Re: Erroneous cost estimation for nested loop join

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: kawamichi(at)tkl(dot)iis(dot)u-tokyo(dot)ac(dot)jp
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Erroneous cost estimation for nested loop join
Date: 2015-11-09 14:37:24
Message-ID: 22565.1447079844@sss.pgh.pa.us
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kawamichi(at)tkl(dot)iis(dot)u-tokyo(dot)ac(dot)jp writes:
> - cost parameter calibration: random_page_cost = 92.89

TBH, you lost me there already. I know of no hardware on which that would
be a sane depiction of reality, so I think you've probably overfitted the
model to some particular case it was already inaccurate on. Any results
you're getting using this setting will likely fall into the category of
"garbage in, garbage out".

What led you to choose that number?

regards, tom lane

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