Multi Field Type

The multi_field type allows to map several core_types of the same value. This can come very handy, for example, when wanting to map a string type, once when it’s analyzed and once when it’s not_analyzed. For example:

{
    "tweet" : {
        "properties" : {
            "name" : {
                "type" : "multi_field",
                "fields" : {
                    "name" : {"type" : "string", "index" : "analyzed"},
                    "untouched" : {"type" : "string", "index" : "not_analyzed"}
                }
            }
        }
    }
}

The above example shows how the name field, which is of simple string type, gets mapped twice, once with it being analyzed under name, and once with it being not_analyzed under untouched.

With multi_field mapping, the field that has the same name as the property is treated as if it was mapped without a multi field. That’s the "default" field. It can be accessed regularly, for example using name or using typed navigation tweet.name.

The path attribute allows to control how non-default fields can be accessed. If the path attribute is set to full, which is the default setting, all non-default fields are prefixed with the name of the property and can be accessed by their full path using the navigation notation: name.untouched, or using the typed navigation notation tweet.name.untouched. If the path attribute is set to just_name the actual field name without a prefix is used. The just_name setting, among other things, allows indexing content of multiple fields under the same name. In the example below the content of both fields first_name and last_name can be accessed by using any_name or tweet.any_name

{
    "tweet" : {
        "properties": {
            "first_name": {
                "type": "multi_field",
                "path": "just_name",
                "fields": {
                    "first_name": {"type": "string", "index": "analyzed"},
                    "any_name": {"type": "string","index": "analyzed"}
                }
            },
            "last_name": {
                "type": "multi_field",
                "path": "just_name",
                "fields": {
                    "last_name": {"type": "string", "index": "analyzed"},
                    "any_name": {"type": "string","index": "analyzed"}
                }
            }
        }
    }
}

The include_in_all setting on the "default" field allows to control if the value of the field should be included in the _all field. Note, the value of the field is copied to _all, not the tokens. So, it only makes sense to copy the field value once. Because of this, the include_in_all setting on all non-default fields is automatically set to false and can’t be changed.

When updating mapping definition using the put_mapping API, a core type mapping can be "upgraded" to a multi_field mapping. This means that if the old mapping has a plain core type mapping, the updated mapping for the same property can be a multi_field type, with the default field being the one being replaced.