Grafana无法解析Elasticsearch的timestamp

添加ES数据源使用timestamp字段无法解析，

官网文档，必须是Date类型

可以用多字段映射解决

POST java-20200712/_mapping
{
  "properties": {
    "start_time": {
      "type": "long",
      "fields": {
        "as_date": {
          "type": "date",
          "format": "epoch_second"
        }
      }
    }
  }
}

然后用这个字段聚合

GET /java-20200712/_search
{
  "size": 0, 
  "query": {
    "match_all": {}
  },
  "aggs": {
    "amount_per_day": {
      "date_histogram": {
        "field": "start_time.as_date",
        "format": "yyyy-MM-dd", 
        "calendar_interval": "1d"
      }
    }
  }
}