Re: Eliminating VACUUM FULL WAS: remove flatfiles.c

Dimitri Fontaine escribió:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> > Dimitri Fontaine escribió:
> >> Why can't MVCC apply here? You'd have two versions of the pg_class entry
> >> that just has been CLUSTERed, and you keep the old relfilenode arround
> >> too. MVCC applies, and you teach vacuum to clean out the old file when
> >> cleaning out the no more visible tuple.
> >
> > It just doesn't work. pg_class (and various other rels) are special
> > because they are needed to bootstrap the catalog system. See
> > RelationCacheInitializePhase3. It wouldn't be possible to figure out
> > what's pg_class relfilenode until you have read it from pg_class, which
> > is precisely what we're trying to do.
>
> Well at bootstrap time I guess noone is able to disturb the system by
> placing a concurrent CLUSTER pg_class; call. Once started, do those rels
> still need to have a special behavior?

The relcache need to be bootstrapped more than once, not just at
initdb's bootstrap. (I guess you could try a breakpoint in formrdesc)

> I guess I'm being dense, will now let people in the know find a solution...

Yeah, well, Tom just posted a possible solution :-)

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