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.

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

 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 _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 using intermediary fields. The following configuration will not copy data from field_1 to field_3:

   PUT bad_example_index {
    "mappings": {
      "properties": {
        "field_1": {
          "type": "text",
          "copy_to": "field_2"
        },
        "field_2": {
          "type": "text",
          "copy_to": "field_3"
        },
        "field_3": {
          "type": "text"
        }
      }
    }
  }
  

  Instead, copy to multiple fields from the source field:

   PUT good_example_index {
    "mappings": {
      "properties": {
        "field_1": {
          "type": "text",
          "copy_to": ["field_2", "field_3"]
        },
        "field_2": {
          "type": "text"
        },
        "field_3": {
          "type": "text"
        }
      }
    }
  }
  

Consider the following points when using copy_to with dynamic mappings:

• If the target field does not exist in the index mappings, the usual dynamic mapping behavior applies. By default, with dynamic set to true, a non-existent target field will be dynamically added to the index mappings.

• If dynamic is set to false, the target field will not be added to the index mappings, and the value will not be copied.

• If dynamic is set to strict, copying to a non-existent field will result in an error.

• If the target field is nested, then copy_to fields must specify the full path to the nested field. Omitting the full path will lead to a strict_dynamic_mapping_exception. Use "copy_to": ["parent_field.child_field"] to correctly target a nested field.

  For example:

   PUT /test_index {
    "mappings": {
      "dynamic": "strict",
      "properties": {
        "description": {
          "properties": {
            "notes": {
              "type": "text",
              "copy_to": [ "description.notes_raw"], 1
              "analyzer": "standard",
              "search_analyzer": "standard"
            },
            "notes_raw": {
              "type": "keyword"
            }
          }
        }
      }
    }
  }
  

  1. The notes field is copied to the notes_raw field. Targeting notes_raw alone instead of description.notes_raw would lead to a strict_dynamic_mapping_exception.In this example, notes_raw is not defined at the root of the mapping, but under the description field. Without the fully qualified path, Elasticsearch would interpret the copy_to target as a root-level field, not as a nested field under description.