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From "Robert Newson (JIRA)" <>
Subject [jira] Commented: (COUCHDB-465) Produce sequential, but unique, document id's
Date Thu, 20 Aug 2009 12:41:14 GMT


Robert Newson commented on COUCHDB-465:


I read your gist and the pre-compact size for sequential is smaller than for random (43,144,791
vs 52,517,614) and post-compaction was smaller for sequential too (2,023,522 vs 2,506,850).
Perhaps you read the numbers the wrong way around? Or did I? :)

I also note that most of this compaction is from not batching as you'll have a 4k footer block
for each write. With ?batch=ok and sequential (and no deletions) I find compaction to be only
a marginal reduction of space.

> 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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