pg_conndefaults
None.
The result is a list describing the possible connection options and their current default values. Each entry in the list is a sublist of the format:
{optname label dispchar dispsize value}
where the optname is usable as an option in pg_connect -conninfo.
pg_conndefaults returns info about the connection options available in pg_connect -conninfo and the current default value for each option.
pg_conndefaults