This chapter introduces you to transactions, a fundamental part of every enterprise-level database system. PostgreSQL has very rich and standard-compliant transaction machinery that allows users to exactly define transaction properties, including nested transactions.

PostgreSQL relies heavily on transactions to keep data consistent across concurrent connections and parallel activities, and thanks to Write-Ahead Logs (WALs), PostgreSQL does its best to keep the data safe and reliable. Moreover, PostgreSQL implements Multi-Version Concurrency Control (MVCC), a way to maintain high concurrency between transactions.

The chapter can be split into two parts: the first one is more practical and provides concrete examples of what transactions are, how to use them, and how to understand MVCC. The second part is much more theoretical and explains...