Finding a distinct set of fields in MongoDB - mongodb

Question

I have the following JSON collection in MongoDB.
{
"_id": ObjectId("57529381551673386c9150a6"),
"team_code": 3,
"team_id": 2
},
{
"_id": ObjectId("57529381551673386c91514a"),
"team_code": 4,
"team_id": 5
},
{
"_id": ObjectId("57529381551673386c91514b"),
"team_code": 3,
"team_id": 2
},
{
"_id": ObjectId("57529381551673386c91514c"),
"team_code": 4,
"team_id": 5,
}
As it can be seen from the data , there a 2 records each with (team_code=3, team_id =2) and (team_code =4, team_id=5).
Is it possible to get the distinct set of team codes and team ids.
Some thing like ,
{
"team_code" : 3, "team_id" : 2
},
{
"team_code" : 4, "team_id" : 5,
}

Answer 1

You can do this using the following Aggregation Pipeline:
var distinctIdCode = { $group: { _id: { team_code: "$team_code", team_id: "$team_id" } } }
db.foo.aggregate([distinctIdCode])
This will give you:
{ "_id" : { "team_code" : 4, "team_id" : 5 } }
{ "_id" : { "team_code" : 3, "team_id" : 2 } }
This query returns new documents created from the documents in your collection. The documents returned have an _id which is the result of grouping the collection documents on the team_code and team_id fields.

Answer 2

For Java code:
Bson field1 = new Document("team_code", "$team_code").append("team_id", "$team_id");Bson groupField = new Document("_id", field1 );
Bson group = new Document("$group", groupField );List<Bson> bsonList = new ArrayList<Bson>();
bsonList.add(group);
com.mongodb.client.AggregateIterable<Document> res=collection.aggregate( bsonList );
for (Document doc : res) {
Document subDoc=(Document)doc.get("_id");
System.out.println(subDoc.get("team_code")+" : "+subDoc.get("team_id"));
//deptEnvs.put(subDoc.getInteger("dept"), subDoc.getString("smEnv"));
}