qgis - Delete duplicate geometry in postgis tables

After - I don't know what happend - all my entries in my PostGIS tables are doubled! I tried this to delete them but it does not delete any/all duplicates:

DELETE FROM planet_osm_point
       WHERE osm_id NOT IN (SELECT min(osm_id)
                        FROM planet_osm_point
                        GROUP BY osm_id)

or this:

DELETE FROM planet_osm_point

WHERE osm_id NOT IN (
    select max(dup.osm_id)
    from planet_osm_point as dup
    group by way);

EDIT:

I finally found an easy way, which is working in my case:

DELETE FROM planet_osm_point WHERE ctid NOT IN
(SELECT max(ctid) FROM planet_osm_point GROUP BY osm_id);

found on this page: http://technobytz.com/most-useful-postgresql-commands.html