On Fri, Aug 30, 2019 at 6:28 AM Peter Geoghegan <pg@bowt.ie> wrote:
> On Thu, Aug 29, 2019 at 8:22 PM Alexander Korotkov
> <a.korotkov@postgrespro.ru> wrote:
> > Alternatively you can encode size in Z-value. But this increases
> > dimensionality of space and decreases efficiency of join. Also,
> > spatial join can be made using two indexes, even just current GiST
> > without Z-values. We've prototyped that, see [1].
>
> I'm pretty sure that spatial joins generally need two spatial indexes
> (usually R-Trees). There seems to have been quite a lot of research in
> it in the 1990s.
Sure, our prototype was an implementation of one of such papers. My
point is that advantages of Z-value ordered GiST for spatial joins are
not yet clear for me. Except faster build and smaller index, which
are general advantages.
------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company