[postgis-users] ST_Simplify and projections

[Paolo Crosato]

Il 09/01/2013 19:02, Sandro Santilli ha scritto:
> On Wed, Jan 09, 2013 at 06:30:03PM +0100, Paolo Crosato wrote:
>
>> test the function against
>> the whole european set in order to have any answer, and it's still
>> building the topology :)
> I hope you're doing it in some incremental way, or the first problem
> is going to rollback the whole work.
> (I feel your pain)
>

Well I tried to load the whole thing at once, and it's still loading 
after more then 24hrs eh eh!
The dataset I'm working with has around 90k features (multipolygon) and 
37 million vertexes.
I can partion it let's say by country and load one country by one, but 
would calling toTopoGeom
in the same topology in this way work incrementally?

Quoting this line of the 2.0.2 docs

"Topological primitives required to represent the input geometry will be 
added, possibly splitting existing ones. Pre-existing TopoGeometry 
objects will retain their shapes. "

It seems so.  My idea is to partition the eu table in one table for each 
country, then load it one by one to the same topology, like this:

SELECT CreateTopology('eu_geom_topo', find_srid('public', 'eu_geom', 
'geom'));
foreach $country
     SELECT AddTopoGeometryColumn('eu_geom_topo', 'public', 
'$country_geom', 'topogeom', 'MULTIPOLYGON');
     UPDATE $country_geom SET topogeom = toTopoGeom(geom, 
'eu_geom_topo', 1);

Would this work? Edges of adjacent polygons are identical, the whole set 
of polygonal geometries is built from a topology by the vendor.

Thank you very much.

Regards,

Paolo

-- 
Paolo Crosato