Re: [postgis-users] Union as an aggregate

dblasby wrote:
> strk wrote:
> > Dave, I made no special 'unite' code, just sql create command:
> > CREATE AGGREGATE unite (
> > sfunc = GeomUnion,
> > basetype = geometry,
> > stype = geometry
> > );
>
> Hum - this shouldnt do anything.
>
> The aggregate should have "null" as its initial value.
>
> GeomUnion(null,<geometry>) --> null.
>
> So, you'll end up with null *very* quickly because
> GeomUnion(null,<geometry>) returns null without any actual execution.

It looks like postgres is behaving differently since I always get
a not-null result.

>
> Are you running this on a big table? At worst I'd expect this to use up
> memory the same size all the geometries in the table.
>

Geometry set size is about 2MB:
gis=# select sum(mem_size(the_geom)) from world where gid < 50;
2148316

Initial postmaster process status is:
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND
566 pgsql 15 0 3288 3288 2684 S 0.0 0.4 0:00 postmaster

After query:
gis=# select box(unite(the_geom)) from plmshp02_1 where gid < 50;
(180,83.1138763427734),(-180,-90)

The postmaster grew of about 66M (having touched a 78MB upper limit):
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND
566 pgsql 19 0 71472 69M 3396 S 0.0 9.2 3:35 postmaster

If I run that again, *exactly the same query*:
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND
566 pgsql 14 0 126M 126M 3396 S 0.0 16.8 7:13 postmaster

It looks like someone is leaking memory, either postgres, postgis or geos.
Does it sound correct ?

PS: postgres is 7.3.4, postgis and geos are latest cvs.
--strk;