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From "Joan Touzet (JIRA)" <>
Subject [jira] Commented: (COUCHDB-465) Produce sequential, but unique, document id's
Date Fri, 14 Aug 2009 00:02:14 GMT


Joan Touzet commented on COUCHDB-465:

This is a great patch, and solves the problem of having to do it in client-side logic. +1
from me too!

It looks like Brian's solution above is intended to allow _all_docs to return all documents
in chronological order, thus getting a time-sorted view "for free," i.e. without an extra
field per document, extra view to maintain and update, extra view storage on the disk, etc.
I admit I did the same for myself ;) but it isn't necessarily a consideration for everyone.
For example, in a replication situation, you'd need to be sure your clocks were well synchronized,
and that you didn't have collisions in the prefix portion.

Perhaps providing a mechanism to declare your own function to override one of the two defaults
(random, or rnewson's) would indeed be the best way forward, and the wiki could have a HOWTO
with a set of small recipes on alternative approaches?

> Produce sequential, but unique, document id's
> ---------------------------------------------
>                 Key: COUCHDB-465
>                 URL:
>             Project: CouchDB
>          Issue Type: Improvement
>            Reporter: Robert Newson
>         Attachments: sequence_id.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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