Re: SKIP LOCKED DATA (work in progress)

On Sat, Aug 2, 2014 at 3:55 AM, Thomas Munro <munro(at)ip9(dot)org> wrote:

> On 1 August 2014 10:37, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> > Apart from this I can't see any other problems with the patch and I'd be
> > very inclined, once the above are fixed up to mark the patch ready for
> > commiter.
> >
> > Good work
>
> Thanks for all the guidance, I appreciate it! My review karma account
> is now well overdrawn.
>

Ok, then I have nothing more so it's time to pass this one along.

The only notes I can think to leave for the commiter would be around the
precedence order of the lock policy, especially around a query such as:

SELECT * FROM (SELECT * FROM a FOR UPDATE SKIP LOCKED) a FOR UPDATE; --
skip locked wins

Of course the current behaviour is that NOWAIT wins over the standard FOR
UPDATE, but with NOWAIT, there's only a chance of an error, there's no
chance of giving incorrect results.

I checked what Oracle did in this situation and I see that they completely
disallow FOR UPDATE inside of views and subqueries.

I could see an argument here that the outer most FOR UPDATE clause should
be used, but I guess that ship has sailed when NOWAIT was added.

Marking as ready for commiter.

Regards

David Rowley