| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Thoughts on maintaining 7.3 |
| Date: | 2003-10-04 03:42:00 |
| Message-ID: | 200310040342.h943g0s02139@candle.pha.pa.us |
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| Lists: | pgsql-hackers |
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Though the new code will put empty index pages into the free-space map,
> > will it also shrink the index file to remove those pages?
>
> If there are free pages at the end, yes --- but it won't move pages
> around. This is about the same story as for plain VACUUM ...
I know indexes behave the same as heap for vacuum. My point was that
the vacuum full case is different. Vacuum full moves heap tuples from
the end to fill slots and then frees the pages at the end via
truncation. (100% compaction, guaranteed.) We can't move index tuples
around like that, of course, so that leaves us with partially filled
pages.
Do we move empty index pages to the end before truncation during 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
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