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Re: Hash support for arrays

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: marcin mank <marcin(dot)mank(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Hash support for arrays
Date: 2010-11-02 21:28:01
Message-ID: 7882D015-FE82-4C9F-94DF-C75F95E1B055@gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Nov 2, 2010, at 1:42 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> However, this is largely beside the point, because that theory, as well
> as the Java code you're arguing from, has to do with the initial hashing
> of a raw sequence of input items.  Not with combining some existing hash
> values.  The rotate-and-xor method I suggested for that is borrowed
> exactly from section 6.4 of Knuth (page 512, in the first edition of
> volume 3).

It seems undesirable to me to have a situation where transposing two array elements doesn't change the hash value.  But I just work here.

...Robert

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