[postgis-devel] [postgis-users] ST_Distance with geography really slow: trees and caches

[Paul Ramsey]

Let's talk on -devel.

Could you point out which version you're looking at, first of all, in
case there's differences between versions?

Thanks,

P.

On Mon, Jan 6, 2014 at 7:35 AM, Nicolás Lichtmaier <nicolasl at wolfram.com> wrote:
> I'm trying to solve a mistery (and I didn't know is I should post here or to
> the the devel list)
>
> ST_Distance between complex polygons is very slow here, despite the work
> done in http://boundlessgeo.com/2012/07/making-geography-faster/ .. It's
> taking like 4 seconds.
>
> Looking harder into this I see there's a _st_distancetree(geo1, geo2) that
> completes the task in 171 ms....
>
> It seems to me that the standard ST_Distance is not using the new "circular
> bounding boxes" code...
>
> So I downloaded the source code and I saw that geography_distance_cache
> always fails because GetCircTreeGeomCache always returns null. I see that a
> cache is initialized and put into a "generic cache" array, but then is reset
> to null in GetGenericCacheCollection when called from GetPROJ4SRSCache
> beacuse "fcinfo->flinfo->fn_extra" is again null... (set in
> MemoryContextAllocZero)
>
> Does this what I am saying make sense? =)
>
> How is this cache supposed to work?
>
> Thanks for any help!
>
> --
> Nicolás.-
>
>
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