Hi
I wonder why osm_id and tags don't match in planet_polygon:
osm_mapnik=> SELECT osm_id, name, tags->'wikipedia' AS wikipedia FROM planet_polygon WHERE osm_id=-1685716; osm_id | name | wikipedia ----------+-------+----------- -1685716 | Utøya | Utøya (1 row)
As if these name and wikipedia tags belong to relation 1685716. Whereas they are actually properities of way 4171584 (http://www.openstreetmap.org/browse/relation/1685716, http://www.openstreetmap.org/browse/way/4171584)
Because you're querying a rendering-database which is preprocessed in order to prduce good rendering results ans -times. One of te preprocessing steps taken is, in the polygon-build phase, "if the relation does not have any interesting tags, copy them from the outer way". This may be wrong or right in the sense of how Relations are defined (there are different definitions for that, btw.), but it's just how our impiorter handles it.
Refer to http://wiki.openstreetmap.org/wiki/Relation:multipolygon#Tagging for one of the definitions.
Peter