[COUCHDB-465] Produce sequential, but unique, document id's

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.11
• Assignee: Unassigned
• Reporter: Robert Newson
• Created: 13/Aug/09 16:04
• Updated: 09/Sep/09 17:00
• Resolved: 09/Sep/09 17:00

Description

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 benefits.