[postgis-users] st_union

[paul.malm at lfv.se]

There was no difference between st_union() and st_unaryunion() when merging all adjacent polygons to  larger polygons.
The st_buffer() method is 3.5 times faster.
/Paul


-----Ursprungligt meddelande-----
Från: postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] För Sandro Santilli
Skickat: den 3 mars 2020 10:18
Till: PostGIS Users Discussion
Ämne: Re: [postgis-users] st_union

On Mon, Mar 02, 2020 at 02:25:52PM +0000, 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?

Try this:

  CREATE TABLE public."Areas_union" AS select
  (st_dump(st_unaryunion(st_collect("the_geom")))).geom from "Areas";

--strk;
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