What do developers mean when they say Postgres is "extensible"? They're referring to low-level APIs which can change the core functionality of the database. In this post, we will explore a secret - meaning undocumented - feature called hooks which allow developers to not only add features to Postgres, but modify the way that queries are executed and data is parsed.
Hooks are used by some of the most popular projects in the Postgres ecosystem, including Timescale, pg_stat_statements, and Supabase. To give you ideas of what can be built, we will see how each of these projects uses specific hooks. At the end of this post, we provide a Makefile, some C code, and compilation instructions to get started customizing Postgres on your own.