Re: Commits 8de72b and 5457a1 (COPY FREEZE)

On 6 December 2012 17:02, Stephen Frost <sfrost@snowman.net> wrote:
> * Simon Riggs (simon@2ndQuadrant.com) wrote:
>> It's not a bug. Requesting a useful, but not critical optimisation is
>> just a hint. The preconditions are not easy to understand, so I see no
>> reason to punish people that misunderstand, or cause programs to fail
>> in ways that need detailed understanding to make them work again.
>
> I tend to agree with Andres on this one.  This feels a bit like
> accepting a command but then not actually following-through on it
> if it turns out we can't actually do it.  If it's truely an optimization
> (and I suspect my other email/question might provide insight into that),
> then it should be something we can 'just do' without needing to be asked
> to do it, along the same lines of not WAL'ing when the appropriate
> conditions are met (table created in this transaction, etc, etc).

That depends whether its a command or a do-if-possible hint. Its
documented as the latter.

Similar to the way VACUUM tries to truncate a relation, but gives up
if it can't. And on an even closer example, VACUUM FREEZE itself,
which doesn't guarantee that all rows are frozen at the end of it...

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services