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From Alexander Shorin <kxe...@gmail.com>
Subject Re: What's the exact definition of 'oldDoc' in a validation function?
Date Sun, 23 Feb 2014 01:01:55 GMT
Not tested / looked in code, but I'm pretty sure that
Situation 1: null - no any stored doc on this revision branch
Situation 2: 1-xxxx since there is no 2-yyyy in database. 2-yyyy is
only known by source db, not target.

Could be there the case when in database older revision will be
available while younger isn't for the same revision branch?
--
,,,^..^,,,


On Sun, Feb 23, 2014 at 4:45 AM, Jens Alfke <jens@couchbase.com> wrote:
> What’s the exact definition of the ‘oldDoc’ parameter that’s passed to a validation
function? The current CouchDB docs just say it’s "the current document stored in the database”.
This is unambiguous during a normal PUT operation, but I’ve just realized I’m unsure what
the exact behavior is during replication or with new_edits=false.
>
> Situation 1: There are no revisions of document “foo” in the database. A replication
pulls in revision 3-zzzz of “foo”, along with a revision history giving the ancestry as
2-yyyy and 1-xxxx.
> —> Is the validation function called with oldDoc=null, or with oldDoc={“_rev”:”2-yyyy”}?
>
> Situation 2: The database contains revision 1-xxxx of “foo”. A replication pulls
in the same revision 3 as described above.
> —> Is the validation function called with oldDoc={“_rev”:”1-xxxx”}, or with
oldDoc={“_rev”:”2-yyyy”}?
>
> This has an impact on fancy validation functions that want to check for invariants between
a new revision and its parent. For example, in the document-signing spec I’m working on,
a document’s signature data needs to include the revision ID of the parent, to avoid certain
types of replay attacks. But if the validation function isn’t called with the exact parent
revision, there isn’t a way for it to determine the parent rev ID to verify the signature.
>
> —Jens

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