Added to TODO:
* Have VACUUM FULL use REINDEX rather than index vacuum
---------------------------------------------------------------------------
Alvaro Herrera wrote:
> On Sat, Oct 04, 2003 at 11:53:49PM -0400, Tom Lane wrote:
> > Alvaro Herrera <alvherre@dcc.uchile.cl> writes:
>
> > > Imagine having to VACUUM FULL a huge
> > > table. Not only it will take the lot required to do the VACUUM in the
> > > heap itself, it will also have to rebuild all indexes from scratch.
> >
> > A very large chunk of VACUUM FULL's runtime is spent fooling with the
> > indexes. Have you looked at the code in any detail? It goes like this:
>
> Hmm. No, I haven't looked at that code too much. You are probably
> right, of course. Maybe the indexes could be dropped altogether and
> then recreated after the vacuum is over, similar to what the cluster
> code does. This would be similar to REINDEX, I suppose. (I haven't
> actually looked at the REINDEX code either.)
>
>
> > > I think there are scenarios where the REINDEX will be much worse, say when
> > > there are not too many deleted tuples (but in that case, why is the user
> > > doing VACUUM FULL in the first place?).
> >
> > Yeah, I think that's exactly the important point. These days there's
> > not a lot of reason to do VACUUM FULL unless you have a major amount of
> > restructuring to do. I would once have favored maintaining two code
> > paths with two strategies, but now I doubt it's worth the trouble.
> > (Or I should say, we have two code paths, the other being lazy VACUUM
> > --- do we need three?)
>
> There are two points that could be made here:
>
> 1. We do not want users having to think too hard about what kind of
> VACUUM they want. This probably botches Bruce's idea of an additional
> VACUUM DATA command.
>
> 2. We do not want to expose the VACUUM command family at all. The
> decisions about what code paths should be taken are best left to the
> backend-integrated vacuum daemon, which has probably much better
> information than users.
>
> --
> Alvaro Herrera (<alvherre[a]dcc.uchile.cl>)
> "You knock on that door or the sun will be shining on places inside you
> that the sun doesn't usually shine" (en Death: "The High Cost of Living")
>
-- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610)
359-1001+ If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square,
Pennsylvania19073
