How PostgreSQL Handles Table Bloat: Autovacuum, VACUUM, and VACUUM FULL Explained

PostgreSQL does not immediately remove old row versions after updates or deletions, instead relying on MVCC, which can cause tables to accumulate dead tuples and consume excess disk space. Three mechanisms address this bloat: Autovacuum runs automatically in the background to mark dead tuple space as reusable without locking the table, while manual VACUUM does the same on demand. VACUUM FULL goes further by physically rebuilding the table with only live rows and returning unused space to the OS, but requires an exclusive lock that blocks all concurrent access. A demonstration using a 2-million-row table showed that deleting 1.8 million rows left the physical table size unchanged at 1116 MB until a vacuum operation ran. This highlights that reclaiming actual disk space in PostgreSQL requires deliberate use of the appropriate vacuum strategy depending on downtime tolerance and storage needs.