Question

I found the following script:

Device.find(function(err, devices) {
  devices.forEach(function(device) {
    device.cid = '';
    device.save();
  });
});

MongoDB has the "multi" flag for an update over multiple documents but I wasn’t able to get this working with mongoose. Is this not yet supported or am I doing something wrong?

Device.update({}, {cid: ''}, false, true, function (err) {
  //...
});

Answer 1

Currently I believe that update() in Mongoose has some problems, see:
https://groups.google.com/forum/#%21topic/mongoose-orm/G8i9S7E8Erg
and https://groups.google.com/d/topic/mongoose-orm/K5pSHT4hJ_A/discussion.

However, check the docs for update: http://mongoosejs.com/docs/api.html (its under Model). The definition is:

Earlier Solution(Depreciated after mongoose 5+ version)

Model.update = function (query, doc, options, callback) { ... }

You need to pass the options inside an object, so your code would be:

Model.update = function ({}, {cid: ''}, {multi: true}, function(err) { ... });

New Solution

Model.updateMany = function (query, doc, callback) { ... }

Model.updateMany = function ({}, {cid: ''}, function(err) { ... });

I believe that Mongoose wraps your cid in a $set, so this is not the same as running that same update in the mongo shell. If you ran that in the shell then all documents would be replaced by one with a single cid: ''.