Re: CLUSTER and MVCC

Gregory Stark wrote:
> "Csaba Nagy" <nagy(at)ecircle-ag(dot)com> writes:
>
> > Wouldn't be possible to do it like Simon (IIRC) suggested, and add a
> > parameter to enable/disable the current behavior, and use the MVCC
> > behavior as default ?
>
> Doing it in CLUSTER would be weird. However perhaps it would be useful to have
> some sort of stand-alone tool that just bumped all the xmin/xmax's. It would
> have to be super-user-only and carry big warning labels saying it breaks MVCC.
>
> But it would be useful any time you have a table that you want to exempt a
> particular table from serializable snapshots. Basically a per-table way to
> force a read-committed snapshot on. Though, actually it's not quite a
> read-committed snapshot is it? Anyone using an old serializable snapshot will
> see what, no tuples at all?

Unless you used FrozenTransactionId ...

But I'm not really seeing the problem here. Why isn't Csaba's problem
fixed by the fact that HOT reduces the number of dead tuples in the
first place? If it does, then he no longer needs the CLUSTER
workaround, or at least, he needs it to a much lesser extent.

--
Alvaro Herrera http://www.CommandPrompt.com/
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