From: Tom Lane <tgl@sss.pgh.pa.us>
To: Ulrich <ulrich.mierendorff@gmx.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: Subquery WHERE IN or WHERE EXISTS faster?
Date: Sat, 28 Jun 2008 11:53:43 -0400
Message-ID: <29009.1214668423@sss.pgh.pa.us> (raw)
In-Reply-To: <48665741.2060900@gmx.net>
References: <48665741.2060900@gmx.net>
Ulrich <ulrich.mierendorff@gmx.net> writes:
> People say that [EXISTS is faster]
People who say that are not reliable authorities, at least as far as
Postgres is concerned. But it is always a bad idea to extrapolate
results on toy tables to large tables --- quite aside from measurement
noise and caching issues, the planner might pick a different plan when
faced with large tables. Load up a realistic amount of data and then
see what you get.
regards, tom lane
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: tgl@sss.pgh.pa.us, ulrich.mierendorff@gmx.net
Subject: Re: Subquery WHERE IN or WHERE EXISTS faster?
In-Reply-To: <29009.1214668423@sss.pgh.pa.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