mysql.install

<?php


/**
 * @file
 * Install, update and uninstall functions for the mysql module.
 */
use Drupal\Core\Database\Database;

/**
 * Implements hook_requirements().
 */
function mysql_requirements($phase) {
    $requirements = [];
    if ($phase === 'runtime') {
        // Test with MySql databases.
        if (Database::isActiveConnection()) {
            $connection = Database::getConnection();
            // Only show requirements when MySQL is the default database connection.
            if (!($connection->driver() === 'mysql' && $connection->getProvider() === 'mysql')) {
                return [];
            }
            $query = 'SELECT @@SESSION.tx_isolation';
            // The database variable "tx_isolation" has been removed in MySQL v8.0.3 and
            // has been replaced by "transaction_isolation".
            // @see https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_tx_isolation
            // @see https://dev.mysql.com/doc/refman/8.0/en/added-deprecated-removed.html
            if (!$connection->isMariaDb() && version_compare($connection->version(), '8.0.2-AnyName', '>')) {
                $query = 'SELECT @@SESSION.transaction_isolation';
            }
            $isolation_level = $connection->query($query)
                ->fetchField();
            $requirements['mysql_transaction_level'] = [
                'title' => t('Database Isolation Level'),
                'severity' => $isolation_level === 'READ-COMMITTED' ? REQUIREMENT_OK : REQUIREMENT_WARNING,
                'value' => $isolation_level,
                'description' => t('For the best performance and to minimize locking issues, the READ-COMMITTED transaction isolation level is recommended. See the <a href=":performance_doc">setting MySQL transaction isolation level</a> page for more information.', [
                    ':performance_doc' => 'https://www.drupal.org/docs/system-requirements/setting-the-mysql-transaction-isolation-level',
                ]),
            ];
        }
    }
    return $requirements;
}