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From Benoit Chesneau <>
Subject Re: Versioned attachment questions
Date Sat, 02 Jul 2011 06:34:38 GMT
On Saturday, July 2, 2011, Randall Leeds <> wrote:
> On Fri, Jul 1, 2011 at 15:10, Jens Alfke <> wrote:
>> A few questions about how attachments interact with document revisions. Since an
attachment is conceptually [if not actually] embedded in a revision, you can end up with multiple
document revisions that contain attachments with the same name but different contents. That
is, attachments are versioned. Right?
>> 1: I haven’t seen this explicitly stated in the docs, but I assume that you can
retrieve an attachment from an earlier revision of a document by doing:
>>        GET /db/document_id/attachment_name?rev=revision_id
> I think so.

>> 2: When I GET a document, I just get stubs in the _attachments dictionary. Presumably
if I PUT a new revision of the document, leaving the _attachments dictionary the same, the
attachments will stay the same in the new revision. And if I remove one of the entries from
_attachments, will the corresponding attachment be deleted?
> Again, I believe this is the case.

yes it is.
>> 3: Is there any way to tell whether the attachment in one revision is the same as
the attachment in another revision, i.e. whether the attachment changed between the two revisions?
Or do you have to compare lengths and, if they’re the same, GET both revisions in their
entirety and byte-compare them?
>> —Jens
> The stubs in the _attachments object each have a "revpos" property
> that should correspond to the first part of the _rev where they were
> last modified. Does that help?
> Anyway, from IRC:
> <davisp> Jens has questions on the ML that seem like things we should
> have in the test suite
> So I'm starring these and I'll look into these when I have more time.
> If you get to it before I do please file anything you think is an
> issue (or file as an improvement) on JIRA.
> Thanks!

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