OpenSearch/docs/reference/mapping/params/copy-to.asciidoc

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

The `copy_to` parameter allows you to copy the values of multiple
fields into a group field, which can then be queried as a single
field.

TIP: If you often search multiple fields, you can improve search speeds by using
`copy_to` to search fewer fields. See <<search-as-few-fields-as-possible>>.

For example, the `first_name` and `last_name` fields can be copied to
the `full_name` field as follows:

[source,console]
--------------------------------------------------
PUT my-index-000001
{
  "mappings": {
    "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-000001/_doc/1
{
  "first_name": "John",
  "last_name": "Smith"
}

GET my-index-000001/_search
{
  "query": {
    "match": {
      "full_name": { <2>
        "query": "John Smith",
        "operator": "and"
      }
    }
  }
}

--------------------------------------------------

<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" ]`
* You cannot copy recursively via intermediary fields such as a `copy_to` on 
`field_1` to `field_2` and `copy_to` on `field_2` to `field_3` expecting 
indexing into `field_1` will eventuate in `field_3`, instead use copy_to 
directly to multiple fields from the originating field.