Revert "Revert "(LDAP) respect DB limits of arguments in an IN statement""

apps/user_ldap/lib/Mapping/AbstractMapping.php

@@ -190,18 +190,30 @@ public function getNameByDN($fdn) {
 	}
 
 	public function getListOfIdsByDn(array $fdns): array {
+		$fdnsSlice = count($fdns) > 1000 ? array_slice($fdns, 0, 1000) : $fdns;
 		$qb = $this->dbc->getQueryBuilder();
 		$qb->select('owncloud_name', 'ldap_dn')
 			->from($this->getTableName(false))
-			->where($qb->expr()->in('ldap_dn', $qb->createNamedParameter($fdns, QueryBuilder::PARAM_STR_ARRAY)));
-		$stmt = $qb->execute();
+			->where($qb->expr()->in('ldap_dn', $qb->createNamedParameter($fdnsSlice, QueryBuilder::PARAM_STR_ARRAY)));
+
+		$slice = 1;
+		while (isset($fdnsSlice[999])) {
+			// Oracle does not allow more than 1000 values in the IN list,
+			// but allows slicing
+			$fdnsSlice = array_slice($fdns, 1000 * $slice, 1000);
+			if (!empty($fdnsSlice)) {
+				$qb->orWhere($qb->expr()->in('ldap_dn', $qb->createNamedParameter($fdnsSlice, QueryBuilder::PARAM_STR_ARRAY)));
+			}
+			$slice++;
+		}
 
-		$results = $stmt->fetchAll(\Doctrine\DBAL\FetchMode::ASSOCIATIVE);
-		foreach ($results as $key => $entry) {
-			unset($results[$key]);
+		$stmt = $qb->execute();
+		$results = [];
+		while ($entry = $stmt->fetch(\Doctrine\DBAL\FetchMode::ASSOCIATIVE)) {
 			$results[$entry['ldap_dn']] = $entry['owncloud_name'];
 			$this->cache[$entry['ldap_dn']] = $entry['owncloud_name'];
 		}
+		$stmt->closeCursor();
 
 		return $results;
 	}

apps/user_ldap/tests/Mapping/AbstractMappingTest.php

@@ -281,4 +281,23 @@ public function testList() {
 		$results = $mapper->getList(1, 1);
 		$this->assertSame(1, count($results));
 	}
+
+	public function testGetListOfIdsByDn() {
+		/** @var AbstractMapping $mapper */
+		list($mapper,) = $this->initTest();
+
+		$listOfDNs = [];
+		for ($i = 0; $i < 65640; $i++) {
+			// Postgres has a limit of 65535 values in a single IN list
+			$name = 'as_' . $i;
+			$dn = 'uid=' . $name . ',dc=example,dc=org';
+			$listOfDNs[] = $dn;
+			if ($i % 20 === 0) {
+				$mapper->map($dn, $name, 'fake-uuid-' . $i);
+			}
+		}
+
+		$result = $mapper->getListOfIdsByDn($listOfDNs);
+		$this->assertSame(65640 / 20, count($result));
+	}
 }