[postgis-devel] ST_UnaryUnion vs ST_Dump + ST_Union

[Paul Ramsey]

On a semi-related note, why the new function signature? Why isn't this
just ST_Union?
P.

On Sun, Oct 2, 2011 at 6:25 AM, Sandro Santilli <strk at keybit.net> wrote:
> On Sun, Oct 02, 2011 at 01:29:07PM +0200, Jose Carlos Martinez Llario wrote:
>> Dear List,
>> ¿What are the differences between an st_unaryunion and a normal
>> union aggregate with the dump geometries from the geom?
>> I just could see that the order of the generated segments change.
>> What am I missing?
>
> UnaryUnion uses an index to merge nearby components first, reducing
> the working and robustness issues earlier.
>
>> In order to node a LineString with selt-intersections, I still have
>> to use st_union (point, geom) because st_unaryunion does not node
>> self-intersection lines.
>
> It should! Please file a ticket for this one.
>
> --strk;
>
>  ()   Free GIS & Flash consultant/developer
>  /\   http://strk.keybit.net/services.html
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