Re: vacuum, performance, and MVCC

Ühel kenal päeval, L, 2006-06-24 kell 19:36, kirjutas Bruce Momjian:
> Hannu Krosing wrote:
> > ?hel kenal p?eval, R, 2006-06-23 kell 13:08, kirjutas Tom Lane:

> > >
> > > Bottom line: there's still lots of low-hanging fruit. Why are people
> > > feeling that we need to abandon or massively complicate our basic
> > > architecture to make progress?
> >
> > Maybe we could start from reusing the index tuples which point to
> > invisible tuples ? The index is not MVCC anyway, so maybe it is easier
> > to do in-place replacement there ?
> >
> > This probably has the same obstacles which have prevented us from
> > removing those in the first place (removing instead of marking as
> > invisible). Does it cause some locking issues ? Or does it go against
> > some other constraints of our index lookups ?
> >
> > I think that just setting the invisible bit in an index leaf node causes
> > nearly as much disk io as removing the node.
> >
> > If we could delete/reuse old index tuples, it would solve a sizable
> > chunk of index-growth problem, especially for cases where referenced key
> > value does not change.
>
> I think heap _and_ index reuse is the only useful direction. Index or
> heap reuse alone seems too marginal for the added complexity.

Sure, but index reuse seems a lot easier, as there is nothing additional
to remember or clean out when doing it.

When reusing a heap tuple you have to clean out all index entries
pointing to it.

--
----------------
Hannu Krosing
Database Architect
Skype Technologies OÜ
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