Brodie Thiesfield <brofield+pgsql@xxxxxxxxx> writes: > Essentially, I have two processes connecting to a single PG database > and simultaneously issuing the following statements: > BEGIN; > SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; > DELETE FROM licence_properties WHERE key = xxx; > INSERT INTO licence_properties ... values with key = xxx; > COMMIT You mean they both want to insert the same key? > One of these processes is getting to the INSERT and failing with > duplicate key error. > ERROR: duplicate key value violates unique constraint If they both insert the same key, this is what *must* happen. Surely you don't expect both to succeed, or one to fail and not tell you. > The DELETE should prevent this duplicate key error from occurring. I > thought that the ISOLATION LEVEL SERIALIZABLE would fix this problem > (being that the second process can see the INSERT from the first > process after it has done the DELETE), but it doesn't. I think you've got the effects of SERIALIZABLE backward, but in any case SERIALIZABLE does not affect uniqueness checks. Unique is unique. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
