How do I find the last time that a PostgreSQL database has been updated?

Question

I am working with a postgreSQL database that gets updated in batches. I need to know when the last time that the database (or a table in the database)has been updated or modifie

Answer 1

You can write a stored procedure in an "untrusted language" (e.g. plpythonu): This allows access to the files in the postgres "base" directory. Return the larges mtime of these files in the stored procedure.

But this is only vague, since vacuum will change these files and the mtime.