Re: Vacuum only with 20% old tuples

how about leaving vacuum as is, but extend REINDEX so that it
drops/rebuilds all indices on a TABLE | DATABASE?  Or does it do that
now?  From reading \h REINDEX, my thought is that it doesn't, but ...



On Tue, 11 Jul 2000, Bruce Momjian wrote:

> > We can't "drop and recreate" without a solution to the relation
> > versioning issue (unless you are prepared to accept a nonfunctional
> > database after a failure partway through index rebuild on a system
> > table).  I think we should do this, but it's not all that simple...
> > 
> > I do not see what your 20% idea has to do with this, though, nor
> > why it's a good idea.  If I've told the thing to vacuum I think
> > it should vacuum.  20% of a big table could be a lot of megabytes,
> > and I don't want some arbitrary decision in the code about whether
> > I can reclaim that space or not.
> 
> Well, I think we should do a sequential scan before starting vacuum to
> find the number of expired rows.
> 
> Now that we are removing indexes, doing that to remove a few tuples is a
> major waste.  The user can not really know if the table is worth
> vacuuming in normal use.  They are just going to use the default.  Now,
> I think a FORCE option would be good, or the ability to change the 20%
> default.
> 
> Remember, commercial db's don't even return unused space if you remove
> all the rows in a table.  At least Informix doesn't and I am sure there
> are others.  I like vacuum, but let's not make it do major hurtles for
> small gain.
> 
> -- 
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman@candle.pha.pa.us               |  (610) 853-3000
>   +  If your life is a hard drive,     |  830 Blythe Avenue
>   +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026
> 

Marc G. Fournier                   ICQ#7615664               IRC Nick: Scrappy
Systems Administrator @ hub.org 
primary: scrappy@hub.org           secondary: scrappy@{freebsd|postgresql}.org