Re: Dead Space Map

Ühel kenal päeval, E, 2006-02-27 kell 13:17, kirjutas Tom Lane:
> Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
> > Vacuum will need to be modified to use index lookups to find index tuples
> > corresponding the dead heap tuples. Otherwise you have to scan through
> > all the indexes anyway.
>
> This strikes me as a fairly bad idea, because it makes VACUUM dependent
> on correct functioning of user-written code --- consider a functional
> index involving a user-written function that was claimed to be immutable
> and is not. There are concurrency-safety issues too, I think, having to
> do with the way that btree ensures we don't delete any index tuple that
> some scan is stopped on.
>
> > * vacuuming pages one by one as they're written by bgwriter
>
> That's not happening. VACUUM has to be a transaction

WHY does vacuum need to be a tranasction ? I thought it was a programmer
workload optimisation (aka. lazyness :) ) to require ordinary lazy
vacuum to be in transaction.

There is no fundamental reason, why vacuum needs to run in a transaction
itselt.

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Hannu