/** The key of the configuration. e.g. 1 */
    String QUERY_FACET_FIELDS_min_doc_count = "query.facet.fields.min_doc_count";

    /** The key of the configuration. e.g. count.desc */
    String QUERY_FACET_FIELDS_SORT = "query.facet.fields.sort";

    /** The key of the configuration. e.g.  */
    String QUERY_FACET_FIELDS_MISSING = "query.facet.fields.missing";