Weird document update conflict on delete

[Michael Hoisie]

Hi,

I'm writing a couchdb library for Go (
http://github.com/hoisie/gocouch ) , and I'm running into this bizarre
issue while testing the document delete method. This sequence of
requests causes a document update conflict:

1. check if a database exists : HEAD http://127.0.0.1:5984/test123
2. create a new database: PUT http://127.0.0.1:5984/test123
3. add a document to the database POST http://127.0.0.1:5984/test123/
--> docid 2b866715d560a2e62e11df4cfcf7258a
--> revid 1-c7176253456a2d0378c55e597ed96ad3
4. delete the same document form the database:
DELETE http://127.0.0.1:5984/test123/2b866715d560a2e62e11df4cfcf7258a?rev=1-c7176253456a2d0378c55e597ed96ad3
--> {"error":"conflict","reason":"Document update conflict."}

I believe this fairly simple sequence of events should work. Is there
anything here that's not allowed? I believe both the POST and DELETE
are run on the same http connection. Could that be causing problems?

I'm running CouchDBX 0.8 ( couchdb 0.10.0) on mac os x 10.6.

Thanks,
Mike

[Markus Jelsma]

Hello Michael,

For as far as i know this is indeed normal behavior. When you add a
document and specifying a revision ID, CouchDB will increment the revision
ID rendering any actions following using the `old` ID useless.

If you add a document using a revision ID, you must use the new revision
ID for all modifying actions for that document.

markus@relax:~$ curl -X PUT http://localhost:5984/bla
{"ok":true}

markus@relax:~$ curl -X PUT
http://localhost:5984/bla/2b866715d560a2e62e11df4cfcf7258a -d
'{"_rev":"1-c7176253456a2d0378c55e597ed96ad3"}'
{"ok":true,"id":"2b866715d560a2e62e11df4cfcf7258a","rev":"2-ce5f1bb80a4b215d152444b303ecd73e"}

Do you see the new revision ID? I cannot issue a delete using the revision
ID i specified during creation, let's see:

markus@relax:~$ curl -X DELETE
http://localhost:5984/bla/2b866715d560a2e62e11df4cfcf7258a?rev=1-c7176253456a2d0378c55e597ed96ad3

{"error":"conflict","reason":"Document update conflict."}

However, i can delete the document using the current revision ID, check it
out:

markus@relax:~$ curl -X DELETE
http://localhost:5984/bla/2b866715d560a2e62e11df4cfcf7258a?rev=2-ce5f1bb80a4b215d152444b303ecd73e
{"ok":true,"id":"2b866715d560a2e62e11df4cfcf7258a","rev":"3-ba96b157226112e17db64f687416aafb"}

Next time, remember the following rule of thumb. Any operation modifying
an existing document without using the _current_ revision ID will fire a
conflict error! Therefore you must always use the current revision ID.

Of course, this can also return a conflict but that will be due to another
person or process that beat you to it

Cheers,

Michael Hoisie zei:

[Michael Hoisie]

Markus, thanks for the clarification and the examples -- the problem
was a bug in the Go http library I use :)

- Mike

[Markus Jelsma]

Michael,

You may want to read up this topic [1] for the sake of total clarity, the
authors have done a much better job in explaining everything all this. And
do not forget that CouchDB can only handle conflict management at the
single document level - something many of us have not understood
correctly.

Good luck with your Go client and do not forget to inform the mailing list
when all things turn out well :)

[1] http://books.couchdb.org/relax/reference/conflict-management

Cheers,

Michael Hoisie zei: