[
  {
    "admin": {
        "ids": {
            "batchId": "xxx"
        },
        "orgId": "yyy"
    },
    "objectId": "abc"
  },
  {
    "admin": {
        "ids": {
            "batchId": "xxy"
        },
        "orgId": "yyy"
    },
    "objectId": "abcd"
  }
]

{
  "org" : "yyy",
  groupBatches : [
    {
      "batchID" : "xxx"
    },
    {
      "batchID" : "xxy"
    }
  ]
}

{
    "_source": [ "objectId", "admin.orgId", "admin.ids.batchId"],
    "query" : {
       "nested": {
           "path": "admin",
           "query": {
                "match": {"admin.orgId": "xxx"}
           }
       }
    },
    "aggs" : {
        "groupBatches" : {
            "nested": {
                "path": "admin"
            },
            "aggs" : {
                "batches" : {
                    "terms" : {"field" : "admin.ids.batchId"}
                }
            }
        }
    }
}