Time-ordered document ids including the database identity
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Key: COUCHDB-1373
URL: https://issues.apache.org/jira/browse/COUCHDB-1373
Project: CouchDB
Issue Type: Improvement
Components: Database Core
Reporter: Nick North
Priority: Minor
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 group, and
would be grateful if someone could point me to the discussions so that I can
understand the issues.
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