limited

Compose $aggregate MongoDB queries for Mongoose as if $push had a $limit operator.

Fetching the "top N commits on each repository with one of these ids" is a hard task due to MongoDB's limitations on $aggregate, specifically the inability to $limit on a $push operator. limited makes this easier for you.

Install

npm install limited --save

limited(options, done)

Configuration options are detailed below.

Property	Description	Example
model	The mongoose model or raw mongodb collection you want to operate on	Commit
field	The field you want to group by	'repo'
query	Optional filter so that the aggregate doesn't run on the entire collection	{ repo: { $in: repoIds } }
sort	Optional sort expression as an object	{ created: -1 }
limit	Number of documents do you want to retrieve from each match	5

A single (albeit complex) query will be issued against the database and you'll get back a list of model documents that match your query requirements, grouped by at most limit documents per field, and sorted by sort.

var _ = require('lodash');
var limited = require('limited');
var models = require('./models');

function getLastCommitInRepositories (ids, done) {
  var options = {
    model: models.Commit,
    field: 'repo',
    query: { repo : { $in: ids } },
    limit: 5,
    sort: { created: -1 }
  };
  limited(options, find);

  function find (err, result) {
    if (err) {
      done(err); return;
    }

    models.Commit
      .find({ _id: { $in: _.flatten(result, 'documents') } })
      .lean()
      .exec(done);
  }
}

The second query isn't executed on your behalf. It's up to you to decide how you want to deal with the document ids you get back from limited.

License

MIT