嵌套聚合在其存储桶中不包括相关文档

我有一个这样的映射(YAML格式):

order:
    mappings:
        number: ~
        createdAt:
            type: date
        customer:
            include_in_parent: true # this is needed so we can use `customer.firstName:<term here>` on the order index
            type: nested
            properties:
                id :
                    type : integer
                    index: not_analyzed
                firstName:
                    type: string
                    index: not_analyzed

然后我尝试搜索订单,并将相关客户作为一个集合。所以根据弹性搜索文档,我应该提出如下请求:

http://shopblender.dev:9200/mango/order/_search

 {
    "size": 0,
    "aggs": {
        "customers": {
            "nested": {
                "path": "customer"
            },
            "aggs": {
                "customer_ids": {
                    "terms": {
                        "field": "customer.id"
                    }
                }
            }
        }
    }
}

但当我执行此搜索时,它将有空的聚合(我有30个订单索引,它们都有一个内联客户对象):

{
  "hits": {
    "total": 30,
    "max_score": 0,
    "hits": [
    ]
  },
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "timed_out": false,
  "aggregations": {
    "customers": {
      "doc_count": 30,
      "customer_ids": {
        "buckets": [
        ],
        "doc_count_error_upper_bound": 0,
        "sum_other_doc_count": 0
      }
    }
  },
  "took": 1
}

为什么我不能使用 terms 嵌套属性上的聚合?我在这里错过了什么?

更新

这是 GET /mango/order/_mapping :

{
    "mango": {
        "mappings": {
            "order": {
                "_meta": {
                    "model": "Mango\\Component\\Core\\Model\\Order"
                },
                "properties": {
                    "createdAt": {
                        "type": "date",
                        "format": "dateOptionalTime"
                    },
                    "customer": {
                        "type": "nested",
                        "include_in_parent": true,
                        "properties": {
                            "email": {
                                "type": "string",
                                "index": "not_analyzed"
                            },
                            "firstName": {
                                "type": "string"
                            },
                            "id": {
                                "type": "integer"
                            },
                            "lastName": {
                                "type": "string"
                            }
                        }
                    },
                    "number": {
                        "type": "string"
                    },
                    "paymentState": {
                        "type": "string"
                    },
                    "shippingState": {
                        "type": "string"
                    },
                    "state": {
                        "type": "string"
                    }
                }
            }
        }
    }
}