Faceting by both document and nested document

nested-facet-mapping.json

{
  "rating": {
    "properties" : {
      "system" : {
        "type" : "string",
        "index" : "not_analyzed"
      },
      "value" : {
        "type" : "float",
        "null_value" : 0,
      }
    }
  },
  "availability" : {
    "type" : "nested",
    "properties" : {
      "date" : {
        "type" : "date",
        "format" : "date"
     },
     "price" : {
       "type" : "integer"
      }
    }
  }
}

nested-facet-query.json

{
  "query": { "match_all": {} },
  "facets": {
    "rating": {
      "range": {
        "key_field": "rating.value",
        "value_field": "availability.price",
        "ranges": [
          { "to": 1 },
          { "from": 1, "to": 2 },
          { "from": 2, "to": 3 },
          { "from": 3, "to": 4 },
          { "from": 5 }
        ]
      }
    }
  }
}