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From: Tom Lane <[email protected]>
To: Gregory Stark <[email protected]>
Cc: 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 11:04:45 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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Gregory Stark <[email protected]> writes:
> "Heikki Linnakangas" <[email protected]> writes:
>> 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.

md5 is designed to be a signature, remember?  If there weren't a very
high probability of its output being different for different inputs,
it wouldn't be good for anything.

The built-in hash functions definitely cannot be relied on to not have
collisions, though.

			regards, tom lane

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