| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Matteo Beccati <php(at)beccati(dot)com> |
| Cc: | Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: -HEAD planner issue wrt hash_joins on dbt3 ? |
| Date: | 2006-09-20 19:52:10 |
| Message-ID: | 17841.1158781930@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
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?
regards, tom lane
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