PostgreSQL can generate gigabytes of logs per day. Lots of data is good in case you want to investigate some specific event, but it is not what you will use for daily monitoring of database health.
Make sure that your PostgreSQL is set up to rotate the log files daily.
A default setup will do exactly the following:
log_rotation_age = 1d
Then get a PostgreSQL log processing program. Here, we describe how to do it using pgFouine.
For most Linux systems, you should be able to use your default package manager to install pgFouine.
Configure your PostgreSQL to produce
logfiles in a format that pgFouine understands. Select logging to
syslog. Use a modern version of
syslogd for high-traffic databases. ...