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From Jens Alfke <j...@couchbase.com>
Subject Re: Attachments and replication
Date Thu, 19 Jan 2012 03:05:42 GMT
What version of CouchDB? Filipe's new replicator should not be copying attachments unnecessarily.

--Jens     [via iPhone]

On Jan 18, 2012, at 5:53 PM, "Steven Ringo" <google@stevenringo.com> wrote:

> Hi all,
> 
> Assuming I have a document with an attachment and some fields, and that 
> this document has been replicated between source and target servers.
> 
> {
>    "_id": "551ffd9dc43cb73c257628d8a31e9e1f",
>    "_rev": "4-387d5d23b62e398421bddb10e16e740f",
>    "foo": "bar",
>    "baz": "quux",
>    "published": false,
>    "_attachments": {
>        "photo.jpg": {
>            "content_type": "image/jpeg",
>            "revpos": 2,
>            "digest": "md5-iOKjYGKWzEmEtMaqmYCtlA==",
>            "length": 3622469,
>            "stub": true
>        }
>    }
> }
> 
> Let's say I change one of the fields on the source server; say "foo": 
> "bar" to "foo": "bar2". I then do a pull replication.
> 
> Sniffing the packets, it seems to me the entire document is replicated, 
> including attachments. I was under the impression couchdb would be able 
> to replicate the document independently of the attachments.
> 
> In other words couchdb would transfer just the "text/json" portion of 
> the document and not the attachment, i.e. less than ~1 kbyte vs. a few 
> megebytes in this case.
> 
> My experience seems to contradict my assumption. It looks like the 
> digest and revpos fields are used for this, as mentioned here: 
> http://stackoverflow.com/questions/1825117/what-is-the-revpos-value-used-for-in-couchdb-attachments
> 
> Is there something I am missing or perhaps a configuration option I am 
> not setting properly?
> 
> Thanks.
> 
> 
> 
> 

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