elasticsearch Elasticsearch：根据评级进行排序

我在Elasticsearch 5.5中存储了一个样本数据，如下所示。我可以创建索引，搜索的基础上匹配，gte等使用邮递员

{
  "name":"Apple",
  "address": {
    "city":"Cupertino",
    "state":"CA",
    "country":"USA"
  },
  "rating":"4.9"
}

我需要根据评级对所有实体进行排序，因此我在下面使用

{
  "query":{
    "match_all":{}
    },
   "sort" : [
      {
        "rating" : {
          "order" : "desc"
        }
      }
   ]
}

但我在邮递员身上看到了下面的错误

"type": "illegal_argument_exception",
        "reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [rating] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead."

---

有什么建议吗？

似乎需要将“评级”字段更改为数字，以便在此字段上执行排序

{
  "name":"Apple",
  "address": {
    "city":"Cupertino",
    "state":"CA",
    "country":"USA"
  },
  "rating":4.9
}

否则，可以使用PUT映射API在现有文本字段上启用fielddata，如下所示：

PUT my_index/_mapping/my_type
{
  "properties": {
    "rating": { 
      "type":     "text",
      "fielddata": true
    }
  }
}

---

似乎需要将rating字段更改为numeric，以便在此字段上执行排序

{
  "name":"Apple",
  "address": {
    "city":"Cupertino",
    "state":"CA",
    "country":"USA"
  },
  "rating":4.9
}

否则，可以使用PUT映射API在现有文本字段上启用fielddata，如下所示：

PUT my_index/_mapping/my_type
{
  "properties": {
    "rating": { 
      "type":     "text",
      "fielddata": true
    }
  }
}