If you don’t know the difference between pg_log, pg_clog and pg_xlog directories, please visit the below article.

PostgreSQL: Difference between pg_log, pg_clog and pg_xlog log directories

In the PostgreSQL, you can switch or rotate your server log file of a pg_log directory using pg_rotate_logfile(). It is mostly available in all versions of PostgreSQL.

Why do we require to do this?

Let me share a small example; We are doing ETL operations like data migration, data processing. Let’s assume that, senior database manager wants to know PostgreSQL Server log after every four hours.

You suppose to send a new log file to senior DBA group at after every four hours.

The simplest solution is, switch or rotate your PostgreSQL database log file at every four hours. For this, you can configure LINUX Cron job, PGAgent job and can take help of any other OS Scheduler.

Once you create a new file, you can send an old log file which has last four hours of PostgreSQL Logs.

Only, you could execute below query, and it will generate a new log file immediately in a pg_log directory.

SELECT *FROM pg_rotate_logfile()

In this post, I am sharing few important and basic commands for Database Administrator of PostgreSQL.

Check the version of PostgreSQL:

SELECT version();

Create a database using the script:

CREATE DATABASE Database_Name WITH OWNER User_Name;

Change the owner of the database:

ALTER DATABASE Database_Name OWNER TO User_Name;

Create a full copy of the database with structure and data:

CREATE DATABASE NewDB WITH TEMPLATE OldDB;

Create a database User using the script:

CREATE USER Anvesh WITH password 'testPassword';

Change the password of the User:

ALTER USER postgres WITH PASSWORD 'temproot';

Upgrade the existing User to Superuser:

ALTER USER TestUser WITH SUPERUSER;

Reload the PostgreSQL configuration file:

SELECT  pg_reload_conf();

Rotate the PostgreSQL Log file:

SELECT pg_rotate_logfile();

Find the Postgres server start time:

SELECT pg_postmaster_start_time();