elasticsearch 6.0.0及之后移除了一个索引允许映射多个类型的操作（Removal of mapping types）

分给线一下内容为理解错误内容，实际允许建立父子分档，只是类型改成来 join

官方demo：

join datatypeedit
The join datatype is a special field that creates parent/child relation within documents of the same index. The relations section defines a set of possible relations within the documents, each relation being a parent name and a child name. A parent/child relation can be defined as follows:

PUT my_index
{
  "mappings": {
    "_doc": {
      "properties": {
        "my_join_field": {
          "type": "join",
          "relations": {
            "question": "answer"
          }
        }
      }
    }
  }
}

链接：https://www.elastic.co/guide/en/elasticsearch/reference/current/parent-join.html

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用到了6.2，还以为像5.X 一样允许建立 父-子关系文档 ，即一个索引下允许映射多个类型，操作后发现行不通

如下代码：

PUT /company
{
  "mappings": {
    "branch": {},
    "employee": {
      "_parent": {
        "type": "branch"
      }
    }
  }
}

找到最新的官方文档，给出了说明，大意是：

6.0.0移除了一个索引允许映射多个类型，虽然还支持同索引多类型查询，但是Elasticsearch 7.0.0的版本将完全放弃。

不过官方给了另外的方案解决

Custom type fieldedit
Of course, there is a limit to how many primary shards can exist in a cluster so you may not want to waste an entire shard for a collection of only a few thousand documents. In this case, you can implement your own custom type field which will work in a similar way to the old _type.

Let’s take the user/tweet example above. Originally, the workflow would have looked something like this:

PUT twitter
{
  "mappings": {
    "user": {
      "properties": {
        "name": { "type": "text" },
        "user_name": { "type": "keyword" },
        "email": { "type": "keyword" }
      }
    },
    "tweet": {
      "properties": {
        "content": { "type": "text" },
        "user_name": { "type": "keyword" },
        "tweeted_at": { "type": "date" }
      }
    }
  }
}

PUT twitter/user/kimchy
{
  "name": "Shay Banon",
  "user_name": "kimchy",
  "email": "shay@kimchy.com"
}

PUT twitter/tweet/1
{
  "user_name": "kimchy",
  "tweeted_at": "2017-10-24T09:00:00Z",
  "content": "Types are going away"
}

GET twitter/tweet/_search
{
  "query": {
    "match": {
      "user_name": "kimchy"
    }
  }
}
You could achieve the same thing by adding a custom type field as follows:

PUT twitter
{
  "mappings": {
    "_doc": {
      "properties": {
        "type": { "type": "keyword" },
        "name": { "type": "text" },
        "user_name": { "type": "keyword" },
        "email": { "type": "keyword" },
        "content": { "type": "text" },
        "tweeted_at": { "type": "date" }
      }
    }
  }
}

PUT twitter/_doc/user-kimchy
{
  "type": "user",
  "name": "Shay Banon",
  "user_name": "kimchy",
  "email": "shay@kimchy.com"
}

PUT twitter/_doc/tweet-1
{
  "type": "tweet",
  "user_name": "kimchy",
  "tweeted_at": "2017-10-24T09:00:00Z",
  "content": "Types are going away"
}

GET twitter/_search
{
  "query": {
    "bool": {
      "must": {
        "match": {
          "user_name": "kimchy"
        }
      },
      "filter": {
        "match": {
          "type": "tweet"
        }
      }
    }
  }
}

The explicit type field takes the place of the implicit _type field.

　　这是官网的6.x的关于此点的描述：https://www.elastic.co/guide/en/elasticsearch/reference/current/removal-of-types.html