Fill in missing daily records in a time-series query against a Mongo datastore using Mongoid.

time_series.rb

activities = Activity.where(:date.gte => dates.first, :date.lte => dates.last)

((Date.today - 60.days)..Date.today).map do |date|
  activities.where(:date.gte => date.beginning_of_day, :date.lte => date.end_of_day).first || Activity.new(:date => date, :stat => 0)
end