From: Dave Dutcher <dave@tridecap.com>
To: 'Steinar H. Gunderson' <sgunderson@bigfoot.com>
To: pgsql-performance@postgresql.org
Subject: Re: simple join uses indexes, very slow
Date: Tue, 28 Mar 2006 19:30:23 -0600
Message-ID: <010a01c652d0$59ccd870$8300a8c0@tridecap.com> (raw)
In-Reply-To: <20060328173442.GA31836@uio.no>
> -----Original Message-----
> From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-
> owner@postgresql.org] On Behalf Of Steinar H. Gunderson
> A merge join requires sorted inputs.
>
> > Most of the time was spent sorting the parameters parameters table
by
> > opset_num even though opset_num is indexed. Isn't Postgres able to
walk
> the
> > index instead of sorting?
>
> The time of an index scan vs. a sequential scan + sort depends on
several
> factors, so it's not just a matter of walking the index whenever there
is
> one.
I was just looking this over again and I realized I misread the query
plan. The slowest step was the Bitmap Heap Scan not the sort. (The
sort was relatively fast.)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: dave@tridecap.com, sgunderson@bigfoot.com
Subject: Re: simple join uses indexes, very slow
In-Reply-To: <010a01c652d0$59ccd870$8300a8c0@tridecap.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox