How To Sort This Data in MongoDB? - node.js

Question

/* 0 */
{
"_id" : ObjectId("5380c9e097632cee5b000007"),
"month" : "5",
"userid" : "53806aac12c75f4b51000001",
"__v" : 7,
"posts" : [{
"postid" : ObjectId("538185cae0c6b8666e000008"),
"ts" : ISODate("2014-05-25T05:55:22.976Z"),
"userid" : "53806aac12c75f4b51000001",
"name" : "BBB",
"text" : "b1",
}]
}
/* 1 */
{
"_id" : ObjectId("5380c80e97632cee5b000001"),
"month" : "5",
"userid" : "5380629ea3b31f864f000001",
"__v" : 24,
"posts" : [{
"postid" : ObjectId("538185b2e0c6b8666e000004"),
"ts" : ISODate("2014-05-25T05:54:58.703Z"),
"userid" : "5380629ea3b31f864f000001",
"name" : "AAA",
"text" : "a1",
}, {
"postid" : ObjectId("538185b7e0c6b8666e000006"),
"ts" : ISODate("2014-05-25T05:55:03.474Z"),
"userid" : "5380629ea3b31f864f000001",
"name" : "AAA",
"text" : "a2",
}, {
"postid" : ObjectId("538185d6e0c6b8666e00000a"),
"ts" : ISODate("2014-05-25T05:55:34.231Z"),
"userid" : "5380629ea3b31f864f000001",
"name" : "AAA",
"text" : "a3",
}]
}
This is my DATA.
I want to Sort This Data for 'Ts' ( Data ).
I want That Sorted List by 'posts.Ts' Like this..
name : AAA, text = a3
name : BBB, text = b1
name : AAA, text = a2
name : AAA, text = a1
but i Don't know How to query this. Please Talk To ME
This is my code in Node and mongoose.
db.collection('walls', function(err, collection) {
collection.find(function(err, data) {
collection.aggregate(
{$match: {userid:userid}},
{$project: {posts: 1,_id:0}},
{$sort:{'posts.ts':1}},
{$unwind: "$posts"}
)}
...

Answer 1

You are onto the right principles but you have pipeline stages the wrong way around. You need to $unwind the arrays before you sort:
db.collection.aggregate([
{ "$match": { "userId": userId" } },
{ "$project": { "_id": 0, "posts": 1 } },
{ "$unwind": "$posts" },
{ "$sort": { "posts.ts": 1, "posts.name": 1 } }
])