how to tell if a tuple has been inserted in current transaction

Hi all,

I have a trigger function which is getting invoked on insert/update and within that trigger I would like to know if some tuple, from a different table referenced by foreign key constraint from the table with the trigger on it, was inserted within the same transaction as the insert/update that caused the trigger to fire.

I found that I can tell if the foreign tuple was inserted or updated by checking if its xmin == select txid_current(), but there doesn't appear to be any way to know if it was modified because of an INSERT or an UPDATE.  I would like to distinguish between whether it was an insert or update that caused the row to be modified.  Is this possible?

Thank you for any information.