Re: Horribly slow hash join - Mailing list pgsql-performance

From Dennis Bjorklund
Subject Re: Horribly slow hash join
Date
Msg-id Pine.LNX.4.44.0404180814280.4551-100000@zigo.dhs.org
Whole thread Raw
In response to Re: Horribly slow hash join  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Horribly slow hash join
List 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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