title: missing data for column xxx
body: <p>I've downloaded multiple metro extracts from openstreetmap as PBF files when i try to import them with osm2pgsql it works for the first and creates the tables. I then want to add a column in the planet_osm_ways with a cityID to know which "way id" belonged to which city after i then try to import another city it says 'ERROR: Missing data for column "city_id". is there a way to modify the planet_osm_ways table without breaking the script? I really need to know which id belonged to which metro extract.</p>