From: Ow Mun Heng <Ow.Mun.Heng@wdc.com>
To: Jonah H. Harris <jonah.harris@gmail.com>
Cc: Dave Dutcher <dave@tridecap.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL vs MySQL, and FreeBSD
Date: Mon, 19 Nov 2007 09:27:47 +0800
Message-ID: <1195435667.11620.5.camel@neuromancer.home.net> (raw)
In-Reply-To: <36e682920711160806k359a8825ia0d962d7ac6f6d7b@mail.gmail.com>
References: <47344D43.5090506@geri.cc.fer.hr>
<47347F9F.1070309@laliluna.de>
<1195206185.29253.56.camel@neuromancer.home.net>
<01c601c82869$3ffb2580$8e00a8c0@tridecap.com>
<36e682920711160806k359a8825ia0d962d7ac6f6d7b@mail.gmail.com>
On Fri, 2007-11-16 at 11:06 -0500, Jonah H. Harris wrote:
> On Nov 16, 2007 10:56 AM, Dave Dutcher <dave@tridecap.com> wrote:
> > I don't know about that. There are times when it is the right plan:
>
> Agreed. IMHO, there's nothing wrong with nested-loop join as long as
> it's being used properly.
I do agree also, but in some other cases, the usage of nested loops (esp
when the number of rows estimated to be returned vs the actual number of
rows being returned differs by up to 100x (or more) then it becomes a
major issue.
The example pointed out by Dave D shows the est rows = 1 and actual
rows=1, then good performance of course.
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To: pgsql-performance@postgresql.org
Cc: Ow.Mun.Heng@wdc.com, jonah.harris@gmail.com, dave@tridecap.com
Subject: Re: PostgreSQL vs MySQL, and FreeBSD
In-Reply-To: <1195435667.11620.5.camel@neuromancer.home.net>
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