From: Bruce Momjian <bruce@momjian.us>
To: Jonah H. Harris <jharris@enterprisedb.com>
Cc: josh@agliodbs.com, pgsql-performance@postgresql.org, Denis Lussier <denisl@enterprisedb.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: korryd@enterprisedb.com <korryd@enterprisedb.com>
Cc: Craig A. James <cjames@modgraph-usa.com>
Subject: Re: Simple join optimized badly?
Date: Sun, 8 Oct 2006 22:12:12 -0400 (EDT)
Message-ID: <200610090212.k992CCP10515@momjian.us> (raw)
In-Reply-To: <267982364.11091160349938551.OPEN-XCHANGE.WebMail.tomcat@edb04.managed.contegix.com>
Jonah H. Harris wrote:
> On Oct 08, 2006 07:05 PM, Josh Berkus <josh@agliodbs.com> wrote:
> > Hints are used because the DBA thinks that they are smarter than
> > the optimizer; 99% of the time, they are wrong.
>
> That's a figure which I'm 100% sure cannot be backed up by fact.
>
> > Just try manually optimizing a complex query, you'll see -- with three
> > join types, several scan types, aggregates, bitmaps, [blah blah blah]
> > it's significantly more than a human can figure out accurately.
>
> Let me get this right... the optimizer is written by humans who know and
> can calculate the proper query plan and generate code to do the same;
> yet humans aren't smart enough to optimize the queries themselves? A bit
> of circular reasoning here?
I can do 100! on my computer, but can't do it in my head.
--
Bruce Momjian bruce@momjian.us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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: bruce@momjian.us, jharris@enterprisedb.com, denisl@enterprisedb.com, tgl@sss.pgh.pa.us, korryd@enterprisedb.com, cjames@modgraph-usa.com
Subject: Re: Simple join optimized badly?
In-Reply-To: <200610090212.k992CCP10515@momjian.us>
* 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