Comparing results

Compare before and after plans.

Compare results

In the last step you compare estimated and actual time with EXPLAIN ANALYZE. You should see the indexed query truly speed up.

EXPLAIN ANALYZE SELECT * FROM orders
WHERE customer_id = 5;

EXPLAIN ANALYZE gives actual time.

All columns are selected from orders. WHERE keeps only the rows where customer_id = 5 holds.

Compare results — details

EXPLAIN gives only an estimate; EXPLAIN ANALYZE runs the query and measures actual time. The gap shows how fresh the statistics are and how accurate the plan is.

Exercise Compare results

Run EXPLAIN ANALYZE SELECT * FROM orders WHERE customer_id = 5 to see the actual time.

Show example solution

CREATE TABLE orders (
  id SERIAL PRIMARY KEY,
  customer_id INT,
  amount NUMERIC,
  created_at TIMESTAMP
);
-- read plan
EXPLAIN SELECT * FROM orders WHERE customer_id = 5;
-- add index
CREATE INDEX idx_orders_customer ON orders (customer_id) INCLUDE (amount);
-- sargable rewrite
SELECT * FROM orders WHERE created_at >= '2026-01-01' AND created_at < '2026-01-02';
-- compare
EXPLAIN ANALYZE SELECT * FROM orders WHERE customer_id = 5;

Test yourself

Compare command

EXPLAIN ____ SELECT * FROM orders WHERE customer_id = 5;

Show answer

EXPLAIN ANALYZE SELECT * FROM orders WHERE customer_id = 5;

What does EXPLAIN ANALYZE measure?
- The actual execution time
- The table size
- The column name
- The user
Show answer

The actual execution time — EXPLAIN ANALYZE measures actual time.
Comparing results: match the terms

EXPLAIN

plan
ANALYZE

actual
actual

measured
compare

compare

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