[OSM-dev] Playing with MapServer WMS and WFS
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Mon Sep 13 16:23:57 BST 2010
Peter Körner schrieb am Montag, den 13. September um 16:53 Uhr:
> Yes, that's a known problem (or feature?). OSM allows invalid
> geometries for polygons and mapnik can render them, but some
> postgis functions will fail. It is possible to use ST_IsValid but
> this adds a medium runtime penalty.
The delay is unacceptable slow for poi applications.
> To come around this we could add an isvalid coumn to the polygon
Invalid polygons need to get dropped alltogether IMO.
> This column can be filled via a trigger or via osm2pgsql.
> This would move the penalty to the import.
A trigger is almost certainly way to slow.
This should go into osm2pgsql - Well it should be impossible to add invalid
polygons to OSM at all, but thats another story.
One could also think about creating another geometry column for the polygon
table which will already contain the result of ST_PointOnSurface.
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