I wanted to know if there is any such system table that we can use to identify and map the fields containing large objects and the respective tables and if it is not already there, do we have any plans to incorporate the same in pg_class like we have for pg_toast?
Large Objects are nothing like TOAST. There is no system level association between large objects and tables. Sure, the DBA can choose to store a large object OID in a table, but how you'd go about figuring out which columns contain those is going to be installation specific. Though hopefully they used a bigint data type and maybe added "oid" to the column name...I suppose it would be interesting if one could define a FK on a table and point it at pg_largeobject_metadata but that I suspect would be the extent to which we'd do something along the lines of your request.
