shrink ldap_dn column to 4000

Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>

apps/user_ldap/lib/Migration/Version1141Date20220323143801.php

@@ -0,0 +1,117 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright Copyright (c) 2022 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\User_LDAP\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IDBConnection;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+class Version1141Date20220323143801 extends SimpleMigrationStep {
+
+	private IDBConnection $dbc;
+
+	public function __construct(IDBConnection $dbc) {
+		$this->dbc = $dbc;
+	}
+
+	/**
+	 * @param IOutput $output
+	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 */
+	public function preSchemaChange(IOutput $output, Closure $schemaClosure, array $options): void {
+		foreach (['ldap_user_mapping', 'ldap_group_mapping'] as $tableName) {
+			$dnsTooLong = [];
+			$lengthExpr = $this->dbc->getDatabasePlatform()->getLengthExpression('ldap_dn');
+
+			$qb = $this->dbc->getQueryBuilder();
+			$qb->select('ldap_dn')
+				->from($tableName)
+				->where($qb->expr()->gt($qb->createFunction($lengthExpr), '255', IQueryBuilder::PARAM_INT));
+
+			$result = $qb->executeQuery();
+			while(($dn = $result->fetchOne()) !== false) {
+				if(mb_strlen($dn) > 4000) {
+					$dnsTooLong[] = $dn;
+				}
+			}
+			$result->closeCursor();
+			$this->shortenDNs($dnsTooLong, $tableName);
+		}
+	}
+
+	protected function shortenDNs(array $dns, string $table): void {
+		$qb = $this->dbc->getQueryBuilder();
+		$qb->update($table)
+			->set('ldap_dn', $qb->createParameter('shortenedDn'))
+			->where($qb->expr()->eq('ldap_dn', $qb->createParameter('originalDn')));
+
+		$pageSize = 1000;
+		$page = 0;
+		do {
+			$subset = array_slice($dns, $page * $pageSize, $pageSize);
+			try {
+				$this->dbc->beginTransaction();
+				foreach ($subset as $dn) {
+					$shortenedDN = mb_substr($dn, 0, 4000);
+					$qb->setParameter('shortenedDn', $shortenedDN);
+					$qb->setParameter('originalDn', $dn);
+					$qb->executeStatement();
+				}
+				$this->dbc->commit();
+			} catch (\Throwable $t) {
+				$this->dbc->rollBack();
+				throw $t;
+			}
+			$page++;
+		} while (count($subset) === $pageSize);
+	}
+
+	/**
+	 * @param IOutput $output
+	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return null|ISchemaWrapper
+	 */
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+
+		foreach (['ldap_user_mapping', 'ldap_group_mapping'] as $tableName) {
+			$table = $schema->getTable($tableName);
+			$column = $table->getColumn('ldap_dn');
+			if ($column->getLength() > 4000) {
+				$column->setLength(4000);
+			}
+		}
+
+		return $schema;
+	}
+}