[postgis-devel] Parallel Support

Rémi Cura remi.cura at gmail.com
Sun Mar 27 14:21:49 PDT 2016

I've been watching the patch discussion on postgres list,
I must say this is a most wanted feature !
It is going to take Postgis to another level in terms of scalability.

Currently I use python for parallel query, and it is a major hassle.
PGadmin scripts are a little bit easier, but quit annoying as well.


2016-03-25 20:20 GMT+01:00 Paul Ramsey <pramsey at cleverelephant.ca>:

> FYI, I have a parallel query/aggregate branch going here
> https://github.com/pramsey/postgis/tree/parallel
> I've marked most of the functions as PARALLEL SAFE, for better or worse.
> Aggregates are frustrating, the one that we probably want to
> parallelize the most, ST_Union, is quite tricky to do. Basically, we
> need to get parallelism into the transfn stage, since by the time you
> get to the combinefn or finalfn the result has already been returned
> to the master. In order to get some work done in the transfn I think
> we basically need to run a union every N records, which means a bad
> magic number in there, as well as washing out the benefits of cascaded
> union.
> You can still test a parallel union aggregate though, the ST_MemUnion
> aggregate is trivial to parallelize, and I have done so. Also
> ST_Extent. ST_Collect doesn't have any benefit to parallelizing (since
> it's mostly about memory copying).
> For testing you'll probably end up messing with the parallel gucs
> which are described here:
> https://gist.github.com/pramsey/ff7cbf70dbe581189565
> P.
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