[postgis-devel] SP-GIST: what to do

[Sandro Santilli]

On Tue, Sep 30, 2014 at 11:45:23AM -0700, Paul Ramsey wrote:
> Hey all,
> 
> So, I’ve now got a working sp-gist implementation
> 
> https://github.com/pramsey/postgis/tree/spgist/
> 
> (Build and install, and after enabling postgis also run the commands in gserialized_spgist_2d.sql to add the spgist functions and opclass)
> 
> This is a copy of the quadtree implementation Teodor put into PgSQL, but bound to our ‘geometry’ type. It is also restricted to points only (though, non-optimally, I cannot throw a “not a point” error until I get into the picksplit routine, so it’s possible to build a small index on non-point features… just how to handle that corner case is something I have yet to figure out).
> 
> The question is whether to continue to pursue this work for 2.2. Given the lack of a “compress” hook for spgist, support for anything other than points seems problematic. Similarly, the corner case above could have potentially deleterious effects. Also, since we have a cast from geometry::point (for geometries that are points), it’s possible for people to build functional spgist indexes *already*, if they like (though they won’t have as good stats/planning as geometry, since the spatial stats code in postgresql proper is lacking)
> 
> I feel like the lack of support for all geometry variants, and the inability to cleanly restrict the index to just a point variant in combination make spending more effort on a direct geometry binding probably not worth it, though I’m willing to entertain counter arguments.

I've recently extended our estimator to work on functional indexes, so
while we can't support non-point geometries we can always create index
on function that convert them to points (ST_Centroid, or whatever).

Or where would you put a large rectangle in a space-partitioned index ?
Is there support for having multiple index rows for a single table row ?

--strk; 

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