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https://issues.apache.org/jira/browse/COUCHDB-465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12745358#action_12745358
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Robert Newson commented on COUCHDB-465:
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I like most of Paul's changes though I thought we'd agreed on IRC to change the
default to sequential and I'd still like to see that happen.
I would also like to see a way to detect very quick delete/create scenarios,
though I don't know if database uuids are the only solution there. If a global
_changes feed would emit "deleted" and "created" events for databases in the
correct order, then couchdb-lucene could work correctly without database uuids.
Antony's suggestion of a fourth algorithm, where the prefix is completely
static, is simple enough to add. This patch allows the deployer to decide how
much he cares about predictability and server origin, so I don't see a reason
not to add it. It is distinct from the sequential algorithm, though. The prefix
there is only used for around 8000 ids and is then never reused, there is also
no correlation between prefix and origin server.
> Produce sequential, but unique, document id's
> ---------------------------------------------
>
> Key: COUCHDB-465
> URL: https://issues.apache.org/jira/browse/COUCHDB-465
> 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
> benefits.
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