pg_ivm: Limitations and Alternatives

What is pg_ivm?

In PostgreSQL, materialized views are a powerful tool for optimizing query performance by precomputing and storing the results of complex queries. However, ensuring these views remain up-to-date with changing data can pose a significant challenge, especially in dynamic environments where data changes frequently.

Enter Incremental View Maintenance (IVM), a concept offered by the pg_ivm module for PostgreSQL. Unlike traditional methods that refresh materialized views by recomputing their contents from scratch, IVM computes and applies only incremental changes.

pg_ivm Limitations

While pg_ivm is a promising solution for incremental materialized view maintenance in PostgreSQL deployments, it comes with notable limitations.

One of its most significant drawbacks is its stability. It is not recommended for production deployments, where reliability and robustness are paramount.

Another area of concern lies in the level of operator support offered by pg_ivm. pg_ivm provides limited support for PostgreSQL operators, notably missing functionalities such as OUTER JOINs and ORDER BY clauses. This severely restricts the scope of queries that can be efficiently handled by pg_ivm.

Furthermore, pg_ivm can only be utilized in self-managed PostgreSQL setups as it requires the installation of a PostgreSQL extension. This prevents organizations operating within managed database environments from using pg_ivm.

Finally, pg_ivm maintains a consistent state by blocking writes until the materialized view update is complete. While this approach ensures data integrity, it may impact write performance, particularly in high-throughput environments where minimizing latency is critical.

pg_ivm vs Epsio

Like pg_ivm, Epsio allows incrementally maintaining materialized views in a PostgreSQL deployment. However, they have a few key differences:

* Epsio is production-ready.

* Epsio supports most commonly used PostgreSQL operators (JOIN, CTEs, GROUP BY, etc.)

* Epsio supports both managed and self-managed deployments of PostgreSQL.

* Epsio processes data post-commit and thereby never effects write performance.

You can find Epsio’s full docs here.