Merge pull request #16498 from nextcloud/feature/noid/room_metadata

Allow calendar resources/rooms to provide metadata
2019-08-05 14:52:45 +02:00 · 2019-08-05 14:52:45 +02:00 · 1d72073e34
parent 7b0e11f709 3e5946bd0d
commit 1d72073e34
18 changed files with 1178 additions and 1021 deletions
--- a/apps/dav/appinfo/info.xml
+++ b/apps/dav/appinfo/info.xml
@ -5,7 +5,7 @@
 	<name>WebDAV</name>
 	<summary>WebDAV endpoint</summary>
 	<description>WebDAV endpoint</description>
-	<version>1.10.0</version>
+	<version>1.11.0</version>
 	<licence>agpl</licence>
 	<author>owncloud.org</author>
 	<namespace>DAV</namespace>
--- a/apps/dav/composer/composer/autoload_classmap.php
+++ b/apps/dav/composer/composer/autoload_classmap.php
@ -179,6 +179,7 @@ return array(
    'OCA\\DAV\\Migration\\Version1008Date20181105110300' => $baseDir . '/../lib/Migration/Version1008Date20181105110300.php',
    'OCA\\DAV\\Migration\\Version1008Date20181105112049' => $baseDir . '/../lib/Migration/Version1008Date20181105112049.php',
    'OCA\\DAV\\Migration\\Version1008Date20181114084440' => $baseDir . '/../lib/Migration/Version1008Date20181114084440.php',
+    'OCA\\DAV\\Migration\\Version1011Date20190725113607' => $baseDir . '/../lib/Migration/Version1011Date20190725113607.php',
    'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningNode' => $baseDir . '/../lib/Provisioning/Apple/AppleProvisioningNode.php',
    'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningPlugin' => $baseDir . '/../lib/Provisioning/Apple/AppleProvisioningPlugin.php',
    'OCA\\DAV\\RootCollection' => $baseDir . '/../lib/RootCollection.php',
--- a/apps/dav/composer/composer/autoload_static.php
+++ b/apps/dav/composer/composer/autoload_static.php
@ -194,6 +194,7 @@ class ComposerStaticInitDAV
        'OCA\\DAV\\Migration\\Version1008Date20181105110300' => __DIR__ . '/..' . '/../lib/Migration/Version1008Date20181105110300.php',
        'OCA\\DAV\\Migration\\Version1008Date20181105112049' => __DIR__ . '/..' . '/../lib/Migration/Version1008Date20181105112049.php',
        'OCA\\DAV\\Migration\\Version1008Date20181114084440' => __DIR__ . '/..' . '/../lib/Migration/Version1008Date20181114084440.php',
+        'OCA\\DAV\\Migration\\Version1011Date20190725113607' => __DIR__ . '/..' . '/../lib/Migration/Version1011Date20190725113607.php',
        'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningNode' => __DIR__ . '/..' . '/../lib/Provisioning/Apple/AppleProvisioningNode.php',
        'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningPlugin' => __DIR__ . '/..' . '/../lib/Provisioning/Apple/AppleProvisioningPlugin.php',
        'OCA\\DAV\\RootCollection' => __DIR__ . '/..' . '/../lib/RootCollection.php',
--- a/apps/dav/lib/BackgroundJob/UpdateCalendarResourcesRoomsBackgroundJob.php
+++ b/apps/dav/lib/BackgroundJob/UpdateCalendarResourcesRoomsBackgroundJob.php
@ -1,6 +1,6 @@
 <?php
 /**
- * @copyright 2018, Georg Ehrke <oc.list@georgehrke.com>
+ * @copyright 2019, Georg Ehrke <oc.list@georgehrke.com>
 *
 * @author Georg Ehrke <oc.list@georgehrke.com>
 *
@ -26,6 +26,8 @@ namespace OCA\DAV\BackgroundJob;
 use OC\BackgroundJob\TimedJob;
 use OCA\DAV\CalDAV\CalDavBackend;
 use OCP\Calendar\BackendTemporarilyUnavailableException;
+use OCP\Calendar\IMetadataProvider;
+use OCP\Calendar\Resource\IBackend as IResourceBackend;
 use OCP\Calendar\Resource\IManager as IResourceManager;
 use OCP\Calendar\Resource\IResource;
 use OCP\Calendar\Room\IManager as IRoomManager;
@ -41,23 +43,11 @@ class UpdateCalendarResourcesRoomsBackgroundJob extends TimedJob {
 	private $roomManager;

 	/** @var IDBConnection */
-	private $db;
+	private $dbConnection;

 	/** @var CalDavBackend */
 	private $calDavBackend;

-	/** @var string */
-	private $resourceDbTable;
-
-	/** @var string */
-	private $resourcePrincipalUri;
-
-	/** @var string */
-	private $roomDbTable;
-
-	/** @var string */
-	private $roomPrincipalUri;
-
 	/**
 	 * UpdateCalendarResourcesRoomsBackgroundJob constructor.
 	 *
@ -66,16 +56,14 @@ class UpdateCalendarResourcesRoomsBackgroundJob extends TimedJob {
 	 * @param IDBConnection $dbConnection
 	 * @param CalDavBackend $calDavBackend
 	 */
-	public function __construct(IResourceManager $resourceManager, IRoomManager $roomManager,
-								IDBConnection $dbConnection, CalDavBackend $calDavBackend) {
+	public function __construct(IResourceManager $resourceManager,
+								IRoomManager $roomManager,
+								IDBConnection $dbConnection,
+								CalDavBackend $calDavBackend) {
 		$this->resourceManager = $resourceManager;
 		$this->roomManager = $roomManager;
-		$this->db = $dbConnection;
+		$this->dbConnection = $dbConnection;
 		$this->calDavBackend = $calDavBackend;
-		$this->resourceDbTable = 'calendar_resources';
-		$this->resourcePrincipalUri = 'principals/calendar-resources';
-		$this->roomDbTable = 'calendar_rooms';
-		$this->roomPrincipalUri = 'principals/calendar-rooms';

 		// run once an hour
 		$this->setInterval(60 * 60);
@ -84,211 +72,132 @@ class UpdateCalendarResourcesRoomsBackgroundJob extends TimedJob {
 	/**
 	 * @param $argument
 	 */
-	public function run($argument) {
-		$this->runResources();
-		$this->runRooms();
+	public function run($argument):void {
+		$this->runForBackend(
+			$this->resourceManager,
+			'calendar_resources',
+			'calendar_resources_md',
+			'resource_id',
+			'principals/calendar-resources'
+		);
+		$this->runForBackend(
+			$this->roomManager,
+			'calendar_rooms',
+			'calendar_rooms_md',
+			'room_id',
+			'principals/calendar-rooms'
+		);
 	}

 	/**
-	 * run timed job for resources
-	 */
-	private function runResources() {
-		$resourceBackends = $this->resourceManager->getBackends();
-		$cachedResources = $this->getCached($this->resourceDbTable);
-		$cachedResourceIds = $this->getCachedResourceIds($cachedResources);
-
-		$remoteResourceIds = [];
-		foreach($resourceBackends as $resourceBackend) {
-			try {
-				$remoteResourceIds[$resourceBackend->getBackendIdentifier()] =
-					$resourceBackend->listAllResources();
-			} catch(BackendTemporarilyUnavailableException $ex) {
-				// If the backend is temporarily unavailable
-				// ignore this backend in this execution
-				unset($cachedResourceIds[$resourceBackend->getBackendIdentifier()]);
-			}
-		}
-
-		$sortedResources = $this->sortByNewDeletedExisting($cachedResourceIds, $remoteResourceIds);
-
-		foreach($sortedResources['new'] as $backendId => $newResources) {
-			foreach ($newResources as $newResource) {
-				$backend = $this->resourceManager->getBackend($backendId);
-				if ($backend === null) {
-					continue;
-				}
-
-				$resource = $backend->getResource($newResource);
-				$this->addToCache($this->resourceDbTable, $resource);
-			}
-		}
-		foreach($sortedResources['deleted'] as $backendId => $deletedResources) {
-			foreach ($deletedResources as $deletedResource) {
-				$this->deleteFromCache($this->resourceDbTable,
-					$this->resourcePrincipalUri, $backendId, $deletedResource);
-			}
-		}
-		foreach($sortedResources['edited'] as $backendId => $editedResources) {
-			foreach ($editedResources as $editedResource) {
-				$backend = $this->resourceManager->getBackend($backendId);
-				if ($backend === null) {
-					continue;
-				}
-
-				$resource = $backend->getResource($editedResource);
-				$this->updateCache($this->resourceDbTable, $resource);
-			}
-		}
-	}
-
-	/**
-	 * run timed job for rooms
-	 */
-	private function runRooms() {
-		$roomBackends = $this->roomManager->getBackends();
-		$cachedRooms = $this->getCached($this->roomDbTable);
-		$cachedRoomIds = $this->getCachedRoomIds($cachedRooms);
-
-		$remoteRoomIds = [];
-		foreach($roomBackends as $roomBackend) {
-			try {
-				$remoteRoomIds[$roomBackend->getBackendIdentifier()] =
-					$roomBackend->listAllRooms();
-			} catch(BackendTemporarilyUnavailableException $ex) {
-				// If the backend is temporarily unavailable
-				// ignore this backend in this execution
-				unset($cachedRoomIds[$roomBackend->getBackendIdentifier()]);
-			}
-		}
-
-		$sortedRooms = $this->sortByNewDeletedExisting($cachedRoomIds, $remoteRoomIds);
-
-		foreach($sortedRooms['new'] as $backendId => $newRooms) {
-			foreach ($newRooms as $newRoom) {
-				$backend = $this->roomManager->getBackend($backendId);
-				if ($backend === null) {
-					continue;
-				}
-
-				$resource = $backend->getRoom($newRoom);
-				$this->addToCache($this->roomDbTable, $resource);
-			}
-		}
-		foreach($sortedRooms['deleted'] as $backendId => $deletedRooms) {
-			foreach ($deletedRooms as $deletedRoom) {
-				$this->deleteFromCache($this->roomDbTable,
-					$this->roomPrincipalUri, $backendId, $deletedRoom);
-			}
-		}
-		foreach($sortedRooms['edited'] as $backendId => $editedRooms) {
-			foreach ($editedRooms as $editedRoom) {
-				$backend = $this->roomManager->getBackend($backendId);
-				if ($backend === null) {
-					continue;
-				}
-
-				$resource = $backend->getRoom($editedRoom);
-				$this->updateCache($this->roomDbTable, $resource);
-			}
-		}
-	}
-
-	/**
-	 * get cached db rows for resources / rooms
-	 * @param string $tableName
-	 * @return array
-	 */
-	private function getCached($tableName):array {
-		$query = $this->db->getQueryBuilder();
-		$query->select('*')->from($tableName);
-
-		$rows = [];
-		$stmt = $query->execute();
-		while($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
-			$rows[] = $row;
-		}
-
-		return $rows;
-	}
-
-	/**
-	 * @param array $cachedResources
-	 * @return array
-	 */
-	private function getCachedResourceIds(array $cachedResources):array {
-		$cachedResourceIds = [];
-		foreach ($cachedResources as $cachedResource) {
-			if (!isset($cachedResourceIds[$cachedResource['backend_id']])) {
-				$cachedResourceIds[$cachedResource['backend_id']] = [];
-			}
-
-			$cachedResourceIds[$cachedResource['backend_id']][] =
-				$cachedResource['resource_id'];
-		}
-
-		return $cachedResourceIds;
-	}
-
-	/**
-	 * @param array $cachedRooms
-	 * @return array
-	 */
-	private function getCachedRoomIds(array $cachedRooms):array {
-		$cachedRoomIds = [];
-		foreach ($cachedRooms as $cachedRoom) {
-			if (!isset($cachedRoomIds[$cachedRoom['backend_id']])) {
-				$cachedRoomIds[$cachedRoom['backend_id']] = [];
-			}
-
-			$cachedRoomIds[$cachedRoom['backend_id']][] =
-				$cachedRoom['resource_id'];
-		}
-
-		return $cachedRoomIds;
-	}
-
-	/**
-	 * sort list of ids by whether they appear only in the backend /
-	 * only in the cache / in both
+	 * Run background-job for one specific backendManager
+	 * either ResourceManager or RoomManager
 	 *
-	 * @param array $cached
-	 * @param array $remote
-	 * @return array
+	 * @param IResourceManager|IRoomManager $backendManager
+	 * @param string $dbTable
+	 * @param string $dbTableMetadata
+	 * @param string $foreignKey
+	 * @param string $principalPrefix
 	 */
-	private function sortByNewDeletedExisting(array $cached, array $remote):array {
-		$sorted = [
-			'new' => [],
-			'deleted' => [],
-			'edited' => [],
-		];
+	private function runForBackend($backendManager,
+								   string $dbTable,
+								   string $dbTableMetadata,
+								   string $foreignKey,
+								   string $principalPrefix):void {
+		$backends = $backendManager->getBackends();

-		$backendIds = array_merge(array_keys($cached), array_keys($remote));
-		foreach($backendIds as $backendId) {
-			if (!isset($cached[$backendId])) {
-				$sorted['new'][$backendId] = $remote[$backendId];
-			} elseif (!isset($remote[$backendId])) {
-				$sorted['deleted'][$backendId] = $cached[$backendId];
-			} else {
-				$sorted['new'][$backendId] = array_diff($remote[$backendId], $cached[$backendId]);
-				$sorted['deleted'][$backendId] = array_diff($cached[$backendId], $remote[$backendId]);
-				$sorted['edited'][$backendId] = array_intersect($remote[$backendId], $cached[$backendId]);
+		foreach($backends as $backend) {
+			$backendId = $backend->getBackendIdentifier();
+
+			try {
+				if ($backend instanceof IResourceBackend) {
+					$list = $backend->listAllResources();
+				} else {
+					$list = $backend->listAllRooms();
+				}
+			} catch(BackendTemporarilyUnavailableException $ex) {
+				continue;
+			}
+
+			$cachedList = $this->getAllCachedByBackend($dbTable, $backendId);
+			$newIds = array_diff($list, $cachedList);
+			$deletedIds = array_diff($cachedList, $list);
+			$editedIds = array_intersect($list, $cachedList);
+
+			foreach($newIds as $newId) {
+				try {
+					if ($backend instanceof IResourceBackend) {
+						$resource = $backend->getResource($newId);
+					} else {
+						$resource = $backend->getRoom($newId);
+					}
+
+					$metadata = [];
+					if ($resource instanceof IMetadataProvider) {
+						$metadata = $this->getAllMetadataOfBackend($resource);
+					}
+				} catch(BackendTemporarilyUnavailableException $ex) {
+					continue;
+				}
+
+				$id = $this->addToCache($dbTable, $backendId, $resource);
+				$this->addMetadataToCache($dbTableMetadata, $foreignKey, $id, $metadata);
+				// we don't create the calendar here, it is created lazily
+				// when an event is actually scheduled with this resource / room
+			}
+
+			foreach($deletedIds as $deletedId) {
+				$id = $this->getIdForBackendAndResource($dbTable, $backendId, $deletedId);
+				$this->deleteFromCache($dbTable, $id);
+				$this->deleteMetadataFromCache($dbTableMetadata, $foreignKey, $id);
+
+				$principalName = implode('-', [$backendId, $deletedId]);
+				$this->deleteCalendarDataForResource($principalPrefix, $principalName);
+			}
+
+			foreach($editedIds as $editedId) {
+				$id = $this->getIdForBackendAndResource($dbTable, $backendId, $editedId);
+
+				try {
+					if ($backend instanceof IResourceBackend) {
+						$resource = $backend->getResource($editedId);
+					} else {
+						$resource = $backend->getRoom($editedId);
+					}
+
+					$metadata = [];
+					if ($resource instanceof IMetadataProvider) {
+						$metadata = $this->getAllMetadataOfBackend($resource);
+					}
+				} catch(BackendTemporarilyUnavailableException $ex) {
+					continue;
+				}
+
+				$this->updateCache($dbTable, $id, $resource);
+
+				if ($resource instanceof IMetadataProvider) {
+					$cachedMetadata = $this->getAllMetadataOfCache($dbTableMetadata, $foreignKey, $id);
+					$this->updateMetadataCache($dbTableMetadata, $foreignKey, $id, $metadata, $cachedMetadata);
+				}
 			}
 		}
-
-		return $sorted;
 	}

 	/**
 	 * add entry to cache that exists remotely but not yet in cache
 	 *
 	 * @param string $table
+	 * @param string $backendId
 	 * @param IResource|IRoom $remote
+	 * @return int Insert id
 	 */
-	private function addToCache($table, $remote) {
-		$query = $this->db->getQueryBuilder();
+	private function addToCache(string $table,
+								string $backendId,
+								$remote):int {
+		$query = $this->dbConnection->getQueryBuilder();
 		$query->insert($table)
 			->values([
-				'backend_id' => $query->createNamedParameter($remote->getBackend()->getBackendIdentifier()),
+				'backend_id' => $query->createNamedParameter($backendId),
 				'resource_id' => $query->createNamedParameter($remote->getId()),
 				'email' => $query->createNamedParameter($remote->getEMail()),
 				'displayname' => $query->createNamedParameter($remote->getDisplayName()),
@ -298,37 +207,70 @@ class UpdateCalendarResourcesRoomsBackgroundJob extends TimedJob {
 					))
 			])
 			->execute();
+		return $query->getLastInsertId();
+	}
+
+	/**
+	 * @param string $table
+	 * @param string $foreignKey
+	 * @param int $foreignId
+	 * @param array $metadata
+	 */
+	private function addMetadataToCache(string $table,
+										string $foreignKey,
+										int $foreignId,
+										array $metadata):void {
+		foreach($metadata as $key => $value) {
+			$query = $this->dbConnection->getQueryBuilder();
+			$query->insert($table)
+				->values([
+					$foreignKey => $query->createNamedParameter($foreignId),
+					'key' => $query->createNamedParameter($key),
+					'value' => $query->createNamedParameter($value),
+				])
+				->execute();
+		}
 	}

 	/**
 	 * delete entry from cache that does not exist anymore remotely
 	 *
 	 * @param string $table
-	 * @param string $principalUri
-	 * @param string $backendId
-	 * @param string $resourceId
+	 * @param int $id
 	 */
-	private function deleteFromCache($table, $principalUri, $backendId, $resourceId) {
-		$query = $this->db->getQueryBuilder();
+	private function deleteFromCache(string $table,
+									 int $id):void {
+		$query = $this->dbConnection->getQueryBuilder();
 		$query->delete($table)
-			->where($query->expr()->eq('backend_id', $query->createNamedParameter($backendId)))
-			->andWhere($query->expr()->eq('resource_id', $query->createNamedParameter($resourceId)))
+			->where($query->expr()->eq('id', $query->createNamedParameter($id)))
 			->execute();
+	}

-		$calendar = $this->calDavBackend->getCalendarByUri($principalUri, implode('-', [$backendId, $resourceId]));
-		if ($calendar !== null) {
-			$this->calDavBackend->deleteCalendar($calendar['id']);
-		}
+	/**
+	 * @param string $table
+	 * @param string $foreignKey
+	 * @param int $id
+	 */
+	private function deleteMetadataFromCache(string $table,
+											 string $foreignKey,
+											 int $id):void {
+		$query = $this->dbConnection->getQueryBuilder();
+		$query->delete($table)
+			->where($query->expr()->eq($foreignKey, $query->createNamedParameter($id)))
+			->execute();
 	}

 	/**
 	 * update an existing entry in cache
 	 *
 	 * @param string $table
+	 * @param int $id
 	 * @param IResource|IRoom $remote
 	 */
-	private function updateCache($table, $remote) {
-		$query = $this->db->getQueryBuilder();
+	private function updateCache(string $table,
+								 int $id,
+								 $remote):void {
+		$query = $this->dbConnection->getQueryBuilder();
 		$query->update($table)
 			->set('email', $query->createNamedParameter($remote->getEMail()))
 			->set('displayname', $query->createNamedParameter($remote->getDisplayName()))
@ -336,11 +278,57 @@ class UpdateCalendarResourcesRoomsBackgroundJob extends TimedJob {
 				$this->serializeGroupRestrictions(
 					$remote->getGroupRestrictions()
 				)))
-			->where($query->expr()->eq('backend_id', $query->createNamedParameter($remote->getBackend()->getBackendIdentifier())))
-			->andWhere($query->expr()->eq('resource_id', $query->createNamedParameter($remote->getId())))
+			->where($query->expr()->eq('id', $query->createNamedParameter($id)))
 			->execute();
 	}

+	/**
+	 * @param string $dbTable
+	 * @param string $foreignKey
+	 * @param int $id
+	 * @param array $metadata
+	 * @param array $cachedMetadata
+	 */
+	private function updateMetadataCache(string $dbTable,
+										 string $foreignKey,
+										 int $id,
+										 array $metadata,
+										 array $cachedMetadata):void {
+		$newMetadata = array_diff_key($metadata, $cachedMetadata);
+		$deletedMetadata = array_diff_key($cachedMetadata, $metadata);
+
+		foreach ($newMetadata as $key => $value) {
+			$query = $this->dbConnection->getQueryBuilder();
+			$query->insert($dbTable)
+				->values([
+					$foreignKey => $query->createNamedParameter($id),
+					'key' => $query->createNamedParameter($key),
+					'value' => $query->createNamedParameter($value),
+				])
+				->execute();
+		}
+
+		foreach($deletedMetadata as $key => $value) {
+			$query = $this->dbConnection->getQueryBuilder();
+			$query->delete($dbTable)
+				->where($query->expr()->eq($foreignKey, $query->createNamedParameter($id)))
+				->andWhere($query->expr()->eq('key', $query->createNamedParameter($key)))
+				->execute();
+		}
+
+		$existingKeys = array_keys(array_intersect_key($metadata, $cachedMetadata));
+		foreach($existingKeys as $existingKey) {
+			if ($metadata[$existingKey] !== $cachedMetadata[$existingKey]) {
+				$query = $this->dbConnection->getQueryBuilder();
+				$query->update($dbTable)
+					->set('value', $query->createNamedParameter($metadata[$existingKey]))
+					->where($query->expr()->eq($foreignKey, $query->createNamedParameter($id)))
+					->andWhere($query->expr()->eq('key', $query->createNamedParameter($existingKey)))
+					->execute();
+			}
+		}
+	}
+
 	/**
 	 * serialize array of group restrictions to store them in database
 	 *
@ -350,4 +338,102 @@ class UpdateCalendarResourcesRoomsBackgroundJob extends TimedJob {
 	private function serializeGroupRestrictions(array $groups):string {
 		return \json_encode($groups);
 	}
+
+	/**
+	 * Gets all metadata of a backend
+	 *
+	 * @param IResource|IRoom $resource
+	 * @return array
+	 */
+	private function getAllMetadataOfBackend($resource):array {
+		if (!($resource instanceof IMetadataProvider)) {
+			return [];
+		}
+
+		$keys = $resource->getAllAvailableMetadataKeys();
+		$metadata = [];
+		foreach($keys as $key) {
+			$metadata[$key] = $resource->getMetadataForKey($key);
+		}
+
+		return $metadata;
+	}
+
+	/**
+	 * @param string $table
+	 * @param string $foreignKey
+	 * @param int $id
+	 * @return array
+	 */
+	private function getAllMetadataOfCache(string $table,
+										   string $foreignKey,
+										   int $id):array {
+		$query = $this->dbConnection->getQueryBuilder();
+		$query->select(['key', 'value'])
+			->from($table)
+			->where($query->expr()->eq($foreignKey, $query->createNamedParameter($id)));
+		$stmt = $query->execute();
+		$rows = $stmt->fetchAll(\PDO::FETCH_ASSOC);
+
+		$metadata = [];
+		foreach($rows as $row) {
+			$metadata[$row['key']] = $row['value'];
+		}
+
+		return $metadata;
+	}
+
+	/**
+	 * Gets all cached rooms / resources by backend
+	 *
+	 * @param $tableName
+	 * @param $backendId
+	 * @return array
+	 */
+	private function getAllCachedByBackend(string $tableName,
+										   string $backendId):array {
+		$query = $this->dbConnection->getQueryBuilder();
+		$query->select('resource_id')
+			->from($tableName)
+			->where($query->expr()->eq('backend_id', $query->createNamedParameter($backendId)));
+		$stmt = $query->execute();
+
+		return array_map(function($row) {
+			return $row['resource_id'];
+		}, $stmt->fetchAll(\PDO::FETCH_NAMED));
+	}
+
+	/**
+	 * @param $principalPrefix
+	 * @param $principalUri
+	 */
+	private function deleteCalendarDataForResource(string $principalPrefix,
+												   string $principalUri):void {
+		$calendar = $this->calDavBackend->getCalendarByUri(
+			implode('/', [$principalPrefix, $principalUri]),
+			CalDavBackend::RESOURCE_BOOKING_CALENDAR_URI);
+
+		if ($calendar !== null) {
+			$this->calDavBackend->deleteCalendar($calendar['id']);
+		}
+	}
+
+	/**
+	 * @param $table
+	 * @param $backendId
+	 * @param $resourceId
+	 * @return int
+	 */
+	private function getIdForBackendAndResource(string $table,
+												string $backendId,
+												string $resourceId):int {
+		$query = $this->dbConnection->getQueryBuilder();
+		$query->select('id')
+			->from($table)
+			->where($query->expr()->eq('backend_id', $query->createNamedParameter($backendId)))
+			->andWhere($query->expr()->eq('resource_id', $query->createNamedParameter($resourceId)));
+		$stmt = $query->execute();
+
+		return $stmt->fetch(\PDO::FETCH_NAMED)['id'];
+	}
 }
--- a/apps/dav/lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php
+++ b/apps/dav/lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php
@ -1,6 +1,6 @@
 <?php
 /**
- * @copyright 2018, Georg Ehrke <oc.list@georgehrke.com>
+ * @copyright 2019, Georg Ehrke <oc.list@georgehrke.com>
 *
 * @author Georg Ehrke <oc.list@georgehrke.com>
 *
@ -50,6 +50,12 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 	/** @var string */
 	private $dbTableName;

+	/** @var string */
+	private $dbMetaDataTableName;
+
+	/** @var string */
+	private $dbForeignKeyName;
+
 	/** @var string */
 	private $cuType;

@ -74,7 +80,9 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 		$this->groupManager = $groupManager;
 		$this->logger = $logger;
 		$this->principalPrefix = $principalPrefix;
-		$this->dbTableName = 'calendar_' . $dbPrefix;
+		$this->dbTableName = 'calendar_' . $dbPrefix . 's';
+		$this->dbMetaDataTableName = $this->dbTableName . '_md';
+		$this->dbForeignKeyName = $dbPrefix . '_id';
 		$this->cuType = $cuType;
 	}

@ -100,8 +108,31 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 				->from($this->dbTableName);
 			$stmt = $query->execute();

+			$metaDataQuery = $this->db->getQueryBuilder();
+			$metaDataQuery->select([$this->dbForeignKeyName, 'key', 'value'])
+				->from($this->dbMetaDataTableName);
+			$metaDataStmt = $metaDataQuery->execute();
+			$metaDataRows = $metaDataStmt->fetchAll(\PDO::FETCH_ASSOC);
+
+			$metaDataById = [];
+			foreach($metaDataRows as $metaDataRow) {
+				if (!isset($metaDataById[$metaDataRow[$this->dbForeignKeyName]])) {
+					$metaDataById[$metaDataRow[$this->dbForeignKeyName]] = [];
+				}
+
+				$metaDataById[$metaDataRow[$this->dbForeignKeyName]][$metaDataRow['key']] =
+					$metaDataRow['value'];
+			}
+
 			while($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
-				$principals[] = $this->rowToPrincipal($row);
+				$id = $row['id'];
+
+				if (isset($metaDataById[$id])) {
+					$principals[] = $this->rowToPrincipal($row, $metaDataById[$id]);
+				} else {
+					$principals[] = $this->rowToPrincipal($row);
+				}
+
 			}

 			$stmt->closeCursor();
@ -138,7 +169,50 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 			return null;
 		}

-		return $this->rowToPrincipal($row);
+		$metaDataQuery = $this->db->getQueryBuilder();
+		$metaDataQuery->select(['key', 'value'])
+			->from($this->dbMetaDataTableName)
+			->where($metaDataQuery->expr()->eq($this->dbForeignKeyName, $metaDataQuery->createNamedParameter($row['id'])));
+		$metaDataStmt = $metaDataQuery->execute();
+		$metaDataRows = $metaDataStmt->fetchAll(\PDO::FETCH_ASSOC);
+		$metadata = [];
+
+		foreach($metaDataRows as $metaDataRow) {
+			$metadata[$metaDataRow['key']] = $metaDataRow['value'];
+		}
+
+		return $this->rowToPrincipal($row, $metadata);
+	}
+
+	/**
+	 * @param int $id
+	 * @return array|null
+	 */
+	public function getPrincipalById($id):?array {
+		$query = $this->db->getQueryBuilder();
+		$query->select(['id', 'backend_id', 'resource_id', 'email', 'displayname'])
+			->from($this->dbTableName)
+			->where($query->expr()->eq('id', $query->createNamedParameter($id)));
+		$stmt = $query->execute();
+		$row = $stmt->fetch(\PDO::FETCH_ASSOC);
+
+		if(!$row) {
+			return null;
+		}
+
+		$metaDataQuery = $this->db->getQueryBuilder();
+		$metaDataQuery->select(['key', 'value'])
+			->from($this->dbMetaDataTableName)
+			->where($metaDataQuery->expr()->eq($this->dbForeignKeyName, $metaDataQuery->createNamedParameter($row['id'])));
+		$metaDataStmt = $metaDataQuery->execute();
+		$metaDataRows = $metaDataStmt->fetchAll(\PDO::FETCH_ASSOC);
+		$metadata = [];
+
+		foreach($metaDataRows as $metaDataRow) {
+			$metadata[$metaDataRow['key']] = $metaDataRow['value'];
+		}
+
+		return $this->rowToPrincipal($row, $metadata);
 	}

 	/**
@ -253,7 +327,15 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 					break;

 				default:
-					$results[] = [];
+					$rowsByMetadata = $this->searchPrincipalsByMetadataKey($prop, $value);
+					$filteredRows = array_filter($rowsByMetadata, function($row) use ($usersGroups) {
+						return $this->isAllowedToAccessResource($row, $usersGroups);
+					});
+
+					$results[] = array_map(function($row) {
+						return $row['uri'];
+					}, $filteredRows);
+
 					break;
 			}
 		}
@ -274,6 +356,39 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 		}
 	}

+	/**
+	 * Searches principals based on their metadata keys.
+	 * This allows to search for all principals with a specific key.
+	 * e.g.:
+	 * '{http://nextcloud.com/ns}room-building-address' => 'ABC Street 123, ...'
+	 *
+	 * @param $key
+	 * @param $value
+	 * @return array
+	 */
+	private function searchPrincipalsByMetadataKey($key, $value):array {
+		$query = $this->db->getQueryBuilder();
+		$query->select([$this->dbForeignKeyName])
+			->from($this->dbMetaDataTableName)
+			->where($query->expr()->eq('key', $query->createNamedParameter($key)))
+			->andWhere($query->expr()->iLike('value', $query->createNamedParameter('%' . $this->db->escapeLikeParameter($value) . '%')));
+		$stmt = $query->execute();
+
+		$rows = [];
+		while($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+			$id = $row[$this->dbForeignKeyName];
+
+			$principalRow = $this->getPrincipalById($id);
+			if (!$principalRow) {
+				continue;
+			}
+
+			$rows[] = $principalRow;
+		}
+
+		return $rows;
+	}
+
 	/**
 	 * @param string $uri
 	 * @param string $principalPrefix
@ -338,14 +453,18 @@ abstract class AbstractPrincipalBackend implements BackendInterface {

 	/**
 	 * convert database row to principal
+	 *
+	 * @param String[] $row
+	 * @param String[] $metadata
+	 * @return Array
 	 */
-	private function rowToPrincipal($row) {
-		return [
+	private function rowToPrincipal(array $row, array $metadata=[]):array {
+		return array_merge([
 			'uri' => $this->principalPrefix . '/' . $row['backend_id'] . '-' . $row['resource_id'],
 			'{DAV:}displayname' => $row['displayname'],
 			'{http://sabredav.org/ns}email-address' => $row['email'],
 			'{urn:ietf:params:xml:ns:caldav}calendar-user-type' => $this->cuType,
-		];
+		], $metadata);
 	}

 	/**
@ -353,7 +472,7 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 	 * @param $userGroups
 	 * @return bool
 	 */
-	private function isAllowedToAccessResource($row, $userGroups) {
+	private function isAllowedToAccessResource(array $row, array $userGroups):bool {
 		if (!isset($row['group_restrictions']) ||
 			$row['group_restrictions'] === null ||
 			$row['group_restrictions'] === '') {
--- a/apps/dav/lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php
+++ b/apps/dav/lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php
@ -40,6 +40,6 @@ class ResourcePrincipalBackend extends AbstractPrincipalBackend {
 								IGroupManager $groupManager,
 								ILogger $logger) {
 		parent::__construct($dbConnection, $userSession, $groupManager, $logger,
-			'principals/calendar-resources', 'resources', 'RESOURCE');
+			'principals/calendar-resources', 'resource', 'RESOURCE');
 	}
 }
--- a/apps/dav/lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php
+++ b/apps/dav/lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php
@ -40,6 +40,6 @@ class RoomPrincipalBackend extends AbstractPrincipalBackend {
 								IGroupManager $groupManager,
 								ILogger $logger) {
 		parent::__construct($dbConnection, $userSession, $groupManager, $logger,
-			'principals/calendar-rooms', 'rooms', 'ROOM');
+			'principals/calendar-rooms', 'room', 'ROOM');
 	}
 }
--- a/apps/dav/lib/Migration/Version1011Date20190725113607.php
+++ b/apps/dav/lib/Migration/Version1011Date20190725113607.php
@ -0,0 +1,69 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\DAV\Migration;
+
+use Closure;
+use Doctrine\DBAL\Types\Type;
+use OCP\DB\ISchemaWrapper;
+use OCP\Migration\SimpleMigrationStep;
+use OCP\Migration\IOutput;
+
+/**
+ * Auto-generated migration step: Please modify to your needs!
+ */
+class Version1011Date20190725113607 extends SimpleMigrationStep {
+
+	/**
+	 * @param IOutput $output
+	 * @param \Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return null|ISchemaWrapper
+	 * @since 13.0.0
+	 */
+	public function changeSchema(IOutput $output, \Closure $schemaClosure, array $options) {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+
+		$types = ['resource', 'room'];
+		foreach($types as $type) {
+			if (!$schema->hasTable($this->getMetadataTableName($type))) {
+				$table = $schema->createTable($this->getMetadataTableName($type));
+
+				$table->addColumn('id', Type::BIGINT, [
+					'autoincrement' => true,
+					'notnull' => true,
+					'length' => 11,
+					'unsigned' => true,
+				]);
+				$table->addColumn($type . '_id', Type::BIGINT, [
+					'notnull' => true,
+					'length' => 11,
+					'unsigned' => true,
+				]);
+				$table->addColumn('key', Type::STRING, [
+					'notnull' => true,
+					'length' => 255,
+				]);
+				$table->addColumn('value', Type::STRING, [
+					'notnull' => false,
+					'length' => 4000,
+				]);
+
+				$table->setPrimaryKey(['id']);
+				$table->addIndex([$type . '_id', 'key'], $this->getMetadataTableName($type) . '_idk');
+			}
+		}
+
+		return $schema;
+	}
+
+	/**
+	 * @param string $type
+	 * @return string
+	 */
+	private function getMetadataTableName(string $type):string {
+		return 'calendar_' . $type . 's_md';
+	}
+}
--- a/apps/dav/tests/unit/BackgroundJob/UpdateCalendarResourcesRoomsBackgroundJobTest.php
+++ b/apps/dav/tests/unit/BackgroundJob/UpdateCalendarResourcesRoomsBackgroundJobTest.php
@ -26,6 +26,7 @@ use OCA\DAV\BackgroundJob\UpdateCalendarResourcesRoomsBackgroundJob;

 use OCA\DAV\CalDAV\CalDavBackend;
 use OCP\Calendar\BackendTemporarilyUnavailableException;
+use OCP\Calendar\IMetadataProvider;
 use OCP\Calendar\Resource\IBackend;
 use OCP\Calendar\Resource\IManager as IResourceManager;
 use OCP\Calendar\Resource\IResource;
@ -61,34 +62,38 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 	protected function tearDown() {
 		$query = self::$realDatabase->getQueryBuilder();
 		$query->delete('calendar_resources')->execute();
+		$query->delete('calendar_resources_md')->execute();
 		$query->delete('calendar_rooms')->execute();
+		$query->delete('calendar_rooms_md')->execute();
 	}

 	/**
 	 * Data in Cache:
 	 * resources:
-	 *  [backend1, res1, Beamer1, {}]
-	 *  [backend1, res2, TV1, {}]
-	 *  [backend2, res3, Beamer2, {}]
-	 *  [backend2, res4, TV2, {}]
-	 *  [backend3, res5, Beamer3, {}]
-	 *  [backend3, res6, Pointer, {foo, bar}]
+	 *  [backend1, res1, Beamer1, {}] - []
+	 *  [backend1, res2, TV1, {}] - []
+	 *  [backend2, res3, Beamer2, {}] - ['meta1' => 'value1', 'meta2' => 'value2']
+	 *  [backend2, res4, TV2, {}] - ['meta1' => 'value1', 'meta3' => 'value3-old']
+	 *  [backend3, res5, Beamer3, {}] - []
+	 *  [backend3, res6, Pointer, {foo, bar}] - ['meta99' => 'value99']
 	 *
 	 * Data in Backend:
 	 *  backend1 gone
 	 *  backend2 throws BackendTemporarilyUnavailableException
-	 *  [backend3, res6, Pointer123, {foo, biz}]
-	 *  [backend3, res7, Resource4, {biz}]
-	 *  [backend4, res8, Beamer, {}]
-	 *  [backend4, res9, Beamer2, {}]
+	 *  [backend3, res6, Pointer123, {foo, biz}] - ['meta99' => 'value99-new', 'meta123' => 'meta456']
+	 *  [backend3, res7, Resource4, {biz}] - ['meta1' => 'value1']
+	 *  [backend4, res8, Beamer, {}] - ['meta2' => 'value2']
+	 *  [backend4, res9, Beamer2, {}] - []
 	 *
 	 * Expected after run:
-	 *  [backend2, res3, Beamer2, {}]
-	 *  [backend2, res4, TV2, {}]
-	 *  [backend3, res6, Pointer123, {foo, biz}]
-	 *  [backend3, res7, Resource4, {biz}]
-	 *  [backend4, res8, Beamer, {}]
-	 *  [backend4, res9, Beamer2, {}]
+	 * 	[backend1, res1, Beamer1, {}] - []
+	 *  [backend1, res2, TV1, {}] - []
+	 *  [backend2, res3, Beamer2, {}] - ['meta1' => 'value1', 'meta2' => 'value2']
+	 *  [backend2, res4, TV2, {}] - ['meta1' => 'value1', 'meta3' => 'value3-old']
+	 *  [backend3, res6, Pointer123, {foo, biz}]  - ['meta99' => 'value99-new', 'meta123' => 'meta456']
+	 *  [backend3, res7, Resource4, {biz}] - ['meta1' => 'value1']
+	 *  [backend4, res8, Beamer, {}] - ['meta2' => 'value2']
+	 *  [backend4, res9, Beamer2, {}] - []
 	 */

 	public function testRun() {
@ -98,9 +103,9 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 		$backend3 = $this->createMock(IBackend::class);
 		$backend4 = $this->createMock(IBackend::class);

-		$res6 = $this->createMock(IResource::class);
-		$res7 = $this->createMock(IResource::class);
-		$res8 = $this->createMock(IResource::class);
+		$res6 = $this->createMock([IResource::class, IMetadataProvider::class]);
+		$res7 = $this->createMock([IResource::class, IMetadataProvider::class]);
+		$res8 = $this->createMock([IResource::class, IMetadataProvider::class]);
 		$res9 = $this->createMock(IResource::class);

 		$backend2->method('getBackendIdentifier')
@ -136,17 +141,51 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 		$res6->method('getEMail')->will($this->returnValue('res6@foo.bar'));
 		$res6->method('getBackend')->will($this->returnValue($backend3));

+		$res6->method('getAllAvailableMetadataKeys')->will($this->returnValue(['meta99', 'meta123']));
+		$res6->method('getMetadataForKey')->will($this->returnCallback(function($key) {
+			switch($key) {
+				case 'meta99':
+					return 'value99-new';
+
+				case 'meta123':
+					return 'meta456';
+
+				default:
+					return null;
+			}
+		}));
+
 		$res7->method('getId')->will($this->returnValue('res7'));
 		$res7->method('getDisplayName')->will($this->returnValue('Resource4'));
 		$res7->method('getGroupRestrictions')->will($this->returnValue(['biz']));
 		$res7->method('getEMail')->will($this->returnValue('res7@foo.bar'));
 		$res7->method('getBackend')->will($this->returnValue($backend3));
+		$res7->method('getAllAvailableMetadataKeys')->will($this->returnValue(['meta1']));
+		$res7->method('getMetadataForKey')->will($this->returnCallback(function($key) {
+			switch($key) {
+				case 'meta1':
+					return 'value1';
+
+				default:
+					return null;
+			}
+		}));

 		$res8->method('getId')->will($this->returnValue('res8'));
 		$res8->method('getDisplayName')->will($this->returnValue('Beamer'));
 		$res8->method('getGroupRestrictions')->will($this->returnValue([]));
 		$res8->method('getEMail')->will($this->returnValue('res8@foo.bar'));
 		$res8->method('getBackend')->will($this->returnValue($backend4));
+		$res8->method('getAllAvailableMetadataKeys')->will($this->returnValue(['meta2']));
+		$res8->method('getMetadataForKey')->will($this->returnCallback(function($key) {
+			switch($key) {
+				case 'meta2':
+					return 'value2';
+
+				default:
+					return null;
+			}
+		}));

 		$res9->method('getId')->will($this->returnValue('res9'));
 		$res9->method('getDisplayName')->will($this->returnValue('Beamer2'));
@ -173,13 +212,29 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 		$query->select('*')->from('calendar_resources');

 		$rows = [];
+		$ids = [];
 		$stmt = $query->execute();
 		while($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+			$ids[$row['backend_id'] . '::' . $row['resource_id']] = $row['id'];
 			unset($row['id']);
 			$rows[] = $row;
 		}

 		$this->assertEquals([
+			[
+				'backend_id' => 'backend1',
+				'resource_id' => 'res1',
+				'displayname' => 'Beamer1',
+				'email' => 'res1@foo.bar',
+				'group_restrictions' => '[]',
+			],
+			[
+				'backend_id' => 'backend1',
+				'resource_id' => 'res2',
+				'displayname' => 'TV1',
+				'email' => 'res2@foo.bar',
+				'group_restrictions' => '[]',
+			],
 			[
 				'backend_id' => 'backend2',
 				'resource_id' => 'res3',
@ -223,6 +278,59 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 				'group_restrictions' => '[]',
 			],
 		], $rows);
+
+		$query2 = self::$realDatabase->getQueryBuilder();
+		$query2->select('*')->from('calendar_resources_md');
+
+		$rows2 = [];
+		$stmt = $query2->execute();
+		while($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+			unset($row['id']);
+			$rows2[] = $row;
+		}
+
+		$this->assertEquals([
+			[
+				'resource_id' => $ids['backend2::res3'],
+				'key' => 'meta1',
+				'value' => 'value1',
+			],
+			[
+				'resource_id' => $ids['backend2::res3'],
+				'key' => 'meta2',
+				'value' => 'value2',
+			],
+			[
+				'resource_id' => $ids['backend2::res4'],
+				'key' => 'meta1',
+				'value' => 'value1',
+			],
+			[
+				'resource_id' => $ids['backend2::res4'],
+				'key' => 'meta3',
+				'value' => 'value3-old',
+			],
+			[
+				'resource_id' => $ids['backend3::res6'],
+				'key' => 'meta99',
+				'value' => 'value99-new',
+			],
+			[
+				'resource_id' => $ids['backend3::res7'],
+				'key' => 'meta1',
+				'value' => 'value1',
+			],
+			[
+				'resource_id' => $ids['backend3::res6'],
+				'key' => 'meta123',
+				'value' => 'meta456',
+			],
+			[
+				'resource_id' => $ids['backend4::res8'],
+				'key' => 'meta2',
+				'value' => 'value2',
+			]
+		], $rows2);
 	}

 	protected function createTestResourcesInCache() {
@ -236,6 +344,7 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 				'group_restrictions' => $query->createNamedParameter('[]'),
 			])
 			->execute();
+
 		$query->insert('calendar_resources')
 			->values([
 				'backend_id' => $query->createNamedParameter('backend1'),
@ -245,6 +354,7 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 				'group_restrictions' => $query->createNamedParameter('[]'),
 			])
 			->execute();
+
 		$query->insert('calendar_resources')
 			->values([
 				'backend_id' => $query->createNamedParameter('backend2'),
@ -254,6 +364,8 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 				'group_restrictions' => $query->createNamedParameter('[]'),
 			])
 			->execute();
+		$id3 = $query->getLastInsertId();
+
 		$query->insert('calendar_resources')
 			->values([
 				'backend_id' => $query->createNamedParameter('backend2'),
@ -263,6 +375,8 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 				'group_restrictions' => $query->createNamedParameter('[]'),
 			])
 			->execute();
+		$id4 = $query->getLastInsertId();
+
 		$query->insert('calendar_resources')
 			->values([
 				'backend_id' => $query->createNamedParameter('backend3'),
@ -272,6 +386,7 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 				'group_restrictions' => $query->createNamedParameter('[]'),
 			])
 			->execute();
+
 		$query->insert('calendar_resources')
 			->values([
 				'backend_id' => $query->createNamedParameter('backend3'),
@ -281,5 +396,42 @@ class UpdateCalendarResourcesRoomsBackgroundJobTest extends TestCase {
 				'group_restrictions' => $query->createNamedParameter('["foo", "bar"]'),
 			])
 			->execute();
+		$id6 = $query->getLastInsertId();
+
+		$query->insert('calendar_resources_md')
+			->values([
+				'resource_id' => $query->createNamedParameter($id3),
+				'key' => $query->createNamedParameter('meta1'),
+				'value' => $query->createNamedParameter('value1')
+			])
+			->execute();
+		$query->insert('calendar_resources_md')
+			->values([
+				'resource_id' => $query->createNamedParameter($id3),
+				'key' => $query->createNamedParameter('meta2'),
+				'value' => $query->createNamedParameter('value2')
+			])
+			->execute();
+		$query->insert('calendar_resources_md')
+			->values([
+				'resource_id' => $query->createNamedParameter($id4),
+				'key' => $query->createNamedParameter('meta1'),
+				'value' => $query->createNamedParameter('value1')
+			])
+			->execute();
+		$query->insert('calendar_resources_md')
+			->values([
+				'resource_id' => $query->createNamedParameter($id4),
+				'key' => $query->createNamedParameter('meta3'),
+				'value' => $query->createNamedParameter('value3-old')
+			])
+			->execute();
+		$query->insert('calendar_resources_md')
+			->values([
+				'resource_id' => $query->createNamedParameter($id6),
+				'key' => $query->createNamedParameter('meta99'),
+				'value' => $query->createNamedParameter('value99')
+			])
+			->execute();
 	}
 }
--- a/apps/dav/tests/unit/CalDAV/ResourceBooking/AbstractPrincipalBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/ResourceBooking/AbstractPrincipalBackendTest.php
--- a/apps/dav/tests/unit/CalDAV/ResourceBooking/ResourcePrincipalBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/ResourceBooking/ResourcePrincipalBackendTest.php
@ -27,10 +27,16 @@ Class ResourcePrincipalBackendTest extends AbstractPrincipalBackendTest {
 	public function setUp() {
 		parent::setUp();

-		$this->principalBackend = new ResourcePrincipalBackend($this->dbConnection,
+		$this->principalBackend = new ResourcePrincipalBackend(self::$realDatabase,
 			$this->userSession, $this->groupManager, $this->logger);
-		$this->expectedDbTable = 'calendar_resources';
+
+		$this->mainDbTable = 'calendar_resources';
+		$this->metadataDbTable = 'calendar_resources_md';
+		$this->foreignKey = 'resource_id';
+
 		$this->principalPrefix = 'principals/calendar-resources';
 		$this->expectedCUType = 'RESOURCE';
+
+		$this->createTestDatasetInDb();
 	}
 }
--- a/apps/dav/tests/unit/CalDAV/ResourceBooking/RoomPrincipalBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/ResourceBooking/RoomPrincipalBackendTest.php
@ -27,10 +27,16 @@ Class RoomPrincipalBackendTest extends AbstractPrincipalBackendTest {
 	public function setUp() {
 		parent::setUp();

-		$this->principalBackend = new RoomPrincipalBackend($this->dbConnection,
+		$this->principalBackend = new RoomPrincipalBackend(self::$realDatabase,
 			$this->userSession, $this->groupManager, $this->logger);
-		$this->expectedDbTable = 'calendar_rooms';
+
+		$this->mainDbTable = 'calendar_rooms';
+		$this->metadataDbTable = 'calendar_rooms_md';
+		$this->foreignKey = 'room_id';
+
 		$this->principalPrefix = 'principals/calendar-rooms';
 		$this->expectedCUType = 'ROOM';
+
+		$this->createTestDatasetInDb();
 	}
 }
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@ -100,12 +100,15 @@ return array(
    'OCP\\Calendar\\BackendTemporarilyUnavailableException' => $baseDir . '/lib/public/Calendar/BackendTemporarilyUnavailableException.php',
    'OCP\\Calendar\\ICalendar' => $baseDir . '/lib/public/Calendar/ICalendar.php',
    'OCP\\Calendar\\IManager' => $baseDir . '/lib/public/Calendar/IManager.php',
+    'OCP\\Calendar\\IMetadataProvider' => $baseDir . '/lib/public/Calendar/IMetadataProvider.php',
    'OCP\\Calendar\\Resource\\IBackend' => $baseDir . '/lib/public/Calendar/Resource/IBackend.php',
    'OCP\\Calendar\\Resource\\IManager' => $baseDir . '/lib/public/Calendar/Resource/IManager.php',
    'OCP\\Calendar\\Resource\\IResource' => $baseDir . '/lib/public/Calendar/Resource/IResource.php',
+    'OCP\\Calendar\\Resource\\IResourceMetadata' => $baseDir . '/lib/public/Calendar/Resource/IResourceMetadata.php',
    'OCP\\Calendar\\Room\\IBackend' => $baseDir . '/lib/public/Calendar/Room/IBackend.php',
    'OCP\\Calendar\\Room\\IManager' => $baseDir . '/lib/public/Calendar/Room/IManager.php',
    'OCP\\Calendar\\Room\\IRoom' => $baseDir . '/lib/public/Calendar/Room/IRoom.php',
+    'OCP\\Calendar\\Room\\IRoomMetadata' => $baseDir . '/lib/public/Calendar/Room/IRoomMetadata.php',
    'OCP\\Capabilities\\ICapability' => $baseDir . '/lib/public/Capabilities/ICapability.php',
    'OCP\\Capabilities\\IPublicCapability' => $baseDir . '/lib/public/Capabilities/IPublicCapability.php',
    'OCP\\Collaboration\\AutoComplete\\AutoCompleteEvent' => $baseDir . '/lib/public/Collaboration/AutoComplete/AutoCompleteEvent.php',
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@ -134,12 +134,15 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
        'OCP\\Calendar\\BackendTemporarilyUnavailableException' => __DIR__ . '/../../..' . '/lib/public/Calendar/BackendTemporarilyUnavailableException.php',
        'OCP\\Calendar\\ICalendar' => __DIR__ . '/../../..' . '/lib/public/Calendar/ICalendar.php',
        'OCP\\Calendar\\IManager' => __DIR__ . '/../../..' . '/lib/public/Calendar/IManager.php',
+        'OCP\\Calendar\\IMetadataProvider' => __DIR__ . '/../../..' . '/lib/public/Calendar/IMetadataProvider.php',
        'OCP\\Calendar\\Resource\\IBackend' => __DIR__ . '/../../..' . '/lib/public/Calendar/Resource/IBackend.php',
        'OCP\\Calendar\\Resource\\IManager' => __DIR__ . '/../../..' . '/lib/public/Calendar/Resource/IManager.php',
        'OCP\\Calendar\\Resource\\IResource' => __DIR__ . '/../../..' . '/lib/public/Calendar/Resource/IResource.php',
+        'OCP\\Calendar\\Resource\\IResourceMetadata' => __DIR__ . '/../../..' . '/lib/public/Calendar/Resource/IResourceMetadata.php',
        'OCP\\Calendar\\Room\\IBackend' => __DIR__ . '/../../..' . '/lib/public/Calendar/Room/IBackend.php',
        'OCP\\Calendar\\Room\\IManager' => __DIR__ . '/../../..' . '/lib/public/Calendar/Room/IManager.php',
        'OCP\\Calendar\\Room\\IRoom' => __DIR__ . '/../../..' . '/lib/public/Calendar/Room/IRoom.php',
+        'OCP\\Calendar\\Room\\IRoomMetadata' => __DIR__ . '/../../..' . '/lib/public/Calendar/Room/IRoomMetadata.php',
        'OCP\\Capabilities\\ICapability' => __DIR__ . '/../../..' . '/lib/public/Capabilities/ICapability.php',
        'OCP\\Capabilities\\IPublicCapability' => __DIR__ . '/../../..' . '/lib/public/Capabilities/IPublicCapability.php',
        'OCP\\Collaboration\\AutoComplete\\AutoCompleteEvent' => __DIR__ . '/../../..' . '/lib/public/Collaboration/AutoComplete/AutoCompleteEvent.php',
--- a/lib/public/Calendar/IMetadataProvider.php
+++ b/lib/public/Calendar/IMetadataProvider.php
@ -0,0 +1,65 @@
+<?php
+/**
+ * @copyright 2019, Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @author Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @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 OCP\Calendar;
+
+/**
+ * Interface IMetadataProvider
+ *
+ * Provider for metadata of a resource or a room
+ *
+ * @package OCP\Calendar
+ * @since 17.0.0
+ */
+interface IMetadataProvider {
+
+	/**
+	 * Get a list of all metadata keys available for this room
+	 *
+	 * Room backends are allowed to return custom keys, beyond the ones
+	 * defined in this class. If they do, they should make sure to use their
+	 * own namespace.
+	 *
+	 * @return String[] - A list of available keys
+	 * @since 17.0.0
+	 */
+	public function getAllAvailableMetadataKeys():array;
+
+	/**
+	 * Get whether or not a metadata key is set for this room
+	 *
+	 * @param string $key - The key to check for
+	 * @return bool - Whether or not key is available
+	 * @since 17.0.0
+	 */
+	public function hasMetadataForKey(string $key):bool;
+
+	/**
+	 * Get the value for a metadata key
+	 *
+	 * @param string $key - The key to check for
+	 * @return string|null - The value stored for the key, null if no value stored
+	 * @since 17.0.0
+	 */
+	public function getMetadataForKey(string $key):?string;
+}
--- a/lib/public/Calendar/Resource/IResourceMetadata.php
+++ b/lib/public/Calendar/Resource/IResourceMetadata.php
@ -0,0 +1,118 @@
+<?php
+/**
+ * @copyright 2019, Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @author Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @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 OCP\Calendar\Resource;
+
+/**
+ * Interface IResourceMetadata
+ *
+ * This interface provides keys for common metadata.
+ * Resource Backends are not limited to this list and can provide
+ * any metadata they want.
+ *
+ * @package OCP\Calendar\Resource
+ * @since 17.0.0
+ */
+interface IResourceMetadata {
+
+	/**
+	 * Type of resource
+	 *
+	 * Allowed values for this key include:
+	 * - projector
+	 * - tv
+	 * - vehicle
+	 * - other
+	 *
+	 * @since 17.0.0
+	 */
+	public const RESOURCE_TYPE = '{http://nextcloud.com/ns}resource-type';
+
+	/**
+	 * If resource is of type vehicle, this describes the type of vehicle
+	 *
+	 * Allowed values:
+	 * - bicycle
+	 * - scooter
+	 * - motorbike
+	 * - car
+	 * - plane
+	 * - helicopter
+	 * - other
+	 *
+	 * @since 17.0.0
+	 */
+	public const VEHICLE_TYPE = '{http://nextcloud.com/ns}resource-vehicle-type';
+
+	/**
+	 * Make of the vehicle
+	 *
+	 * @since 17.0.0
+	 */
+	public const VEHICLE_MAKE = '{http://nextcloud.com/ns}resource-vehicle-make';
+
+	/**
+	 * Model of the vehicle
+	 *
+	 * @since 17.0.0
+	 */
+	public const VEHICLE_MODEL = '{http://nextcloud.com/ns}resource-vehicle-model';
+
+	/**
+	 * Whether or not the car is electric
+	 *
+	 * use '1' for electric, '0' for non-electric
+	 *
+	 * @since 17.0.0
+	 */
+	public const VEHICLE_IS_ELECTRIC = '{http://nextcloud.com/ns}resource-vehicle-is-electric';
+
+	/**
+	 * Range of vehicle with a full tank
+	 *
+	 * @since 17.0.0
+	 */
+	public const VEHICLE_RANGE = '{http://nextcloud.com/ns}resource-vehicle-range';
+
+	/**
+	 * Seating capacity of the vehicle
+	 *
+	 * @since 17.0.0
+	 */
+	public const VEHICLE_SEATING_CAPACITY = '{http://nextcloud.com/ns}resource-vehicle-seating-capacity';
+
+	/**
+	 * Contact information about the person who is responsible to administer / maintain this resource
+	 * This key stores a textual description of name and possible ways to contact the person
+	 *
+	 * @since 17.0.0
+	 */
+	public const CONTACT_PERSON = '{http://nextcloud.com/ns}resource-contact-person';
+
+	/**
+	 * Link to the vcard of the contact person
+	 *
+	 * @since 17.0.0
+	 */
+	public const CONTACT_PERSON_VCARD = '{http://nextcloud.com/ns}resource-contact-person-vcard';
+}
--- a/lib/public/Calendar/Room/IRoom.php
+++ b/lib/public/Calendar/Room/IRoom.php
@ -32,7 +32,7 @@ namespace OCP\Calendar\Room;
 interface IRoom {

 	/**
-	 * get the room id
+	 * Get a unique ID for the room
 	 *
 	 * This id has to be unique within the backend
 	 *
@ -42,7 +42,7 @@ interface IRoom {
 	public function getId():string;

 	/**
-	 * get the display name for a room
+	 * Get the display name for the room
 	 *
 	 * @return string
 	 * @since 14.0.0
@ -61,9 +61,9 @@ interface IRoom {
 	public function getGroupRestrictions():array;

 	/**
-	 * get email-address for room
+	 * Get the email-address for the room
 	 *
-	 * The email address has to be globally unique
+	 * The email-address has to be globally unique
 	 *
 	 * @return string
 	 * @since 14.0.0
--- a/lib/public/Calendar/Room/IRoomMetadata.php
+++ b/lib/public/Calendar/Room/IRoomMetadata.php
@ -0,0 +1,95 @@
+<?php
+/**
+ * @copyright 2019, Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @author Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @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 OCP\Calendar\Room;
+
+/**
+ * Interface IRoomMetadata
+ *
+ * This interface provides keys for common metadata.
+ * Room Backends are not limited to this list and can provide
+ * any metadata they want.
+ *
+ * @package OCP\Calendar\Room
+ * @since 17.0.0
+ */
+interface IRoomMetadata {
+
+	/**
+	 * Type of room
+	 *
+	 * Allowed values for this key include:
+	 * - meeting-room
+	 * - lecture-hall
+	 * - seminar-room
+	 * - other
+	 *
+	 * @since 17.0.0
+	 */
+	public const ROOM_TYPE = '{http://nextcloud.com/ns}room-type';
+
+	/**
+	 * Seating capacity of the room
+	 *
+	 * @since 17.0.0
+	 */
+	public const CAPACITY = '{http://nextcloud.com/ns}room-seating-capacity';
+
+	/**
+	 * The physical address of the building this room is located in
+	 *
+	 * @since 17.0.0
+	 */
+	public const BUILDING_ADDRESS = '{http://nextcloud.com/ns}room-building-address';
+
+	/**
+	 * The story of the building this rooms is located in
+	 *
+	 * @since 17.0.0
+	 */
+	public const BUILDING_STORY = '{http://nextcloud.com/ns}room-building-story';
+
+	/**
+	 * The room-number
+	 *
+	 * @since 17.0.0
+	 */
+	public const BUILDING_ROOM_NUMBER = '{http://nextcloud.com/ns}room-building-room-number';
+
+	/**
+	 * Features provided by the room.
+	 * This is a stringified list of features.
+	 * Example: "PHONE,VIDEO-CONFERENCING"
+	 *
+	 * Standard features include:
+	 * - PHONE: This room is fitted with a phone
+	 * - VIDEO-CONFERENCING: This room is fitted with a video-conferencing system
+	 * - TV: This room is fitted with a TV
+	 * - PROJECTOR: This room is fitted with a projector
+	 * - WHITEBOARD: This room is fitted with a whiteboard
+	 * - WHEELCHAIR-ACCESSIBLE: This room is wheelchair-accessible
+	 *
+	 * @since 17.0.0
+	 */
+	public const FEATURES = '{http://nextcloud.com/ns}room-features';
+}