WPINC wp class tax query.php Notes - WordPress-Thinstall/wordpress-develop GitHub Wiki

interface TaxQueryInterface {
    public function sanitize_query( $queries );
    public function sanitize_relation( $relation );
    public function get_sql( $primary_table, $primary_id_column );
    public function get_sql_for_clause( &$clause, $parent_query );
    public function transform_query( &$query, $resulting_field );
}

Notes Query API's seem to be really non-standard and lump as much functionality into one-place as possible. Would be nice to find the commonly needed points and delegate some responsibilities elsewhere