GET /idx/mytype/_search
    {
      "size" : 0,
      "query" : {
        "bool" : { }
      },
      "aggregations" : {
        "myAgg" : {
          "filter" : {
            "nested" : {
              "query" : {
                "query_string" : {
                  "query" : "n1.category:(\"c1\")"
                }
              },
              "path" : "n1"
            }
          },
          "aggregations" : {
            "sub_nested" : {
              "nested" : {
                "path" : "n1"
              },
              "aggregations" : {
                "sub" : {
                  "terms" : {
                    "field" : "n1.category"
                  },
                  "aggregations" : {
                    "sub2_nested" : {
                      "nested" : {
                        "path" : "n1"
                      },
                      "aggregations" : {
                        "sub2" : {
                          "terms" : {
                            "field" : "n1.title"
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }