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Date: Thu, 20 Oct 2011 13:57:17 +0200
From: Patrick Petermair <patrick.petermair@openforce.com>
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To: user@couchdb.apache.org
Subject: unique constraint in couchdb
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hey!

ist there a way to ensure some kind of unique constraint in couchdb 
other than the document id?

for example:
we have multiple documents that each represent a timestamp of a user.

{ user: "foobar@foo.at", timestamp: "2011-10-20T10:10" }
{ user: "foobar@foo.at", timestamp: "2011-10-20T11:50" }
{ user: "otheruser@foo.at", timestamp: "2011-08-20T08:11" }
...
...

we now want to ensure, that a user can't have 2 documents with the same 
timestamp .. basically creating a key for user + timestamp.

the solution so far is to create a view with a key of [user, timestamp] 
and check after every document creation/update if there are more than 1 
documents for a given user + timestamp tuple.
this obviously has the performance penalty of having to do a seperate db 
call. it also leaves the db in an inconsistent state until it is resolved.

the other solution is to use the user + timestamp as document id. but 
this would require to update the document id whenever the timestamp is 
edited.

are there any other solutions? is there something on the roadmap for 
couchdb that would solve our unique key problem? or is couchdb simply 
the wrong tool for the job?

thanks!
patrick