Thread: Schedule pg_repack job with pg_cron

To schedule a pg_repack job using pg_cron on an Amazon RDS for PostgreSQL instance, you need to follow a few steps. However, it’s important to note that pg_cron is only supported on certain versions of Amazon RDS, and pg_repack is also a separate extension that must be installed and enabled.

Here’s a general guide on how you can set this up:

Prerequisites

1. Check Compatibility: Ensure that your RDS instance supports pg_cron and pg_repack. Both extensions need to be available and supported by the RDS version you are using.
2. Install pg_repack: Ensure pg_repack is installed on your RDS instance. You can install it via the AWS Management Console if it's available for your PostgreSQL version. For example:
   • Go to RDS Dashboard -> Parameter Groups.
   • Modify the parameter group associated with your RDS instance to add pg_repack to the shared_preload_libraries parameter.
3. Enable pg_cron: Similarly, ensure that pg_cron is enabled. You may need to add pg_cron to the shared_preload_libraries in your parameter group and reboot your instance.

Setting Up the Job

1. Create the pg_cron Extension: First, create the pg_cron extension in your database:

sql

Copy code

CREATE EXTENSION IF NOT EXISTS pg_cron;

2. Create the pg_repack Extension: Similarly, create the pg_repack extension:

sql

Copy code

CREATE EXTENSION IF NOT EXISTS pg_repack;

3. Schedule a pg_repack Job: You can schedule a job using pg_cron to run pg_repack. Here is an example of how to set up a weekly job:

sql

Copy code

SELECT cron.schedule(

  'weekly_repack',

  '0 3 * * 0',  -- This runs every Sunday at 3 AM

  $$

  SELECT pg_repack.repack_database();

  $$);

In this example, pg_repack.repack_database() is called to reorganize the database. Adjust the schedule expression (0 3 * * 0) as needed to fit your desired schedule.

Considerations

• Permissions: Ensure the user running the pg_cron job has the necessary permissions to execute pg_repack.
• Performance Impact: Running pg_repack can be resource-intensive. Schedule the job during off-peak hours to minimize the impact on your database.
• Testing: Before scheduling the job, test pg_repack on a non-production instance to ensure it behaves as expected.
• Monitoring: Monitor the job to ensure it completes successfully and troubleshoot any issues that arise.

By setting up pg_repack with pg_cron on Amazon RDS for PostgreSQL, you can automate the process of reclaiming disk space and improving database performance without significant downtime.

Thanks!

Jake