Skip site navigation (1) Skip section navigation (2)

Re: vacuum locking

From: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
To: Rob Nagler <nagler(at)bivio(dot)biz>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: vacuum locking
Date: 2003-10-30 14:29:32
Message-ID: Pine.LNX.4.33.0310300728240.23153-100000@css120.ihs.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, 29 Oct 2003, Rob Nagler wrote:

> Greg Stark writes:
> > > > SELECT a, (SELECT name FROM t2 WHERE t2.f2 = t1.f2)
> > > >   FROM t1
> > > >  GROUP BY f2 
> > > 
> > > This doesn't solve the problem.  It's the GROUP BY that is doing the
> > > wrong thing.  It's grouping, then aggregating.
> > 
> > But at least in the form above it will consider using an index on f2, and it
> > will consider using indexes on t1 and t2 to do the join.
> 
> There are 20 rows in t2, so an index actually slows down the join.
> I had to drop the index on t1.f2, because it was trying to use it
> instead of simply sorting 20 rows.

t2 was 'vacuum full'ed and analyzed, right?  Just guessing.


In response to

Responses

pgsql-performance by date

Next:From: Christopher BrowneDate: 2003-10-30 15:10:47
Subject: Re: Query puts 7.3.4 on endless loop but 7.4beta5 is fine. [ with better indenting ]
Previous:From: mallahDate: 2003-10-30 14:12:00
Subject: Re: Query puts 7.3.4 on endless loop but 7.4beta5 is fine. [ with better indenting ]

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group