Example dataset for http://stackoverflow.com/a/16350492/432929.

data.json

[
  {
    "_id": "1",
    "guests": [
      {
        "_id": "4",
        "status": "invited",
        "player_id": "aaa"
      },
      {
        "_id": "5",
        "status": "invited",
        "player_id": "bbb"
      }
    ]
  },
  {
    "_id": "2",
    "guests": [
      {
        "_id": "6",
        "status": "invited",
        "player_id": "bbb"
      },
      {
        "_id": "7",
        "status": "invited",
        "player_id": "aaa"
      }
    ]
  },
  {
    "_id": "3",
    "guests": [
      {
        "_id": "8",
        "status": "invited",
        "player_id": "aaa"
      },
      {
        "_id": "9",
        "status": "invited",
        "player_id": "bbb"
      },
      {
        "_id": "10",
        "status": "invited",
        "player_id": "ccc"
      }
    ]
  }
]