Re: Serializable Isolation without blocking

On Mon, May 11, 2009 at 3:11 PM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> Greg Stark <stark(at)enterprisedb(dot)com> wrote:
>
>> I thought the big problem with providing true serializability was
>> the predicate locking. If it doesn't address that need then does
>> this get us any closer?
>
> I thought the big problem was the perception that performance would
> suffer and that the level of blocking required would be unacceptable.

This thread has really been one of those cases where everyone thought
they were having a different kind of discussion.

If predicate locking is so well understood and if someone who
understands it and understands what kind of implementation would work
well in Postgres steps forward with an implementation which doesn't
cause major downsides then I suspect we might revisit our prejudices
against it. But as it stands I think the assumption is that having to
maintain locks on hypothetical records which don't exist would be an
expensive cost to impose on every query which would unduly impact
performance.

I, for one, certainly assumed if we did anything like that it would
work like our existing locks in that it wouldn't impose any additional
blocking. If there was any question of that then it sounds like this
paper might be a step forward in that you're on-side at least on that
question now?

--
greg