[PostgreSQL] Resolving "Permission Denied for Table" Error in PostgreSQL pg_dump

Resolving “Permission Denied for Table” Error in PostgreSQL pg_dump

When managing PostgreSQL databases, one of the common tasks is creating backups using the pg_dump utility. However, you might encounter a frustrating error during this process, especially when your user lacks the necessary permissions. A common error looks like this:

pg_dump -E UTF8 --username=<user> --dbname=<db_name> --compress=9 -f database.sql

pg_dump: [archiver (db)] query failed: ERROR:  permission denied for table <table_name> 
pg_dump: [archiver (db)] query was: LOCK TABLE public.<table_name> IN ACCESS SHARE MODE

This error indicates that the user performing the pg_dump operation does not have sufficient permissions on a specific table (<table_name>) in the database (<db_name>). Let’s explore why this happens and how to resolve it.

Understanding the Issue

Why the Error Occurs

In PostgreSQL, each table and database has an owner—typically the user who created them. The owner has full control over the table or database, including the ability to grant permissions to other users. When pg_dump tries to lock a table to ensure data consistency during the dump, it requires the user executing the command to have the appropriate permissions on the table.

If the user (<user>) is not the owner of the table or has not been granted sufficient privileges, PostgreSQL will deny the request, resulting in the “permission denied” error.

Common Scenario

This error often arises when:

• A new table (<table_name>) has been added to the database, and the user performing the pg_dump operation has not been granted access to it.
• The user executing the dump is not the owner of the database or specific tables within the database.

Solutions

1. Grant Necessary Permissions

The quickest way to resolve this issue is to grant the user the necessary privileges on the table causing the problem. You can do this by executing the following SQL command:

GRANT ALL PRIVILEGES ON TABLE public.<table_name> TO <db_user>;

Replace <table_name> with the actual name of the table and <db_user> with the username that needs the access. This command grants all privileges on the specified table to the user, allowing pg_dump to perform its operations without permission issues.

2. Change the Ownership of the Database

If the user will regularly need to perform administrative tasks like backups, it might be more practical to change the ownership of the entire database to that user. This can be done with:

ALTER DATABASE <db_name> OWNER TO <new_owner>;

Replace <db_name> with the name of your database and <new_owner> with the username that should become the new owner. With ownership, the user gains full control over all objects within the database, eliminating permission issues during tasks like pg_dump.

Conclusion

Permission errors during pg_dump can disrupt your database management workflow. By ensuring that your user has the necessary privileges or by transferring ownership of the database, you can avoid these issues and ensure smooth, uninterrupted backups.