How to create a compound index in MongoDB through Java driver?

Question

I want to create compound index on Age and Name in MongoDB through Java driver and here is my syntax:

coll.ensureIndex(new BasicDBObject("Age", 1),new BasicDBObject("Name", -1));
List <DBObject> list = coll.getIndexInfo();

  for (DBObject o : list) {
       System.out.println(o);
    }

but it create only 1 index not compund index and give me result this:

{ "v" : 1 , "key" : { "_id" : 1} ,"ns" :"EmployeeData.EmpPersonalData", "name":"_id_"}
{ "v" : 1 , "key" : { "Age" : 1} , "ns" : "EmployeeData.EmpPersonalData" , "name" : "Age_1" , "Name" : -1}

So how can compund index on collection can be created through java driver?

Answer 1

If you look at your code, you have actually called ensureIndex with two parameters. Your first parameter was the key and your second parameter became some extra field: Name: -1.

What you are looking to pass in the first parameter is this object {"Age":1, "Name":-1}. What you actually passed was {"Age":1}, {"Name":-1}.

So you want to do something like this:

BasicDBObject obj = new BasicDBObject();
obj.put("Age", 1);
obj.put("Name", -1);
coll.ensureIndex(obj);

Note that the index will be created with a default name. To provide a specific name do the following:

coll.ensureIndex(obj, "MyName");