pg_conndefaults
Name
pg_conndefaults -- get connection options and their defaults
Description
      pg_conndefaults returns information about the
      connection options available in pg_connect
      -conninfo and the current default value for each option.
    
Return Value
      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.