Re: Pre-calculate hash join

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От Robert Gravsjö
Тема Re: Pre-calculate hash join
Дата
Msg-id 4B4CA123.6090309@blogg.se
обсуждение исходный текст
Ответ на Re: Pre-calculate hash join  (Dimitri Fontaine <dfontaine@hi-media.com>)
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Dimitri Fontaine skrev 2010-01-12 12.01:
> warren@warrenandrachel.com writes:
>
>> When joining two large tables [common in warehousing], a hash join is
>> commonly selected. Calculating hash values for the merge phase is CPU
>> intensive. Is there any way to pre-calculate value hashes to save that
>> time? Would it even grant any performance to skip the build phase of
>> the hash join?
>
> Maybe maintaining a materialized view then using it in the queries would
> be sufficient to solve your problem?
>

Depending on your case creating a temporary table in the beginning of
the session might save you a lot of time if multiple similar queries is
done.

Regards,
roppert

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