What are the steps to set up a cross-reference database with DBLINK for pg_cron

Steps to Set Up a Cross-Reference Database with DBLINK

1. Create a Separate Database for `pg_cron` Metadata:
- Create a new database, e.g., `pg_cron`, to store the `pg_cron` metadata tables.
- In the `postgresql.conf` file, set the `cron.database_name` parameter to `'pg_cron'`:

     cron.database_name = 'pg_cron'
     

2. Create DBLINK Connections:
- In the `pg_cron` database, create DBLINK connections to the other databases where you want to schedule jobs.
- For example, to create a DBLINK connection to the `foo` database:

sql
     CREATE SERVER foo_server FOREIGN DATA WRAPPER postgres_fdw
     OPTIONS (host 'localhost', dbname 'foo', port '5432');

     CREATE USER MAPPING FOR current_user SERVER foo_server
     OPTIONS (user 'your_username', password 'your_password');
     

3. Schedule Jobs in Other Databases:
- In the `pg_cron` database, use the `cron.schedule_in_database()` function to schedule jobs in the other databases.
- For example, to schedule a job in the `foo` database:

sql
     SELECT cron.schedule_in_database('my_job', '* * * * *', 'SELECT my_function();', 'foo');
     

4. Manage Jobs Across Databases:
- You can use the `cron.job` table in the `pg_cron` database to view, modify, or delete scheduled jobs across all databases.
- For example, to view all scheduled jobs:

sql
     SELECT * FROM cron.job;
     

By following these steps, you can use `pg_cron` to schedule jobs across multiple databases in your PostgreSQL environment, even if `pg_cron` is only installed in a single database (the `pg_cron` database).