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From Jan Lehnardt <...@apache.org>
Subject Re: Time-ordered document ids including the database identity
Date Thu, 26 Jan 2012 19:30:43 GMT
Hi Nick,

this sounds useful. Would you mind posting the patch to a new JIRA issue?

Cheers
Jan
-- 

On Dec 29, 2011, at 14:34 , Nick North wrote:

> This suggestion is for an enhancement to the document id generation
> algorithms in CouchDb. I am new to CouchDb, and this question addresses an
> old issue (https://issues.apache.org/jira/browse/COUCHDB-465) so please
> forgive me if I am retreading old ground.
> 
> My application has a number of mutually replicating CouchDb instances and I
> would like document ids to be monotonically-increasing per-instance, and
> globally unique, and for the instance where the document was created to be
> determinable from the id. (To be more accurate - I don't need to know
> anything about the instance itself; just whether any two documents
> originated from the same instance.) The utc_random algorithm is not far
> from meeting these requirements, as ids are monotonic and almost certainly
> globally unique. However, the instance cannot be determined from the id,
> and there is a tiny chance of an id clash between two instances. Both of
> these issues could be solved if the random part of the id could be replaced
> with a suffix that is fixed in the ini file for each instance.
> 
> To addresses this I have a modified version of couch_uuids.erl introducing
> a new utc_machine_id algorithm which reads a machine_id string from the ini
> file and then generates ids using an internal utc_suffix method that just
> appends the string to the usual utc 14-byte string. utc_random then also
> uses the utc_suffix method, but its suffix is the usual random byte string.
> 
> However, it is obviously a nuisance to have to maintain a non-standard
> distribution, so I wondered if there is enough call for this sort of thing
> to make it a part of the standard distribution? If there is, I'd be very
> happy to make my code available for discussion/modification/inclusion. If
> there are good reasons why this is a bad idea, then I'd also be very
> interested to hear them so that I can rethink my ideas. (It happens that
> the privacy and guessability concerns raised in the original discussion do
> not apply in my case.) If this question has been beaten to death, then I'm
> sorry for bothering the list, and would be grateful if someone could point
> me to the discussions so that I can understand the issues. Many thanks,
> 
> Nick North


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