GitHub user carlosduclos opened an issue:
https://github.com/apache/couchdb-nano/issues/9
DB.insert: Can not insert extra headers like If-Match:rev to handle
'Document update conflict'
[Original issue](https://github.com/dscape/nano/issues/281)
__cloidjgreen__
This might be just pure ignorance but in attempting to set up CRUD from
Angular through Express/nano to CouchDB I of course ran into the need to handle
'Document update conflict'.
There seemed to be no path to resolve the problem through DB.insert. The
second parameter accepting only docName at line 372 of nano before assigning
the object passed in to qs. I had set up the insert call with
DB.insert(req.body,{docNname:'name',headers{'If-Match':'rev#'}},cb(){});
Following the pass off of the insertDoc function in nano to the relax
function I found that the code danced all around opts and qs and never included
qs.headers into the request header.
So on line 111 of nano I changed
req.headers = _.extend(req.headers, opts.headers, cfg.defaultHeaders);
to
req.headers = _.extend(req.headers, opts.headers, qs.headers,
cfg.defaultHeaders);
Now after failing on a DB.insert with a 'Document update conflict' I can
get the current doc rev, add the headers object with and appropriate "If-Match"
to the PARAMS, second argument to insert, and force the update.
Comments??
__jo__
The revision does not necessarily have to be in the If-Match header. Just
include the revision in the doc body, eg
```javascript
db.insert({ foo: bar, _rev: '1-asd' }, 'mydoc')
```
__cloidjgreen__
Yes I can do that too but reviewing the document and resolving differences
does not suit the specific use case I have.
Thanks for the update.
Other than this I have found nano to be very elegant. Makes for a very easy
marriage between CouchDB -- Express,
Regards
Cloid
__jo__
Sorry, I maybe did not understand your use case. Could you explain it
further please?
However, I really like the change you propose, because its a minimal change
which extends nanos flexibility.
__cloidjgreen__
Two use cases actually.
I am developing json data templates and as I edit those I am not
inserting a revision field or maintaining it. I want to be able to load
these on system boot and apply updates them through an admin utility so do
not want to have to concern myself with revisions in the case of these
templates.
The application is an collaboration offering system where parties can
negotiate or bid to collaborate and the offering party will have "GOD"
rights over the offer. ( offer and bidding all happening on the same
document. ) So when the offering party decides to accept a collaboration
the offering party will premtively change the state on the offer document
regardless of unseen inputs.
So those are the two things I think I want to do. Not sure it will work
out this way though. It might turn out to be necessary to deal with these
race conditions in a different way.
Still on the learning curve and experimenting continuously.
Regards
Cloid
__jo__
Although I recommend to use a different data model approach for 2 (see
Document Modeling to Avoid Conflicts) you can achieve what you want in current
nano by just setting doc._rev. The If-Match header does nothing special than
the doc._rev or rev query parameter.
That said you can also supply the revision as a query string:
```javascript
DB.insert(req.body, { docNname: 'name', rev: 'rev#' }, cb)
```
Does this help?
PS: While working with express and nano you might also find connect-nano
useful.
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