PostgreSQL 9.4 Vol6

PostgreSQL is an object-relational database management system (ORDBMS) developed at the University of California at Berkeley Computer Science Department.

This comprehensive reference manual consists of 6 books. This is Volume 6 with the main part "Internals".
To keep it consistent with the digital PostgreSQL manual, the references and page numbers cover all volumes as it were one. Therefore please note that you probably want to have all volumes.