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From Robert Newson <robert.new...@gmail.com>
Subject Re: change notifications question
Date Sat, 09 Apr 2011 11:45:13 GMT
It's essential as it's the only way to reclaim disk space. Without it,
all your database files will grow with every addition, update and
deletion (and so will your views).

It would be better if your documents modelled the change itself,
rather than attempting to derive a diff from two revisions of a
document. CouchDB does not show you the previous revision as it should
be regarded as unavailable.

B.

On 9 April 2011 10:59, Thomas Vander Stichele <thomas@apestaart.org> wrote:
> On Sat, 2011-04-09 at 10:42 +0100, Robert Newson wrote:
>> CouchDB does not provide revisioning or history features to the end
>> user at all. This is a common mistake.
>>
>> The use of _rev and MVCC is purely a mechanism to enable sane
>> replication between servers where writes are permitted everywhere.
>> CouchDB's replication will only ensure that the current version* of
>> any document is replicated, earlier revisions are *not* replicated.
>
> I'm not interested in replicating earlier revisions.
>
> I'm interested in receiving the change notification (either because of
> replication or because of a local update) and showing what changed.
>
> I'm pretty sure that:
> - in the case of a local update, the previous revision is still there at
> the moment the change notification happens
> - in the case of a replication update, the previous local revision is
> still locally available too.
>
> Those are the changes I'm interested in showing, and hence I see no
> reason why couchdb couldn't inform both the new revid and the revid just
> before the change.
>
>> Earlier revisions are also removed on compaction, which is an
>> essential maintenance operation.
>
> Essential how ? It's not going to stop working if you don't compact,
> just slow down.  Depends on your usage model.  And in any case,
> compaction is triggered, so I would be completely ok with once in a
> while not being able to get an older revision and not correctly show
> changes because I triggered compaction.  99% of the time this wouldn't
> be the case.
>
> Thomas
>
> --
>
> --
> you own me
> there's nothing you can do
> you own me
> lucky you
> --
> Flumotion - the only way to stream!
> http://www.flumotion.net/
>
>
>

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