MySQL testing large tables

loop_insert.sql

-- CREATE TABLE IF NOT EXISTS balances
-- (
--     address VARCHAR(40) NOT NULL,
--     timestamp BIGINT UNSIGNED NOT NULL,
--     balance BIGINT UNSIGNED NOT NULL,
--     PRIMARY KEY(address, timestamp)
-- );
-- 
-- SELECT balance FROM balances WHERE address=%s AND timestamp<%s ORDER BY timestamp DESC LIMIT 1;

DROP PROCEDURE IF EXISTS loop_insert;
CREATE PROCEDURE loop_insert()
BEGIN
  DECLARE int_val INT DEFAULT 0;
  test_loop : LOOP
      IF (int_val = 1000000) THEN
      LEAVE test_loop;
    END IF;
   INSERT INTO `balances`(`address`, `timestamp`, `balance`) VALUES
   ((int_val % 20), ROUND(int_val / 3), ROUND(RAND() * 100000));
    SET int_val = int_val +1;
  END LOOP; 
END;
call loop_insert;