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Subject: Handling unique URL friendly identifiers
From: Bernd Lutz <iberndlu@googlemail.com>
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Date: Wed, 30 Dec 2009 20:01:08 +0100
To: user@couchdb.apache.org
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Hello everyone,

I'm currently exploring the possibility to port an app from MySQL to =
CouchDB. The app uses friendly URLs, e.g. =
http://myapp.com/content/friendly-identifier. Every content has an =
unique identifier which derives from the content title.

If there would be only a few users creating content a simple check for =
the identifier's uniqueness would be enough. But what if there are =
multiple database nodes and let's say thousand users creating =
identifiers.
So we cannot get a consistent view result on a single node nor being =
sure that another user doesn't add a same identifier on another node in =
parallel.

I hope you got the problem. How would you handle it?

My approach:
Setting up a special node and database handling idenifiers with a view =
having the identifier as key.
1. Adding a new document with the identifier.
2. Check the uniqueness by queriing the view.
3. If ok, all right. Otherwise: Recursively add a postfix "-n" until the =
result is unique.

Of course the identifier won't be used as document _id.
I think this is a common problem not only for url friendly identifiers. =
A common usage could be also the unique user name.

Best regards and a happy new year,
Bernd=