Cleanup tags and Share component

- Port to LoggerInterface
- Use IDBConnection and IQueryBuilder instead of raw SQL and OC_DB
- Use IEventListener instead of hooks
- Remove the now unused OC_DB and OC_DB_StatementWrapper legacy utils

Signed-off-by: Carl Schwan <carl@carlschwan.eu>

13 files changed, 480 insertions, 778 deletions

diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index dad4a864f8d..ededda8d55c 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -1595,8 +1595,6 @@ return array(
     'OC\\User\\User' => $baseDir . '/lib/private/User/User.php',
     'OC_API' => $baseDir . '/lib/private/legacy/OC_API.php',
     'OC_App' => $baseDir . '/lib/private/legacy/OC_App.php',
-    'OC_DB' => $baseDir . '/lib/private/legacy/OC_DB.php',
-    'OC_DB_StatementWrapper' => $baseDir . '/lib/private/legacy/OC_DB_StatementWrapper.php',
     'OC_Defaults' => $baseDir . '/lib/private/legacy/OC_Defaults.php',
     'OC_EventSource' => $baseDir . '/lib/private/legacy/OC_EventSource.php',
     'OC_FileChunking' => $baseDir . '/lib/private/legacy/OC_FileChunking.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index f2436f4302f..d2cdea38a81 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -1628,8 +1628,6 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OC\\User\\User' => __DIR__ . '/../../..' . '/lib/private/User/User.php',
         'OC_API' => __DIR__ . '/../../..' . '/lib/private/legacy/OC_API.php',
         'OC_App' => __DIR__ . '/../../..' . '/lib/private/legacy/OC_App.php',
-        'OC_DB' => __DIR__ . '/../../..' . '/lib/private/legacy/OC_DB.php',
-        'OC_DB_StatementWrapper' => __DIR__ . '/../../..' . '/lib/private/legacy/OC_DB_StatementWrapper.php',
         'OC_Defaults' => __DIR__ . '/../../..' . '/lib/private/legacy/OC_Defaults.php',
         'OC_EventSource' => __DIR__ . '/../../..' . '/lib/private/legacy/OC_EventSource.php',
         'OC_FileChunking' => __DIR__ . '/../../..' . '/lib/private/legacy/OC_FileChunking.php',
diff --git a/lib/private/Accounts/Hooks.php b/lib/private/Accounts/Hooks.php
index 93918284180..b440bc394d6 100644
--- a/lib/private/Accounts/Hooks.php
+++ b/lib/private/Accounts/Hooks.php
@@ -32,6 +32,9 @@ use OCP\IUser;
 use OCP\User\Events\UserChangedEvent;
 use Psr\Log\LoggerInterface;
 
+/**
+ * @template-implements IEventListener<UserChangedEvent>
+ */
 class Hooks implements IEventListener {
 
 	/** @var IAccountManager */
diff --git a/lib/private/Files/View.php b/lib/private/Files/View.php
index e5394e72ffe..294912e698b 100644
--- a/lib/private/Files/View.php
+++ b/lib/private/Files/View.php
@@ -50,6 +50,8 @@ use Icewind\Streams\CallbackWrapper;
 use OC\Files\Mount\MoveableMount;
 use OC\Files\Storage\Storage;
 use OC\User\LazyUser;
+use OC\Share\Share;
+use OC\User\User;
 use OCA\Files_Sharing\SharedMount;
 use OCP\Constants;
 use OCP\Files\Cache\ICacheEntry;
@@ -1800,10 +1802,10 @@ class View {
 		}
 
 		// check if any of the parents were shared by the current owner (include collections)
-		$shares = \OCP\Share::getItemShared(
+		$shares = Share::getItemShared(
 			'folder',
 			$fileId,
-			\OCP\Share::FORMAT_NONE,
+			\OC\Share\Constants::FORMAT_NONE,
 			null,
 			true
 		);
diff --git a/lib/private/Metadata/FileEventListener.php b/lib/private/Metadata/FileEventListener.php
index 6d41ccdef30..162e85ff3aa 100644
--- a/lib/private/Metadata/FileEventListener.php
+++ b/lib/private/Metadata/FileEventListener.php
@@ -33,6 +33,11 @@ use OCP\Files\NotFoundException;
 use OCP\Files\FileInfo;
 use Psr\Log\LoggerInterface;
 
+/**
+ * @template-implements IEventListener<NodeRemovedFromCache>
+ * @template-implements IEventListener<NodeDeletedEvent>
+ * @template-implements IEventListener<NodeWrittenEvent>
+ */
 class FileEventListener implements IEventListener {
 	private IMetadataManager $manager;
 	private LoggerInterface $logger;
diff --git a/lib/private/Share/Share.php b/lib/private/Share/Share.php
index f47c042df29..9e7b913d60a 100644
--- a/lib/private/Share/Share.php
+++ b/lib/private/Share/Share.php
@@ -32,9 +32,13 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>
  *
  */
+
 namespace OC\Share;
 
+use OCA\Files_Sharing\ShareBackend\File;
+use OCP\DB\Exception;
 use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IDBConnection;
 use OCP\Share\IShare;
 use Psr\Log\LoggerInterface;
 
@@ -59,11 +63,13 @@ class Share extends Constants {
 	 *
 	 * Apps are required to handle permissions on their own, this class only
 	 * stores and manages the permissions of shares
+	 *
 	 * @see lib/public/constants.php
 	 */
 
 	/**
 	 * Register a sharing backend class that implements OCP\Share_Backend for an item type
+	 *
 	 * @param string $itemType Item type
 	 * @param string $class Backend class
 	 * @param string $collectionOf (optional) Depends on item type
@@ -83,13 +89,14 @@ class Share extends Constants {
 			\OC::$server->get(LoggerInterface::class)->warning(
 				'Sharing backend '.$class.' not registered, '.self::$backendTypes[$itemType]['class']
 				.' is already registered for '.$itemType,
-				['app' => 'OCP\Share']);
+				['app' => 'files_sharing']);
 		}
 		return false;
 	}
 
 	/**
 	 * Get the items of item type shared with the current user
+	 *
 	 * @param string $itemType
 	 * @param int $format (optional) Format type must be defined by the backend
 	 * @param mixed $parameters (optional)
@@ -106,6 +113,7 @@ class Share extends Constants {
 
 	/**
 	 * Get the items of item type shared with a user
+	 *
 	 * @param string $itemType
 	 * @param string $user id for which user we want the shares
 	 * @param int $format (optional) Format type must be defined by the backend
@@ -123,53 +131,46 @@ class Share extends Constants {
 
 	/**
 	 * Get the item of item type shared with a given user by source
+	 *
 	 * @param string $itemType
 	 * @param string $itemSource
-	 * @param string $user User to whom the item was shared
-	 * @param string $owner Owner of the share
-	 * @param int $shareType only look for a specific share type
+	 * @param ?string $user User to whom the item was shared
+	 * @param ?string $owner Owner of the share
+	 * @param ?int $shareType only look for a specific share type
 	 * @return array Return list of items with file_target, permissions and expiration
+	 * @throws Exception
 	 */
-	public static function getItemSharedWithUser($itemType, $itemSource, $user, $owner = null, $shareType = null) {
+	public static function getItemSharedWithUser(string $itemType, string $itemSource, ?string $user = null, ?string $owner = null, ?int $shareType = null) {
 		$shares = [];
-		$fileDependent = false;
-
-		$where = 'WHERE';
-		$fileDependentWhere = '';
-		if ($itemType === 'file' || $itemType === 'folder') {
-			$fileDependent = true;
+		$fileDependent = $itemType === 'file' || $itemType === 'folder';
+		$qb = self::getSelectStatement(self::FORMAT_NONE, $fileDependent);
+		$qb->from('share', 's');
+		if ($fileDependent) {
+			$qb->innerJoin('s', 'filecache', 'f', $qb->expr()->eq('file_source', 'f.fileid'));
+			$qb->innerJoin('s', 'storages', 'st', $qb->expr()->eq('numeric_id', 'f.storage'));
 			$column = 'file_source';
-			$fileDependentWhere = 'INNER JOIN `*PREFIX*filecache` ON `file_source` = `*PREFIX*filecache`.`fileid` ';
-			$fileDependentWhere .= 'INNER JOIN `*PREFIX*storages` ON `numeric_id` = `*PREFIX*filecache`.`storage` ';
 		} else {
 			$column = 'item_source';
 		}
 
-		$select = self::createSelectStatement(self::FORMAT_NONE, $fileDependent);
+		$qb->where($qb->expr()->eq($column, $qb->createNamedParameter($itemSource)))
+			->andWhere($qb->expr()->eq('item_type', $qb->createNamedParameter($itemType)));
 
-		$where .= ' `' . $column . '` = ? AND `item_type` = ? ';
-		$arguments = [$itemSource, $itemType];
 		// for link shares $user === null
 		if ($user !== null) {
-			$where .= ' AND `share_with` = ? ';
-			$arguments[] = $user;
+			$qb->andWhere($qb->expr()->eq('share_with', $qb->createNamedParameter($user)));
 		}
 
 		if ($shareType !== null) {
-			$where .= ' AND `share_type` = ? ';
-			$arguments[] = $shareType;
+			$qb->andWhere($qb->expr()->eq('share_type', $qb->createNamedParameter($shareType, IQueryBuilder::PARAM_INT)));
 		}
 
 		if ($owner !== null) {
-			$where .= ' AND `uid_owner` = ? ';
-			$arguments[] = $owner;
+			$qb->andWhere($qb->expr()->eq('uid_owner', $qb->createNamedParameter($owner)));
 		}
 
-		$query = \OC_DB::prepare('SELECT ' . $select . ' FROM `*PREFIX*share` '. $fileDependentWhere . $where);
-
-		$result = \OC_DB::executeAudited($query, $arguments);
-
-		while ($row = $result->fetchRow()) {
+		$result = $qb->executeQuery();
+		while ($row = $result->fetch()) {
 			if ($fileDependent && !self::isFileReachable($row['path'], $row['storage_id'])) {
 				continue;
 			}
@@ -183,7 +184,7 @@ class Share extends Constants {
 					$path = substr($path, strlen($owner) + 1); //normalize path to 'files/foo.txt`
 					$row['path'] = $path;
 				} else {
-					\OC::$server->getLogger()->warning(
+					\OC::$server->get(LoggerInterface::class)->warning(
 						'Could not resolve mount point for ' . $row['storage_id'],
 						['app' => 'OCP\Share']
 					);
@@ -193,7 +194,7 @@ class Share extends Constants {
 		}
 		$result->closeCursor();
 
-		//if didn't found a result than let's look for a group share.
+		// if we didn't found a result then let's look for a group share.
 		if (empty($shares) && $user !== null) {
 			$userObject = \OC::$server->getUserManager()->get($user);
 			$groups = [];
@@ -202,28 +203,27 @@ class Share extends Constants {
 			}
 
 			if (!empty($groups)) {
-				$where = $fileDependentWhere . ' WHERE `' . $column . '` = ? AND `item_type` = ? AND `share_with` in (?)';
-				$arguments = [$itemSource, $itemType, $groups];
-				$types = [null, null, IQueryBuilder::PARAM_STR_ARRAY];
+				$qb = self::getSelectStatement(self::FORMAT_NONE, $fileDependent);
+				$qb->from('share', 's');
 
-				if ($owner !== null) {
-					$where .= ' AND `uid_owner` = ?';
-					$arguments[] = $owner;
-					$types[] = null;
+				if ($fileDependent) {
+					$qb->innerJoin('s', 'filecache', 'f', $qb->expr()->eq('file_source', 'f.fileid'))
+						->innerJoin('s', 'storages', 'st', $qb->expr()->eq('numeric_id', 'f.storage'));
 				}
 
-				// TODO: inject connection, hopefully one day in the future when this
-				// class isn't static anymore...
-				$conn = \OC::$server->getDatabaseConnection();
-				$result = $conn->executeQuery(
-					'SELECT ' . $select . ' FROM `*PREFIX*share` ' . $where,
-					$arguments,
-					$types
-				);
+				$qb->where($qb->expr()->eq($column, $qb->createNamedParameter($itemSource)))
+					->andWhere($qb->expr()->eq('item_type', $qb->createNamedParameter($itemType, IQueryBuilder::PARAM_STR)))
+					->andWhere($qb->expr()->in('share_with', $qb->createNamedParameter($groups, IQueryBuilder::PARAM_STR_ARRAY)));
+
+				if ($owner !== null) {
+					$qb->andWhere($qb->expr()->eq('uid_owner', $qb->createNamedParameter($owner)));
+				}
+				$result = $qb->executeQuery();
 
 				while ($row = $result->fetch()) {
 					$shares[] = $row;
 				}
+				$result->closeCursor();
 			}
 		}
 
@@ -232,6 +232,7 @@ class Share extends Constants {
 
 	/**
 	 * Get the shared item of item type owned by the current user
+	 *
 	 * @param string $itemType
 	 * @param string $itemSource
 	 * @param int $format (optional) Format type must be defined by the backend
@@ -250,9 +251,10 @@ class Share extends Constants {
 
 	/**
 	 * Get the backend class for the specified item type
+	 *
 	 * @param string $itemType
-	 * @throws \Exception
 	 * @return \OCP\Share_Backend
+	 * @throws \Exception
 	 */
 	public static function getBackend($itemType) {
 		$l = \OC::$server->getL10N('lib');
@@ -285,6 +287,7 @@ class Share extends Constants {
 
 	/**
 	 * Check if resharing is allowed
+	 *
 	 * @return boolean true if allowed or false
 	 *
 	 * Resharing is allowed by default if not configured
@@ -302,10 +305,11 @@ class Share extends Constants {
 
 	/**
 	 * Get a list of collection item types for the specified item type
+	 *
 	 * @param string $itemType
-	 * @return array
+	 * @return array|false
 	 */
-	private static function getCollectionItemTypes($itemType) {
+	private static function getCollectionItemTypes(string $itemType) {
 		$collectionTypes = [$itemType];
 		foreach (self::$backendTypes as $type => $backend) {
 			if (in_array($backend['collectionOf'], $collectionTypes)) {
@@ -326,6 +330,7 @@ class Share extends Constants {
 
 	/**
 	 * Get shared items from the database
+	 *
 	 * @param string $itemType
 	 * @param string $item Item source or target (optional)
 	 * @param int $shareType SHARE_TYPE_USER, SHARE_TYPE_GROUP, SHARE_TYPE_LINK, $shareTypeUserAndGroups, or $shareTypeGroupUserUnique
@@ -344,31 +349,36 @@ class Share extends Constants {
 	 * Refactoring notes:
 	 *   * defacto $limit, $itemsShareWithBySource, $checkExpireDate, $parameters and $format is always the default and therefore is removed in the subsequent call
 	 */
-	public static function getItems($itemType, $item = null, $shareType = null, $shareWith = null,
+	public static function getItems($itemType, ?string $item = null, ?int $shareType = null, $shareWith = null,
 									$uidOwner = null, $format = self::FORMAT_NONE, $parameters = null, $limit = -1,
 									$includeCollections = false, $itemShareWithBySource = false, $checkExpireDate = true) {
 		if (\OC::$server->getConfig()->getAppValue('core', 'shareapi_enabled', 'yes') != 'yes') {
 			return [];
 		}
+		$fileDependent = $itemType == 'file' || $itemType == 'folder';
+		$qb = self::getSelectStatement(self::FORMAT_NONE, $fileDependent, $uidOwner);
+		$qb->from('share', 's');
+
 		$backend = self::getBackend($itemType);
 		$collectionTypes = false;
 		// Get filesystem root to add it to the file target and remove from the
 		// file source, match file_source with the file cache
-		if ($itemType == 'file' || $itemType == 'folder') {
+		if ($fileDependent) {
 			if (!is_null($uidOwner)) {
 				$root = \OC\Files\Filesystem::getRoot();
 			} else {
 				$root = '';
 			}
-			$where = 'INNER JOIN `*PREFIX*filecache` ON `file_source` = `*PREFIX*filecache`.`fileid` ';
-			if (!isset($item)) {
-				$where .= ' AND `file_target` IS NOT NULL ';
+			if (isset($item)) {
+				$qb->innerJoin('s', 'filecache', 'f', $qb->expr()->eq('file_source', 'f.fileid'));
+			} else {
+				$qb->innerJoin('s', 'filecache', 'f', $qb->expr()->andX(
+					$qb->expr()->eq('file_source', 'f.fileid'),
+					$qb->expr()->isNotNull('file_target')
+				));
 			}
-			$where .= 'INNER JOIN `*PREFIX*storages` ON `numeric_id` = `*PREFIX*filecache`.`storage` ';
-			$fileDependent = true;
-			$queryArgs = [];
+			$qb->innerJoin('s', 'storages', 'st', $qb->expr()->eq('numeric_id', 'f.storage'));
 		} else {
-			$fileDependent = false;
 			$root = '';
 			$collectionTypes = self::getCollectionItemTypes($itemType);
 			if ($includeCollections && !isset($item) && $collectionTypes) {
@@ -378,25 +388,21 @@ class Share extends Constants {
 				} else {
 					$itemTypes = $collectionTypes;
 				}
-				$placeholders = implode(',', array_fill(0, count($itemTypes), '?'));
-				$where = ' WHERE `item_type` IN ('.$placeholders.'))';
-				$queryArgs = $itemTypes;
+				$qb->where($qb->expr()->in('item_type', $qb->createNamedParameter($itemTypes, IQueryBuilder::PARAM_STR_ARRAY)));
 			} else {
-				$where = ' WHERE `item_type` = ?';
-				$queryArgs = [$itemType];
+				$qb->where($qb->expr()->eq('item_type', $qb->createNamedParameter($itemType)));
 			}
 		}
 		if (\OC::$server->getConfig()->getAppValue('core', 'shareapi_allow_links', 'yes') !== 'yes') {
-			$where .= ' AND `share_type` != ?';
-			$queryArgs[] = IShare::TYPE_LINK;
+			$qb->andWhere($qb->expr()->neq('share_type', $qb->createNamedParameter(IShare::TYPE_LINK, IQueryBuilder::PARAM_INT)));
 		}
 		if (isset($shareType)) {
 			// Include all user and group items
-			if ($shareType == self::$shareTypeUserAndGroups && isset($shareWith)) {
-				$where .= ' AND ((`share_type` in (?, ?) AND `share_with` = ?) ';
-				$queryArgs[] = IShare::TYPE_USER;
-				$queryArgs[] = self::$shareTypeGroupUserUnique;
-				$queryArgs[] = $shareWith;
+			if ($shareType === self::$shareTypeUserAndGroups && isset($shareWith)) {
+				$qb->andWhere($qb->expr()->andX(
+					$qb->expr()->in('share_type', $qb->createNamedParameter([IShare::TYPE_USER, self::$shareTypeGroupUserUnique], IQueryBuilder::PARAM_INT_ARRAY)),
+					$qb->expr()->eq('share_with', $qb->createNamedParameter($shareWith))
+				));
 
 				$user = \OC::$server->getUserManager()->get($shareWith);
 				$groups = [];
@@ -404,31 +410,26 @@ class Share extends Constants {
 					$groups = \OC::$server->getGroupManager()->getUserGroupIds($user);
 				}
 				if (!empty($groups)) {
-					$placeholders = implode(',', array_fill(0, count($groups), '?'));
-					$where .= ' OR (`share_type` = ? AND `share_with` IN ('.$placeholders.')) ';
-					$queryArgs[] = IShare::TYPE_GROUP;
-					$queryArgs = array_merge($queryArgs, $groups);
+					$qb->orWhere($qb->expr()->andX(
+						$qb->expr()->eq('share_type', $qb->createNamedParameter(IShare::TYPE_GROUP, IQueryBuilder::PARAM_INT)),
+						$qb->expr()->in('share_with', $qb->createNamedParameter($groups, IQueryBuilder::PARAM_STR_ARRAY))
+					));
 				}
-				$where .= ')';
+
 				// Don't include own group shares
-				$where .= ' AND `uid_owner` != ?';
-				$queryArgs[] = $shareWith;
+				$qb->andWhere($qb->expr()->neq('uid_owner', $qb->createNamedParameter($shareWith)));
 			} else {
-				$where .= ' AND `share_type` = ?';
-				$queryArgs[] = $shareType;
+				$qb->andWhere($qb->expr()->eq('share_type', $qb->createNamedParameter($shareType, IQueryBuilder::PARAM_INT)));
 				if (isset($shareWith)) {
-					$where .= ' AND `share_with` = ?';
-					$queryArgs[] = $shareWith;
+					$qb->andWhere($qb->expr()->eq('share_with', $qb->createNamedParameter($shareWith, IQueryBuilder::PARAM_STR)));
 				}
 			}
 		}
 		if (isset($uidOwner)) {
-			$where .= ' AND `uid_owner` = ?';
-			$queryArgs[] = $uidOwner;
+			$qb->andWhere($qb->expr()->eq('uid_owner', $qb->createNamedParameter($uidOwner)));
 			if (!isset($shareType)) {
 				// Prevent unique user targets for group shares from being selected
-				$where .= ' AND `share_type` != ?';
-				$queryArgs[] = self::$shareTypeGroupUserUnique;
+				$qb->andWhere($qb->expr()->neq('share_type', $qb->createNamedParameter(self::$shareTypeGroupUserUnique, IQueryBuilder::PARAM_INT)));
 			}
 			if ($fileDependent) {
 				$column = 'file_source';
@@ -444,54 +445,53 @@ class Share extends Constants {
 		}
 		if (isset($item)) {
 			$collectionTypes = self::getCollectionItemTypes($itemType);
-			if ($includeCollections && $collectionTypes && !in_array('folder', $collectionTypes)) {
-				$where .= ' AND (';
-			} else {
-				$where .= ' AND';
-			}
 			// If looking for own shared items, check item_source else check item_target
 			if (isset($uidOwner)) {
 				// If item type is a file, file source needs to be checked in case the item was converted
 				if ($fileDependent) {
-					$where .= ' `file_source` = ?';
+					$expr = $qb->expr()->eq('file_source', $qb->createNamedParameter($item));
 					$column = 'file_source';
 				} else {
-					$where .= ' `item_source` = ?';
+					$expr = $qb->expr()->eq('item_source', $qb->createNamedParameter($item));
 					$column = 'item_source';
 				}
 			} else {
 				if ($fileDependent) {
-					$where .= ' `file_target` = ?';
 					$item = \OC\Files\Filesystem::normalizePath($item);
+					$expr = $qb->expr()->eq('file_target', $qb->createNamedParameter($item));
 				} else {
-					$where .= ' `item_target` = ?';
+					$expr = $qb->expr()->eq('item_target', $qb->createNamedParameter($item));
 				}
 			}
-			$queryArgs[] = $item;
 			if ($includeCollections && $collectionTypes && !in_array('folder', $collectionTypes)) {
-				$placeholders = implode(',', array_fill(0, count($collectionTypes), '?'));
-				$where .= ' OR `item_type` IN ('.$placeholders.'))';
-				$queryArgs = array_merge($queryArgs, $collectionTypes);
-			}
+				$qb->andWhere($qb->expr()->orX(
+					$expr,
+					$qb->expr()->in('item_type', $qb->createNamedParameter($collectionTypes, IQueryBuilder::PARAM_STR_ARRAY))
+				));
+			} else {
+				$qb->andWhere($expr);
+			}
+		}
+		$qb->orderBy('s.id', 'ASC');
+		try {
+			$result = $qb->executeQuery();
+		} catch (\Exception $e) {
+			\OCP\Server::get(LoggerInterface::class)->error(
+				'Error while selecting shares: ' . $qb->getSQL(),
+				[
+					'app' => 'files_sharing',
+					'exception' => $e
+				]);
+			throw new \RuntimeException('Wrong SQL query', 500, $e);
 		}
 
-		$where .= ' ORDER BY `*PREFIX*share`.`id` ASC';
-
-		$queryLimit = null;
-		$select = self::createSelectStatement(self::FORMAT_NONE, $fileDependent, $uidOwner);
 		$root = strlen($root);
-		$query = \OC_DB::prepare('SELECT '.$select.' FROM `*PREFIX*share` '.$where, $queryLimit);
-		$result = $query->execute($queryArgs);
-		if ($result === false) {
-			\OC::$server->get(LoggerInterface::class)->error(
-				\OC_DB::getErrorMessage() . ', select=' . $select . ' where=',
-				['app' => 'OCP\Share']);
-		}
 		$items = [];
 		$targets = [];
 		$switchedItems = [];
 		$mounts = [];
-		while ($row = $result->fetchRow()) {
+		while ($row = $result->fetch()) {
+			//var_dump($row);
 			self::transformDBResults($row);
 			// Filter out duplicate group shares for users with unique targets
 			if ($fileDependent && !self::isFileReachable($row['path'], $row['storage_id'])) {
@@ -548,16 +548,12 @@ class Share extends Constants {
 						->from('share')
 						->where($query->expr()->eq('id', $query->createNamedParameter($row['parent'])));
 
-					$parentResult = $query->execute();
-					$parentRow = $parentResult->fetch();
-					$parentResult->closeCursor();
+					$parentRow = false;
+					try {
+						$parentResult = $query->executeQuery();
+						$parentRow = $parentResult->fetchOne();
+						$parentResult->closeCursor();
 
-					if ($parentRow === false) {
-						\OC::$server->get(LoggerInterface::class)->error(
-							'Can\'t select parent: ' .
-							\OC_DB::getErrorMessage() . ', select=' . $select . ' where=' . $where,
-							['app' => 'OCP\Share']);
-					} else {
 						$tmpPath = $parentRow['file_target'];
 						// find the right position where the row path continues from the target path
 						$pos = strrpos($row['path'], $parentRow['file_target']);
@@ -567,6 +563,12 @@ class Share extends Constants {
 							$tmpPath = $tmpPath . '/' . $pathPart;
 						}
 						$row['path'] = $tmpPath;
+					} catch (Exception $e) {
+						\OCP\Server::get(LoggerInterface::class)
+							->error('Can\'t select parent :' . $e->getMessage() . ' query=' . $query->getSQL(), [
+								'exception' => $e,
+								'app' => 'core'
+							]);
 					}
 				} else {
 					if (!isset($mounts[$row['storage']])) {
@@ -576,7 +578,7 @@ class Share extends Constants {
 						}
 					}
 					if (!empty($mounts[$row['storage']])) {
-						$path = $mounts[$row['storage']]->getMountPoint().$row['path'];
+						$path = $mounts[$row['storage']]->getMountPoint() . $row['path'];
 						$relPath = substr($path, $root); // path relative to data/user
 						$row['path'] = rtrim($relPath, '/');
 					}
@@ -618,6 +620,7 @@ class Share extends Constants {
 				$items[$row['id']] = $row;
 			}
 		}
+		$result->closeCursor();
 
 		// group items if we are looking for items shared with the current user
 		if (isset($shareWith) && $shareWith === \OC_User::getUser()) {
@@ -641,7 +644,7 @@ class Share extends Constants {
 								$collection['path'] = basename($row['path']);
 							}
 							$row['collection'] = $collection;
-							// Fetch all of the children sources
+							// Fetch all the children sources
 							$children = $collectionBackend->getChildren($row[$column]);
 							foreach ($children as $child) {
 								$childItem = $row;
@@ -739,7 +742,7 @@ class Share extends Constants {
 					if (!isset($result[$key]['grouped'])) {
 						$result[$key]['grouped'][] = $result[$key];
 					}
-					$result[$key]['permissions'] = (int) $item['permissions'] | (int) $r['permissions'];
+					$result[$key]['permissions'] = (int)$item['permissions'] | (int)$r['permissions'];
 					$result[$key]['grouped'][] = $item;
 					$grouped = true;
 					break;
@@ -755,83 +758,142 @@ class Share extends Constants {
 	}
 
 	/**
-	 * construct select statement
-	 * @param int $format
-	 * @param boolean $fileDependent ist it a file/folder share or a general share
-	 * @param string $uidOwner
-	 * @return string select statement
+	 * Construct select statement
+	 *
+	 * @param bool $fileDependent ist it a file/folder share or a general share
 	 */
-	private static function createSelectStatement($format, $fileDependent, $uidOwner = null) {
-		$select = '*';
+	private static function getSelectStatement(int $format, bool $fileDependent, ?string $uidOwner = null): IQueryBuilder {
+		/** @var IDBConnection $connection */
+		$connection = \OC::$server->get(IDBConnection::class);
+		$qb = $connection->getQueryBuilder();
 		if ($format == self::FORMAT_STATUSES) {
 			if ($fileDependent) {
-				$select = '`*PREFIX*share`.`id`, `*PREFIX*share`.`parent`, `share_type`, `path`, `storage`, '
-					. '`share_with`, `uid_owner` , `file_source`, `stime`, `*PREFIX*share`.`permissions`, '
-					. '`*PREFIX*storages`.`id` AS `storage_id`, `*PREFIX*filecache`.`parent` as `file_parent`, '
-					. '`uid_initiator`';
-			} else {
-				$select = '`id`, `parent`, `share_type`, `share_with`, `uid_owner`, `item_source`, `stime`, `*PREFIX*share`.`permissions`';
-			}
-		} else {
-			if (isset($uidOwner)) {
-				if ($fileDependent) {
-					$select = '`*PREFIX*share`.`id`, `item_type`, `item_source`, `*PREFIX*share`.`parent`,'
-						. ' `share_type`, `share_with`, `file_source`, `file_target`, `path`, `*PREFIX*share`.`permissions`, `stime`,'
-						. ' `expiration`, `token`, `storage`, `mail_send`, `uid_owner`, '
-						. '`*PREFIX*storages`.`id` AS `storage_id`, `*PREFIX*filecache`.`parent` as `file_parent`';
-				} else {
-					$select = '`id`, `item_type`, `item_source`, `parent`, `share_type`, `share_with`, `*PREFIX*share`.`permissions`,'
-						. ' `stime`, `file_source`, `expiration`, `token`, `mail_send`, `uid_owner`';
-				}
-			} else {
-				if ($fileDependent) {
-					if ($format == \OCA\Files_Sharing\ShareBackend\File::FORMAT_GET_FOLDER_CONTENTS || $format == \OCA\Files_Sharing\ShareBackend\File::FORMAT_FILE_APP_ROOT) {
-						$select = '`*PREFIX*share`.`id`, `item_type`, `item_source`, `*PREFIX*share`.`parent`, `uid_owner`, '
-							. '`share_type`, `share_with`, `file_source`, `path`, `file_target`, `stime`, '
-							. '`*PREFIX*share`.`permissions`, `expiration`, `storage`, `*PREFIX*filecache`.`parent` as `file_parent`, '
-							. '`name`, `mtime`, `mimetype`, `mimepart`, `size`, `encrypted`, `etag`, `mail_send`';
-					} else {
-						$select = '`*PREFIX*share`.`id`, `item_type`, `item_source`, `item_target`,'
-							. '`*PREFIX*share`.`parent`, `share_type`, `share_with`, `uid_owner`,'
-							. '`file_source`, `path`, `file_target`, `*PREFIX*share`.`permissions`,'
-							. '`stime`, `expiration`, `token`, `storage`, `mail_send`,'
-							. '`*PREFIX*storages`.`id` AS `storage_id`, `*PREFIX*filecache`.`parent` as `file_parent`';
-					}
-				}
-			}
+				return $qb->select(
+					's.id',
+					's.parent',
+					'share_type',
+					'path',
+					'storage',
+					'share_with',
+					'uid_owner',
+					'file_source',
+					'stime',
+					's.permissions',
+					'uid_initiator'
+				)->selectAlias('st.id', 'storage_id')
+					->selectAlias('f.parent', 'file_parent');
+			}
+			return $qb->select('id', 'parent', 'share_type', 'share_with', 'uid_owner', 'item_source', 'stime', 's.permissions');
 		}
-		return $select;
+
+		if (isset($uidOwner)) {
+			if ($fileDependent) {
+				return $qb->select(
+					's.id',
+					'item_type',
+					'item_source',
+					's.parent',
+					'share_type',
+					'share_with',
+					'file_source',
+					'file_target',
+					'path',
+					's.permissions',
+					'stime',
+					'expiration',
+					'token',
+					'storage',
+					'mail_send',
+					'uid_owner',
+					'uid_initiator'
+				)->selectAlias('st.id', 'storage_id')
+					->selectAlias('f.parent', 'file_parent');
+			}
+			return $qb->select('id', 'item_type', 'item_source', 'parent', 'share_type',
+				'share_with', 'uid_owner', 'file_source', 'stime', 's.permissions',
+				'expiration', 'token', 'mail_send');
+		}
+
+		if ($fileDependent) {
+			if ($format == File::FORMAT_GET_FOLDER_CONTENTS || $format == File::FORMAT_FILE_APP_ROOT) {
+				return $qb->select(
+					's.id',
+					'item_type',
+					'item_source',
+					's.parent',
+					'uid_owner',
+					'share_type',
+					'share_with',
+					'file_source',
+					'path',
+					'file_target',
+					's.permissions',
+					'stime',
+					'expiration',
+					'storage',
+					'name',
+					'mtime',
+					'mimepart',
+					'size',
+					'encrypted',
+					'etag',
+					'mail_send'
+				)->selectAlias('f.parent', 'file_parent');
+			}
+			return $qb->select(
+				's.id',
+				'item_type',
+				'item_source',
+				'item_target',
+				's.parent',
+				'share_type',
+				'share_with',
+				'uid_owner',
+				'file_source',
+				'path',
+				'file_target',
+				's.permissions',
+				'stime',
+				'expiration',
+				'token',
+				'storage',
+				'mail_send',
+			)->selectAlias('f.parent', 'file_parent')
+				->selectAlias('st.id', 'storage_id');
+		}
+		return $qb->select('*');
 	}
 
 
 	/**
 	 * transform db results
+	 *
 	 * @param array $row result
 	 */
 	private static function transformDBResults(&$row) {
 		if (isset($row['id'])) {
-			$row['id'] = (int) $row['id'];
+			$row['id'] = (int)$row['id'];
 		}
 		if (isset($row['share_type'])) {
-			$row['share_type'] = (int) $row['share_type'];
+			$row['share_type'] = (int)$row['share_type'];
 		}
 		if (isset($row['parent'])) {
-			$row['parent'] = (int) $row['parent'];
+			$row['parent'] = (int)$row['parent'];
 		}
 		if (isset($row['file_parent'])) {
-			$row['file_parent'] = (int) $row['file_parent'];
+			$row['file_parent'] = (int)$row['file_parent'];
 		}
 		if (isset($row['file_source'])) {
-			$row['file_source'] = (int) $row['file_source'];
+			$row['file_source'] = (int)$row['file_source'];
 		}
 		if (isset($row['permissions'])) {
-			$row['permissions'] = (int) $row['permissions'];
+			$row['permissions'] = (int)$row['permissions'];
 		}
 		if (isset($row['storage'])) {
-			$row['storage'] = (int) $row['storage'];
+			$row['storage'] = (int)$row['storage'];
 		}
 		if (isset($row['stime'])) {
-			$row['stime'] = (int) $row['stime'];
+			$row['stime'] = (int)$row['stime'];
 		}
 		if (isset($row['expiration']) && $row['share_type'] !== IShare::TYPE_LINK) {
 			// discard expiration date for non-link shares, which might have been
@@ -842,6 +904,7 @@ class Share extends Constants {
 
 	/**
 	 * format result
+	 *
 	 * @param array $items result
 	 * @param string $column is it a file share or a general share ('file_target' or 'item_target')
 	 * @param \OCP\Share_Backend $backend sharing backend
diff --git a/lib/private/Share20/UserRemovedListener.php b/lib/private/Share20/UserRemovedListener.php
index 6bf184a9309..6db0f2e0910 100644
--- a/lib/private/Share20/UserRemovedListener.php
+++ b/lib/private/Share20/UserRemovedListener.php
@@ -30,6 +30,9 @@ use OCP\EventDispatcher\IEventListener;
 use OCP\Group\Events\UserRemovedEvent;
 use OCP\Share\IManager;
 
+/**
+ * @template-implements IEventListener<UserRemovedEvent>
+ */
 class UserRemovedListener implements IEventListener {
 
 	/** @var IManager */
diff --git a/lib/private/TagManager.php b/lib/private/TagManager.php
index 8c9dca98c92..82c4dd2188d 100644
--- a/lib/private/TagManager.php
+++ b/lib/private/TagManager.php
@@ -28,26 +28,30 @@ namespace OC;
 
 use OC\Tagging\TagMapper;
 use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\EventDispatcher\Event;
+use OCP\EventDispatcher\IEventListener;
 use OCP\IDBConnection;
 use OCP\ITagManager;
 use OCP\ITags;
 use OCP\IUserSession;
+use OCP\User\Events\UserDeletedEvent;
+use OCP\Db\Exception as DBException;
+use Psr\Log\LoggerInterface;
 
-class TagManager implements ITagManager {
-
-	/** @var TagMapper */
-	private $mapper;
-
-	/** @var IUserSession */
-	private $userSession;
-
-	/** @var IDBConnection */
-	private $connection;
+/**
+ * @template-implements IEventListener<UserDeletedEvent>
+ */
+class TagManager implements ITagManager, IEventListener {
+	private TagMapper $mapper;
+	private IUserSession $userSession;
+	private IDBConnection $connection;
+	private LoggerInterface $logger;
 
-	public function __construct(TagMapper $mapper, IUserSession $userSession, IDBConnection $connection) {
+	public function __construct(TagMapper $mapper, IUserSession $userSession, IDBConnection $connection, LoggerInterface $logger) {
 		$this->mapper = $mapper;
 		$this->userSession = $userSession;
 		$this->connection = $connection;
+		$this->logger = $logger;
 	}
 
 	/**
@@ -72,7 +76,7 @@ class TagManager implements ITagManager {
 			}
 			$userId = $this->userSession->getUser()->getUId();
 		}
-		return new Tags($this->mapper, $userId, $type, $defaultTags);
+		return new Tags($this->mapper, $userId, $type, $this->logger, $this->connection, $defaultTags);
 	}
 
 	/**
@@ -97,4 +101,57 @@ class TagManager implements ITagManager {
 
 		return $users;
 	}
+
+	public function handle(Event $event): void {
+		if (!($event instanceof UserDeletedEvent)) {
+			return;
+		}
+
+		// Find all objectid/tagId pairs.
+		$user = $event->getUser();
+		$qb = $this->connection->getQueryBuilder();
+		$qb->select('id')
+			->from('vcategory')
+			->where($qb->expr()->eq('uid', $qb->createNamedParameter($user->getUID())));
+		try {
+			$result = $qb->executeQuery();
+		} catch (DBException $e) {
+			$this->logger->error($e->getMessage(), [
+				'app' => 'core',
+				'exception' => $e,
+			]);
+			return;
+		}
+
+		$tagsIds = array_map(fn (array $row) => (int)$row['id'], $result->fetchAll());
+		$result->closeCursor();
+
+		if (count($tagsIds) === 0) {
+			return;
+		}
+
+		// Clean vcategory_to_object table
+		$qb = $this->connection->getQueryBuilder();
+		$qb = $qb->delete('vcategory_to_object')
+			->where($qb->expr()->in('categoryid', $qb->createParameter('chunk')));
+
+		// Clean vcategory
+		$qb1 = $this->connection->getQueryBuilder();
+		$qb1 = $qb1->delete('vcategory')
+			->where($qb1->expr()->in('uid', $qb1->createParameter('chunk')));
+
+		foreach (array_chunk($tagsIds, 1000) as $tagChunk) {
+			$qb->setParameter('chunk', $tagChunk, IQueryBuilder::PARAM_INT_ARRAY);
+			$qb1->setParameter('chunk', $tagChunk, IQueryBuilder::PARAM_INT_ARRAY);
+			try {
+				$qb->executeStatement();
+				$qb1->executeStatement();
+			} catch (DBException $e) {
+				$this->logger->error($e->getMessage(), [
+					'app' => 'core',
+					'exception' => $e,
+				]);
+			}
+		}
+	}
 }
diff --git a/lib/private/Tags.php b/lib/private/Tags.php
index c11d83e41cf..8da1e7edc3b 100644
--- a/lib/private/Tags.php
+++ b/lib/private/Tags.php
@@ -32,72 +32,49 @@ namespace OC;
 
 use OC\Tagging\Tag;
 use OC\Tagging\TagMapper;
+use OCP\DB\Exception;
 use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IDBConnection;
 use OCP\ILogger;
 use OCP\ITags;
+use OCP\Share_Backend;
+use Psr\Log\LoggerInterface;
 
 class Tags implements ITags {
-
-	/**
-	 * Tags
-	 *
-	 * @var array
-	 */
-	private $tags = [];
-
 	/**
 	 * Used for storing objectid/categoryname pairs while rescanning.
-	 *
-	 * @var array
 	 */
-	private static $relations = [];
-
-	/**
-	 * Type
-	 *
-	 * @var string
-	 */
-	private $type;
-
-	/**
-	 * User
-	 *
-	 * @var string
-	 */
-	private $user;
+	private static array $relations = [];
+	private string $type;
+	private string $user;
+	private IDBConnection $db;
+	private LoggerInterface $logger;
+	private array $tags = [];
 
 	/**
 	 * Are we including tags for shared items?
-	 *
-	 * @var bool
 	 */
-	private $includeShared = false;
+	private bool $includeShared = false;
 
 	/**
 	 * The current user, plus any owners of the items shared with the current
 	 * user, if $this->includeShared === true.
-	 *
-	 * @var array
 	 */
-	private $owners = [];
+	private array $owners = [];
 
 	/**
-	 * The Mapper we're using to communicate our Tag objects to the database.
-	 *
-	 * @var TagMapper
+	 * The Mapper we are using to communicate our Tag objects to the database.
 	 */
-	private $mapper;
+	private TagMapper $mapper;
 
 	/**
 	 * The sharing backend for objects of $this->type. Required if
 	 * $this->includeShared === true to determine ownership of items.
-	 *
-	 * @var \OCP\Share_Backend
 	 */
-	private $backend;
+	private ?Share_Backend $backend = null;
 
-	public const TAG_TABLE = '*PREFIX*vcategory';
-	public const RELATION_TABLE = '*PREFIX*vcategory_to_object';
+	public const TAG_TABLE = 'vcategory';
+	public const RELATION_TABLE = 'vcategory_to_object';
 
 	/**
 	 * Constructor.
@@ -109,12 +86,14 @@ class Tags implements ITags {
 	 *
 	 * since 20.0.0 $includeShared isn't used anymore
 	 */
-	public function __construct(TagMapper $mapper, $user, $type, $defaultTags = []) {
+	public function __construct(TagMapper $mapper, string $user, string $type, LoggerInterface $logger, IDBConnection $connection, array $defaultTags = []) {
 		$this->mapper = $mapper;
 		$this->user = $user;
 		$this->type = $type;
 		$this->owners = [$this->user];
 		$this->tags = $this->mapper->loadTags($this->owners, $this->type);
+		$this->db = $connection;
+		$this->logger = $logger;
 
 		if (count($defaultTags) > 0 && count($this->tags) === 0) {
 			$this->addMultiple($defaultTags, true);
@@ -126,7 +105,7 @@ class Tags implements ITags {
 	 *
 	 * @return boolean
 	 */
-	public function isEmpty() {
+	public function isEmpty(): bool {
 		return count($this->tags) === 0;
 	}
 
@@ -137,7 +116,7 @@ class Tags implements ITags {
 	 * @param string $id The ID of the tag that is going to be mapped
 	 * @return array|false
 	 */
-	public function getTag($id) {
+	public function getTag(string $id) {
 		$key = $this->getTagById($id);
 		if ($key !== false) {
 			return $this->tagMap($this->tags[$key]);
@@ -154,9 +133,9 @@ class Tags implements ITags {
 	 * 	['id' => 1, 'name' = 'Shared tag', 'owner' = 'Other user', 'type' => 'tagtype'],
 	 * ]
 	 *
-	 * @return array
+	 * @return array<array-key, array{id: int, name: string}>
 	 */
-	public function getTags() {
+	public function getTags(): array {
 		if (!count($this->tags)) {
 			return [];
 		}
@@ -181,7 +160,7 @@ class Tags implements ITags {
 	 * @param string $user The user whose tags are to be checked.
 	 * @return array An array of Tag objects.
 	 */
-	public function getTagsForUser($user) {
+	public function getTagsForUser(string $user): array {
 		return array_filter($this->tags,
 			function ($tag) use ($user) {
 				return $tag->getOwner() === $user;
@@ -193,23 +172,26 @@ class Tags implements ITags {
 	 * Get the list of tags for the given ids.
 	 *
 	 * @param array $objIds array of object ids
-	 * @return array|boolean of tags id as key to array of tag names
+	 * @return array|false of tags id as key to array of tag names
 	 * or false if an error occurred
 	 */
 	public function getTagsForObjects(array $objIds) {
 		$entries = [];
 
 		try {
-			$conn = \OC::$server->getDatabaseConnection();
 			$chunks = array_chunk($objIds, 900, false);
+			$qb = $this->db->getQueryBuilder();
+			$qb->select('category', 'categoryid', 'objid')
+				->from(self::RELATION_TABLE, 'r')
+				->join('r', self::TAG_TABLE, 't', $qb->expr()->eq('r.categoryid', 't.id'))
+				->where($qb->expr()->eq('uid', $qb->createParameter('uid')))
+				->andWhere($qb->expr()->eq('r.type', $qb->createParameter('type')))
+				->andWhere($qb->expr()->in('objid', $qb->createParameter('chunk')));
 			foreach ($chunks as $chunk) {
-				$result = $conn->executeQuery(
-					'SELECT `category`, `categoryid`, `objid` ' .
-					'FROM `' . self::RELATION_TABLE . '` r, `' . self::TAG_TABLE . '` ' .
-					'WHERE `categoryid` = `id` AND `uid` = ? AND r.`type` = ? AND `objid` IN (?)',
-					[$this->user, $this->type, $chunk],
-					[null, null, IQueryBuilder::PARAM_INT_ARRAY]
-				);
+				$qb->setParameter('uid', $this->user, IQueryBuilder::PARAM_STR);
+				$qb->setParameter('type', $this->type, IQueryBuilder::PARAM_STR);
+				$qb->setParameter('chunk', $chunk, IQueryBuilder::PARAM_INT_ARRAY);
+				$result = $qb->executeQuery();
 				while ($row = $result->fetch()) {
 					$objId = (int)$row['objid'];
 					if (!isset($entries[$objId])) {
@@ -217,11 +199,11 @@ class Tags implements ITags {
 					}
 					$entries[$objId][] = $row['category'];
 				}
+				$result->closeCursor();
 			}
 		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
+			$this->logger->error($e->getMessage(), [
+				'exception' => $e,
 				'app' => 'core',
 			]);
 			return false;
@@ -236,18 +218,17 @@ class Tags implements ITags {
 	 * Throws an exception if the tag could not be found.
 	 *
 	 * @param string $tag Tag id or name.
-	 * @return array|false An array of object ids or false on error.
+	 * @return int[]|false An array of object ids or false on error.
 	 * @throws \Exception
 	 */
 	public function getIdsForTag($tag) {
-		$result = null;
 		$tagId = false;
 		if (is_numeric($tag)) {
 			$tagId = $tag;
 		} elseif (is_string($tag)) {
 			$tag = trim($tag);
 			if ($tag === '') {
-				\OCP\Util::writeLog('core', __METHOD__.', Cannot use empty tag names', ILogger::DEBUG);
+				$this->logger->debug(__METHOD__ . ' Cannot use empty tag names', ['app' => 'core']);
 				return false;
 			}
 			$tagId = $this->getTagId($tag);
@@ -261,32 +242,24 @@ class Tags implements ITags {
 		}
 
 		$ids = [];
-		$sql = 'SELECT `objid` FROM `' . self::RELATION_TABLE
-			. '` WHERE `categoryid` = ?';
-
 		try {
-			$stmt = \OC_DB::prepare($sql);
-			$result = $stmt->execute([$tagId]);
-			if ($result === null) {
-				$stmt->closeCursor();
-				\OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
-				return false;
-			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
+			$qb = $this->db->getQueryBuilder();
+			$qb->select('objid')
+				->from(self::RELATION_TABLE)
+				->where($qb->expr()->eq('categoryid', $qb->createNamedParameter($tagId, IQueryBuilder::PARAM_STR)));
+			$result = $qb->executeQuery();
+		} catch (Exception $e) {
+			$this->logger->error($e->getMessage(), [
 				'app' => 'core',
+				'exception' => $e,
 			]);
 			return false;
 		}
 
-		if (!is_null($result)) {
-			while ($row = $result->fetchRow()) {
-				$ids[] = (int)$row['objid'];
-			}
-			$result->closeCursor();
+		while ($row = $result->fetch()) {
+			$ids[] = (int)$row['objid'];
 		}
+		$result->closeCursor();
 
 		return $ids;
 	}
@@ -297,9 +270,8 @@ class Tags implements ITags {
 	 *
 	 * @param string $name The tag name to check for.
 	 * @param string $user The user whose tags are to be checked.
-	 * @return bool
 	 */
-	public function userHasTag($name, $user) {
+	public function userHasTag(string $name, string $user): bool {
 		$key = $this->array_searchi($name, $this->getTagsForUser($user));
 		return ($key !== false) ? $this->tags[$key]->getId() : false;
 	}
@@ -308,9 +280,8 @@ class Tags implements ITags {
 	 * Checks whether a tag is saved for or shared with the current user.
 	 *
 	 * @param string $name The tag name to check for.
-	 * @return bool
 	 */
-	public function hasTag($name) {
+	public function hasTag(string $name): bool {
 		return $this->getTagId($name) !== false;
 	}
 
@@ -320,15 +291,16 @@ class Tags implements ITags {
 	 * @param string $name A string with a name of the tag
 	 * @return false|int the id of the added tag or false on error.
 	 */
-	public function add($name) {
+	public function add(string $name) {
 		$name = trim($name);
 
 		if ($name === '') {
-			\OCP\Util::writeLog('core', __METHOD__.', Cannot add an empty tag', ILogger::DEBUG);
+			$this->logger->debug(__METHOD__ . ' Cannot add an empty tag', ['app' => 'core']);
 			return false;
 		}
 		if ($this->userHasTag($name, $this->user)) {
-			\OCP\Util::writeLog('core', __METHOD__.', name: ' . $name. ' exists already', ILogger::DEBUG);
+			// TODO use unique db properties instead of an additional check
+			$this->logger->debug(__METHOD__ . ' Tag with name already exists', ['app' => 'core']);
 			return false;
 		}
 		try {
@@ -336,14 +308,13 @@ class Tags implements ITags {
 			$tag = $this->mapper->insert($tag);
 			$this->tags[] = $tag;
 		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
+			$this->logger->error($e->getMessage(), [
+				'exception' => $e,
 				'app' => 'core',
 			]);
 			return false;
 		}
-		\OCP\Util::writeLog('core', __METHOD__.', id: ' . $tag->getId(), ILogger::DEBUG);
+		$this->logger->debug(__METHOD__ . ' Added an tag with ' . $tag->getId(), ['app' => 'core']);
 		return $tag->getId();
 	}
 
@@ -354,12 +325,12 @@ class Tags implements ITags {
 	 * @param string $to The new name of the tag.
 	 * @return bool
 	 */
-	public function rename($from, $to) {
+	public function rename($from, string $to): bool {
 		$from = trim($from);
 		$to = trim($to);
 
 		if ($to === '' || $from === '') {
-			\OCP\Util::writeLog('core', __METHOD__.', Cannot use empty tag names', ILogger::DEBUG);
+			$this->logger->debug(__METHOD__ . 'Cannot use an empty tag names', ['app' => 'core']);
 			return false;
 		}
 
@@ -369,13 +340,13 @@ class Tags implements ITags {
 			$key = $this->getTagByName($from);
 		}
 		if ($key === false) {
-			\OCP\Util::writeLog('core', __METHOD__.', tag: ' . $from. ' does not exist', ILogger::DEBUG);
+			$this->logger->debug(__METHOD__ . 'Tag ' . $from . 'does not exist', ['app' => 'core']);
 			return false;
 		}
 		$tag = $this->tags[$key];
 
 		if ($this->userHasTag($to, $tag->getOwner())) {
-			\OCP\Util::writeLog('core', __METHOD__.', A tag named ' . $to. ' already exists for user ' . $tag->getOwner() . '.', ILogger::DEBUG);
+			$this->logger->debug(__METHOD__ . 'A tag named' . $to . 'already exists for user' . $tag->getOwner(), ['app' => 'core']);
 			return false;
 		}
 
@@ -383,9 +354,8 @@ class Tags implements ITags {
 			$tag->setName($to);
 			$this->tags[$key] = $this->mapper->update($tag);
 		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
+			$this->logger->error($e->getMessage(), [
+				'exception' => $e,
 				'app' => 'core',
 			]);
 			return false;
@@ -396,13 +366,13 @@ class Tags implements ITags {
 	/**
 	 * Add a list of new tags.
 	 *
-	 * @param string[] $names A string with a name or an array of strings containing
+	 * @param string|string[] $names A string with a name or an array of strings containing
 	 * the name(s) of the tag(s) to add.
 	 * @param bool $sync When true, save the tags
 	 * @param int|null $id int Optional object id to add to this|these tag(s)
 	 * @return bool Returns false on error.
 	 */
-	public function addMultiple($names, $sync = false, $id = null) {
+	public function addMultiple($names, bool $sync = false, ?int $id = null): bool {
 		if (!is_array($names)) {
 			$names = [$names];
 		}
@@ -430,122 +400,50 @@ class Tags implements ITags {
 	/**
 	 * Save the list of tags and their object relations
 	 */
-	protected function save() {
-		if (is_array($this->tags)) {
-			foreach ($this->tags as $tag) {
-				try {
-					if (!$this->mapper->tagExists($tag)) {
-						$this->mapper->insert($tag);
-					}
-				} catch (\Exception $e) {
-					\OC::$server->getLogger()->logException($e, [
-						'message' => __METHOD__,
-						'level' => ILogger::ERROR,
-						'app' => 'core',
-					]);
-				}
-			}
-
-			// reload tags to get the proper ids.
-			$this->tags = $this->mapper->loadTags($this->owners, $this->type);
-			\OCP\Util::writeLog('core', __METHOD__.', tags: ' . print_r($this->tags, true),
-				ILogger::DEBUG);
-			// Loop through temporarily cached objectid/tagname pairs
-			// and save relations.
-			$tags = $this->tags;
-			// For some reason this is needed or array_search(i) will return 0..?
-			ksort($tags);
-			$dbConnection = \OC::$server->getDatabaseConnection();
-			foreach (self::$relations as $relation) {
-				$tagId = $this->getTagId($relation['tag']);
-				\OCP\Util::writeLog('core', __METHOD__ . 'catid, ' . $relation['tag'] . ' ' . $tagId, ILogger::DEBUG);
-				if ($tagId) {
-					try {
-						$dbConnection->insertIfNotExist(self::RELATION_TABLE,
-							[
-								'objid' => $relation['objid'],
-								'categoryid' => $tagId,
-								'type' => $this->type,
-							]);
-					} catch (\Exception $e) {
-						\OC::$server->getLogger()->logException($e, [
-							'message' => __METHOD__,
-							'level' => ILogger::ERROR,
-							'app' => 'core',
-						]);
-					}
-				}
-			}
-			self::$relations = []; // reset
-		} else {
-			\OCP\Util::writeLog('core', __METHOD__.', $this->tags is not an array! '
-				. print_r($this->tags, true), ILogger::ERROR);
-		}
-	}
-
-	/**
-	 * Delete tags and tag/object relations for a user.
-	 *
-	 * For hooking up on post_deleteUser
-	 *
-	 * @param array $arguments
-	 */
-	public static function post_deleteUser($arguments) {
-		// Find all objectid/tagId pairs.
-		$result = null;
-		try {
-			$stmt = \OC_DB::prepare('SELECT `id` FROM `' . self::TAG_TABLE . '` '
-				. 'WHERE `uid` = ?');
-			$result = $stmt->execute([$arguments['uid']]);
-			if ($result === null) {
-				\OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
-			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-		}
-
-		if (!is_null($result)) {
+	protected function save(): void {
+		foreach ($this->tags as $tag) {
 			try {
-				$stmt = \OC_DB::prepare('DELETE FROM `' . self::RELATION_TABLE . '` '
-					. 'WHERE `categoryid` = ?');
-				while ($row = $result->fetchRow()) {
-					try {
-						$stmt->execute([$row['id']]);
-					} catch (\Exception $e) {
-						\OC::$server->getLogger()->logException($e, [
-							'message' => __METHOD__,
-							'level' => ILogger::ERROR,
-							'app' => 'core',
-						]);
-					}
+				if (!$this->mapper->tagExists($tag)) {
+					$this->mapper->insert($tag);
 				}
-				$result->closeCursor();
 			} catch (\Exception $e) {
-				\OC::$server->getLogger()->logException($e, [
-					'message' => __METHOD__,
-					'level' => ILogger::ERROR,
+				$this->logger->error($e->getMessage(), [
+					'exception' => $e,
 					'app' => 'core',
 				]);
 			}
 		}
-		try {
-			$stmt = \OC_DB::prepare('DELETE FROM `' . self::TAG_TABLE . '` '
-				. 'WHERE `uid` = ?');
-			$result = $stmt->execute([$arguments['uid']]);
-			if ($result === null) {
-				\OCP\Util::writeLog('core', __METHOD__. ', DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
+
+		// reload tags to get the proper ids.
+		$this->tags = $this->mapper->loadTags($this->owners, $this->type);
+		$this->logger->debug(__METHOD__ . 'tags' . print_r($this->tags, true), ['app' => 'core']);
+		// Loop through temporarily cached objectid/tagname pairs
+		// and save relations.
+		$tags = $this->tags;
+		// For some reason this is needed or array_search(i) will return 0..?
+		ksort($tags);
+		foreach (self::$relations as $relation) {
+			$tagId = $this->getTagId($relation['tag']);
+			$this->logger->debug(__METHOD__ . 'catid ' . $relation['tag'] . ' ' . $tagId, ['app' => 'core']);
+			if ($tagId) {
+				$qb = $this->db->getQueryBuilder();
+				$qb->insert(self::RELATION_TABLE)
+					->values([
+						'objid' => $qb->createNamedParameter($relation['objid'], IQueryBuilder::PARAM_INT),
+						'categoryid' => $qb->createNamedParameter($tagId, IQueryBuilder::PARAM_INT),
+						'type' => $qb->createNamedParameter($this->type),
+					]);
+				try {
+					$qb->executeStatement();
+				} catch (Exception $e) {
+					$this->logger->error($e->getMessage(), [
+						'exception' => $e,
+						'app' => 'core',
+					]);
+				}
 			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
 		}
+		self::$relations = []; // reset
 	}
 
 	/**
@@ -554,28 +452,21 @@ class Tags implements ITags {
 	 * @param array $ids The ids of the objects
 	 * @return boolean Returns false on error.
 	 */
-	public function purgeObjects(array $ids) {
+	public function purgeObjects(array $ids): bool {
 		if (count($ids) === 0) {
 			// job done ;)
 			return true;
 		}
 		$updates = $ids;
+		$qb = $this->db->getQueryBuilder();
+		$qb->delete(self::RELATION_TABLE)
+			->where($qb->expr()->in('objid', $qb->createNamedParameter($ids)));
 		try {
-			$query = 'DELETE FROM `' . self::RELATION_TABLE . '` ';
-			$query .= 'WHERE `objid` IN (' . str_repeat('?,', count($ids) - 1) . '?) ';
-			$query .= 'AND `type`= ?';
-			$updates[] = $this->type;
-			$stmt = \OC_DB::prepare($query);
-			$result = $stmt->execute($updates);
-			if ($result === null) {
-				\OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
-				return false;
-			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
+			$qb->executeStatement();
+		} catch (Exception $e) {
+			$this->logger->error($e->getMessage(), [
 				'app' => 'core',
+				'exception' => $e,
 			]);
 			return false;
 		}
@@ -648,18 +539,19 @@ class Tags implements ITags {
 		} else {
 			$tagId = $tag;
 		}
+		$qb = $this->db->getQueryBuilder();
+		$qb->insert(self::RELATION_TABLE)
+			->values([
+				'objid' => $qb->createNamedParameter($objid, IQueryBuilder::PARAM_INT),
+				'categoryid' => $qb->createNamedParameter($tagId, IQueryBuilder::PARAM_INT),
+				'type' => $qb->createNamedParameter($this->type, IQueryBuilder::PARAM_STR),
+			]);
 		try {
-			\OC::$server->getDatabaseConnection()->insertIfNotExist(self::RELATION_TABLE,
-				[
-					'objid' => $objid,
-					'categoryid' => $tagId,
-					'type' => $this->type,
-				]);
+			$qb->executeStatement();
 		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
+			\OC::$server->getLogger()->error($e->getMessage(), [
 				'app' => 'core',
+				'exception' => $e,
 			]);
 			return false;
 		}
@@ -686,15 +578,17 @@ class Tags implements ITags {
 		}
 
 		try {
-			$sql = 'DELETE FROM `' . self::RELATION_TABLE . '` '
-					. 'WHERE `objid` = ? AND `categoryid` = ? AND `type` = ?';
-			$stmt = \OC_DB::prepare($sql);
-			$stmt->execute([$objid, $tagId, $this->type]);
+			$qb = $this->db->getQueryBuilder();
+			$qb->delete(self::RELATION_TABLE)
+				->where($qb->expr()->andX(
+					$qb->expr()->eq('objid', $qb->createNamedParameter($objid)),
+					$qb->expr()->eq('categoryid', $qb->createNamedParameter($tagId)),
+					$qb->expr()->eq('type', $qb->createNamedParameter($this->type)),
+				))->executeStatement();
 		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
+			$this->logger->error($e->getMessage(), [
 				'app' => 'core',
+				'exception' => $e,
 			]);
 			return false;
 		}
@@ -736,21 +630,14 @@ class Tags implements ITags {
 			}
 			if (!is_null($id) && $id !== false) {
 				try {
-					$sql = 'DELETE FROM `' . self::RELATION_TABLE . '` '
-							. 'WHERE `categoryid` = ?';
-					$stmt = \OC_DB::prepare($sql);
-					$result = $stmt->execute([$id]);
-					if ($result === null) {
-						\OCP\Util::writeLog('core',
-							__METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(),
-							ILogger::ERROR);
-						return false;
-					}
+					$qb = $this->db->getQueryBuilder();
+					$qb->delete(self::RELATION_TABLE)
+						->where($qb->expr()->eq('categoryid', $qb->createNamedParameter($id, IQueryBuilder::PARAM_INT)))
+						->executeStatement();
 				} catch (\Exception $e) {
-					\OC::$server->getLogger()->logException($e, [
-						'message' => __METHOD__,
-						'level' => ILogger::ERROR,
+					$this->logger->error($e->getMessage(), [
 						'app' => 'core',
+						'exception' => $e,
 					]);
 					return false;
 				}
diff --git a/lib/private/legacy/OC_DB.php b/lib/private/legacy/OC_DB.php
deleted file mode 100644
index 39faf8e80aa..00000000000
--- a/lib/private/legacy/OC_DB.php
+++ /dev/null
@@ -1,184 +0,0 @@
-<?php
-/**
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- *
- * @author Andreas Fischer <bantu@owncloud.com>
- * @author Bart Visscher <bartv@thisnet.nl>
- * @author Christoph Wurst <christoph@winzerhof-wurst.at>
- * @author Joas Schilling <coding@schilljs.com>
- * @author Jörn Friedrich Dreyer <jfd@butonic.de>
- * @author Lukas Reschke <lukas@statuscode.ch>
- * @author Morris Jobke <hey@morrisjobke.de>
- * @author Robin Appelman <robin@icewind.nl>
- * @author Thomas Müller <thomas.mueller@tmit.eu>
- * @author Vincent Petry <vincent@nextcloud.com>
- *
- * @license AGPL-3.0
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * 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, version 3,
- * along with this program. If not, see <http://www.gnu.org/licenses/>
- *
- */
-class OC_DB {
-
-	/**
-	 * Prepare a SQL query
-	 * @param string $query Query string
-	 * @param int|null $limit
-	 * @param int|null $offset
-	 * @param bool|null $isManipulation
-	 * @throws \OC\DatabaseException
-	 * @return OC_DB_StatementWrapper prepared SQL query
-	 * @deprecated 21.0.0 Please use \OCP\IDBConnection::getQueryBuilder() instead
-	 *
-	 * SQL query via Doctrine prepare(), needs to be execute()'d!
-	 */
-	public static function prepare($query, $limit = null, $offset = null, $isManipulation = null) {
-		$connection = \OC::$server->getDatabaseConnection();
-
-		if ($isManipulation === null) {
-			//try to guess, so we return the number of rows on manipulations
-			$isManipulation = self::isManipulation($query);
-		}
-
-		// return the result
-		try {
-			$result = $connection->prepare($query, $limit, $offset);
-		} catch (\Doctrine\DBAL\Exception $e) {
-			throw new \OC\DatabaseException($e->getMessage());
-		}
-		// differentiate between query and manipulation
-		return new OC_DB_StatementWrapper($result, $isManipulation);
-	}
-
-	/**
-	 * tries to guess the type of statement based on the first 10 characters
-	 * the current check allows some whitespace but does not work with IF EXISTS or other more complex statements
-	 *
-	 * @param string $sql
-	 * @return bool
-	 */
-	public static function isManipulation($sql) {
-		$sql = trim($sql);
-		$selectOccurrence = stripos($sql, 'SELECT');
-		if ($selectOccurrence === 0) {
-			return false;
-		}
-		$insertOccurrence = stripos($sql, 'INSERT');
-		if ($insertOccurrence === 0) {
-			return true;
-		}
-		$updateOccurrence = stripos($sql, 'UPDATE');
-		if ($updateOccurrence === 0) {
-			return true;
-		}
-		$deleteOccurrence = stripos($sql, 'DELETE');
-		if ($deleteOccurrence === 0) {
-			return true;
-		}
-
-		// This is triggered with "SHOW VERSION" and some more, so until we made a list, we keep this out.
-		// \OC::$server->getLogger()->logException(new \Exception('Can not detect if query is manipulating: ' . $sql));
-
-		return false;
-	}
-
-	/**
-	 * execute a prepared statement, on error write log and throw exception
-	 * @param mixed $stmt OC_DB_StatementWrapper,
-	 *					  an array with 'sql' and optionally 'limit' and 'offset' keys
-	 *					.. or a simple sql query string
-	 * @param array $parameters
-	 * @return OC_DB_StatementWrapper
-	 * @throws \OC\DatabaseException
-	 * @deprecated 21.0.0 Please use \OCP\IDBConnection::getQueryBuilder() instead
-	 */
-	public static function executeAudited($stmt, array $parameters = []) {
-		if (is_string($stmt)) {
-			// convert to an array with 'sql'
-			if (stripos($stmt, 'LIMIT') !== false) { //OFFSET requires LIMIT, so we only need to check for LIMIT
-				// TODO try to convert LIMIT OFFSET notation to parameters
-				$message = 'LIMIT and OFFSET are forbidden for portability reasons,'
-						 . ' pass an array with \'limit\' and \'offset\' instead';
-				throw new \OC\DatabaseException($message);
-			}
-			$stmt = ['sql' => $stmt, 'limit' => null, 'offset' => null];
-		}
-		if (is_array($stmt)) {
-			// convert to prepared statement
-			if (! array_key_exists('sql', $stmt)) {
-				$message = 'statement array must at least contain key \'sql\'';
-				throw new \OC\DatabaseException($message);
-			}
-			if (! array_key_exists('limit', $stmt)) {
-				$stmt['limit'] = null;
-			}
-			if (! array_key_exists('limit', $stmt)) {
-				$stmt['offset'] = null;
-			}
-			$stmt = self::prepare($stmt['sql'], $stmt['limit'], $stmt['offset']);
-		}
-		self::raiseExceptionOnError($stmt, 'Could not prepare statement');
-		if ($stmt instanceof OC_DB_StatementWrapper) {
-			$result = $stmt->execute($parameters);
-			self::raiseExceptionOnError($result, 'Could not execute statement');
-		} else {
-			if (is_object($stmt)) {
-				$message = 'Expected a prepared statement or array got ' . get_class($stmt);
-			} else {
-				$message = 'Expected a prepared statement or array got ' . gettype($stmt);
-			}
-			throw new \OC\DatabaseException($message);
-		}
-		return $result;
-	}
-
-	/**
-	 * check if a result is an error and throws an exception, works with \Doctrine\DBAL\Exception
-	 * @param mixed $result
-	 * @param string $message
-	 * @return void
-	 * @throws \OC\DatabaseException
-	 */
-	public static function raiseExceptionOnError($result, $message = null) {
-		if ($result === false) {
-			if ($message === null) {
-				$message = self::getErrorMessage();
-			} else {
-				$message .= ', Root cause:' . self::getErrorMessage();
-			}
-			throw new \OC\DatabaseException($message);
-		}
-	}
-
-	/**
-	 * returns the error code and message as a string for logging
-	 * works with DoctrineException
-	 * @return string
-	 */
-	public static function getErrorMessage() {
-		$connection = \OC::$server->getDatabaseConnection();
-		return $connection->getError();
-	}
-
-	/**
-	 * Checks if a table exists in the database - the database prefix will be prepended
-	 *
-	 * @param string $table
-	 * @return bool
-	 * @throws \OC\DatabaseException
-	 */
-	public static function tableExists($table) {
-		$connection = \OC::$server->getDatabaseConnection();
-		return $connection->tableExists($table);
-	}
-}
diff --git a/lib/private/legacy/OC_DB_StatementWrapper.php b/lib/private/legacy/OC_DB_StatementWrapper.php
deleted file mode 100644
index d6214a49a33..00000000000
--- a/lib/private/legacy/OC_DB_StatementWrapper.php
+++ /dev/null
@@ -1,135 +0,0 @@
-<?php
-/**
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- *
- * @author Bart Visscher <bartv@thisnet.nl>
- * @author Christoph Wurst <christoph@winzerhof-wurst.at>
- * @author Joas Schilling <coding@schilljs.com>
- * @author Jörn Friedrich Dreyer <jfd@butonic.de>
- * @author Lukas Reschke <lukas@statuscode.ch>
- * @author Morris Jobke <hey@morrisjobke.de>
- * @author Robin Appelman <robin@icewind.nl>
- * @author Thomas Müller <thomas.mueller@tmit.eu>
- *
- * @license AGPL-3.0
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * 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, version 3,
- * along with this program. If not, see <http://www.gnu.org/licenses/>
- *
- */
-use OCP\DB\IPreparedStatement;
-
-/**
- * small wrapper around \Doctrine\DBAL\Driver\Statement to make it behave, more like an MDB2 Statement
- *
- * @method boolean bindValue(mixed $param, mixed $value, integer $type = null);
- * @method string errorCode();
- * @method array errorInfo();
- * @method integer rowCount();
- * @method array fetchAll(integer $fetchMode = null);
- */
-class OC_DB_StatementWrapper {
-	/** @var IPreparedStatement */
-	private $statement = null;
-
-	/** @var bool */
-	private $isManipulation = false;
-
-	/** @var array */
-	private $lastArguments = [];
-
-	/**
-	 * @param IPreparedStatement $statement
-	 * @param boolean $isManipulation
-	 */
-	public function __construct(IPreparedStatement $statement, $isManipulation) {
-		$this->statement = $statement;
-		$this->isManipulation = $isManipulation;
-	}
-
-	/**
-	 * pass all other function directly to the \Doctrine\DBAL\Driver\Statement
-	 */
-	public function __call($name, $arguments) {
-		return call_user_func_array([$this->statement,$name], $arguments);
-	}
-
-	/**
-	 * make execute return the result instead of a bool
-	 *
-	 * @param mixed[] $input
-	 * @return \OC_DB_StatementWrapper|int|bool
-	 * @deprecated
-	 */
-	public function execute($input = []) {
-		$this->lastArguments = $input;
-		try {
-			if (count($input) > 0) {
-				$result = $this->statement->execute($input);
-			} else {
-				$result = $this->statement->execute();
-			}
-		} catch (\Doctrine\DBAL\Exception $e) {
-			return false;
-		}
-
-		if ($this->isManipulation) {
-			return $this->statement->rowCount();
-		}
-
-		return $this;
-	}
-
-	/**
-	 * provide an alias for fetch
-	 *
-	 * @return mixed
-	 * @deprecated
-	 */
-	public function fetchRow() {
-		return $this->statement->fetch();
-	}
-
-	/**
-	 * Provide a simple fetchOne.
-	 *
-	 * fetch single column from the next row
-	 * @return string
-	 * @deprecated
-	 */
-	public function fetchOne() {
-		return $this->statement->fetchOne();
-	}
-
-	/**
-	 * Closes the cursor, enabling the statement to be executed again.
-	 *
-	 * @deprecated Use Result::free() instead.
-	 */
-	public function closeCursor(): void {
-		$this->statement->closeCursor();
-	}
-
-	/**
-	 * Binds a PHP variable to a corresponding named or question mark placeholder in the
-	 * SQL statement that was use to prepare the statement.
-	 *
-	 * @param mixed $column Either the placeholder name or the 1-indexed placeholder index
-	 * @param mixed $variable The variable to bind
-	 * @param integer|null $type one of the  PDO::PARAM_* constants
-	 * @param integer|null $length max length when using an OUT bind
-	 * @return boolean
-	 */
-	public function bindParam($column, &$variable, $type = null, $length = null) {
-		return $this->statement->bindParam($column, $variable, $type, $length);
-	}
-}
diff --git a/lib/private/legacy/OC_Util.php b/lib/private/legacy/OC_Util.php
index bf9ed6e29ff..4778fe33097 100644
--- a/lib/private/legacy/OC_Util.php
+++ b/lib/private/legacy/OC_Util.php
@@ -69,6 +69,7 @@ use OC\AppFramework\Http\Request;
 use OC\Files\SetupManager;
 use OCP\Files\Template\ITemplateManager;
 use OCP\IConfig;
+use OCP\IDBConnection;
 use OCP\IGroupManager;
 use OCP\IURLGenerator;
 use OCP\IUser;
@@ -749,9 +750,13 @@ class OC_Util {
 		$dbType = \OC::$server->getSystemConfig()->getValue('dbtype', 'sqlite');
 		if ($dbType === 'pgsql') {
 			// check PostgreSQL version
+			// TODO latest postgresql 8 released was 8 years ago, maybe remove the
+			// check completely?
 			try {
-				$result = \OC_DB::executeAudited('SHOW SERVER_VERSION');
-				$data = $result->fetchRow();
+				/** @var IDBConnection $connection */
+				$connection = \OC::$server->get(IDBConnection::class);
+				$result = $connection->executeQuery('SHOW SERVER_VERSION');
+				$data = $result->fetch();
 				$result->closeCursor();
 				if (isset($data['server_version'])) {
 					$version = $data['server_version'];
diff --git a/lib/public/ITags.php b/lib/public/ITags.php
index 03bcb845f4e..06497781bee 100644
--- a/lib/public/ITags.php
+++ b/lib/public/ITags.php
@@ -32,9 +32,6 @@ namespace OCP;
 
 use OC\Tags;
 
-// FIXME: Where should I put this? Or should it be implemented as a Listener?
-\OC_Hook::connect('OC_User', 'post_deleteUser', Tags::class, 'post_deleteUser');
-
 /**
  * Class for easily tagging objects by their id
  *
@@ -55,11 +52,9 @@ interface ITags {
 
 	/**
 	 * Check if any tags are saved for this type and user.
-	 *
-	 * @return boolean
 	 * @since 6.0.0
 	 */
-	public function isEmpty();
+	public function isEmpty(): bool;
 
 	/**
 	 * Returns an array mapping a given tag's properties to its values:
@@ -69,34 +64,40 @@ interface ITags {
 	 * @return array|false
 	 * @since 8.0.0
 	 */
-	public function getTag($id);
+	public function getTag(string $id);
 
 	/**
 	 * Get the tags for a specific user.
 	 *
 	 * This returns an array with id/name maps:
+	 *
+	 * ```php
 	 * [
 	 * 	['id' => 0, 'name' = 'First tag'],
 	 * 	['id' => 1, 'name' = 'Second tag'],
 	 * ]
+	 * ```
 	 *
-	 * @return array
+	 * @return array<array-key, array{id: int, name: string}>
 	 * @since 6.0.0
 	 */
-	public function getTags();
+	public function getTags(): array;
 
 	/**
 	 * Get a list of tags for the given item ids.
 	 *
 	 * This returns an array with object id / tag names:
+	 *
+	 * ```php
 	 * [
 	 *   1 => array('First tag', 'Second tag'),
 	 *   2 => array('Second tag'),
 	 *   3 => array('Second tag', 'Third tag'),
 	 * ]
+	 * ```
 	 *
 	 * @param array $objIds item ids
-	 * @return array|boolean with object id as key and an array
+	 * @return array|false with object id as key and an array
 	 * of tag names as value or false if an error occurred
 	 * @since 8.0.0
 	 */
@@ -117,10 +118,9 @@ interface ITags {
 	 * Checks whether a tag is already saved.
 	 *
 	 * @param string $name The name to check for.
-	 * @return bool
 	 * @since 6.0.0
 	 */
-	public function hasTag($name);
+	public function hasTag(string $name): bool;
 
 	/**
 	 * Checks whether a tag is saved for the given user,
@@ -131,7 +131,7 @@ interface ITags {
 	 * @return bool
 	 * @since 8.0.0
 	 */
-	public function userHasTag($name, $user);
+	public function userHasTag(string $name, string $user): bool;
 
 	/**
 	 * Add a new tag.
@@ -140,7 +140,7 @@ interface ITags {
 	 * @return int|false the id of the added tag or false if it already exists.
 	 * @since 6.0.0
 	 */
-	public function add($name);
+	public function add(string $name);
 
 	/**
 	 * Rename tag.
@@ -150,19 +150,19 @@ interface ITags {
 	 * @return bool
 	 * @since 6.0.0
 	 */
-	public function rename($from, $to);
+	public function rename($from, string $to): bool;
 
 	/**
 	 * Add a list of new tags.
 	 *
-	 * @param string[] $names A string with a name or an array of strings containing
+	 * @param string|string[] $names A string with a name or an array of strings containing
 	 * the name(s) of the to add.
 	 * @param bool $sync When true, save the tags
 	 * @param int|null $id int Optional object id to add to this|these tag(s)
 	 * @return bool Returns false on error.
 	 * @since 6.0.0
 	 */
-	public function addMultiple($names, $sync = false, $id = null);
+	public function addMultiple($names, bool $sync = false, ?int $id = null): bool;
 
 	/**
 	 * Delete tag/object relations from the db