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From Robert Newson <rnew...@apache.org>
Subject Re: Changes API - purged?
Date Fri, 23 Aug 2013 08:22:12 GMT
Compaction does not affect the changes feed.

On 23 August 2013 09:01, Jens Rantil <jens.rantil@gmail.com> wrote:
> Robert,
>
> Thanks you for your e-mail. This was great information!
>
> Just to be clear, does compaction influence the changes feed in any way?
>
> Thanks,
> Jens
>
> Den torsdagen den 22:e augusti 2013 skrev Robert Newson:
>
>> If you use _purge then, yes, the information is purged, which is one
>> of the many reasons you should not use _purge. :)
>>
>> The replicator uses changes for the same purpose as you intent, where
>> the 'external state' is also a couchdb database in another server. You
>> can rely on it to contain everything you need to synchronize an
>> external stateful system with your database.
>>
>> For the avoidance of doubt, the changes feed does *not* preserve every
>> change made to your database. It has one entry for every doc id that
>> has ever been present in your database, in the order of their most
>> recent update. Starting from an empty database, the first document
>> added will have update sequence 1. If you update or delete that
>> document, then the changes feed will have no entry for update sequence
>> 1 but will have an entry for update sequence 2. If you apply every
>> update in the order you receive it from _changes to your target
>> system, you will end up in the correct state.
>>
>> B.
>>
>>
>> On 22 August 2013 10:26, Jens Rantil <jens.rantil@gmail.com <javascript:;>>
>> wrote:
>> > Hi,
>> >
>> > I have a use case where I'd like to build up an external state by
>> following
>> > the changes of a database. Obviously, the /db/_changes will be a great
>> > source to start for this. My question is, can I always be sure that
>> simply
>> > following /db/_changes from seqnum=0 will bring me to a consistent state
>> of
>> > the current database? Are /db/_changes purged (on /db/_purge?) in any way
>> > throughout the lifetime of a database?
>> >
>> > I've tried finding this information in documentation, but have failed so
>> > far.
>> >
>> > Thanks,
>> > Jens
>>

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