Re: Horribly slow hash join

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Dennis Bjorklund <db(at)zigo(dot)dhs(dot)org>
Cc: "Jim C(dot) Nasby" <jim(at)nasby(dot)net>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Horribly slow hash join
Date: 2004-04-18 15:39:10
Message-ID: 19681.1082302750@sss.pgh.pa.us
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Dennis Bjorklund <db(at)zigo(dot)dhs(dot)org> writes:
> 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.

That creates portability issues though. We do not depend on there being
a 64-bit-int type for anything except int8 itself, and I don't want to
start doing so.

regards, tom lane

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