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

Fabrízio de Royes Mello wrote:
> On Mon, Apr 6, 2015 at 12:53 AM, Alvaro Herrera <alvherre@2ndquadrant.com>
> wrote:
> >
> > Fabrízio de Royes Mello wrote:
> >
> > > Ok guys. The attached patch refactor the reloptions adding a new field
> > > "lockmode" in "relopt_gen" struct and a new method to determine the
> > > required lock level from an option list.
> > >
> > > We need determine the appropriate lock level for each reloption:
> >
> > I don't think AccessShareLock is appropriate for any option change.  You
> > should be using a lock level that's self-conflicting, as a minimum
> > requirement, to avoid two processes changing the value concurrently.
> 
> What locklevel do you suggest? Maybe ShareLock?

ShareUpdateExclusive probably.  ShareLock doesn't conflict with itself.

> > (I would probably go as far as ensuring that the lock level specified in
> > the table DoLockModesConflict() with itself in an Assert somewhere.)
> 
> If I understood this is to check if the locklevel of the reloption list
> don't conflict one each other, is it?

I meanAssert(DoLockModesConflict(relopt_gen->locklevel, relopt_gen->locklevel));

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
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