Re: ALTER TABLE SET STATISTICS requires AccessExclusiveLock

On Thu, 2010-07-08 at 06:08 -0400, Robert Haas wrote:
> On Thu, Jul 8, 2010 at 2:16 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> > On Wed, 2010-07-07 at 22:26 -0400, Robert Haas wrote:
> >> Rereading the thread, I'm a bit confused by why we're proposing to use
> >> a SHARE lock; it seems to me that a self-conflicting lock type would
> >> simplify things. There's a bunch of discussion on the thread about
> >> how to handle pg_class updates atomically, but doesn't using a
> >> self-conflicting lock type eliminate that problem?
> >
> > The use of the SHARE lock had nothing to do with the pg_class update
> > requirement, so that suggestion won't help there.
>
> Forgive me if I press on this just a bit further, but ISTM that an
> atomic pg_class update functionality isn't intrinsically required,
> because if it were the current code would need it. So what is
> changing in this patch that makes it necessary when it isn't now?
> ISTM it must be that the lock is weaker. What am I missing?

Not sure I follow that logic. Discussion on the requirement is in the
archives. I don't wish to question that aspect myself.

--
Simon Riggs www.2ndQuadrant.com
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