Foreign Keys are Not Free
PostgreSQL is a pretty good database, and I enjoy working with it. However, there is an implementation detail that not everyone knows about, which can drastically affect table performance. What is this mysterious feature? I am, of course, referring to foreign keys.
Foreign keys are normally a part of good database design, and for good reason. They inform about entity relationships, and they verify, enforce, and maintain those relationships. Yet all of this comes at a cost that might surprise you.