full meta query

$meta_query = array(
	'relation' => 'AND',
	array(
		'relation' => 'OR',
		array(
			'relation' => 'AND',
			array(
				'key'     => 'restricted_access',
				'value'   => '1',
				'compare' => '=',
			),
			array(
				'key'     => 'allowed_user',
				'value'   => 'currentUserID',
				'compare' => '=',
			),
		),
		array(
			'relation' => 'OR',
			array(
				'key'     => 'restricted_access',
				'compare' => '=',
				'type'    => 'CHAR',
			),
			array(
				'key'     => 'restricted_access',
				'compare' => 'NOT EXISTS',
			),
		),
	),
);