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From Apache Wiki <>
Subject [Couchdb Wiki] Update of "DocumentRevisions" by JimLindley
Date Mon, 14 Apr 2008 14:20:47 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Couchdb Wiki" for change notification.

The following page has been changed by JimLindley:

The comment on the change is:
initial document revisions 

New page:
== Overview ==

CouchDB does not overwrite updated documents in place, instead it creates a new document at
the end of the database file, with the same `_id` but a new `_revision` identifier. Document
revisions are also used to handle conflicting updates. Outdated revisions are not exposed
to views. Conflicts may be resolved by your application, the default conflict resolution scheme
is to use the potential candidate that made the most changes to the subject document.

The storage system is disk-wasteful so ["Compaction"] is needed. The revisions are not, at
least at this point, meant to implement revision control systems, they rather exists for the
optimistic concurrency control that allows any number of parallel readers while serialised
writes are happening and to power replication.

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