If no parent can be found for an interpolation, there is most
likely a data error involved. So don' t show these interpolations
in reverse search results.
The fairly complex where condition of idx_placex_geometry_placenode
won't always be matched by the query planner if the condition
part doesn't appear verbatim in the query.
Fixes#2480.
Always look up the closest housenumber before looking up
interpolations. This ensures that closer housenumbers are
preferred over interpolations.
Fixes#2214.
