| 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 |
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| 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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