Difference between terminating and cancelling a process

Question

What's the difference between functions: pg_cancel_backend(pid int) and pg_terminate_backend(pid int)? For me they work pretty the same.

Answer 1

pg_cancel_backend() cancels the running query while pg_terminate_backend() terminates the entire process and thus the database connection.

When a program creates a database connection and sends queries, you can cancel one query without destroying the connection and stopping the other queries. If you destroy the entire connection, everything will be stopped.