Cost model

Learn cost-based planning.

The cost model computes the CPU and IO cost of each plan step as a number. The plan with the lowest total cost wins.

-- EXPLAIN çıktısı:
-- Seq Scan on orders (cost=0.00..34.00 rows=1000)

Cost is the sum of CPU and IO.

Cost model — details

Cost is an estimated resource use, not real time. EXPLAIN ANALYZE shows both estimate and actual time; it reveals the gap between plan and reality.

Run EXPLAIN ANALYZE on all rows of orders to compare estimate and actual time.

Show example solution

EXPLAIN ANALYZE SELECT * FROM orders;

See actual time

EXPLAIN ____ SELECT * FROM orders;

Show answer

EXPLAIN ANALYZE SELECT * FROM orders;