Kevin Grittner wrote:
> > I still haven't actually read the paper so I should probably bow out
> > from the conversation until I do. I was apparently already under
> > one misapprehension as Laurenz just claimed the paper does not show
> > how to prevent "phantoms" (phantom reads I assume?). Perhaps it's
> > not as ambitious as achieving true serializability after all?
>
> It does achieve true serializability in terms of the definitions I've
> read, although I've discovered at least one way in which its
> guarantees aren't as strong as traditional blocking techniques -- it
> doesn't guarantee that transactions at a level less strict than
> serializable will see a state which would exist between some serial
> execution of serializable transactions which modify the data, as the
> blocking schemes do.
I still don't buy that this implementation guarantees serializability.
All the authors show with regard to predicate handling is handwaving,
and while you tried to come up with ideas how that could be improved
that is not what the implementation described in the paper does.
So this paper shows a performant implementation of something that is
closer to serializability than "snapshot isolation", but did not go
all the way.
As I said, I think it is promising, and it can only be hoped that
the authors pursue the path they have taken and share their experiences
with an implementation of full serializability with their technique.
Yours,
Laurenz Albe