automatically truncating PostgreSQL logfile

To keep 7 days of logs, one log file per day named postgresql-Mon.log, postgresql-Tue.log, etc, and automatically overwrite last week’s log with this week’s log.

logging_collector=on
log_filename = 'postgresql-%a.log'
log_directory = 'log'
log_rotation_age = 1d
log_truncate_on_rotation=on