>> >
>> > --
>> > Jorge Arevalo
>> > Freelance developer
>> >
>> > http://www.krop.com/jorgearevalo
>> > http://about.me/jorgeas80
>> >
>> > Enviado con Sparrow (http://www.sparrowmailapp.com/?sig)
>> >
>> >
>> > El sábado 23 de marzo de 2013 a las 18:30, Bborie Park escribió:
>> >
>> > > I'd suggest using the variant that runs in raster space. If I
>> > > remember correctly, some changes have been made to this in 2.1.
>> > >
>> > > -bborie
>> > >
>> > > On Sat, Mar 23, 2013 at 10:20 AM, Jorge Arévalo
>> > > <jorgearevalo at libregis.org (mailto:jorgearevalo at libregis.org)> wrote:
>> > > > Hello,
>> > > >
>> > > > I don't know if this is a naive question, but in ST_Intersects description (http://postgis.net/docs/manual-2.0/RT_ST_Intersects.html) I read:
>> > > >
>> > > > "Depending on the order that the raster and geometry is passed to ST_Intersects(), the test will operate in either raster-space or geometry-space. If ST_Intersects(raster, ....), the test is in raster-space (the geometry is converted to a raster). If ST_Intersects(geometry, ...), the test is in geometry-space (the raster is converted to a set of pixel polygons)."
>> > > >
>> > > > My question: in equal conditions, which version should be faster?
>> > > >
>> > > > ST_Intersects(raster, vector) --> in raster space
>> > > > ST_Intersects(vector, raster) --> in vector space
>> > > >
>> > > > Many thanks in advance,
>> > > >
>> > > > --
>> > > > Jorge Arevalo
>> > > > Freelance developer
>> > > >
>> > > > http://www.krop.com/jorgearevalo
>> > > > http://about.me/jorgeas80
>> > > >
>> > > > Enviado con Sparrow (http://www.sparrowmailapp.com/?sig)
>> > > >
>> > > >
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