1 files changed, 78 insertions, 0 deletions
diff --git a/core/modules/mysqli/mysqli.install b/core/modules/mysqli/mysqli.install
new file mode 100644
index 000000000000..7f1147d63adb
--- /dev/null
+++ b/core/modules/mysqli/mysqli.install
@@ -0,0 +1,78 @@
+<?php
+
+/**
+ * @file
+ * Install, update and uninstall functions for the mysqli module.
+ */
+
+use Drupal\Core\Database\Database;
+use Drupal\Core\Extension\Requirement\RequirementSeverity;
+use Drupal\Core\Render\Markup;
+
+/**
+ * Implements hook_requirements().
+ */
+function mysqli_requirements($phase): array {
+  $requirements = [];
+
+  if ($phase === 'runtime') {
+    // Test with MySql databases.
+    if (Database::isActiveConnection()) {
+      $connection = Database::getConnection();
+      // Only show requirements when MySQLi is the default database connection.
+      if (!($connection->driver() === 'mysqli' && $connection->getProvider() === 'mysqli')) {
+        return [];
+      }
+
+      $query = $connection->isMariaDb() ? 'SELECT @@SESSION.tx_isolation' : 'SELECT @@SESSION.transaction_isolation';
+
+      $isolation_level = $connection->query($query)->fetchField();
+
+      $tables_missing_primary_key = [];
+      $tables = $connection->schema()->findTables('%');
+      foreach ($tables as $table) {
+        $primary_key_column = Database::getConnection()->query("SHOW KEYS FROM {" . $table . "} WHERE Key_name = 'PRIMARY'")->fetchAllAssoc('Column_name');
+        if (empty($primary_key_column)) {
+          $tables_missing_primary_key[] = $table;
+        }
+      }
+
+      $description = [];
+      if ($isolation_level == 'READ-COMMITTED') {
+        if (empty($tables_missing_primary_key)) {
+          $severity_level = RequirementSeverity::OK;
+        }
+        else {
+          $severity_level = RequirementSeverity::Error;
+        }
+      }
+      else {
+        if ($isolation_level == 'REPEATABLE-READ') {
+          $severity_level = RequirementSeverity::Warning;
+        }
+        else {
+          $severity_level = RequirementSeverity::Error;
+          $description[] = t('This is not supported by Drupal.');
+        }
+        $description[] = t('The recommended level for Drupal is "READ COMMITTED".');
+      }
+
+      if (!empty($tables_missing_primary_key)) {
+        $description[] = t('For this to work correctly, all tables must have a primary key. The following table(s) do not have a primary key: @tables.', ['@tables' => implode(', ', $tables_missing_primary_key)]);
+      }
+
+      $description[] = t('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',
+      ]);
+
+      $requirements['mysql_transaction_level'] = [
+        'title' => t('Transaction isolation level'),
+        'severity' => $severity_level,
+        'value' => $isolation_level,
+        'description' => Markup::create(implode(' ', $description)),
+      ];
+    }
+  }
+
+  return $requirements;
+}