MongoDB lookup match two values - mongodb

Question

I have two collections, tennis matches with two players and players.
matches looks like this:
{
"_id" : ObjectId("5ce51febc6dd820a820f20a5"),
"players" : [
ObjectId("5ce51c1af3cd6009a171a5b3"),
ObjectId("5ce51c1af3cd6009a171a350")
],
"result" : "4:6 6:3 7:6(7) 7:6(8)"
},
{
"_id" : ObjectId("5ce51febc6dd820a820f20a6"),
"players" : [
ObjectId("5ce51c1af3cd6009a171a005"),
ObjectId("5ce51c1af3cd6009a171a16c")
],
"result" : "6:2 4:6 6:3"
},
[...]
and players like this:
{
"_id" : ObjectId("5ce51c1af3cd6009a171a5b3"),
"name" : "Serena Williams",
"country" : "USA"
},
{
"_id" : ObjectId("5ce51c1af3cd6009a171a350"),
"name" : "Garbiñe Muguruza",
"country" : "Spain"
},
[...]
I need all matches where players[0] is equal to a name and players[1] to another name.
I've tried this without success:
db.matches.aggregate([
{
$unwind: "$players"
},
{
$lookup: {
from: "players",
localField: "players",
foreignField: "_id",
as: "tmp_join"
}
},
{
$match: {
"tmp_join.name": ["Serena Williams","Garbiñe Muguruza"]
}
}
])

Answer 1

You have to first $unwind the tmp_join array and then you can use $in to find the documents contain name.
db.matches.aggregate([
{ "$lookup": {
"from": "players",
"localField": "players",
"foreignField": "_id",
"as": "tmp_join"
}},
{ "$unwind": "$tmp_join" },
{ "$match": {
"tmp_join.name": {
"$in": ["Serena Williams","Garbiñe Muguruza"]
}
}}
])
Use below aggregation if you are using mongodb 3.6 and above
db.matches.aggregate([
{ "$lookup": {
"from": "players",
"let": { "players": "$players" },
"pipeline": [
{ "$match": {
"$expr": { "$in": ["$_id", "$$players"] },
"name": { "$in": ["Serena Williams", "Garbiñe Muguruza"] }
}}
],
"as": "tmp_join"
}},
{ "$match": { "$expr": { "$gt": [{ "$size": "$tmp_join" }, 1] }}}
])