Re: Optimization via explicit JOINs

From: Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com>
To: David Olbersen <dave(at)slickness(dot)org>
Cc: pgsql-sql(at)postgresql(dot)org
Subject: Re: Optimization via explicit JOINs
Date: 2001-03-10 02:18:47
Message-ID: Pine.BSF.4.21.0103091817560.82859-100000@megazone23.bigpanda.com
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Actually, just thought of something else. If you remove
the probably redundant p.song_id=s.song_id from the second
query (since the join ... using should do that) does it
change the explain output?

On Fri, 9 Mar 2001, David Olbersen wrote:

> On Fri, 9 Mar 2001, Stephan Szabo wrote:
>
> ->As a question, how many rows does
> ->select * from playlist p join songs s using (song_id) where
> ->p.waiting=TRUE;
> ->actually result in?
>
> Well it depends. Most of the time that playlist table is "empty" (no rows where
> waiting = TRUE), however users can (in a round about way) insert into that
> table, so that there could be anywhere from 10, to 2,342, to more.
>
> Why do you ask?
>
> (The reason those plans chose 14 was because, at the time, there were 14 rows in
> playlist)

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