عرض عملي: معاملة خاملة تعطّل vacuum

خطوة بخطوة

1. Create a hot table stock_log and a loop that updates rows continuously; show baseline size and n_dead_tup.
2. In another session run BEGIN; SELECT count(*) FROM stock_log; and leave it open.
3. Run VACUUM (VERBOSE) stock_log; it reports dead rows "not yet removable".
4. Planned mistake: disable autovacuum to "fix" growth; bloat gets worse. Fix: re-enable it.
5. Terminate the idle session (or set idle_in_transaction_session_timeout) and vacuum again; dead tuples drop.
6. Note table size stays large (reusable space, not returned to the OS).

Prepares MID-014-LAB1.

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