Re: ANALYZE after restore - Mailing list pgsql-hackers

Justin Clift wrote:
> Tom Lane wrote:
> >
> > Gavin Sherry <swm@linuxworld.com.au> writes:
> > > On Wed, 3 Apr 2002, Christopher Kings-Lynne wrote:
> > >> Would it be an idea to have pg_dump append an ANALYZE; command to the end of
> > >> its dumps to assist newbies / inexperienced admins?
> >
> > > I do not think this is desired behaviour.
> >
> > I agree with Gavin here ... a forced VACUUM or ANALYZE after a restore
> > will just get in the way of people who know what they're doing, and it's
> > not at all clear that it will help people who do not.
>
> Sorry Tom and Gavin, but I feel it really comes down to our idea of what
> we're
> trying to do here :
>
> a) A database which is very self-maintaining, so people DON'T HAVE to
>    learn it's intricacies in order to be getting decent performance.
>    (They'll have to learn the intricacies if they want *better*
> performance)
   The  defaults  after  a  restore should result in index scans   most  of  the  time,  resulting   in   some   medium
 decent   performance.   And  PostgreSQL  needs  some  frequent  VACUUM   anyway, so after a while this problem solves
itself for  the   average user.
 
   A  database  wide  forced  VACUUM  on the other hand can make   things worse.  I have  seen  scenarios,  where  you
have to   explicitly  leave out ANALYZE for specific tables in order to   keep them index-scanned. So what you're
proposingis to force   professional  PostgreSQL  users  to  wait after restore for a   useless ANALYZE to complete,
before they  can  reset  things   with  a normal VACUUM to get their required performance back?   And all that just to
makedummies happier?
 


Jan

> b) A database which works.  But if you want decent performance, you'd
> better
>    take the time and effort to learn it.
>    (This is the approach the commercial vendors take)
>
> I feel we should always target a) where it's possible to without it
> seriously
> getting in the way of people who've take the time to learn the skills.
>
> The far majority of people who use PostgreSQL are in the category which
> will
> benefit from a) so they can put their time to other uses instead of
> having to
> learn and keep-up-to-date-with PostgreSQL.  This will *always* be the
> case.
>
> Having decent performance by default should definitely be an important
> objective, so having an ANALYZE command run at the end of a restore - by
> default only - is a good idea.
>
> Regards and best wishes,
>
> Justin Clift
>
> >                         regards, tom lane
> >
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> "My grandfather once told me that there are two kinds of people: those
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