elasticsearch/docs/reference/mapping/fields/index-field.asciidoc

[[mapping-index-field]]
=== `_index`

The ability to store in a document the index it belongs to. By default
it is disabled, in order to enable it, the following mapping should be
defined:

[source,js]
--------------------------------------------------
{
    "tweet" : {
        "_index" : { "enabled" : true }
    }
}
--------------------------------------------------