Forum OpenACS Q&A: Response to Disable constraints in PG

to answer your original question, you can disable constraints on a table (in 7.2, I don't think you can do this in older versions) with

UPDATE "pg_class" SET "reltriggers" = 0 WHERE "relname" = 'mytable';

and to re-enable

UPDATE pg_class SET reltriggers =
    (SELECT count(*) FROM pg_trigger where pg_class.oid = tgrelid)
WHERE relname = 'mytable';

this is NOT how you want to solve your problem of deleting a few rows, but I mention it because it can be useful at other times, e.g. populating tables who each have a FK referencing the other.