From: | "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com> |
---|---|
To: | "Chris Kratz" <chris(dot)kratz(at)vistashare(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Planner mis-estimation using nested loops followup |
Date: | 2008-03-18 15:50:59 |
Message-ID: | 20080318085059.7c5da59a@commandprompt.com |
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Thread: | |
Lists: | pgsql-performance |
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On Tue, 18 Mar 2008 11:35:08 -0400
"Chris Kratz" <chris(dot)kratz(at)vistashare(dot)com> wrote:
> Nondefault settings of interest from postgresql.conf
>
>
> shared_buffers = 1024MB # min 128kB or
> max_connections*16kB work_mem = 256MB
> # min 64kB maintenance_work_mem = 256MB # min 1MB
> random_page_cost = 1.75 # same scale as above
> effective_cache_size = 4096MB
> default_statistics_target = 100 # range 1-1000
>
>
> If nothing else, perhaps this will help somebody else who has run
> into the same problem. If explain analyze of a query shows a large
> mis-estimation of rows returned on a join (estimate=1, actual=2k)
> causing the planner to choose nested loops instead of another join
> type, you might try running the query with nested loops set to off
> and see if that helps w/ performance.
Did you try that? Did it work?
Joshua D. Drake
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