MVCC, VACUUM and Autovacuum: Dead Tuples, Bloat, HOT Updates and Transaction ID Wraparound
In PostgreSQL an UPDATE doesn't change a row in place but writes a new version; VACUUM removes the old one but doesn't shrink the file, it makes the space reusable. A single UPDATE that doubles a 40,000-row table, the lock of VACUUM FULL that stops even reads, 100% HOT updates with fillfactor 80, per-table autovacuum thresholds, an open transaction stopping VACUUM, and freezing against transaction ID wraparound.
14 Nov 2026
·
12 min
·
3
