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From Robert Newson <rnew...@apache.org>
Subject Re: Database size seems off even after compaction runs.
Date Fri, 23 Dec 2011 09:52:26 GMT
An update to the wiki would be be very helpful.

It's worth saying again that compaction does *not* remove "deleted
documents’ contents". We keep the latest revision of every document
ever seen, even if that revision has _deleted:true in it. This is so
that replication can ensure eventual consistency between replicas. Not
only will all replicas agree on which documents are present and which
are not, but also the contents of both.

B.

On 23 December 2011 08:11, Marcello Nuccio <marcello.nuccio@gmail.com> wrote:
> 2011/12/23 Paul Davis <paul.joseph.davis@gmail.com>:
>> On Thu, Dec 22, 2011 at 7:00 PM, Jens Alfke <jens@couchbase.com> wrote:
>>>
>>> On Dec 22, 2011, at 1:44 PM, Chris Stockton wrote:
>>>
>>> Okay, so this catches me a bit off guard, always thought compaction
>>> cleaned those up.
>>>
>>> Compaction removes old revisions’ and deleted documents’ contents, but their
revision histories are still there. Those should be pretty small, though, since they’re
just trees of revision IDs.
>>>
>>> (Unless you did delete the docs by just setting a “_deleted” attribute? I
don’t know what the behavior of that would be; sounds like it doesn’t actually delete
the document from the database, in which case maybe the last revision data does get left behind.)
>>>
>>> —Jens
>>
>> Deleted documents specifically allow for a body to be set in the
>> deleted revision. The intention for this is to have a "who deleted
>> this" type of meta data for the doc. Some client libraries delete docs
>> by grabbing the current object blob, adding a '"_deleted": true'
>> member, and then sending it back which inadvertently (in most cases)
>> keeps the last doc body around after compaction.
>
> Can I write these informations in the wiki?
> I think it would be very useful in
> http://wiki.apache.org/couchdb/Compaction
> and in http://wiki.apache.org/couchdb/FUQ
>
> Marcello

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