Re: Disk Utilization Increases And Time for Vacuum Increases.

Bruce Momjian wrote:
> > > AFAIK, VACUUM doesn't reclaim space taken up by indexes. In fact, the more
> > > deletes you do, the larger the index space gets, and the *slower* the index
> > > performs. A periodic REINDEX cleans up a lot of problems.
> >
> > Note that in 7.4 the fix for this is in, so if you have a chance to test
> > it out with your indexes and their growth problem please test it to see if
> > it works right.
> >
> > I haven't tested 7.4 beta1 yet very hard, just on my workstation, with
> > relatively low level stuff.
>
> I am not sure we have completely dealt with index growth in 7.4. What
> we have new in 7.4 is the ability for non-FULL VACUUM to collect info on
> free index pages and reuse them.
>
> However, VACUUM FULL does not shrink the index table unless those pages
> are the last pages of the file. (Could it shift free pages to the end
> and then truncate index?) Also, does VACUUM FULL on an index put the
> empty index pages in the FSM map? It doesn't do that for heap pages
> because there are none after vacuum, but there might be free index pages
> that we should record.

I haven't seen anyone comment on this. I think we need to address this
for 7.4. (Collecting index free space in FSM is new in 7.4.) I am
concerned that people who are only running VACUUM FULL at night will
have problems with index growth. Also, why can't we move totally-empty
index pages to the end and truncate the file?

> Interesting I found a reference of doing an auto-reindex as part of
> VACUUM FULL:
>
> #ifdef NOT_USED
>
> /*
> * reindex in VACUUM is dangerous under WAL. ifdef out until it
> * becomes safe.
> */
> if (reindex)
> {
> vac_close_indexes(nindexes, Irel);
> Irel = (Relation *) NULL;
> activate_indexes_of_a_table(onerel, false);
> }
> #endif /* NOT_USED */

Will we ever reindex as part of VACUUM FULL?

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073