[postgis-users] remove polygon from multipolygon

[Frank Durstewitz]

Hello list,

i must remove from multipolygon some polygons, for example remove all 
polygons from "russia", where latitude of centroid of polygon is <= 0 
(in this case the part of russia  which is near alaska).

I think this should be possible (ST_Dump...), but i cannot find any way 
to do so.
Deleting the vertices by hand via a desktop gis is painfull slow and 
will take ages - i tried this and need ~ 5 minutes for a very small 
island of ~ 20 points... (i found no desktop gis where i can select 
multiple vertices by a bounding box and delete them at once).

Thanks,

Frank

ST_Summarize gives

MultiPolygon[BS] with 1393 elements
  Polygon[] with 1 rings
   ring 0 has 15 points
...
  Polygon[] with 1 rings
   ring 0 has 25 points