Functions and Triggers

Part of the PostgreSQL course

Every table in your schema has an updated_at column, and every one of them is wrong. Not always, just on the code paths where somebody forgot to set it: the admin script, the data fix you ran by hand, the third service that writes to the same table. The column is supposed to be a fact about the row, and instead it is a promise that every writer has to remember to keep. Postgres offers a way out.

A function is a named piece of logic you can call from SQL, like any built-in. A trigger is a function that Postgres runs automatically whenever a row is inserted, updated or deleted. Used precisely, they make certain mistakes impossible. Used loosely, they hide behaviour in a place nobody thinks to look. This lesson covers both halves of that. ...