Mongoose - find all documents whose array property contains a given subset?

Question

I have a (simplified) model based on the following schema:

schema = mongoose.Schema({
    foo: { type: String },
    bars: [{ type: String }]
});
model = mongoose.model ('model', schema);

and I want to create an API to return all documents that contain all of the 'bars' which are provided in a comma separated list. So I have:

exports.findByBars = function (req, res) {
  var barsToFind = req.body.bars.split(',');
  // find the matching document
};

Does Mongoose provide an API for this or is there a query param I can pass to Model#find to get this functionality? I only want a document to be returned if its bar property contains all of the values in the barsToFind array.

Answer 1

There are ways to structure your query to do this, the approaches are different depending on your mongodb server version. So following on from your code:

For MongoDB version 2.6 and above, use the $all operator:

model.find({
    "bars": { "$all": barsToFind }
},

And though the operator does exist for previous versions, it behaves differently so you actually need to generate an $and statement to explicitly match each entry:

var andBars = [];

barsToFind.forEach(function(bar) {
    andBars.push({ "bars": bar })
});

model.find({
    "$and": andBars
},

Both ensure that you only match documents that contain all of the entries in the array as you have specified, it's just that the syntax available to MongoDB 2.6 is a little nicer.