From: Scott Marlowe <scott.marlowe@gmail.com>
To: Chris Kratz <chris.kratz@vistashare.com>
Cc: Joshua D. Drake <jd@commandprompt.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Planner mis-estimation using nested loops followup
Date: Tue, 18 Mar 2008 13:46:51 -0600
Message-ID: <dcc563d10803181246sbdc7425u838ff2baf70faeb6@mail.gmail.com> (raw)
In-Reply-To: <3642025c0803180858k704d8c6ah39e30b8ab75f4df0@mail.gmail.com>
References: <3642025c0803180835n20062314g94870b137d8c3ff7@mail.gmail.com>
<20080318085059.7c5da59a@commandprompt.com>
<3642025c0803180858k704d8c6ah39e30b8ab75f4df0@mail.gmail.com>
On Tue, Mar 18, 2008 at 9:58 AM, Chris Kratz <chris.kratz@vistashare.com> wrote:
> Y, turning nested loops off in specific cases has increased performance
> greatly. It didn't fix the planner mis-estimation, just the plan it chose.
> It's certainly not a panacea, but it's something we now try early on when
> trying to speed up a query that matches these characteristics.
I have to admit I've had one or two reporting queries in the past that
turning off nested_loop was the only reasonable fix due to
misestimation. I'd tried changing the stats targets etc and nothing
really worked reliably to prevent the nested_loop from showing up in
the wrong places.
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To: pgsql-performance@postgresql.org
Cc: scott.marlowe@gmail.com, chris.kratz@vistashare.com, jd@commandprompt.com
Subject: Re: Planner mis-estimation using nested loops followup
In-Reply-To: <dcc563d10803181246sbdc7425u838ff2baf70faeb6@mail.gmail.com>
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