Re: Horribly slow hash join

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От Dennis Bjorklund
Тема Re: Horribly slow hash join
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Msg-id Pine.LNX.4.44.0404180814280.4551-100000@zigo.dhs.org
обсуждение исходный текст
Ответ на Re: Horribly slow hash join  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: Horribly slow hash join  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-performance
On Sat, 17 Apr 2004, Tom Lane wrote:

> *some* set of inputs.  (Also, I have been harboring some notions of
> supporting cross-type hash joins for integer types, which will not work
> unless small int8 values hash the same as int4 etc.)

The simple solution would be to always extend integers to 64 bits (or
whatever the biggest integer is) before calculating the hash. It makes the
hash function a little slower for smaller types, but it's mostly an
operation in the cpu and no memory involved, so it's probably not
noticable.

--
/Dennis Björklund


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