Attempt at pl/pgsql drop-in replacement for the dated table_log C extension AKA pg Table Audit / PostgreSQL Table Log / tablelog by Andreas Scherbaum: http://www.postgresql.org/ftp/projects/pgFoundry/tablelog/tablelog/ http://github.com/andreasscherbaum/table_log
Naturally this is slower in pl/pgsql than C, and a slightly more up to date version of the original C extension can also be found here: https://github.com/glynastill/pg_table_audit
There are now many better ways to audit DML, using json types or advanced extensions like pgaudit, however if for some reason you're stuck with table_log this may help.