Identifying object from file on disk

I have a very strange situation where all of a sudden my database growth
has increased dramatically.
I made some schema changes, bit these were made to some tables which do
not have the massive insertion rate (a few fields were changed from
varchar to inet data types.
The tables which have the massive insertion rates of records were not
changed.
The tables with the high insertion rate are partitioned tables.

I would like to identify the objects which all of a sudden are frowing
at the high growth rate by using the filename (which I assune is the
OID). I have looked at the pg_catalog schema to see if I could see an
obvious way to do this, but to no avail. Furthermore, I hate to keep
bothering the ng with these types of questions - is there a reference
which lists the functions/views available in pg_catalog which can be
used for this type of check?

TA,

Benjamin