Exam Mongo

Q1.json

var recipient = "[email protected]";
db.messages.aggregate([
	{
		"$match": {
			"headers.From": "[email protected]"
		}
	},
	{
		"$unwind": "$headers.To"
	},
	{
		"$match": {
			"$or": [
				{"headers.To": recipient},
				{"headers.Bcc": {"$regex":".*" + recipient + ".*"}},
				{"headers.Cc": {"$regex":".*" + recipient + ".*"}}
			]
		}
	},
	{
		"$group": {
			_id: null,
			count: { $sum: 1 }
		}
	}
])

Q2.json

db.messages.aggregate([
	{"$project": {"to":"$headers.To", "from":"$headers.From"}},
	{"$unwind": "$to"},
	{"$group": {"_id":"$_id", "from": {"$first": "$from"},"to": {"$addToSet": "$to"}}},
	{"$unwind": "$to"},
	{"$group": {"_id": {"from":"$from", "to": "$to"}, "count": {"$sum": 1 }}},
	{"$sort": {"count": -1}}
]);