Why not the _ingest/pipeline/_simulate api support custom pattern?

[felayman (方磊)]

when i use the _ingest/pipeline/_simulate api as flollow:

POST _ingest/pipeline/_simulate
{
  "pipeline": {
    "description": "转换成指定格式的日期格式字段",
    "processors": [
      {
      "date": {
        "field": "date",
        "formats": ["UNIX"],
        "target_field": "@timestamp", 
        "timezone": "Asia/Shanghai"
      }
      }
    ]
  },
  "docs": [
    {
      "_index": "index",
      "_type": "type",
      "_id": "id",
      "_source": {
        "code":"000001",
        "tag": "衣柜",
        "price":"999.8",
        "date":"1511696379"
      }
    }
  ]
}

i find that i only can get the result for ISO format as follow：

{
  "docs": [
    {
      "doc": {
        "_index": "index",
        "_type": "type",
        "_id": "id",
        "_source": {
          "date": "1511696379",
          "code": "000001",
          "@timestamp": "2017-11-26T19:39:39.000+08:00",
          "price": "999.8",
          "tag": "衣柜"
        },
        "_ingest": {
          "timestamp": "2017-11-26T12:25:43.321Z"
        }
      }
    }
  ]
}

now what should i do to get another format for the "@timestamp" field in the result like "2017-11-26 19:39:39".

[dadoonet (David Pilato)]

The goal of the ingest date processor is to read a String and convert it to a Date object.
The Date object is then stored as a date.

This explains why you see that format.

IMO the only way to transform it to another format is to use a Painless script.
But you should may be do that at query time when you want to render the result to your user.