* Andrew - Supernews (andrew+nonews@supernews.com) wrote:
> On 2005-07-07, Stephen Frost <sfrost@snowman.net> wrote:
> >
> >> * truncate is not MVCC-safe.
> >
> > Erm, that's why it gets a stronger lock, so I don't really see what
> > this has to do with it.
>
> It's not MVCC-safe even with the AccessExclusive lock; it damages snapshots
> that were taken before the truncate operation but which don't have a lock
> on the table yet. The only reason it doesn't break pg_dump is that the
> first thing that pg_dump does is to take AccessShare locks on every table
> that it's going to dump.
This seems like something which should probably be fixed, but which is
probably too late to fix for 8.1. Of course, if we could fix this then
it seems like it would be possible for us to just change 'delete from x'
to behave as truncate does now given appropriate conditions. I'm not as
familiar with that area as others are; is this a very difficult thing to
do? If not then I may take a look at it, it'd be a very nice
improvement.
Thanks,
Stephen
