mongoDB, MapReduce with calendar

gistfile1.rb

## coding: utf-8

# Demo mongoDB mapreduce with callendar

require 'date'
require 'mongo'
require 'securerandom'
require 'pp'

# Create calendar collection with random string name,
# return the generated collection name.
def prepare_callendar(db, from, to, init_val)
  out_coll_name = 'callendar' + SecureRandom.hex(8)
  (from.to_date..to.to_date).each do |day|
    db[out_coll_name].insert('_id' => day.to_time, 'value' => init_val)
  end
  out_coll_name
end

include Mongo

db = Connection.new.db('callendar-demo')
# include js libraries
db.eval(File.read('underscore-min.js'))
db.eval(File.read('moment.js'))

coll = db['todo']
# sample data
coll.save content: 'hoge', done: Time.local(2012, 6, 19), insert: Time.local(2012, 6, 17)
coll.save content: 'piyo', insert: Time.local(2012, 6, 19)
coll.save content: 'foo', done: Time.local(2012, 6, 21), insert: Time.local(2012, 6, 19)

map = <<EOS
function() {
  var ts = moment(this.done).sod().toDate();
  emit(ts, { done_count : 1 });
}
EOS

reduce = <<EOS
function(key, values) {
  var sum = _.reduce(values, function(memo, v) { return memo + v.done_count; }, 0);
  return { done_count : sum };
}
EOS

from = Time.local(2012, 6, 17)
to = Time.local(2012, 6, 23)

# First create calendar collection
out_coll_name = prepare_callendar(db, from, to, 'done_count' => 0)

# then do MapReduce so the output is merged into callendar collection.
begin
  coll.map_reduce(map, reduce, 
    query: {
      'done' => { '$exists' => true },
      'insert' => {
        '$gte' => from,
        '$lt' => to
      }
    },
    out: { 'merge' => out_coll_name }
  )
  db[out_coll_name].find.sort_by{ |doc| doc['_id'] }.each{ |doc| pp doc }
rescue Exception => e
  p e
ensure
  # drop the tmporary collection
  db[out_coll_name].drop()
end