How to flatten sub-documents in mongo db - json

Question

My collection has document like this
{
"_id" : ObjectId("587c8d0364b6e32706f7edef"),
"first_name" : "John",
"last_name" : "Doe",
"password" : "aasdjsabb12213b21bbcghc1h2",
"shift" : "A",
"dept" : "Management"
"Requests" : [
{
"weekId" : 1,
"MO" : 1,
"TU" : 2,
"W" : 3,
"TH" : 9,
"FR" : 10,
"SA" : 6,
"SU" : 1
}
]
}
I want to export the result of my query to csv and need fields flattened out like this
{
"_id" : ObjectId("587c8d0364b6e32706f7edef"),
"first_name" : "John",
"last_name" : "Doe",
"password" : "aasdjsabb12213b21bbcghc1h2",
"shift" : "A",
"dept" : "Management"
"weekId" : 1,
"MO" : 1,
"TU" : 2,
"W" : 3,
"TH" : 9,
"FR" : 10,
"SA" : 6,
"SU" : 1
}
I am trying to use aggregate function but to no avail. Can anyone suggest me how to do this?
This is my working code but I don't think this is the right way
db.req.aggregate([{$unwind:'$Requests'},{$project: {first_name:1,last_name:1,dept:1,"WeekId":"$Requests.weekdId","Mon":"$Requests.MO","Tue":"$Requests.TU","Wed":"$Requests.W","Thu":"$Requests.TH","Fri":"$Requests.FR","Sat":"$Requests.SA","Sun":"$Requests.SU"}},{$out:"results"}]);

Answer 1

You can do this with an aggregate query, but its not very pretty:
db.test.aggregate([
{$unwind:"$Requests"},
{$project:
{_id:1,
first_name:1,
last_name:1,
password:1,
shift:1,
dept:1,
weekId:"$Requests.weekId",
MO:"$Requests.MO",
TU:"$Requests.TU",
W:"$Requests.W",
TH:"$Requests.TH",
FR:"$Requests.FR",
SA:"$Requests.SA",
SU:"$Requests.SU"}}])
.pretty()
So basically unwind the Requests array, then project out the document you want to produce. Hope this makes sense.