Wrong DB table example?

[zraly]

In docs, there is this DB table example:

CREATE TABLE `messages` (
    `id` varchar(191) NOT NULL,
    `locale` char(5) NOT NULL,
    `message` varchar(191) NOT NULL,
    UNIQUE KEY `id` (`id`),
    KEY `locale` (`locale`),
    KEY `message` (`message`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

But maybe the UNIQUE KEY should be multi-column (id, locale)? This example would work for only one language.

Also, why the varchars are set to exactly 191 chars?

[aleswita]

You are right, UNIQUE key must be over id-locale, but it is possible without any unique key. And no idea, why varchar set for 191 characters.

How the table will look, it is only on you.

[darkWolf-PR]

@zraly Hi, varchar 191 is max that u can use when adding key on that column in UTF8MB4 table, at least in some versions of MySQL or MariaDB database, so it´s because of compatibility. http://mysql.rjweb.org/doc.php/limits#767_limit_in_innodb_indexes