PostgreSQL Materialized Views: Boosting Query Performance

PostgreSQL’s Materialized Views allow developers to store query results for faster access, making them ideal for optimizing slow queries. This brief guide explains their basic usage and examples to help you get started.

Basic Materialized View

Materialized Views act like cached tables. Instead of running a query every time you need data, the query result is saved for quick access. Here’s how to create a simple Materialized View to store data for employees in the IT department:

CREATE MATERIALIZED VIEW it_employees AS
SELECT first_name, last_name, position
FROM employees
WHERE department_id = 1;

This view stores all employees from the IT department in a materialized format. The benefit is that when you query this view later, the data is already computed and stored, speeding up data retrieval.

Using Joins in Views

You can also use Materialized Views to store the result of a query that joins data from multiple tables. In the following example, the view combines data from the employees table and the departments table to store each employee’s name and their respective department:

CREATE MATERIALIZED VIEW employee_departments AS
SELECT e.first_name, e.last_name, d.department_name
FROM employees e
INNER JOIN departments d ON e.department_id = d.id;

By storing the result of this join in a Materialized View, you avoid having to repeatedly run this complex query when retrieving data.

FAQ

What is a Materialized View?

It’s a view that stores the result of a query, making data retrieval faster by avoiding repetitive calculations.

How can you refresh them?

Materialized Views need to be refreshed when the underlying data changes. You can refresh them using this command:

REFRESH MATERIALIZED VIEW view_name;

When should you use them?

They are useful when dealing with heavy queries that don’t change frequently, such as for reporting or dashboard data.

Can you modify a Materialized View?

You can rename or drop a Materialized View, but to modify the query that created it, you’ll need to create a new one.

Conclusion

Materialized Views in PostgreSQL are perfect for improving query efficiency. For more advanced examples and operations, check out the full guide.