[postgis-users] st_union

[Alexandre Neto]

Uhmmm... So, if there's no join or where clause, the index is not used at
all?

Somehow, I thought that internally ST_union would still use it to decide
which geometries need be merged together in the same part.

Thanks for clarifying.

Alexandre Neto

A segunda, 2/03/2020, 22:02, Paul Ramsey <pramsey at cleverelephant.ca>
escreveu:

> On Mon, Mar 2, 2020 at 1:16 PM Alexandre Neto <senhor.neto at gmail.com>
> wrote:
> >
> > Stating the obvious,
> >
> > Do you have a spatial index on your geom column?
>
> That will make no difference, the query is reading the whole contents
> of the column, a spatial index will do nothing.
>
> P
>
>
> >
> > Alexandre Neto
> >
> > A segunda, 2/03/2020, 17:04, Paul Ramsey <pramsey at cleverelephant.ca>
> escreveu:
> >>
> >> No, if it’s returning the answer you want, that’s the way to do it, and
> there’s no way around it.
> >>
> >> > On Mar 2, 2020, at 6:25 AM, <paul.malm at lfv.se> <paul.malm at lfv.se>
> wrote:
> >> >
> >> > Hi list,
> >> > I would like to do this:
> >> > CREATE TABLE public."Areas_union" AS select
> (st_dump(st_union("the_geom"))).geom from "Areas";
> >> >
> >> > But it takes such a long time to execute, is there a smarter way to
> do it?
> >> >
> >> > Kind regards,
> >> > Paul
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