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From Randall Leeds <>
Subject Re: Versioned attachment questions
Date Sat, 02 Jul 2011 00:38:43 GMT
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.

> 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.

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