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From Jim Klo <jim....@sri.com>
Subject Deleted and Replacement documents and VDU behavior
Date Fri, 17 May 2013 17:03:34 GMT
So Bob suggested that I raise this topic over here… Attaching the relevant thread from user@
here.

I suppose this is a feature request to be able to optionally enable the passing of the document
"stub" as the oldDoc, if exists to the VDU, if the design doc contains a flag to enable this
behavior.

I have a couple use cases:
	1. DCMA takedown; I want to add additional data to the deleted marker, that would permit
the VDU to inspect the deleted "stub" doc for the additional data and determine whether to
permit the reinstatement of the doc. 
	2. Want to prevent reuse of an _id.  I want docs to be immutable except for a one time delete.

In response to Bob's last response on user@ is how is this behavior any different than an
document update?  My workaround is that I don't actually delete documents, but just update
them into a "tombstone" document that removes the contents and then add the extra details
I need for the VDU to work.  The major difference is that I must encode logic into my views
to avoid the tombstone document which adds some unneeded complexity to the potentially every
view.  My case is not so bad in that all my documents are 'typed' so my tombstone documents
change the type such that they are excluded from views - however I had to carefully check
to ensure that was the case.

Thoughts, explanation why this is bad, etc?

Jim Klo
Senior Software Engineer
Center for Software Engineering
SRI International
t.	@nsomnac

On May 17, 2013, at 9:35 AM, Robert Newson <rnewson@apache.org>
 wrote:

> Hm, I dislike that, but you could raise it as a topic in the dev@
> mailing list. I think couchdb's core behavior should be predictable,
> it shouldn't change based on where you are. Consider that this would
> break eventual consistency (a validate_doc_update would have a
> different result based on that flags value).
> 
> B.
> 
> On 17 May 2013 17:29, Jim Klo <jim.klo@sri.com> wrote:
>> If there were a way to enable this sort of feature via a flag, like
>> local_seq that would be a good compromise IMO. :)  I don't know what the
>> ramifications of this would be on performance, but would be a 'nice to
>> have'.
>> 
>> Jim Klo
>> Senior Software Engineer
>> Center for Software Engineering
>> SRI International
>> t. @nsomnac
>> 
>> On May 17, 2013, at 8:39 AM, Robert Newson <rnewson@apache.org>
>> wrote:
>> 
>> Aha, ok, that makes more sense. oldDoc will be null in that case to
>> match the behavior when there was never a document there, but it's
>> definitely a debatable nuance. I'm in favor of the existing behavior
>> but I do see your point.
>> 
>> B.
>> 
>> On 17 May 2013 16:31, Jim Klo <jim.klo@sri.com> wrote:
>> 
>> No, I think I incorrectly described the condition where this happens.
>> 
>> If I first delete a doc with extra info like you illustrated, and then
>> re-insert the doc as new, the VDU does not get the existing delete "stub" in
>> my experience. If this has changed in 1.3, I'd welcome it.
>> 
>> It would be useful if the VDU got the existing "deleted" document in certain
>> use cases, like a document got removed for DCMA violation - I don't want it
>> to reappear by mistake. I'd like to have the right logic in my VDU to check
>> the notes in the existing deleted stub before permitting the insert. There's
>> ways around this which I use instead, but think that if there's a stub that
>> could be handed to VDU, it should.
>> 
>> 
>> - JK
>> 
>> Sent from my iPhone
>> 
>> On May 17, 2013, at 7:41 AM, "Robert Newson" <rnewson@apache.org> wrote:
>> 
>> VDU does receive the 'stub', which is always a document. The term
>> 'stub' can mislead people into thinking a deleted document is not an
>> actual document (it is).
>> 
>> Here I insist that deleted documents have a reason;
>> 
>> ➜  ~  curl localhost:5984/db1/_design/foo -XPUT -d
>> '{"validate_doc_update":"function(newDoc) { if(newDoc._deleted &&
>> !newDoc.reason) { throw({forbidden:\"must have a reason\"});  }  }"}'
>> {"ok":true,"id":"_design/foo","rev":"1-ab8a8ecd8cf3de35ed7541facfb75029"}
>> 
>> An empty doc;
>> 
>> ➜  ~  curl localhost:5984/db1/bar -XPUT -d {}
>> {"ok":true,"id":"bar","rev":"1-967a00dff5e02add41819138abb3284d"}
>> 
>> I try delete with DELETE method, which just does _id, _rev, _deleted.
>> 
>> ➜  ~  curl 'localhost:5984/db1/bar?rev=1-967a00dff5e02add41819138abb3284d'
>> -XDELETE
>> {"error":"forbidden","reason":"must have a reason"}
>> 
>> Now I delete with a PUT and a reason;
>> 
>> ➜ curl 'localhost:5984/db1/bar?rev=1-967a00dff5e02add41819138abb3284d'
>> -XPUT -d '{"reason":"because I said so","_deleted":true}'
>> {"ok":true,"id":"bar","rev":"2-6e10b3cc9ea15f6a9d81aa72aaa6e098"}
>> 
>> And it's really deleted;
>> 
>> ➜  ~  curl localhost:5984/db1/bar
>> {"error":"not_found","reason":"deleted"}
>> 
>> And my reason is recorded;
>> 
>> ➜  ~ curl 'localhost:5984/db1/bar?rev=2-6e10b3cc9ea15f6a9d81aa72aaa6e098'
>> {"_id":"bar","_rev":"2-6e10b3cc9ea15f6a9d81aa72aaa6e098","reason":"because
>> I said so","_deleted":true}
>> 
>> B.
>> 
>> On 17 May 2013 14:52, Jim Klo <jim.klo@sri.com> wrote:
>> 
>> It's a great tip, my only complaint about it is that the deleted stub
>> doesn't get handed to the VDU function, unless that's changed in 1.3
>> 
>> - Jim
>> 
>> 
>> On May 17, 2013, at 12:04 AM, "Dave Cottlehuber" <dch@jsonified.com> wrote:
>> 
>> On 17 May 2013 01:32, Randall Leeds <randall.leeds@gmail.com> wrote:
>> 
>> Actually, it's even easier than this. It is acceptable to put a body in the
>> DELETE. You can store whatever fields you want accessible in your deletion
>> stubs.
>> 
>> 
>> **WIN** best tip of the month!
>> 
>> 


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