Mastering PostgreSQL 12 - Third Edition

Careless connection management

In PostgreSQL, every database connection is a separate process. All of those processes are synchronized using shared memory (technically, in most cases, it is mapped memory, but for this example, this makes no difference). This shared memory contains the I/O cache, the list of active database connections, locks, and other vital things that make the system function properly.

When a connection is closed, it will remove all the relevant entries from the shared memory and leave the system in a sane state. However, what happens when a database connection simply crashes, for whatever reason?

The postmaster (the main process) will detect that one of the child processes is missing. Then, all of the other connections ...