Question

I have a MongoDB document structured like this:

{
  "user_id": 7387,
  "first_name": "Daniel",
  "roles": [
    {
      "role_id": "509c20144fd846549e8d42ef",
      "role_name": "Writer",
      "is_lead": 0
    },
    {
      "role_id": "509c20344fd846549e8d42f0",
      "role_name": "Editor",
      "is_lead": 1
    }
  ]
},
{
  "user_id": 15735,
  "first_name": "Tom",
  "roles": [
    {
      "role_id": "509c203f4fd846549e8d42f1",
      "role_name": "Admin",
      "is_lead": 0
    },
    {
      "role_id": "509c20144fd846549e8d42ef",
      "role_name": "Writer",
      "is_lead": 1
    },
    {
      "role_id": "509c20344fd846549e8d42f0",
      "role_name": "Editor",
      "is_lead": 0
    }
  ]
}

How do I find all users who have roles.role_name as Writer and roles.is_lead as 1 (all writers who are also a lead)?

I tried:

db.users.find({$and:[{"roles.role_name":"Writer","roles.is_lead":1}]});

In the above example, it should only return “Tom”. But this returns both “Tom” and “Daniel” (I guess it picks {roles.is_lead:1} for the Editor role of “Daniel”. How do I fix this query?

Thanks.

Answer 1

What you are looking for is $elemMatch to make sure your search matches a specific element and not a mixture of any elements within the same document.

db.test.find({roles: {$elemMatch: {role_name:"Writer", is_lead:1}}})

Your original query was also the same as just doing a default basic search, since that will be an AND as well. The problem is that the AND was applying to any part of the document.