[[copy-to]]
=== `copy_to`

The `copy_to` parameter allows you to create custom
<<mapping-all-field,`_all`>> fields.  In other words, the values of multiple
fields can be copied into a group field, which can then be queried as a single
field.  For instance, the `first_name` and `last_name` fields can be copied to
the `full_name` field as follows:

[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "properties": {
        "first_name": {
          "type": "text",
          "copy_to": "full_name" <1>
        },
        "last_name": {
          "type": "text",
          "copy_to": "full_name" <1>
        },
        "full_name": {
          "type": "text"
        }
      }
    }
  }
}

PUT my_index/my_type/1
{
  "first_name": "John",
  "last_name": "Smith"
}

GET my_index/_search
{
  "query": {
    "match": {
      "full_name": { <2>
        "query": "John Smith",
        "operator": "and"
      }
    }
  }
}

--------------------------------------------------
// CONSOLE
<1>  The values of the `first_name` and `last_name` fields are copied to the
     `full_name` field.

<2>  The `first_name` and `last_name` fields can still be queried for the
     first name and last name respectively, but the `full_name` field can be
     queried for both first and last names.

Some important points:

* It is the field _value_ which is copied, not the terms (which result from the analysis process).
* The original <<mapping-source-field,`_source`>> field will not be modified to show the copied values.
* The same value can be copied to multiple fields, with `"copy_to": [ "field_1", "field_2" ]`
