Delete duplicate rows from table with no unique key

Question

How do I delete duplicates rows in Postgres 9 table, the rows are completely duplicates on every field AND there is no individual field that could be used as a unique key so

Answer 1

If you can afford to rewrite the whole table, this is probably the simplest approach:

WITH Deleted AS (
  DELETE FROM discogs.releases_labels
  RETURNING *
)
INSERT INTO discogs.releases_labels
SELECT DISTINCT * FROM Deleted

If you need to specifically target the duplicated records, you can make use of the internal ctid field, which uniquely identifies a row:

DELETE FROM discogs.releases_labels
WHERE ctid NOT IN (
  SELECT MIN(ctid)
  FROM discogs.releases_labels
  GROUP BY label, release_id, catno
)

Be very careful with ctid; it changes over time. But you can rely on it staying the same within the scope of a single statement.