Interview Q&A / PostgreSQL
PostgreSQL interview questions
Indexes, EXPLAIN, transactions and isolation, JSONB and the Postgres specifics backend interviews probe.
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- What do VACUUM and autovacuum do in PostgreSQL?
Because of MVCC, updates and deletes leave dead row versions behind. VACUUM marks that space as reusable, updates the visibility map and freezes old transaction IDs so they cannot wrap around. Autovacuum is a background process that runs VACUUM and ANALYZE automatically when enough rows have changed.
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