Re: Drawbacks of using BYTEA for PK? - Mailing list pgsql-general

> Tom Lane wrote:
>
>> Adding an MD5 hash contributes *absolutely zero*, except waste of space,
>> to any attempt to make a GUID.  The hash will add no uniqueness that was
>> not there before.
>
The cool thing about a 'GUID' (or in my example a hashed sequence number
[sure
toss in some entropy if you want it]) is that if you happen to reference
that
value as a primary key on a table, the URL that passes the argument can not
be guessed at easily.  For example using a sequence:

    http://domain.com/application/load_record.html?customer_id=12345

Then, users of the web will assume that you have at most 12345
customers.  And
they can try to look up information on other customers by doing:

    http://domain.com/application/load_record.html?customer_id=12346
    http://domain.com/application/load_record.html?customer_id=12344

...basically walking the sequence.  Sure, you will protect against this with
access rights, BUT...seeing the sequence is a risk and not something you
want
to happen.  NOW, if you use a GUID:


http://domain.com/application/load_record.html?customer_id=f46d6296-5362-2526-42e3-1b8ce9dcccc1

Right, so now try to guess the next value in this sequence.  It's a little
more protective and obfuscated (an advantage in using GUIDs).

Dante