InnoDB がデータを保存する仕組み

CREATE TABLE orders (
    id          INT PRIMARY KEY AUTO_INCREMENT,
    customer_id INT NOT NULL,
    amount      DECIMAL(10,2) NOT NULL,
    created_at  DATETIME NOT NULL
);

CREATE INDEX idx_customer ON orders (customer_id);

-- This query uses idx_customer, then does a row lookup for each match
SELECT amount FROM orders WHERE customer_id = 42;

-- Check buffer pool size
SHOW VARIABLES LIKE 'innodb_buffer_pool_size';

-- Check hit rate (should be > 99% on a healthy server)
SHOW STATUS LIKE 'Innodb_buffer_pool_read%';
-- Innodb_buffer_pool_reads: pages read from disk
-- Innodb_buffer_pool_read_requests: total page read requests
-- Hit rate = 1 - (reads / read_requests)