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From "Paul Joseph Davis (JIRA)" <>
Subject [jira] Updated: (COUCHDB-465) Produce sequential, but unique, document id's
Date Thu, 20 Aug 2009 06:35:14 GMT


Paul Joseph Davis updated COUCHDB-465:

    Attachment: couch_uuids.patch

Refactored a bit.
couch_uuid_generator -> couch_uuids
sequential -> hybrid (this was mostly playing, thoughts?)
random is back to default and should stay that way
call to random:uniform() -> crypto:rand_uniform() (someone forgot to call random:seed(),
tsk tsk :)
[uuid_generator] -> [uuids] in config
added short description of choices next to option
probably an unneccessary optimization to allow for couch_uuids:new(N) to return N ids.
added simple checks to the uuids.js Futon tests
Pulled in a contribution by Bob Dionne for etap tests.
All calls to couch_util:new_uuid() are replaced with couch_uuuids:random()

We should make the prefix length a configuration parameter I think.

We might also think about adding Brian's algorithm for more diversity as well.

> Produce sequential, but unique, document id's
> ---------------------------------------------
>                 Key: COUCHDB-465
>                 URL:
>             Project: CouchDB
>          Issue Type: Improvement
>            Reporter: Robert Newson
>         Attachments: couch_uuids.patch, uuid_generator.patch
> Currently, if the client does not specify an id (POST'ing a single document or using
_bulk_docs) a random 16 byte value is created. This kind of key is particularly brutal on
b+tree updates and the append-only nature of couchdb files.
> Attached is a patch to change this to a two-part identifier. The first part is a random
12 byte value and the remainder is a counter. The random prefix is rerandomized when the counter
reaches its maximum. The rollover in the patch is at 16 million but can obviously be changed.
The upshot is that the b+tree is updated in a better fashion, which should lead to performance

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