What Is TOAST (and Why It Isn’t Enough for Data Compression in Postgres)

TOAST (The Oversized Attribute Storage Technique) is a mechanism used by PostgreSQL to efficiently store and manage large values within the structural confines of a page, but it's not effective for optimizing database storage use in modern applications. TOAST uses compression as one of its techniques, but its primary role isn't to serve as a traditional data compression mechanism. Instead, it aims to reduce storage space by compressing specific large values. However, accessing TOASTed data can add overhead, and the lack of a high-level mechanism for dictating compression policies is a significant limitation. To overcome these limitations, PostgreSQL users have a better alternative in TimescaleDB, which adds columnar compression functionality to PostgreSQL, allowing for up to 10x reduction in database size through defined time-based compression policies.