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help / color / mirror / Atom feedFrom: Gregory Stark <[email protected]>
To: Heikki Linnakangas <[email protected]>
Cc: Juho Saarikko <[email protected]>
Cc: [email protected]
Subject: Re: BUG #3965: UNIQUE constraint fails on long column values
Date: Wed, 20 Feb 2008 11:51:47 +0000
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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"Heikki Linnakangas" <[email protected]> writes:
"Heikki Linnakangas" <[email protected]> writes:
> Gregory Stark wrote:
>> "Heikki Linnakangas" <[email protected]> writes:
>>
>>> As others have pointed out, CREATE UNIQUE INDEX i ON ((md5(column)) is a pretty
>>> good work-around.
>>
>> Unless you need cryptographic security I would not suggest using MD5. MD5 is
>> intentionally designed to take a substantial amount of CPU resources to
>> calculate.
>
> Return type of hash* functions is just 32 bits. I wonder if that's wide enough
> to avoid accidental collisions? Depends on the application of course...
Oh, I missed that you were suggesting a UNIQUE index. That seems unsafe to me
even for md5 or its ilk. But that would depend on the application too.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's RemoteDBA services!
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