`add-trigger`

warning

CREATE TRIGGER

Why it's unsafe

CREATE TRIGGER takes a SHARE ROW EXCLUSIVE lock (blocking writes and other DDL, though not reads) and changes behavior for every subsequent write to the table.

Safe rewrite

Create the trigger during a low-traffic window; its lock conflicts with concurrent writes on the table.

Example

Try it in the playground →

Unsafe

CREATE TRIGGER trg_audit AFTER INSERT ON users FOR EACH ROW EXECUTE FUNCTION audit();