"Christopher Kings-Lynne" <chriskl@familyhealth.com.au> writes:
> I can't try the insert and then the update because the INSERT, in Postgres,
> will cause an outright transaction failure.
Do the update, then try to insert if the update found nothing, and put
a retry loop around the whole transaction in case you fail because of
concurrent inserts.
Realistically you will need a retry loop in all but the most trivial
cases anyway --- certainly so if you want to use serializable
transaction mode. So I don't think this solution is unworkably complex.
regards, tom lane