Re: TRUNCATE SERIALIZABLE and frozen COPY

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Fri, Nov 9, 2012 at 3:31 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> So what we're talking about here is a new mode for COPY, that when
>> requested will pre-freeze tuples when loading into a newly
>> created/truncated table. If the table isn't newly created/truncated
>> then we'll just ignore it and continue. I see no need to throw an
>> error, since that will just cause annoying usability issues.

> Actually, why not just have it work always? If people want to load
> frozen tuples into a table that's not newly created/truncated, why not
> let them? Sure, there could be MVCC violations, but as long as the
> behavior is opt-in, who cares? I think it'd be useful to a lot of
> people.

I thought about that too, but there's a big problem. It wouldn't be
just MVCC that would be broken, but transactional integrity: if the
COPY fails partway through, the already-loaded rows still look valid.
The new-file requirement provides a way to roll them back.

I'm willing to have an option that compromises MVCC semantics
transiently, but giving up transactional integrity seems a bit much.

regards, tom lane