Re: -HEAD planner issue wrt hash_joins on dbt3 ?

From: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Matteo Beccati <php(at)beccati(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: -HEAD planner issue wrt hash_joins on dbt3 ?
Date: 2006-09-22 16:56:00
Message-ID: 451415A0.2090608@kaltenbrunner.cc
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Tom Lane wrote:
> Matteo Beccati <php(at)beccati(dot)com> writes:
>> Tom Lane ha scritto:
>>> Matteo Beccati <php(at)beccati(dot)com> writes:
>>>> I cannot see anything bad by using something like that:
>>>> if (histogram is large/representative enough)
>>> Well, the question is exactly what is "large enough"? I feel a bit
>>> uncomfortable about applying the idea to a histogram with only 10
>>> entries (especially if we ignore two of 'em). With 100 or more,
>>> it sounds all right. What's the breakpoint?
>
>> Yes, I think 100-200 could be a good breakpoint.
>
> I've committed this change with (for now) 100 as the minimum histogram
> size to use. Stefan, are you interested in retrying your benchmark?

sure - but I'm having hardware (harddisk firmware) related issues on my
testbox which will take a few further days to be resolved ...

Stefan

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