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

From Tom Lane
Subject Re: Horribly slow hash join
Date
Msg-id 15053.1082259958@sss.pgh.pa.us
Whole thread Raw
In response to Re: Horribly slow hash join  (Greg Stark <gsstark@mit.edu>)
Responses Re: Horribly slow hash join
List pgsql-performance
Greg Stark <gsstark@mit.edu> writes:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
>> (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 obvious way to modify the hash function is to xor the high 32 bits with
> the low 32 bits. That maintains the property you need

No it doesn't ...

            regards, tom lane

pgsql-performance by date:

Previous
From: Mark Kirkwood
Date:
Subject: Re: Poor performance of group by query
Next
From: Dennis Bjorklund
Date:
Subject: Re: Horribly slow hash join