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From Adam Kocoloski <kocol...@apache.org>
Subject Re: Number of surviving revisions after compaction
Date Mon, 20 Jan 2014 16:36:00 GMT
On Jan 20, 2014, at 11:29 AM, Vladimir Ralev <vladimir.ralev@gmail.com> wrote:

> Hello all
> 
> I was reading about  _revs_limit
> <http://wiki.apache.org/couchdb/HTTP_database_API#Accessing_Database-specific_options>
> which
> defaults to 1000 or so here
> http://wiki.apache.org/couchdb/HTTP_database_API#Accessing_Database-specific_options
> 
> It seems to imply that those 1000 revisions will be preserved even after
> compaction.Is this correct and does it mean that the database will be as
> much as 1000x bigger than it needs to be after compaction.
> 
> I have a database that I want to perform maintenance on so i remove it from
> traffic and want to reduce the number of revisions to 1 again safely. Is
> there some shortcut to do that?

Hi, that setting controls the number of revisions about which the server keeps a record, not
the number where the actual body of the rev is preserved.  Compaction only ever preserves
the last revision of each edit branch; this is not configurable.  The _revs_limit setting
impacts replication, e.g. if you make 1001 edits on a source server in between replications
to a target the replicator will not be able to piece together edit 1 and edit 1002 and you'll
end up with a spurious conflict on the target.

Adam
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