[wp-hackers] Why URL in GUID?
codehooligans at codehooligans.com
Tue Oct 3 01:19:07 GMT 2006
Thanks for clearing that up. I had no idea.
On Oct 2, 2006, at 7:53 PM, Owen Winkler wrote:
> Paul Menard wrote:
>> The only I have is if this value must be unique, why is it not a
>> unique key in the database. More specific, why is it not 'the'
>> unique key?
> Because it's not the "ID" field, it's the "Globally Unique ID" field.
> That means the value stored in that field must be unique not just
> for one site, but for any site anywhere. The GUID is used, for one
> example, to differentiate posts on different sites for feed
> Presumably, if you switched sites and also changed the URL in your
> aggregator to the new setting, it would know not to re-load posts
> with the old GUIDs because they haven't changed. Unfortunately,
> there is plenty of aggregator software that doesn't obey the spec,
> and when they ignore this, it causes some issues. But you can also
> see why the GUID should not change when you change the slug.
> You can't use the ID field of the posts table as the GUID because
> that value is *very* common among all blogs. Creating hashes from
> existing data is never going to produce a more globally unique ID
> for a post than the actual URL for the post.
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