[postgis-users] polygon/multipolygon limitation?

[Hubert Fröhlich]

Hello list,


Application: I have ca. 100000 polygons ( a neighborhood of land 
register parcels) and want to get the outer boundary of the area 
enclosing all polygons exactly.

PostGIS could do this by applying several successive operations of 
GeomUnion(geometry, geometry) in a loop (n=100000) . It is clear that I 
will get huge polygons (with several 1000 vertices).

My trials so far have not been very successful: High disk I/O load 
leading even sometimes to postgres errors like

"invalid page header in block ..."

and, therefore, VERY strange results

My question now:
- Is there a way for PostGIS to process this task?
- I am looking for a better way than the one I originally proposed.
- The way I proposed seems to produce too much load. How to reduce it?
- Is there a limitation on vertices in polygons etc. turning my 
application into crash?


Regards,

Hubert



-- 
-------------------------------------------------------------------------------
Dr.-Ing. Hubert Fröhlich			
Bezirksfinanzdirektion München 			
Alexandrastr. 3, D-80538 München, GERMANY
Tel. :+49 (0)89 / 2190 - 2980
Fax  :+49 (0)89 / 2190 - 2997
hubert dot froehlich at bvv dot bayern dot de