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From "Paul Davis" <paul.joseph.da...@gmail.com>
Subject Re: Can I guarantee uniqueness in a field without using _id?
Date Mon, 12 Jan 2009 22:24:20 GMT
> Unless anybody can think of a way to guarantee uniqueness in CouchDB, I
> think I am going to abandon the notion of GUARANTEED uniqueness and instead
> implementcode to PREFER uniqueness. Then at the end of the day, we can write
> some code that will tell us if that 1 in a million chance (i.e. two
> simultaneous inserts/updates) left our database in a state where there are
> two docs with the same unique field.
>
> Since the odds are quite low that it will actually happen, I think we can
> deal with the times that it happens manually so long as we know about it.
>
> Sunny
>

You have just identified the problem and solution that CouchDB solves
with using a traditional RDBMS in a distributed environment. Check out
the discussion on the CAP hypothesis (Others call it a theorem, I'm
not convinced, but the basic idea is there).

Or more succinctly, guaranteed uniqueness requires global state,
global state does not scale.

HTH,
Paul Davis

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