Re: Triggered Data Change check

Tom Lane wrote:
> 
> Stephan Szabo <sszabo@megazone23.bigpanda.com> writes:
> > Well, I wonder if the check is so weak as to be fairly useless in the
> > first place really, even if applied to the statement as opposed to the
> > transaction.
> 
> Looking back at our discussion around 24-Oct, I recall that I was
> leaning to the idea that the correct interpretation of the spec's
> "triggered data change" rule is that it prohibits scenarios that are
> impossible anyway under MVCC, because of the MVCC tuple visibility
> rules. 

Strictly speaking MVCC is only for read-only queries.
Even under MVCC, update, delete and select .. for update have
to see the newest tuples. Constraints shouldn't ignore the
update/delete operations in the future from MVCC POV.

regards,
Hiroshi Inoue