index occurrence ids

gistfile1.js

// nb. we have a typo with occurrences -- sometimes they are called "occurences".

var filter = {};

var projection = {
  _id                    : true,
  facebook_occurence_ids : true
};

db.movies.find(filter, projection)
  .forEach(function (movie) {
    var x = ( movie.facebook_occurence_ids || [] ).length;
    db.movies.update( { _id: movie._id }, { '$set': { occurrence_count: x } } );
  });