Copy documents within same bucket matching condition

[Subasish]

@vsr1

SELECT OBJECT_CONCAT(d, $obj.[META(d).id]) AS x
FROM Schedules AS d USE KEYS OBJECT_NAMES($obj);

Could you please explain the working of the below query? Does it mean I have to get the $obj through a N1QL query?
SELECT OBJECT_CONCAT(d, $obj.[META(d).id]) AS x
FROM Schedules AS d USE KEYS OBJECT_NAMES($obj);