Robert Haas wrote:
> Well, there's no guarantee that any index at all exists on the target
> table, so any solution based on index locks can't be fully general.
>
Sure, but in the most common use case I think we're targeting at first,
no indexes means there's also no unique constraints either. I don't
think people can reasonable expect to MERGE or anything else to
guarantee they won't accidentally create two rows that conflict via the
terms of some non-database enforced key.
I am too brain-dead this particular Sunday to think of exactly how to
deal with the 3-tuple case you described, except to say that I think
it's OK for complicated situations to give up and throw a serialization
error. I'm already collecting a list of pathological tests and will try
to add something based on your problem case, then see what we can do
with it later.
--
Greg Smith, 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us