Mongoose limit and total count in mapReduce

Question

Mongoose limit and total count in mapReduce

I need to run a query which returns total count of documents together with documents and that can be limited and offset. It's similar to this and this question. The difference is that I run map/reduce and total count is already available in stats argument so hopefully I don't have to call the query twice.

list: function (options, cb) {
    ...
    this.mapReduce(o, function (err, model, stats) {
        console.log('# of documents: %d ', stats.counts.output);
        model.find()
            .limit(criteria.perPage)
            .skip(criteria.perPage * criteria.page)
            .exec(cb);
    });
});

I call the list function from controller like this:

Track.list(options, function (err, docs) {
    res.json(docs);
});

Is it somehow possible to pass stats.counts.output to the controller together with returned documents?

node.js
mongodb
mongoose

Answer 1

You could wrap the cb within a function in the argument to exec:

model.find()
    .limit(criteria.perPage)
    .skip(criteria.perPage * criteria.page)
    .exec(function (err, docs) {
      cb(err, docs, stats.counts.output)
    });

Track.list(options, function (err, docs, count) {
    res.json({docs: docs, count: count})
})