[GitHub] wohali opened a new issue #1280: Add PATCH/partial update support

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wohali opened a new issue #1280: Add PATCH/partial update support
URL: https://github.com/apache/couchdb/issues/1280
 
 
   A mechanism that allowed server-side field updating of a document would be lovely. Ideally this would use [RFC 5789 - HTTP PATCH](http://tools.ietf.org/html/rfc5789).
   
   ## Expected Behaviour
   The PATCH request provides a partial object that is merged with the original doc and stored in the database.
   
   ```
   $ curl -X PUT http://127.0.0.1:5984/foo/bar -d '{"user": { "firstname" : "Walter", "lastname": "Carlos" } }'
   {"ok":true,"id":"bar","rev":"1-0f958fa6ab68dffc4ac5b76efb229e39"}
   $ curl -X PATCH -H "Content-Type: application/json" http://127.0.0.1:5984/foo/bar -d '{"user": { "firstname": "Wendy" }, "profession": "Musician" }'
   {"ok":true,"id":"bar","rev":"2-900ae13b0644ed3a92be1a79f54d59d6"}
   $ curl http://127.0.0.1:5984/foo/bar
   {"_id":"bar","_rev":"2-900ae13b0644ed3a92be1a79f54d59d6","user":{"firstname":"Wendy","lastname":"Carlos"},"profession":"Musician"}
   ```
   
   It would be nice to allow `PATCH` to avoid providing the `rev` token, as shown above. This supports performing the entire `GET-MODIFY-PUT` cycle with a single HTTP request.
   
   ## Current Behaviour
   It is possible to implement this with a carefully crafted VDU, as written by Mark Hahn, contributed to the old wiki and licensed under ALv2.
   
   coffeescript version:
   ```coffeescript
     partialUpdate: (doc, req) ->
       if not doc then return [null, JSON.stringify status: 'nodoc']
       for k, v of JSON.parse req.body
         if k[0] is '/'
           nestedDoc = doc
           nestedKeys = k.split '/'
           for nestedKey in nestedKeys[1..-2]
             nestedDoc = (nestedDoc[nestedKey] ?= {})
           k = nestedKeys[-1..-1][0]
           if v is '__delete__' then delete nestedDoc[k]
           else nestedDoc[k] = v
           continue
         if v is '__delete__' then delete doc[k]
         else doc[k] = v
       [doc, JSON.stringify {doc, status: 'updated'}]
   ```
   javascript version:
   ```javascript
   partialUpdate: function(doc, req) {
     if (!doc) {
       return [
         null, JSON.stringify({
           status: 'nodoc'
         })
       ];
     }
     _ref = JSON.parse(req.body);
     for (k in _ref) {
       v = _ref[k];
       if (k[0] === '/') {
         nestedDoc = doc;
         nestedKeys = k.split('/');
         _ref1 = nestedKeys.slice(1, -1);
         for (_i = 0, _len = _ref1.length; _i < _len; _i++) {
           nestedKey = _ref1[_i];
           nestedDoc = ((_ref2 = nestedDoc[nestedKey]) != null ? _ref2 : nestedDoc[nestedKey] = {});
         }
         k = nestedKeys.slice(-1)[0];
         if (v === '__delete__') {
           delete nestedDoc[k];
         } else {
           nestedDoc[k] = v;
         }
         continue;
       }
       if (v === '__delete__') {
         delete doc[k];
       } else {
         doc[k] = v;
       }
     }
     return [
       doc, JSON.stringify({
         doc: doc,
         status: 'updated'
       })
     ];
   }
   ```
   
   The above VDU doesn't take a partial object as in the proposal, but a specially formatted object to merge:
   
   ```
   {
     field_one: "AAA",
     "/topLevelObject/nestedField_one": "__delete__",
     "/topLevelObject/nestedField_two": 99,
     "/topLevelObject/nestedField_three/dblNest": 73
   }
   ```
   
   ## Context
   Avoiding the entire `GET-MODIFY-PUT` cycle reduces latency.
   
   ## Your Environment
   <!--- Include as many relevant details about the environment you experienced the bug in -->
   * Version used:
   * Browser Name and version:
   * Operating System and version (desktop or mobile):
   * Link to your project:

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