A intensive exploration of transactional integrity without locking overhead. This chapter covers the hidden system columns (xmin, xmax), snapshot isolation, and how PostgreSQL resolves row visibility. We will examine the physical bloat caused by MVCC and the inner workings of the VACUUM and autovacuum processes to reclaim space and prevent transaction ID wraparound.

Outside Reading

• Official Docs: Chapter 13: Concurrency Control. (Deep dive into Transaction Isolation levels).
• Official Docs: Chapter 25.1: Routine Vacuuming. (The mechanics of transaction ID wraparound).
• Whitepaper: Concurrency Control in Distributed Database Systems (Philip Bernstein, 1981).
• GitHub Source: src/include/access/htup_details.h. Have students map out the physical bytes of the HeapTupleHeaderData struct (xmin, xmax, etc.).