Transactions, MVCC, WALs, and Checkpoints

This chapter introduces you to transactions, a fundamental part of every enterprise-level database system. Transactions are a way for a database to manage multiple operations, making them as though they were a single atomic operation. PostgreSQL has very rich and standard-compliant transaction machinery that allows users to specifically 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 among transactions.

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