MySQLで、ランダムな文字列を挿入するだけのプロシージャ ref: https://qiita.com/kentatogashi/items/6c24a5460bb7f3f9a930

file0.txt

CREATE TABLE `test` (id INT(11) NOT NULL AUTO_INCREMENT, string VARCHAR(32), created_date TIMESTAMP, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

file1.txt

DELIMITER //
CREATE PROCEDURE f(n INT)
BEGIN
    DECLARE i int DEFAULT 0;
    WHILE i < n DO
        INSERT INTO `test` (`string`) SELECT MD5(RAND());
        SET i = i + 1;
    END WHILE;
END //
DELIMITER ;

file2.txt

CALL f(1000);

インデックスをあり、なしの際の速度検証

MariaDB [dev]> SELECT * FROM test WHERE string = '4001b73c63742787c4f45ed89cb4b3f7';
+----+----------------------------------+---------------------+
| id | string                           | created_date        |
+----+----------------------------------+---------------------+
|  1 | 4001b73c63742787c4f45ed89cb4b3f7 | 2018-07-24 10:32:35 |
+----+----------------------------------+---------------------+
1 row in set (0.07 sec)

MariaDB [dev]> ALTER TABLE `test` ADD INDEX index_string(string);
Query OK, 0 rows affected (1.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

MariaDB [dev]> SELECT * FROM test WHERE string = '4001b73c63742787c4f45ed89cb4b3f7';
+----+----------------------------------+---------------------+
| id | string                           | created_date        |
+----+----------------------------------+---------------------+
|  1 | 4001b73c63742787c4f45ed89cb4b3f7 | 2018-07-24 10:32:35 |
+----+----------------------------------+---------------------+
1 row in set (0.00 sec)