PostgreSQL – MATERIALIZED VIEWS

A materialized view is a database object that stores the result of a query and allows you to access that result like a table. Unlike regular views, which are essentially saved queries that are executed every time they are accessed, materialized views store the data from the query and are particularly useful for improving query performance in scenarios where the underlying data changes infrequently compared to the frequency of query execution.

Here’s an overview of materialized views in PostgreSQL:

Creating a Materialized View

To create a materialized view, you use the CREATE MATERIALIZED VIEW statement. You provide the view’s name, the columns it should have (if not inferred from the query), and the query itself.

CREATE MATERIALIZED VIEW mv_name AS 
SELECT column1, column2, ... 
FROM source_table 
WHERE condition;

Refreshing Materialized Views

Materialized views do not automatically update when the underlying data changes. You need to explicitly refresh the materialized view to update its data. There are different ways to refresh a materialized view:

REFRESH MATERIALIZED VIEW mv_name;--Refreshes the materialized view without locking the view.

REFRESH MATERIALIZED VIEW CONCURRENTLY mv_name;

Above sql refreshes the materialized view while allowing other transactions to access it simultaneously. However, this option is not always available, as it depends on the complexity of the query and its dependencies.

Querying Materialized Views

Once a materialized view is created and refreshed, you can query it just like you would query a regular table.

SELECT * FROM mv_name WHERE condition;

Benefits of Materialized Views:

Query Performance

Materialized views can significantly improve query performance for complex or frequently executed queries. Since the data is precomputed and stored, query execution times can be much faster compared to running the original query on the fly.

Reduced Load

Materialized views can help reduce the load on your main database tables by precomputing and storing aggregated or derived data.

Limitations:

Data Staleness

Materialized views need to be manually refreshed, so there can be a delay between changes in the underlying data and updates to the materialized view.

Maintenance

Materialized views consume storage space and require maintenance, including regular refreshing to keep the data up-to-date.

Concurrency

Refreshing a materialized view can lock the view temporarily, which might impact concurrent access.

Complexity

Materialized views work best for queries that are relatively stable and not too complex. Highly dynamic or frequently changing data might not be suitable for materialized views.

Materialized views are a powerful tool for optimizing query performance in PostgreSQL, particularly for scenarios where the trade-off between data freshness and query performance is acceptable. However, their use requires careful consideration of the data update frequency and query patterns.