[[dynamic-field-mapping]]
=== Dynamic field mapping

By default, when a previously unseen field is found in a document,
Elasticsearch will add the new field to the type mapping.   This behaviour can
be disabled, both at the document and at the <<object,`object`>>  level, by
setting the <<dynamic,`dynamic`>> parameter to `false` or to `strict`.

Assuming `dynamic` field mapping is enabled, some simple rules are used to
determine which datatype the field should have:

[horizontal]
*JSON datatype*::                   *Elasticsearch datatype*

`null`::                            No field is added.
`true` or `false`::                 <<boolean,`boolean`>> field
floating{nbsp}point{nbsp}number::   <<number,`double`>> field
integer::                           <<number,`long`>> field
object::                            <<object,`object`>> field
array::                             Depends on the first non-`null` value in the array.
string::                            Either a <<date,`date`>> field
                                        (if the value passes <<date-detection,date detection>>),
                                    a <<number,`double`>> or <<number,`long`>> field
                                        (if the value passes <<numeric-detection,numeric detection>>)
                                    or an <<text,`text`>> field.

These are the only <<mapping-types,field datatypes>> that are dynamically
detected.  All other datatypes must be mapped explicitly.

Besides the options listed below, dynamic field mapping rules can be further
customised with <<dynamic-templates,`dynamic_templates`>>.

[[mapping-limit-settings]]
==== Settings to prevent mappings explosion

Two settings allow to control mapping explosion, in order to prevent adversary
documents to create huge mappings through dynamic mappings for instance:

`index.mapping.total_fields.limit`::
    The maximum number of fields in an index. The default value is `1000`.
`index.mapping.depth.limit`::
    The maximum depth for a field, which is measured as the number of nested
    objects. For instance, if all fields are defined at the root object level,
    then the depth is `1`. If there is one object mapping, then the depth is
    `2`, etc. The default is `20`.

[[date-detection]]
==== Date detection

If `date_detection` is enabled (default), then new string fields are checked
to see whether their contents match any of the date patterns specified in
`dynamic_date_formats`.  If a match is found, a new <<date,`date`>> field is
added with the corresponding format.

The default value for `dynamic_date_formats` is:

&#91; <<strict-date-time,`"strict_date_optional_time"`>>,`"yyyy/MM/dd HH:mm:ss Z||yyyy/MM/dd Z"`]

For example:


[source,js]
--------------------------------------------------
PUT my_index/my_type/1
{
  "create_date": "2015/09/02"
}

GET my_index/_mapping <1>
--------------------------------------------------
// AUTOSENSE
<1> The `create_date` field has been added as a <<date,`date`>>
    field with the <<mapping-date-format,`format`>>: +
    `"yyyy/MM/dd HH:mm:ss Z||yyyy/MM/dd Z"`.

===== Disabling date detection

Dynamic date detection can be disabled by setting `date_detection` to `false`:

[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "date_detection": false
    }
  }
}

PUT my_index/my_type/1 <1>
{
  "create": "2015/09/02"
}
--------------------------------------------------
// AUTOSENSE

<1> The `create_date` field has been added as a <<text,`text`>> field.

===== Customising detected date formats

Alternatively, the `dynamic_date_formats` can be customised to support your
own <<mapping-date-format,date formats>>:

[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "dynamic_date_formats": ["MM/dd/yyyy"]
    }
  }
}

PUT my_index/my_type/1
{
  "create_date": "09/25/2015"
}
--------------------------------------------------
// AUTOSENSE


[[numeric-detection]]
==== Numeric detection

While JSON has support for native floating point and integer datatypes, some
applications or languages may sometimes render numbers as strings. Usually the
correct solution is to map these fields explicitly, but numeric detection
(which is disabled by default) can be enabled to do this automatically:


[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "numeric_detection": true
    }
  }
}

PUT my_index/my_type/1
{
  "my_float":   "1.0", <1>
  "my_integer": "1" <2>
}
--------------------------------------------------
// AUTOSENSE
<1> The `my_float` field is added as a <<number,`double`>> field.
<2> The `my_integer` field is added as a <<number,`long`>> field.