Re: -HEAD planner issue wrt hash_joins on dbt3 ?

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От Tom Lane
Тема Re: -HEAD planner issue wrt hash_joins on dbt3 ?
Дата
Msg-id 17841.1158781930@sss.pgh.pa.us
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Ответ на Re: -HEAD planner issue wrt hash_joins on dbt3 ?  (Matteo Beccati <php@beccati.com>)
Ответы Re: -HEAD planner issue wrt hash_joins on dbt3 ?  (Matteo Beccati <php@beccati.com>)
Re: -HEAD planner issue wrt hash_joins on dbt3 ?  (Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>)
Re: -HEAD planner issue wrt hash_joins on dbt3 ?  (Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>)
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Matteo Beccati <php@beccati.com> writes:
> Tom Lane ha scritto:
>> Matteo Beccati <php@beccati.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?
        regards, tom lane


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