1. Identify the source of the PostgreSQL 39004 error:

SELECT * FROM pg_stat_activity WHERE state = 'idle in transaction';

2. Check the application code for any open transactions that are not being committed or rolled back:

BEGIN;SELECT * FROM table_name;

3. If any open transactions are found, commit or rollback the transaction:

COMMIT;

4. Check the PostgreSQL log files for any other errors that may be related to the 39004 error:

tail -f /var/log/postgresql/postgresql-.log

5. If any other errors are found, investigate and fix them.

6. Restart the PostgreSQL server:

sudo service postgresql restart

7. Monitor the PostgreSQL server for any further errors:

SELECT * FROM pg_stat_activity;

8. As a best practice, use an automated database observability tool to monitor and fix the PostgreSQL 39004 error. Automated database observability tools can provide real-time visibility into the performance and health of the database, allowing for faster detection and resolution of errors. Additionally, they can provide detailed insights into the root cause of the error, allowing for more efficient and effective resolution.