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Re: Hash function for numeric (WIP)

From: Neil Conway <neilc(at)samurai(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Hash function for numeric (WIP)
Date: 2007-04-28 22:47:10
Message-ID: 1177800430.6440.182.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-patches
Sorry for fat-fingering the previous reply -- I wanted to add:

On Fri, 2007-04-27 at 10:02 -0400, Tom Lane wrote:
> Perhaps a sufficiently robust way would be to form the hash as the
> XOR of each supplied digit, circular-shifted by say 3 times the
> digit's weight. 

The only objection I have to this is that it means we need to have
another hash function in the backend. The Jenkins hash we use in
hash_any() has been studied and we can have at least some confidence in
its collision-resistance, etc.

Anyway, attached is a revised version of the hash_any()-based patch.

-Neil


Attachment: numeric_hash_func-3.patch
Description: text/x-patch (8.1 KB)

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