How to Create a PostgreSQL Read Only User


By squashlabs, Last Updated: October 30, 2023

How to Create a PostgreSQL Read Only User

PostgreSQL is a useful open-source relational database management system that allows users to store and retrieve data efficiently. In many cases, it is necessary to provide read-only access to certain users or applications to ensure data integrity and security. A read-only user in PostgreSQL is a user account that has permission to view data but cannot make any modifications to the database.

When creating a read-only user, it is important to understand the implications and limitations. The read-only user will only be able to perform SELECT queries and view the data in the database. They will not have the ability to insert, update, or delete any data. This can be useful in scenarios where you want to provide access to data for reporting purposes or restrict certain users from making changes to the database.

Granting Read Access to a User in PostgreSQL

To grant read access to a user in PostgreSQL, you need to create a new user account and assign the necessary privileges. Here’s an example of how to create a read-only user named “reporting_user”:

CREATE USER reporting_user WITH PASSWORD 'password';
GRANT CONNECT ON DATABASE your_database TO reporting_user;
GRANT USAGE ON SCHEMA public TO reporting_user;

Let’s break down the above code snippet:

– The first line creates a new user account named “reporting_user” with the specified password.
– The second line grants the user the ability to connect to the specified database.
– The third line grants the user the ability to use the “public” schema.
– The fourth line grants the user the ability to select data from all tables in the “public” schema.

With these privileges, the “reporting_user” will be able to connect to the database and execute SELECT queries on all tables within the “public” schema.

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Restricting a User’s Access to Specific Tables in PostgreSQL

In some cases, you may want to restrict a read-only user’s access to specific tables instead of granting access to all tables within a schema. This can be useful when you only want the user to view certain data and not have access to other sensitive information.

To restrict a user’s access to specific tables, you can use the following syntax:

GRANT SELECT ON table_name TO reporting_user;

Replace “table_name” with the name of the table you want to grant access to. You can repeat this command for each table you want to provide access to.

For example, if you have a table named “customers” and you want to grant read access to the “reporting_user”, you would use the following command:

GRANT SELECT ON customers TO reporting_user;

This will allow the “reporting_user” to select data from the “customers” table but not from any other table in the database.

Revoking Read Access from a User in PostgreSQL

If you need to revoke read access from a user in PostgreSQL, you can use the following syntax:

REVOKE SELECT ON table_name FROM reporting_user;

Replace “table_name” with the name of the table you want to revoke access from. You can repeat this command for each table you want to revoke access from.

For example, if you want to revoke read access from the “reporting_user” for the “customers” table, you would use the following command:

REVOKE SELECT ON customers FROM reporting_user;

This will remove the read access for the “reporting_user” to the “customers” table.

Authenticating a Read Only User in PostgreSQL

To authenticate a read-only user in PostgreSQL, you can use various authentication methods such as password-based authentication or certificate-based authentication.

Password-based authentication is the most common method and involves providing a username and password to connect to the database. When creating a read-only user, you can set a password for the user account using the following command:

ALTER USER reporting_user WITH PASSWORD 'new_password';

Replace “reporting_user” with the name of the user account and “new_password” with the desired password.

Certificate-based authentication involves using SSL certificates to authenticate users. This method provides an additional layer of security and is often used in production environments. However, configuring certificate-based authentication is beyond the scope of this article.

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Performance Implications of Using Read Only Users in PostgreSQL

Using read-only users in PostgreSQL can have performance implications depending on the workload and the number of read-only users accessing the database. When a read-only user executes a SELECT query, it can consume system resources such as CPU, memory, and disk I/O.

However, compared to read-write operations, read-only operations generally have a lower impact on performance. This is because read-only operations do not involve modifying data and do not require acquiring locks or performing data consistency checks.

To optimize performance when using read-only users, you can consider the following best practices:

– Use appropriate indexing: Ensure that the tables accessed by read-only users are properly indexed to improve query performance.
– Implement caching mechanisms: Implement caching mechanisms such as query caching or object caching to reduce the load on the database server.
– Monitor resource usage: Regularly monitor the resource usage of the database server to identify any performance bottlenecks and optimize accordingly.

Common Security Risks Associated with Read Only Users in PostgreSQL

While read-only users can provide an additional layer of security, there are some common security risks associated with their usage. It is important to be aware of these risks and take appropriate measures to mitigate them.

1. Privilege escalation: If a read-only user account is compromised, an attacker may attempt to escalate privileges and gain read-write access to the database. To mitigate this risk, it is important to regularly review and update user privileges, as well as implement strong authentication mechanisms.

2. Data leakage: Read-only users still have access to view sensitive data in the database. It is crucial to ensure that proper access controls and data encryption mechanisms are in place to prevent unauthorized access or data leakage.

3. SQL injection: Even though read-only users cannot modify data, they can still be vulnerable to SQL injection attacks. It is essential to validate and sanitize user input to prevent SQL injection vulnerabilities.

4. Denial of Service (DoS) attacks: Read-only users can potentially execute resource-intensive queries that consume excessive system resources, leading to a Denial of Service (DoS) attack. Implementing query throttling or rate limiting mechanisms can help mitigate this risk.

Best Practices for Managing Read Only Users in PostgreSQL

To effectively manage read-only users in PostgreSQL, consider the following best practices:

1. Use strong passwords: Set strong and unique passwords for read-only user accounts to prevent unauthorized access.

2. Regularly review and update privileges: Regularly review and update the privileges of read-only users to ensure they have the necessary access and no unnecessary access.

3. Implement proper authentication mechanisms: Use secure authentication mechanisms such as password-based or certificate-based authentication to authenticate read-only users.

4. Monitor and log user activity: Implement monitoring and logging mechanisms to track user activity and detect any suspicious or unauthorized access.

5. Regularly review and update access controls: Regularly review and update access controls to ensure that read-only users have access to the necessary data and do not have access to sensitive information.

Related Article: How to Restore a Postgresql Backup File Using the Command Line

Difference Between a Read Only User and a Superuser in PostgreSQL

In PostgreSQL, a read-only user and a superuser are two different types of user accounts with distinct privileges and capabilities.

A read-only user is a user account that has been granted read access to the database. They can execute SELECT queries to view data but cannot modify or delete data. Read-only users have limited privileges and cannot perform administrative tasks such as creating or modifying database objects, altering schemas, or managing user accounts.

On the other hand, a superuser is a user account with full administrative privileges. Superusers have the ability to perform any action on the database, including creating and modifying database objects, altering schemas, managing user accounts, and executing any type of query, including write operations.

It is important to exercise caution when granting superuser privileges to user accounts, as they have unrestricted access to the database and can potentially cause significant damage if misused.

Additional Resources

Permissions of a read-only user in PostgreSQL
Grant read-only access to specific tables in PostgreSQL

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