CouchDB clears document on insert?

Question

I'm using nano with couchDB, and I am just trying to do a simple update on a document to add a new field. For example, let's say I have a document called foo. The only field in it right now is 'bar', with some value. I then attempt to do db.insert with the code I'll post at the end, but instead of now having both fields, bar is erased, and I instead just have my new field. How can I fix this?

The code I'm using:

    dB.get('foo', function(err, body) {
        if (!err){

            if(typeof body.qwax === 'undefined'){
                dB.insert({qwax : [data], "_rev" : body._rev}, 'foo', function(err, body, header) {
                    if (err) {
                        console.log(err.message);
                        return;
                    }
                });
            }
            else{
                body.qwax.push(data);
                dB.insert({qwax : body.qwax, "_rev" : body._rev}, 'foo', function(err, body, header) {
                  if (err) {
                    console.log(err.message);
                    return;
                  }

                });
            }
        }
        else{console.log(err);}
    });

Where data is defined elsewhere.

AndyD · Answer 1 · 2012-12-21T10:57:02.073

In nano there is an atomic function you can call to call a specific update functionon a design document: https://github.com/dscape/nano#dbatomicdesignname-updatename-docname-body-callback

Here's the usage example that is mentioned in the docs: https://github.com/dscape/nano/blob/master/tests/design/atomic.js

for example, you could create this updates attribute to your _foo design document:

updates: {
        setBar: function (doc, req) {
          var body = JSON.parse(req.body);
          doc.bar = body.bar;
          return [doc, 'OK'];
        }

You would then call this setBar update function using nano like this:

db.atomic('_foo', 'setBar', your_foo_document_id, { bar: barvalue }, function (err, headers) {
    if (err) {
      return callback(err);
    }
    ... rest of your code

Davorin Ruševljan · Answer 2 · 2012-12-20T11:07:10.110

0

For each update you need to provide whole document, not just fields to add to the document. So you need to fetch current version of the document, add filed to it and then do the db update.

dB.insert({qwax : [data], "_rev" : body._rev, "bar" : body.bar}, 'foo', function(err, body, header) {
                if (err) {
                    console.log(err.message);
                    return;
                }
            });

edited Dec 20 '12 at 11:07

answered Dec 20 '12 at 10:02

Davorin Ruševljan

4,353
21
27

Hmm, would you mind adding a bit of example code, or maybe just explaining your answer a bit further? – Ari Dec 20 '12 at 10:50

score 0 · Answer 3 · answered Dec 20 '12 at 14:36

0

You can use update handlers (wiki) in the design document for that. You simply write a JS function and instead of sending whole document again you call this function and it can make the updates "in place".

The function will get two parameters: the document to update and some data provided by from the client, and it will return in the HTTP header the new version of the updated document.

answered Dec 20 '12 at 14:36

Marcin Skórzewski

2,854
1
17
27

This seems to be what I'm looking for, however, I'm not sure how I would go about implementing this with nano. Is there a function to call for it, or any change in syntax? – Ari Dec 21 '12 at 08:16
I do not use nano. But I guess, whatever client API you use, writing design documents with function run on server is the same. Simply edit the design document with futon and query it with Your Favorite API. It may be difficult to pass additional parameters to the update function if your API does not support it, but update function can parse `body`. You can use it to make updates with the standard API for inserting new documents. Just insert doc `PATH_TO_UPDATE_FUN/OLD_DOC_ID` and make the update function that will merge the `body` (new, fake, doc) and the `DOC_ID`. Hope it will work :) – Marcin Skórzewski Dec 21 '12 at 15:01

CouchDB clears document on insert?

3 Answers3