sunny0425 · December 5, 2012 08:43
diff --git a/mongo_aggregate.rb b/mongo_aggregate.rb
 # Here comments are embedded_in letters
 $ mongo
 > db.letters.aggregate(
  { $unwind : "$comments"},
  { $match: { "comments.created_at": { $gt: new Date('01/01/2012') }  } },
  { $group: {
     _id : "$_id",
     comment_count: { $sum : 1 }
  } },
  { $sort : { comment_count : -1 }},
  { $limit : 5}
 );
	# Here comments are embedded_in letters
	$ mongo
	> db.letters.aggregate(
	{ $unwind : "$comments"},
	{ $match: { "comments.created_at": { $gt: new Date('01/01/2012') } } },
	{ $group: {
	_id : "$_id",
	comment_count: { $sum : 1 }
	} },
	{ $sort : { comment_count : -1 }},
	{ $limit : 5}
	);