Re: [Q] string to int hash function for small range

From: John R Pierce <pierce(at)hogranch(dot)com>
To: V S P <toreason(at)fastmail(dot)fm>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: [Q] string to int hash function for small range
Date: 2009-03-08 03:23:25
Message-ID: 49B33A2D.4070601@hogranch.com
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V S P wrote:
> I would like to have a function
> given a user id varchar(64) to get a hash number between 0 and 255.
>
> I first tried md5 but the number it returns is very big and cannot
> be converted to an INT
>
> there is likely a way to simply add ascii values of the userId together
> to get a small integer, but wanted to know if there are any other
> 'built-in' ways
>
> this is to get the database id based on user id.
>

maybe take the last byte (2 chars) of the md5, and convert to integer?
something like....

get_byte(decode(md5(id),'hex'),16)

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