From: | "Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com> |
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To: | "Chris Kratz" <chris(dot)kratz(at)vistashare(dot)com> |
Cc: | "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Planner mis-estimation using nested loops followup |
Date: | 2008-03-18 19:46:51 |
Message-ID: | dcc563d10803181246sbdc7425u838ff2baf70faeb6@mail.gmail.com |
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Lists: | pgsql-performance |
On Tue, Mar 18, 2008 at 9:58 AM, Chris Kratz <chris(dot)kratz(at)vistashare(dot)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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