[[removal-of-types]]
== Removal of mapping types

IMPORTANT: Indices created in Elasticsearch 7.0.0 or later no longer accept a
`_default_` mapping. Indices created in 6.x will continue to function as before
in Elasticsearch 6.x. Types are deprecated in APIs in 7.0, with breaking changes
to the index creation, put mapping, get mapping, put template, get template and
get field mappings APIs.

[discrete]
=== What are mapping types?

Since the first release of Elasticsearch, each document has been stored in a
single index and assigned a single mapping type. A mapping type was used to
represent the type of document or entity being indexed, for instance a
`twitter` index might have a `user` type and a `tweet` type.

Each mapping type could have its own fields, so the `user` type might have a
`full_name` field, a `user_name` field, and an `email` field, while the
`tweet` type could have a `content` field, a `tweeted_at` field and, like the
`user` type, a `user_name` field.

Each document had a `_type` metadata field containing the type name, and searches
could be limited to one or more types by specifying the type name(s) in the
URL:

[source,js]
----
GET twitter/user,tweet/_search
{
  "query": {
    "match": {
      "user_name": "kimchy"
    }
  }
}
----
// NOTCONSOLE

The `_type` field was combined with the document's `_id` to generate a `_uid`
field, so documents of different types with the same `_id` could exist in a
single index.

Mapping types were also used to establish a
<<parent-join,parent-child relationship>>
between documents, so documents of type `question` could be parents to
documents of type `answer`.

[discrete]
=== Why are mapping types being removed?

Initially, we spoke about an ``index'' being similar to a ``database'' in an
SQL database, and a ``type'' being equivalent to a
``table''.

This was a bad analogy that led to incorrect assumptions. In an SQL database,
tables are independent of each other. The columns in one table have no
bearing on columns with the same name in another table. This is not the case
for fields in a mapping type.

In an Elasticsearch index, fields that have the same name in different mapping
types are backed by the same Lucene field internally. In other words, using
the example above, the `user_name` field in the `user` type is stored in
exactly the same field as the `user_name` field in the `tweet` type, and both
`user_name` fields must have the same mapping (definition) in both types.

This can lead to frustration when, for example, you want `deleted` to be a
`date` field in one type and a `boolean` field in another type in the same
index.

On top of that, storing different entities that have few or no fields in
common in the same index leads to sparse data and interferes with Lucene's
ability to compress documents efficiently.

For these reasons, we have decided to remove the concept of mapping types from
Elasticsearch.

[discrete]
=== Alternatives to mapping types

[discrete]
==== Index per document type

The first alternative is to have an index per document type. Instead of
storing tweets and users in a single `twitter` index, you could store tweets
in the `tweets` index and users in the `user` index. Indices are completely
independent of each other and so there will be no conflict of field types
between indices.

This approach has two benefits:

* Data is more likely to be dense and so benefit from compression techniques
  used in Lucene.

* The term statistics used for scoring in full text search are more likely to
  be accurate because all documents in the same index represent a single
  entity.

Each index can be sized appropriately for the number of documents it will
contain: you can use a smaller number of primary shards for `users` and a
larger number of primary shards for `tweets`.

[discrete]
==== Custom type field

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:

[source,js]
----
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"
    }
  }
}
----
// NOTCONSOLE

You can achieve the same thing by adding a custom `type` field as follows:

[source,js]
----
PUT twitter
{
  "mappings": {
    "_doc": {
      "properties": {
        "type": { "type": "keyword" }, <1>
        "name": { "type": "text" },
        "user_name": { "type": "keyword" },
        "email": { "type": "keyword" },
        "content": { "type": "text" },
        "tweeted_at": { "type": "date" }
      }
    }
  }
}

PUT twitter/_doc/user-kimchy
{
  "type": "user", <1>
  "name": "Shay Banon",
  "user_name": "kimchy",
  "email": "shay@kimchy.com"
}

PUT twitter/_doc/tweet-1
{
  "type": "tweet", <1>
  "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" <1>
        }
      }
    }
  }
}
----
// NOTCONSOLE
<1> The explicit `type` field takes the place of the implicit `_type` field.

[discrete]
[[parent-child-mapping-types]]
==== Parent/Child without mapping types

Previously, a parent-child relationship was represented by making one mapping
type the parent, and one or more other mapping types the children. Without
types, we can no longer use this syntax. The parent-child feature will
continue to function as before, except that the way of expressing the
relationship between documents has been changed to use the new
<<parent-join,`join` field>>.


[discrete]
=== Schedule for removal of mapping types

This is a big change for our users, so we have tried to make it as painless as
possible. The change will roll out as follows:

Elasticsearch 5.6.0::

* Setting `index.mapping.single_type: true` on an index will enable the
  single-type-per-index behaviour which will be enforced in 6.0.

* The <<parent-join,`join` field>> replacement for parent-child is available
  on indices created in 5.6.

Elasticsearch 6.x::

* Indices created in 5.x will continue to function in 6.x as they did in 5.x.

* Indices created in 6.x only allow a single-type per index. Any name
  can be used for the type, but there can be only one. The preferred type name
  is `_doc`, so that index APIs have the same path as they will have in 7.0:
  `PUT {index}/_doc/{id}` and `POST {index}/_doc`

* The `_type` name can no longer be combined with the `_id` to form the `_uid`
  field. The `_uid` field has become an alias for the `_id` field.

* New indices no longer support the old-style of parent/child and should
  use the <<parent-join,`join` field>> instead.

* The `_default_` mapping type is deprecated.

* In 6.8, the index creation, index template, and mapping APIs support a query
  string parameter (`include_type_name`) which indicates whether requests and
  responses should include a type name. It defaults to `true`, and should be set
  to an explicit value to prepare to upgrade to 7.0. Not setting `include_type_name`
  will result in a deprecation warning. Indices which don't have an explicit type will
  use the dummy type name `_doc`.

Elasticsearch 7.x::

* Specifying types in requests is deprecated. For instance, indexing a
  document no longer requires a document `type`. The new index APIs
  are `PUT {index}/_doc/{id}` in case of explicit ids and `POST {index}/_doc`
  for auto-generated ids. Note that in 7.0, `_doc` is a permanent part of the
  path, and represents the endpoint name rather than the document type.

* The `include_type_name` parameter in the index creation, index template,
  and mapping APIs will default to `false`. Setting the parameter at all will
  result in a deprecation warning.

* The `_default_` mapping type is removed.

Elasticsearch 8.x::

* Specifying types in requests is no longer supported.

* The `include_type_name` parameter is removed.

[discrete]
=== Migrating multi-type indices to single-type

The <<docs-reindex,Reindex API>> can be used to convert multi-type indices to
single-type indices. The following examples can be used in Elasticsearch 5.6
or Elasticsearch 6.x. In 6.x, there is no need to specify
`index.mapping.single_type` as that is the default.

[discrete]
==== Index per document type

This first example splits our `twitter` index into a `tweets` index and a
`users` index:

[source,js]
----
PUT users
{
  "settings": {
    "index.mapping.single_type": true
  },
  "mappings": {
    "_doc": {
      "properties": {
        "name": {
          "type": "text"
        },
        "user_name": {
          "type": "keyword"
        },
        "email": {
          "type": "keyword"
        }
      }
    }
  }
}

PUT tweets
{
  "settings": {
    "index.mapping.single_type": true
  },
  "mappings": {
    "_doc": {
      "properties": {
        "content": {
          "type": "text"
        },
        "user_name": {
          "type": "keyword"
        },
        "tweeted_at": {
          "type": "date"
        }
      }
    }
  }
}

POST _reindex
{
  "source": {
    "index": "twitter",
    "type": "user"
  },
  "dest": {
    "index": "users",
    "type": "_doc"
  }
}

POST _reindex
{
  "source": {
    "index": "twitter",
    "type": "tweet"
  },
  "dest": {
    "index": "tweets",
    "type": "_doc"
  }
}
----
// NOTCONSOLE

[discrete]
==== Custom type field

This next example adds a custom `type` field and sets it to the value of the
original `_type`. It also adds the type to the `_id` in case there are any
documents of different types which have conflicting IDs:

[source,js]
----
PUT new_twitter
{
  "mappings": {
    "_doc": {
      "properties": {
        "type": {
          "type": "keyword"
        },
        "name": {
          "type": "text"
        },
        "user_name": {
          "type": "keyword"
        },
        "email": {
          "type": "keyword"
        },
        "content": {
          "type": "text"
        },
        "tweeted_at": {
          "type": "date"
        }
      }
    }
  }
}


POST _reindex
{
  "source": {
    "index": "twitter"
  },
  "dest": {
    "index": "new_twitter"
  },
  "script": {
    "source": """
      ctx._source.type = ctx._type;
      ctx._id = ctx._type + '-' + ctx._id;
      ctx._type = '_doc';
    """
  }
}
----
// NOTCONSOLE

[discrete]
=== Typeless APIs in 7.0

In Elasticsearch 7.0, each API will support typeless requests,
and specifying a type will produce a deprecation warning.

NOTE: Typeless APIs work even if the target index contains a custom type.
For example, if an index has the custom type name `my_type`, we can add
documents to it using typeless `index` calls, and load documents with typeless
`get` calls.

[discrete]
==== Index APIs

Index creation, index template, and mapping APIs support a new `include_type_name`
URL parameter that specifies whether mapping definitions in requests and responses
should contain the type name. The parameter defaults to `true` in version 6.8 to
match the pre-7.0 behavior of using type names in mappings. It defaults to `false`
in version 7.0 and will be removed in version 8.0.

It should be set explicitly in 6.8 to prepare to upgrade to 7.0. To avoid deprecation
warnings in 6.8, the parameter can be set to either `true` or `false`. In 7.0, setting
`include_type_name` at all will result in a deprecation warning.

See some examples of interactions with Elasticsearch with this option set to `false`:

[source,console]
--------------------------------------------------
PUT /my-index-000001?include_type_name=false
{
  "mappings": {
    "properties": { <1>
      "foo": {
        "type": "keyword"
      }
    }
  }
}
--------------------------------------------------

<1> Mappings are included directly under the `mappings` key, without a type name.

[source,console]
--------------------------------------------------
PUT /my-index-000001/_mappings?include_type_name=false
{
  "properties": { <1>
    "bar": {
      "type": "text"
    }
  }
}
--------------------------------------------------
// TEST[continued]

<1> Mappings are included directly under the `mappings` key, without a type name.

[source,console]
--------------------------------------------------
GET /my-index-000001/_mappings?include_type_name=false
--------------------------------------------------
// TEST[continued]

The above call returns

[source,console-result]
--------------------------------------------------
{
  "my-index-000001": {
    "mappings": {
      "properties": { <1>
        "foo": {
          "type": "keyword"
        },
        "bar": {
          "type": "text"
        }
      }
    }
  }
}
--------------------------------------------------

<1> Mappings are included directly under the `mappings` key, without a type name.

[discrete]
==== Document APIs

In 7.0, index APIs must be called with the `{index}/_doc` path for automatic
generation of the `_id` and `{index}/_doc/{id}` with explicit ids.

[source,console]
--------------------------------------------------
PUT /my-index-000001/_doc/1
{
  "foo": "baz"
}
--------------------------------------------------

[source,console-result]
--------------------------------------------------
{
  "_index": "my-index-000001",
  "_id": "1",
  "_type": "_doc",
  "_version": 1,
  "result": "created",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "_seq_no": 0,
  "_primary_term": 1
}
--------------------------------------------------

Similarly, the `get` and `delete` APIs use the path `{index}/_doc/{id}`:

[source,console]
--------------------------------------------------
GET /my-index-000001/_doc/1
--------------------------------------------------
// TEST[continued]

NOTE: In 7.0, `_doc` represents the endpoint name instead of the document type.
The `_doc` component is a permanent part of the path for the document `index`,
`get`, and `delete` APIs going forward, and will not be removed in 8.0.

For API paths that contain both a type and endpoint name like `_update`,
in 7.0 the endpoint will immediately follow the index name:

[source,console]
--------------------------------------------------
POST /my-index-000001/_update/1
{
  "doc" : {
    "foo" : "qux"
  }
}

GET /my-index-000001/_source/1
--------------------------------------------------
// TEST[continued]

Types should also no longer appear in the body of requests. The following
example of bulk indexing omits the type both in the URL, and in the individual
bulk commands:

[source,console]
--------------------------------------------------
POST _bulk
{ "index" : { "_index" : "my-index-000001", "_id" : "3" } }
{ "foo" : "baz" }
{ "index" : { "_index" : "my-index-000001", "_id" : "4" } }
{ "foo" : "qux" }
--------------------------------------------------

[discrete]
==== Search APIs

When calling a search API such `_search`, `_msearch`, or `_explain`, types
should not be included in the URL. Additionally, the `_type` field should not
be used in queries, aggregations, or scripts.

[discrete]
==== Types in responses

The document and search APIs will continue to return a `_type` key in
responses, to avoid breaks to response parsing. However, the key is
considered deprecated and should no longer be referenced. Types will
be completely removed from responses in 8.0.

Note that when a deprecated typed API is used, the index's mapping type will be
returned as normal, but that typeless APIs will return the dummy type `_doc`
in the response. For example, the following typeless `get` call will always
return `_doc` as the type, even if the mapping has a custom type name like
`my_type`:

[source,console]
--------------------------------------------------
PUT /my-index-000001/my_type/1
{
  "foo": "baz"
}

GET /my-index-000001/_doc/1
--------------------------------------------------

[source,console-result]
--------------------------------------------------
{
  "_index" : "my-index-000001",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 1,
  "_seq_no" : 0,
  "_primary_term" : 1,
  "found": true,
  "_source" : {
    "foo" : "baz"
  }
}
--------------------------------------------------

[discrete]
==== Index templates

It is recommended to make index templates typeless by re-adding them with
`include_type_name` set to `false`. Under the hood, typeless templates will use
the dummy type `_doc` when creating indices.

In case typeless templates are used with typed index creation calls or typed
templates are used with typeless index creation calls, the template will still
be applied but the index creation call decides whether there should be a type
or not. For instance in the below example, `index-1-01` will have a type in
spite of the fact that it matches a template that is typeless, and `index-2-01`
will be typeless in spite of the fact that it matches a template that defines
a type. Both `index-1-01` and `index-2-01` will inherit the `foo` field from
the template that they match.

[source,console]
--------------------------------------------------
PUT _template/template1
{
  "index_patterns":[ "index-1-*" ],
  "mappings": {
    "properties": {
      "foo": {
        "type": "keyword"
      }
    }
  }
}

PUT _template/template2?include_type_name=true
{
  "index_patterns":[ "index-2-*" ],
  "mappings": {
    "type": {
      "properties": {
        "foo": {
          "type": "keyword"
        }
      }
    }
  }
}

PUT index-1-01?include_type_name=true
{
  "mappings": {
    "type": {
      "properties": {
        "bar": {
          "type": "long"
        }
      }
    }
  }
}

PUT index-2-01
{
  "mappings": {
    "properties": {
      "bar": {
        "type": "long"
      }
    }
  }
}
--------------------------------------------------

//////////////////////////

[source,console]
--------------------------------------------------
DELETE /_template/template1
DELETE /_template/template2
--------------------------------------------------
// TEST[continued]

//////////////////////////

In case of implicit index creation, because of documents that get indexed in
an index that doesn't exist yet, the template is always honored. This is
usually not a problem due to the fact that typeless index calls work on typed
indices.

[discrete]
==== Mixed-version clusters

In a cluster composed of both 6.8 and 7.0 nodes, the parameter
`include_type_name` should be specified in index APIs like index
creation. This is because the parameter has a different default between
6.8 and 7.0, so the same mapping definition will not be valid for both
node versions.

Typeless document APIs such as `bulk` and `update` are only available as of
7.0, and will not work with 6.8 nodes. This also holds true for the typeless
versions of queries that perform document lookups, such as `terms`.
