| From: | Rob Sargent <robjsargent(at)gmail(dot)com> |
|---|---|
| To: | Craig Ringer <craig(at)postnewspapers(dot)com(dot)au> |
| Cc: | Greg Smith <greg(at)2ndQuadrant(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: pervasiveness of surrogate (also called synthetic) keys |
| Date: | 2011-05-03 04:57:29 |
| Message-ID: | 4DBF8B39.5030908@gmail.com |
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| Thread: | |
| Lists: | pgsql-general |
Craig Ringer wrote:
> On 03/05/11 11:07, Greg Smith wrote:
>
>
>> That doesn't mean you can't use
>> them as a sort of foreign key indexing the data; it just means you can't
>> make them the sole unique identifier for a particular entity, where that
>> entity is a person, company, or part.
>>
>
> Classic case: a database here has several tables indexed by MAC address.
> It's used for asset reporting and software inventory.
>
> Problem: VMs generate random MAC addresses by default. They're not
> guaranteed to be globally unique. Collisions have happened and will
> probably happen again. In this case, it wasn't a big deal, but it just
> goes to show that even the "obviously" globally unique isn't necessarily so.
>
> --
> Craig Ringer
>
Hm.. Virtual machines as assets. Mortgage backed securities, anyone.
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