Q22. What does VACUUM do?
VACUUM makes space from dead row versions reusable and supports transaction ID maintenance. Autovacuum normally performs routine maintenance; VACUUM FULL rewrites the table and takes stronger locks.
Interview tip: explain the core behavior, then mention one operational trade-off or edge case.
Note
Interview approach: define the concept, explain when you use it, and mention one limitation or production consideration.
Concept example
-- Demonstrate the concept with a small query or schema example
SELECT current_database();💡 This short query illustrates the PostgreSQL environment used during examples. In an interview, adapt the example to the specific concept and explain the underlying behavior.
Key Takeaways
- Give a concise definition.
- Explain a real-world use case.
- Mention one trade-off or safety consideration.
Knowledge Check
What is one purpose of VACUUM?