Re: Doubt about AccessExclusiveLock in ALTER TABLE .. SET ( .. );

On Tue, Aug 4, 2015 at 5:55 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> On 2015-08-03 14:15:27 +0900, Michael Paquier wrote:
> > On Sat, Aug 1, 2015 at 9:20 PM, Andres Freund wrote:
> > > On August 1, 2015 2:17:24 PM GMT+02:00, Michael Paquier wrote:
> > >>> For instance, if you told me to choose between ShareLock and
> > >>> ShareUpdateExclusiveLock I wouldn't know which one is strongest. I
> > >>> don't it's sensible to have the "lock mode compare" primitive
> > >>honestly.
> > >>> I don't have any great ideas to offer ATM sadly.
> > >>
> > >>Yes, the thing is that lowering the lock levels is good for
> > >>concurrency, but the non-monotony of the lock levels makes it
> > >>impossible to choose an intermediate state correctly.
> > >
> > > How about simply acquiring all the locks individually of they're
different types? These few acquisitions won't matter.
> >
> > As long as this only applies on master, this may be fine... We could
> > basically pass a LOCKMASK to the multiple layers of tablecmds.c
> > instead of LOCKMODE to track all the locks that need to be taken, and
> > all the relations open during operations.
>
> This sounds far too complicated to me. Just LockRelationOid() the
> relation with the appropriate level everytime you pass through the
> function?

Hi all,

IMHO is more simply we just fallback to AccessExclusiveLock if there are
different lockmodes in reloptions as Michael suggested before.

Look at the new version attached.

Regards,

*** This work is funded by Zenvia Mobile Results (http://www.zenvia.com.br)

--
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