Skip site navigation (1) Skip section navigation (2)

Re: [PATCHES] updated hash functions for postgresql v1

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Jeff Davis <pgsql(at)j-davis(dot)com>
Cc: Kenneth Marshall <ktm(at)rice(dot)edu>, pgsql-hackers(at)postgresql(dot)org, pgsql-patches(at)postgresql(dot)org
Subject: Re: [PATCHES] updated hash functions for postgresql v1
Date: 2009-01-10 18:36:25
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> I ran 5 times on both old and new code, eliminating the top and bottom
> and taking the average of the remaining 3, and I got a 6.9% performance
> improvement with the new code.

The question that has been carefully evaded throughout the discussion
of this patch is whether the randomness of the hash result is decreased,
and if so what is that likely to cost us in performance of the various
hash-dependent algorithms.  I would still like to have an answer to that
before we make a change to gain marginal performance improvement in
the hash function itself (which is already shown to be barely measurable
in the total context of a hash-dependent operation...)

			regards, tom lane

In response to


pgsql-hackers by date

Next:From: Tom LaneDate: 2009-01-10 18:51:05
Subject: Re: [SPAM] Re: posix_fadvise v22
Previous:From: Heikki LinnakangasDate: 2009-01-10 18:30:12
Subject: Re: [HACKERS] BUG #4516: FOUND variable does not work after RETURN QUERY

Privacy Policy | About PostgreSQL
Copyright © 1996-2018 The PostgreSQL Global Development Group