Bump doctrine/dbal from 2.12.0 to 3.0.0

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

21 files changed, 491 insertions, 357 deletions

diff --git a/lib/private/DB/Adapter.php b/lib/private/DB/Adapter.php
index 26fd018dec1..49b831301be 100644
--- a/lib/private/DB/Adapter.php
+++ b/lib/private/DB/Adapter.php
@@ -52,7 +52,7 @@ class Adapter {
 	 * @return int id of last insert statement
 	 */
 	public function lastInsertId($table) {
-		return $this->conn->realLastInsertId($table);
+		return (int) $this->conn->realLastInsertId($table);
 	}
 
 	/**
@@ -94,7 +94,7 @@ class Adapter {
 	 *				If this is null or an empty array, all keys of $input will be compared
 	 *				Please note: text fields (clob) must not be used in the compare array
 	 * @return int number of inserted rows
-	 * @throws \Doctrine\DBAL\DBALException
+	 * @throws \Doctrine\DBAL\Exception
 	 * @deprecated 15.0.0 - use unique index and "try { $db->insert() } catch (UniqueConstraintViolationException $e) {}" instead, because it is more reliable and does not have the risk for deadlocks - see https://github.com/nextcloud/server/pull/12371
 	 */
 	public function insertIfNotExist($table, $input, array $compare = null) {
diff --git a/lib/private/DB/AdapterPgSql.php b/lib/private/DB/AdapterPgSql.php
index 77f0b6b7722..0d8794d59ac 100644
--- a/lib/private/DB/AdapterPgSql.php
+++ b/lib/private/DB/AdapterPgSql.php
@@ -31,7 +31,10 @@ class AdapterPgSql extends Adapter {
 	protected $compatModePre9_5 = null;
 
 	public function lastInsertId($table) {
-		return $this->conn->fetchColumn('SELECT lastval()');
+		$result = $this->conn->executeQuery('SELECT lastval()');
+		$val = $result->fetchOne();
+		$result->free();
+		return (int)$val;
 	}
 
 	public const UNIX_TIMESTAMP_REPLACEMENT = 'cast(extract(epoch from current_timestamp) as integer)';
@@ -62,7 +65,9 @@ class AdapterPgSql extends Adapter {
 			return $this->compatModePre9_5;
 		}
 
-		$version = $this->conn->fetchColumn('SHOW SERVER_VERSION');
+		$result = $this->conn->executeQuery('SHOW SERVER_VERSION');
+		$version = $result->fetchOne();
+		$result->free();
 		$this->compatModePre9_5 = version_compare($version, '9.5', '<');
 
 		return $this->compatModePre9_5;
diff --git a/lib/private/DB/AdapterSqlite.php b/lib/private/DB/AdapterSqlite.php
index 5731ee1721a..a62960bae1a 100644
--- a/lib/private/DB/AdapterSqlite.php
+++ b/lib/private/DB/AdapterSqlite.php
@@ -62,7 +62,7 @@ class AdapterSqlite extends Adapter {
 	 *				If this is null or an empty array, all keys of $input will be compared
 	 *				Please note: text fields (clob) must not be used in the compare array
 	 * @return int number of inserted rows
-	 * @throws \Doctrine\DBAL\DBALException
+	 * @throws \Doctrine\DBAL\Exception
 	 * @deprecated 15.0.0 - use unique index and "try { $db->insert() } catch (UniqueConstraintViolationException $e) {}" instead, because it is more reliable and does not have the risk for deadlocks - see https://github.com/nextcloud/server/pull/12371
 	 */
 	public function insertIfNotExist($table, $input, array $compare = null) {
diff --git a/lib/private/DB/Connection.php b/lib/private/DB/Connection.php
index b024989ac04..c67c6df0826 100644
--- a/lib/private/DB/Connection.php
+++ b/lib/private/DB/Connection.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 /**
  * @copyright Copyright (c) 2016, ownCloud, Inc.
  *
@@ -36,20 +39,21 @@ namespace OC\DB;
 use Doctrine\Common\EventManager;
 use Doctrine\DBAL\Cache\QueryCacheProfile;
 use Doctrine\DBAL\Configuration;
-use Doctrine\DBAL\DBALException;
 use Doctrine\DBAL\Driver;
+use Doctrine\DBAL\Exception;
 use Doctrine\DBAL\Exception\ConstraintViolationException;
 use Doctrine\DBAL\Exception\NotNullConstraintViolationException;
-use Doctrine\DBAL\Platforms\MySqlPlatform;
+use Doctrine\DBAL\Platforms\MySQLPlatform;
+use Doctrine\DBAL\Result;
 use Doctrine\DBAL\Schema\Schema;
+use Doctrine\DBAL\Statement;
 use OC\DB\QueryBuilder\QueryBuilder;
 use OC\SystemConfig;
 use OCP\DB\QueryBuilder\IQueryBuilder;
-use OCP\IDBConnection;
 use OCP\ILogger;
 use OCP\PreConditionNotMetException;
 
-class Connection extends ReconnectWrapper implements IDBConnection {
+class Connection extends ReconnectWrapper {
 	/** @var string */
 	protected $tablePrefix;
 
@@ -73,9 +77,9 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	public function connect() {
 		try {
 			return parent::connect();
-		} catch (DBALException $e) {
+		} catch (Exception $e) {
 			// throw a new exception to prevent leaking info from the stacktrace
-			throw new DBALException('Failed to connect to the database: ' . $e->getMessage(), $e->getCode());
+			throw new Exception('Failed to connect to the database: ' . $e->getMessage(), $e->getCode());
 		}
 	}
 
@@ -88,13 +92,11 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 
 	/**
 	 * Returns a QueryBuilder for the connection.
-	 *
-	 * @return \OCP\DB\QueryBuilder\IQueryBuilder
 	 */
-	public function getQueryBuilder() {
+	public function getQueryBuilder(): IQueryBuilder {
 		$this->queriesBuilt++;
 		return new QueryBuilder(
-			$this,
+			new ConnectionAdapter($this),
 			$this->systemConfig,
 			$this->logger
 		);
@@ -181,9 +183,9 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	 * @param string $statement The SQL statement to prepare.
 	 * @param int $limit
 	 * @param int $offset
-	 * @return \Doctrine\DBAL\Driver\Statement The prepared statement.
+	 * @return Statement The prepared statement.
 	 */
-	public function prepare($statement, $limit = null, $offset = null) {
+	public function prepare($statement, $limit = null, $offset = null): Statement {
 		if ($limit === -1) {
 			$limit = null;
 		}
@@ -208,18 +210,18 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	 * @param array                                       $types  The types the previous parameters are in.
 	 * @param \Doctrine\DBAL\Cache\QueryCacheProfile|null $qcp    The query cache profile, optional.
 	 *
-	 * @return \Doctrine\DBAL\Driver\Statement The executed statement.
+	 * @return Result The executed statement.
 	 *
-	 * @throws \Doctrine\DBAL\DBALException
+	 * @throws \Doctrine\DBAL\Exception
 	 */
-	public function executeQuery($sql, array $params = [], $types = [], QueryCacheProfile $qcp = null) {
+	public function executeQuery(string $sql, array $params = [], $types = [], QueryCacheProfile $qcp = null): Result {
 		$sql = $this->replaceTablePrefix($sql);
 		$sql = $this->adapter->fixupStatement($sql);
 		$this->queriesExecuted++;
 		return parent::executeQuery($sql, $params, $types, $qcp);
 	}
 
-	public function executeUpdate($sql, array $params = [], array $types = []) {
+	public function executeUpdate(string $sql, array $params = [], array $types = []): int {
 		$sql = $this->replaceTablePrefix($sql);
 		$sql = $this->adapter->fixupStatement($sql);
 		$this->queriesExecuted++;
@@ -236,11 +238,11 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	 * @param array  $params The query parameters.
 	 * @param array  $types  The parameter types.
 	 *
-	 * @return integer The number of affected rows.
+	 * @return int The number of affected rows.
 	 *
-	 * @throws \Doctrine\DBAL\DBALException
+	 * @throws \Doctrine\DBAL\Exception
 	 */
-	public function executeStatement($sql, array $params = [], array $types = []) {
+	public function executeStatement($sql, array $params = [], array $types = []): int {
 		$sql = $this->replaceTablePrefix($sql);
 		$sql = $this->adapter->fixupStatement($sql);
 		$this->queriesExecuted++;
@@ -256,7 +258,7 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	 * columns or sequences.
 	 *
 	 * @param string $seqName Name of the sequence object from which the ID should be returned.
-	 * @return string A string representation of the last inserted ID.
+	 * @return string the last inserted ID.
 	 */
 	public function lastInsertId($seqName = null) {
 		if ($seqName) {
@@ -281,7 +283,7 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	 *				If this is null or an empty array, all keys of $input will be compared
 	 *				Please note: text fields (clob) must not be used in the compare array
 	 * @return int number of inserted rows
-	 * @throws \Doctrine\DBAL\DBALException
+	 * @throws \Doctrine\DBAL\Exception
 	 * @deprecated 15.0.0 - use unique index and "try { $db->insert() } catch (UniqueConstraintViolationException $e) {}" instead, because it is more reliable and does not have the risk for deadlocks - see https://github.com/nextcloud/server/pull/12371
 	 */
 	public function insertIfNotExist($table, $input, array $compare = null) {
@@ -310,7 +312,7 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	 * @param array $values (column name => value)
 	 * @param array $updatePreconditionValues ensure values match preconditions (column name => value)
 	 * @return int number of new rows
-	 * @throws \Doctrine\DBAL\DBALException
+	 * @throws \Doctrine\DBAL\Exception
 	 * @throws PreConditionNotMetException
 	 */
 	public function setValues($table, array $keys, array $values, array $updatePreconditionValues = []) {
@@ -393,7 +395,7 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	public function getError() {
 		$msg = $this->errorCode() . ': ';
 		$errorInfo = $this->errorInfo();
-		if (is_array($errorInfo)) {
+		if (!empty($errorInfo)) {
 			$msg .= 'SQLSTATE = '.$errorInfo[0] . ', ';
 			$msg .= 'Driver Code = '.$errorInfo[1] . ', ';
 			$msg .= 'Driver Message = '.$errorInfo[2];
@@ -401,6 +403,14 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 		return $msg;
 	}
 
+	public function errorCode() {
+		return -1;
+	}
+
+	public function errorInfo() {
+		return [];
+	}
+
 	/**
 	 * Drop a table from the database if it exists
 	 *
@@ -462,7 +472,7 @@ class Connection extends ReconnectWrapper implements IDBConnection {
 	 * @since 11.0.0
 	 */
 	public function supports4ByteText() {
-		if (!$this->getDatabasePlatform() instanceof MySqlPlatform) {
+		if (!$this->getDatabasePlatform() instanceof MySQLPlatform) {
 			return true;
 		}
 		return $this->getParams()['charset'] === 'utf8mb4';
diff --git a/lib/private/DB/ConnectionAdapter.php b/lib/private/DB/ConnectionAdapter.php
new file mode 100644
index 00000000000..97a0b60044d
--- /dev/null
+++ b/lib/private/DB/ConnectionAdapter.php
@@ -0,0 +1,172 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2020 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2020 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @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 OC\DB;
+
+use Doctrine\DBAL\Platforms\AbstractPlatform;
+use Doctrine\DBAL\Schema\Schema;
+use OCP\DB\IPreparedStatement;
+use OCP\DB\IResult;
+use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IDBConnection;
+
+/**
+ * Adapts the public API to our internal DBAL connection wrapper
+ */
+class ConnectionAdapter implements IDBConnection {
+
+	/** @var Connection */
+	private $inner;
+
+	public function __construct(Connection $inner) {
+		$this->inner = $inner;
+	}
+
+	public function getQueryBuilder(): IQueryBuilder {
+		return $this->inner->getQueryBuilder();
+	}
+
+	public function prepare($sql, $limit = null, $offset = null): IPreparedStatement {
+		return new PreparedStatement(
+			$this->inner->prepare($sql, $limit, $offset)
+		);
+	}
+
+	public function executeQuery(string $sql, array $params = [], $types = []): IResult {
+		return new ResultAdapter(
+			$this->inner->executeQuery($sql, $params, $types)
+		);
+	}
+
+	public function executeUpdate(string $sql, array $params = [], array $types = []): int {
+		return $this->inner->executeUpdate($sql, $params, $types);
+	}
+
+	public function executeStatement($sql, array $params = [], array $types = []): int {
+		return $this->inner->executeStatement($sql, $params, $types);
+	}
+
+	public function lastInsertId(string $table): int {
+		return (int) $this->inner->lastInsertId($table);
+	}
+
+	public function insertIfNotExist(string $table, array $input, array $compare = null) {
+		return $this->inner->insertIfNotExist($table, $input, $compare);
+	}
+
+	public function insertIgnoreConflict(string $table, array $values): int {
+		return $this->inner->insertIgnoreConflict($table, $values);
+	}
+
+	public function setValues($table, array $keys, array $values, array $updatePreconditionValues = []): int {
+		return $this->inner->setValues($table, $keys, $values, $updatePreconditionValues);
+	}
+
+	public function lockTable($tableName): void {
+		$this->inner->lockTable($tableName);
+	}
+
+	public function unlockTable(): void {
+		$this->inner->unlockTable();
+	}
+
+	public function beginTransaction(): void {
+		$this->inner->beginTransaction();
+	}
+
+	public function inTransaction(): bool {
+		return $this->inner->inTransaction();
+	}
+
+	public function commit(): void {
+		$this->inner->commit();
+	}
+
+	public function rollBack(): void {
+		$this->inner->rollBack();
+	}
+
+	public function getError(): string {
+		return $this->inner->getError();
+	}
+
+	public function errorCode() {
+		return $this->inner->errorCode();
+	}
+
+	public function errorInfo() {
+		return $this->inner->errorInfo();
+	}
+
+	public function connect(): bool {
+		return $this->inner->connect();
+	}
+
+	public function close(): void {
+		$this->inner->close();
+	}
+
+	public function quote($input, $type = IQueryBuilder::PARAM_STR) {
+		return $this->inner->quote($input, $type);
+	}
+
+	/**
+	 * @todo we are leaking a 3rdparty type here
+	 */
+	public function getDatabasePlatform(): AbstractPlatform {
+		return $this->inner->getDatabasePlatform();
+	}
+
+	public function dropTable(string $table): void {
+		$this->inner->dropTable($table);
+	}
+
+	public function tableExists(string $table): bool {
+		return $this->inner->tableExists($table);
+	}
+
+	public function escapeLikeParameter(string $param): string {
+		return $this->inner->escapeLikeParameter($param);
+	}
+
+	public function supports4ByteText(): bool {
+		return $this->inner->supports4ByteText();
+	}
+
+	/**
+	 * @todo leaks a 3rdparty type
+	 */
+	public function createSchema(): Schema {
+		return $this->inner->createSchema();
+	}
+
+	public function migrateToSchema(Schema $toSchema): void {
+		$this->inner->migrateToSchema($toSchema);
+	}
+
+	public function getInner(): Connection {
+		return $this->inner;
+	}
+}
diff --git a/lib/private/DB/MDB2SchemaManager.php b/lib/private/DB/MDB2SchemaManager.php
index 44ea3986214..18549eb1fa2 100644
--- a/lib/private/DB/MDB2SchemaManager.php
+++ b/lib/private/DB/MDB2SchemaManager.php
@@ -31,36 +31,24 @@
 
 namespace OC\DB;
 
-use Doctrine\DBAL\Platforms\MySqlPlatform;
+use Doctrine\DBAL\Platforms\MySQLPlatform;
 use Doctrine\DBAL\Platforms\OraclePlatform;
-use Doctrine\DBAL\Platforms\PostgreSqlPlatform;
+use Doctrine\DBAL\Platforms\PostgreSQL94Platform;
 use Doctrine\DBAL\Platforms\SqlitePlatform;
 use Doctrine\DBAL\Schema\Schema;
-use OCP\IDBConnection;
 
 class MDB2SchemaManager {
-	/** @var \OC\DB\Connection $conn */
+	/** @var Connection $conn */
 	protected $conn;
 
 	/**
-	 * @param IDBConnection $conn
+	 * @param Connection $conn
 	 */
 	public function __construct($conn) {
 		$this->conn = $conn;
 	}
 
 	/**
-	 * saves database scheme to xml file
-	 * @param string $file name of file
-	 * @return bool
-	 *
-	 * TODO: write more documentation
-	 */
-	public function getDbStructure($file) {
-		return \OC\DB\MDB2SchemaWriter::saveSchemaToFile($file, $this->conn);
-	}
-
-	/**
 	 * Creates tables from XML file
 	 * @param string $file file to read structure from
 	 * @return bool
@@ -86,9 +74,9 @@ class MDB2SchemaManager {
 			return new SQLiteMigrator($this->conn, $random, $config, $dispatcher);
 		} elseif ($platform instanceof OraclePlatform) {
 			return new OracleMigrator($this->conn, $random, $config, $dispatcher);
-		} elseif ($platform instanceof MySqlPlatform) {
+		} elseif ($platform instanceof MySQLPlatform) {
 			return new MySQLMigrator($this->conn, $random, $config, $dispatcher);
-		} elseif ($platform instanceof PostgreSqlPlatform) {
+		} elseif ($platform instanceof PostgreSQL94Platform) {
 			return new PostgreSqlMigrator($this->conn, $random, $config, $dispatcher);
 		} else {
 			return new Migrator($this->conn, $random, $config, $dispatcher);
diff --git a/lib/private/DB/MDB2SchemaWriter.php b/lib/private/DB/MDB2SchemaWriter.php
deleted file mode 100644
index 2c1f6a5e545..00000000000
--- a/lib/private/DB/MDB2SchemaWriter.php
+++ /dev/null
@@ -1,181 +0,0 @@
-<?php
-/**
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- *
- * @author Bart Visscher <bartv@thisnet.nl>
- * @author Christoph Wurst <christoph@winzerhof-wurst.at>
- * @author Jörn Friedrich Dreyer <jfd@butonic.de>
- * @author Morris Jobke <hey@morrisjobke.de>
- * @author tbelau666 <thomas.belau@gmx.de>
- * @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/>
- *
- */
-
-namespace OC\DB;
-
-use Doctrine\DBAL\Schema\Column;
-use Doctrine\DBAL\Schema\Index;
-
-class MDB2SchemaWriter {
-
-	/**
-	 * @param string $file
-	 * @param \OC\DB\Connection $conn
-	 * @return bool
-	 */
-	public static function saveSchemaToFile($file, \OC\DB\Connection $conn) {
-		$config = \OC::$server->getConfig();
-
-		$xml = new \SimpleXMLElement('<database/>');
-		$xml->addChild('name', $config->getSystemValue('dbname', 'owncloud'));
-		$xml->addChild('create', 'true');
-		$xml->addChild('overwrite', 'false');
-		if ($config->getSystemValue('dbtype', 'sqlite') === 'mysql' && $config->getSystemValue('mysql.utf8mb4', false)) {
-			$xml->addChild('charset', 'utf8mb4');
-		} else {
-			$xml->addChild('charset', 'utf8');
-		}
-
-		// FIX ME: bloody work around
-		if ($config->getSystemValue('dbtype', 'sqlite') === 'oci') {
-			$filterExpression = '/^"' . preg_quote($conn->getPrefix()) . '/';
-		} else {
-			$filterExpression = '/^' . preg_quote($conn->getPrefix()) . '/';
-		}
-		$conn->getConfiguration()->setFilterSchemaAssetsExpression($filterExpression);
-
-		foreach ($conn->getSchemaManager()->listTables() as $table) {
-			self::saveTable($table, $xml->addChild('table'));
-		}
-		file_put_contents($file, $xml->asXML());
-		return true;
-	}
-
-	/**
-	 * @param \Doctrine\DBAL\Schema\Table $table
-	 * @param \SimpleXMLElement $xml
-	 */
-	private static function saveTable($table, $xml) {
-		$xml->addChild('name', $table->getName());
-		$declaration = $xml->addChild('declaration');
-		foreach ($table->getColumns() as $column) {
-			self::saveColumn($column, $declaration->addChild('field'));
-		}
-		foreach ($table->getIndexes() as $index) {
-			if ($index->getName() == 'PRIMARY') {
-				$autoincrement = false;
-				foreach ($index->getColumns() as $column) {
-					if ($table->getColumn($column)->getAutoincrement()) {
-						$autoincrement = true;
-					}
-				}
-				if ($autoincrement) {
-					continue;
-				}
-			}
-			self::saveIndex($index, $declaration->addChild('index'));
-		}
-	}
-
-	/**
-	 * @param Column $column
-	 * @param \SimpleXMLElement $xml
-	 */
-	private static function saveColumn($column, $xml) {
-		$xml->addChild('name', $column->getName());
-		switch ($column->getType()) {
-			case 'SmallInt':
-			case 'Integer':
-			case 'BigInt':
-				$xml->addChild('type', 'integer');
-				$default = $column->getDefault();
-				if (is_null($default) && $column->getAutoincrement()) {
-					$default = '0';
-				}
-				$xml->addChild('default', $default);
-				$xml->addChild('notnull', self::toBool($column->getNotnull()));
-				if ($column->getAutoincrement()) {
-					$xml->addChild('autoincrement', '1');
-				}
-				if ($column->getUnsigned()) {
-					$xml->addChild('unsigned', 'true');
-				}
-				$length = '4';
-				if ($column->getType() == 'SmallInt') {
-					$length = '2';
-				} elseif ($column->getType() == 'BigInt') {
-					$length = '8';
-				}
-				$xml->addChild('length', $length);
-				break;
-			case 'String':
-				$xml->addChild('type', 'text');
-				$default = trim($column->getDefault());
-				if ($default === '') {
-					$default = false;
-				}
-				$xml->addChild('default', $default);
-				$xml->addChild('notnull', self::toBool($column->getNotnull()));
-				$xml->addChild('length', $column->getLength());
-				break;
-			case 'Text':
-				$xml->addChild('type', 'clob');
-				$xml->addChild('notnull', self::toBool($column->getNotnull()));
-				break;
-			case 'Decimal':
-				$xml->addChild('type', 'decimal');
-				$xml->addChild('default', $column->getDefault());
-				$xml->addChild('notnull', self::toBool($column->getNotnull()));
-				$xml->addChild('length', '15');
-				break;
-			case 'Boolean':
-				$xml->addChild('type', 'integer');
-				$xml->addChild('default', $column->getDefault());
-				$xml->addChild('notnull', self::toBool($column->getNotnull()));
-				$xml->addChild('length', '1');
-				break;
-			case 'DateTime':
-				$xml->addChild('type', 'timestamp');
-				$xml->addChild('default', $column->getDefault());
-				$xml->addChild('notnull', self::toBool($column->getNotnull()));
-				break;
-
-		}
-	}
-
-	/**
-	 * @param Index $index
-	 * @param \SimpleXMLElement $xml
-	 */
-	private static function saveIndex($index, $xml) {
-		$xml->addChild('name', $index->getName());
-		if ($index->isPrimary()) {
-			$xml->addChild('primary', 'true');
-		} elseif ($index->isUnique()) {
-			$xml->addChild('unique', 'true');
-		}
-		foreach ($index->getColumns() as $column) {
-			$field = $xml->addChild('field');
-			$field->addChild('name', $column);
-			$field->addChild('sorting', 'ascending');
-		}
-	}
-
-	private static function toBool($bool) {
-		return $bool ? 'true' : 'false';
-	}
-}
diff --git a/lib/private/DB/MigrationService.php b/lib/private/DB/MigrationService.php
index 6a1cb4be016..44707911092 100644
--- a/lib/private/DB/MigrationService.php
+++ b/lib/private/DB/MigrationService.php
@@ -30,7 +30,7 @@ namespace OC\DB;
 
 use Doctrine\DBAL\Exception\DriverException;
 use Doctrine\DBAL\Platforms\OraclePlatform;
-use Doctrine\DBAL\Platforms\PostgreSqlPlatform;
+use Doctrine\DBAL\Platforms\PostgreSQL94Platform;
 use Doctrine\DBAL\Schema\Index;
 use Doctrine\DBAL\Schema\Schema;
 use Doctrine\DBAL\Schema\SchemaException;
@@ -42,7 +42,6 @@ use OC\IntegrityCheck\Helpers\AppLocator;
 use OC\Migration\SimpleOutput;
 use OCP\AppFramework\App;
 use OCP\AppFramework\QueryException;
-use OCP\IDBConnection;
 use OCP\Migration\IMigrationStep;
 use OCP\Migration\IOutput;
 
@@ -65,12 +64,12 @@ class MigrationService {
 	 * MigrationService constructor.
 	 *
 	 * @param $appName
-	 * @param IDBConnection $connection
+	 * @param Connection $connection
 	 * @param AppLocator $appLocator
 	 * @param IOutput|null $output
 	 * @throws \Exception
 	 */
-	public function __construct($appName, IDBConnection $connection, IOutput $output = null, AppLocator $appLocator = null) {
+	public function __construct($appName, Connection $connection, IOutput $output = null, AppLocator $appLocator = null) {
 		$this->appName = $appName;
 		$this->connection = $connection;
 		$this->output = $output;
@@ -591,7 +590,7 @@ class MigrationService {
 				$indexName = strtolower($primaryKey->getName());
 				$isUsingDefaultName = $indexName === 'primary';
 
-				if ($this->connection->getDatabasePlatform() instanceof PostgreSqlPlatform) {
+				if ($this->connection->getDatabasePlatform() instanceof PostgreSQL94Platform) {
 					$defaultName = $table->getName() . '_pkey';
 					$isUsingDefaultName = strtolower($defaultName) === $indexName;
 
diff --git a/lib/private/DB/Migrator.php b/lib/private/DB/Migrator.php
index 569b1a6c282..f62735ea6b2 100644
--- a/lib/private/DB/Migrator.php
+++ b/lib/private/DB/Migrator.php
@@ -31,7 +31,8 @@
 
 namespace OC\DB;
 
-use Doctrine\DBAL\DBALException;
+use Doctrine\DBAL\Exception;
+use Doctrine\DBAL\Schema\AbstractAsset;
 use Doctrine\DBAL\Schema\Comparator;
 use Doctrine\DBAL\Schema\Index;
 use Doctrine\DBAL\Schema\Schema;
@@ -43,6 +44,7 @@ use OCP\IConfig;
 use OCP\Security\ISecureRandom;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\EventDispatcher\GenericEvent;
+use function preg_match;
 
 class Migrator {
 
@@ -102,34 +104,6 @@ class Migrator {
 	}
 
 	/**
-	 * @param Schema $targetSchema
-	 * @throws \OC\DB\MigrationException
-	 */
-	public function checkMigrate(Schema $targetSchema) {
-		$this->noEmit = true;
-		/**@var \Doctrine\DBAL\Schema\Table[] $tables */
-		$tables = $targetSchema->getTables();
-		$filterExpression = $this->getFilterExpression();
-		$this->connection->getConfiguration()->
-			setFilterSchemaAssetsExpression($filterExpression);
-		$existingTables = $this->connection->getSchemaManager()->listTableNames();
-
-		$step = 0;
-		foreach ($tables as $table) {
-			if (strpos($table->getName(), '.')) {
-				list(, $tableName) = explode('.', $table->getName());
-			} else {
-				$tableName = $table->getName();
-			}
-			$this->emitCheckStep($tableName, $step++, count($tables));
-			// don't need to check for new tables
-			if (array_search($tableName, $existingTables) !== false) {
-				$this->checkTableMigrate($table);
-			}
-		}
-	}
-
-	/**
 	 * Create a unique name for the temporary table
 	 *
 	 * @param string $name
@@ -160,7 +134,7 @@ class Migrator {
 		try {
 			$this->applySchema($schema);
 			$this->dropTable($tmpName);
-		} catch (DBALException $e) {
+		} catch (Exception $e) {
 			// pgsql needs to commit it's failed transaction before doing anything else
 			if ($this->connection->isTransactionActive()) {
 				$this->connection->commit();
@@ -193,12 +167,18 @@ class Migrator {
 		}
 
 		// foreign keys are not supported so we just set it to an empty array
-		return new Table($newName, $table->getColumns(), $newIndexes, [], 0, $table->getOptions());
+		return new Table($newName, $table->getColumns(), $newIndexes, [], [], $table->getOptions());
 	}
 
 	public function createSchema() {
-		$filterExpression = $this->getFilterExpression();
-		$this->connection->getConfiguration()->setFilterSchemaAssetsExpression($filterExpression);
+		$this->connection->getConfiguration()->setSchemaAssetsFilter(function ($asset) {
+			/** @var string|AbstractAsset $asset */
+			$filterExpression = $this->getFilterExpression();
+			if ($asset instanceof AbstractAsset) {
+				return preg_match($filterExpression, $asset->getName()) !== false;
+			}
+			return preg_match($filterExpression, $asset) !== false;
+		});
 		return $this->connection->getSchemaManager()->createSchema();
 	}
 
@@ -206,7 +186,6 @@ class Migrator {
 	 * @param Schema $targetSchema
 	 * @param \Doctrine\DBAL\Connection $connection
 	 * @return \Doctrine\DBAL\Schema\SchemaDiff
-	 * @throws DBALException
 	 */
 	protected function getDiff(Schema $targetSchema, \Doctrine\DBAL\Connection $connection) {
 		// adjust varchar columns with a length higher then getVarcharMaxLength to clob
@@ -221,8 +200,14 @@ class Migrator {
 			}
 		}
 
-		$filterExpression = $this->getFilterExpression();
-		$this->connection->getConfiguration()->setFilterSchemaAssetsExpression($filterExpression);
+		$this->connection->getConfiguration()->setSchemaAssetsFilter(function ($asset) {
+			/** @var string|AbstractAsset $asset */
+			$filterExpression = $this->getFilterExpression();
+			if ($asset instanceof AbstractAsset) {
+				return preg_match($filterExpression, $asset->getName()) !== false;
+			}
+			return preg_match($filterExpression, $asset) !== false;
+		});
 		$sourceSchema = $connection->getSchemaManager()->createSchema();
 
 		// remove tables we don't know about
diff --git a/lib/private/DB/MySqlTools.php b/lib/private/DB/MySqlTools.php
index 007388d5615..e738a2bd94a 100644
--- a/lib/private/DB/MySqlTools.php
+++ b/lib/private/DB/MySqlTools.php
@@ -32,7 +32,7 @@ use OCP\IDBConnection;
 class MySqlTools {
 
 	/**
-	 * @param Connection $connection
+	 * @param IDBConnection $connection
 	 * @return bool
 	 */
 	public function supports4ByteCharset(IDBConnection $connection) {
diff --git a/lib/private/DB/OracleMigrator.php b/lib/private/DB/OracleMigrator.php
index cad5390f092..7a327a42797 100644
--- a/lib/private/DB/OracleMigrator.php
+++ b/lib/private/DB/OracleMigrator.php
@@ -30,7 +30,7 @@
 
 namespace OC\DB;
 
-use Doctrine\DBAL\DBALException;
+use Doctrine\DBAL\Exception;
 use Doctrine\DBAL\Schema\Column;
 use Doctrine\DBAL\Schema\ColumnDiff;
 use Doctrine\DBAL\Schema\ForeignKeyConstraint;
@@ -113,7 +113,7 @@ class OracleMigrator extends Migrator {
 	 * @param Schema $targetSchema
 	 * @param \Doctrine\DBAL\Connection $connection
 	 * @return \Doctrine\DBAL\Schema\SchemaDiff
-	 * @throws DBALException
+	 * @throws Exception
 	 */
 	protected function getDiff(Schema $targetSchema, \Doctrine\DBAL\Connection $connection) {
 		$schemaDiff = parent::getDiff($targetSchema, $connection);
@@ -128,10 +128,10 @@ class OracleMigrator extends Migrator {
 				array_map(function (Index $index) {
 					return $this->quoteIndex($index);
 				}, $table->getIndexes()),
+				[],
 				array_map(function (ForeignKeyConstraint $fck) {
 					return $this->quoteForeignKeyConstraint($fck);
 				}, $table->getForeignKeys()),
-				0,
 				$table->getOptions()
 			);
 		}, $schemaDiff->newTables);
@@ -141,8 +141,8 @@ class OracleMigrator extends Migrator {
 				$this->connection->quoteIdentifier($table->getName()),
 				$table->getColumns(),
 				$table->getIndexes(),
+				[],
 				$table->getForeignKeys(),
-				0,
 				$table->getOptions()
 			);
 		}, $schemaDiff->removedTables);
diff --git a/lib/private/DB/PgSqlTools.php b/lib/private/DB/PgSqlTools.php
index 724344ac2a1..d555bfb391b 100644
--- a/lib/private/DB/PgSqlTools.php
+++ b/lib/private/DB/PgSqlTools.php
@@ -26,7 +26,10 @@
 
 namespace OC\DB;
 
+use Doctrine\DBAL\Schema\AbstractAsset;
 use OCP\IConfig;
+use function preg_match;
+use function preg_quote;
 
 /**
  * Various PostgreSQL specific helper functions.
@@ -50,20 +53,30 @@ class PgSqlTools {
 	 * @return null
 	 */
 	public function resynchronizeDatabaseSequences(Connection $conn) {
-		$filterExpression = '/^' . preg_quote($this->config->getSystemValue('dbtableprefix', 'oc_')) . '/';
 		$databaseName = $conn->getDatabase();
-		$conn->getConfiguration()->setFilterSchemaAssetsExpression($filterExpression);
+		$conn->getConfiguration()->setSchemaAssetsFilter(function ($asset) {
+			/** @var string|AbstractAsset $asset */
+			$filterExpression = '/^' . preg_quote($this->config->getSystemValue('dbtableprefix', 'oc_')) . '/';
+			if ($asset instanceof AbstractAsset) {
+				return preg_match($filterExpression, $asset->getName()) !== false;
+			}
+			return preg_match($filterExpression, $asset) !== false;
+		});
 
 		foreach ($conn->getSchemaManager()->listSequences() as $sequence) {
 			$sequenceName = $sequence->getName();
 			$sqlInfo = 'SELECT table_schema, table_name, column_name
 				FROM information_schema.columns
 				WHERE column_default = ? AND table_catalog = ?';
-			$sequenceInfo = $conn->fetchAssoc($sqlInfo, [
+			$result = $conn->executeQuery($sqlInfo, [
 				"nextval('$sequenceName'::regclass)",
 				$databaseName
 			]);
+			$sequenceInfo = $result->fetchAssociative();
+			$result->free();
+			/** @var string $tableName */
 			$tableName = $sequenceInfo['table_name'];
+			/** @var string $columnName */
 			$columnName = $sequenceInfo['column_name'];
 			$sqlMaxId = "SELECT MAX($columnName) FROM $tableName";
 			$sqlSetval = "SELECT setval('$sequenceName', ($sqlMaxId))";
diff --git a/lib/private/DB/PreparedStatement.php b/lib/private/DB/PreparedStatement.php
new file mode 100644
index 00000000000..f679576a428
--- /dev/null
+++ b/lib/private/DB/PreparedStatement.php
@@ -0,0 +1,101 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @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 OC\DB;
+
+use Doctrine\DBAL\Exception;
+use Doctrine\DBAL\ParameterType;
+use Doctrine\DBAL\Statement;
+use OCP\DB\IPreparedStatement;
+use OCP\DB\IResult;
+use PDO;
+
+/**
+ * Adapts our public API to what doctrine/dbal exposed with 2.6
+ *
+ * The old dbal statement had stateful methods e.g. to fetch data from an executed
+ * prepared statement. To provide backwards compatibility to apps we need to make
+ * this class stateful. As soon as those now deprecated exposed methods are gone,
+ * we can limit the API of this adapter to the methods that map to the direct dbal
+ * methods without much magic.
+ */
+class PreparedStatement implements IPreparedStatement {
+
+	/** @var Statement */
+	private $statement;
+
+	/** @var IResult|null */
+	private $result;
+
+	public function __construct(Statement $statement) {
+		$this->statement = $statement;
+	}
+
+	public function closeCursor(): bool {
+		$this->getResult()->closeCursor();
+
+		return true;
+	}
+
+	public function fetch(int $fetchMode = PDO::FETCH_ASSOC) {
+		return $this->getResult()->fetch($fetchMode);
+	}
+
+	public function fetchAll(int $fetchMode = PDO::FETCH_ASSOC): array {
+		return $this->getResult()->fetchAll($fetchMode);
+	}
+
+	public function fetchColumn() {
+		return $this->getResult()->fetchOne();
+	}
+
+	public function fetchOne() {
+		return $this->getResult()->fetchOne();
+	}
+
+	public function bindValue($param, $value, $type = ParameterType::STRING): bool {
+		return $this->statement->bindValue($param, $value, $type);
+	}
+
+	public function bindParam($param, &$variable, $type = ParameterType::STRING, $length = null): bool {
+		return $this->statement->bindParam($param, $variable, $type, $length);
+	}
+
+	public function execute($params = null): IResult {
+		return ($this->result = new ResultAdapter($this->statement->execute($params)));
+	}
+
+	public function rowCount(): int {
+		return $this->getResult()->rowCount();
+	}
+
+	private function getResult(): IResult {
+		if ($this->result !== null) {
+			return $this->result;
+		}
+
+		throw new Exception("You have to execute the prepared statement before accessing the results");
+	}
+}
diff --git a/lib/private/DB/QueryBuilder/ExpressionBuilder/ExpressionBuilder.php b/lib/private/DB/QueryBuilder/ExpressionBuilder/ExpressionBuilder.php
index 61eea80640e..d4c1a9db881 100644
--- a/lib/private/DB/QueryBuilder/ExpressionBuilder/ExpressionBuilder.php
+++ b/lib/private/DB/QueryBuilder/ExpressionBuilder/ExpressionBuilder.php
@@ -27,6 +27,7 @@
 namespace OC\DB\QueryBuilder\ExpressionBuilder;
 
 use Doctrine\DBAL\Query\Expression\ExpressionBuilder as DoctrineExpressionBuilder;
+use OC\DB\ConnectionAdapter;
 use OC\DB\QueryBuilder\CompositeExpression;
 use OC\DB\QueryBuilder\FunctionBuilder\FunctionBuilder;
 use OC\DB\QueryBuilder\Literal;
@@ -55,13 +56,13 @@ class ExpressionBuilder implements IExpressionBuilder {
 	/**
 	 * Initializes a new <tt>ExpressionBuilder</tt>.
 	 *
-	 * @param IDBConnection $connection
+	 * @param ConnectionAdapter $connection
 	 * @param IQueryBuilder $queryBuilder
 	 */
-	public function __construct(IDBConnection $connection, IQueryBuilder $queryBuilder) {
+	public function __construct(ConnectionAdapter $connection, IQueryBuilder $queryBuilder) {
 		$this->connection = $connection;
 		$this->helper = new QuoteHelper();
-		$this->expressionBuilder = new DoctrineExpressionBuilder($connection);
+		$this->expressionBuilder = new DoctrineExpressionBuilder($connection->getInner());
 		$this->functionBuilder = $queryBuilder->func();
 	}
 
diff --git a/lib/private/DB/QueryBuilder/ExpressionBuilder/MySqlExpressionBuilder.php b/lib/private/DB/QueryBuilder/ExpressionBuilder/MySqlExpressionBuilder.php
index 899f9277439..3e4119bb11c 100644
--- a/lib/private/DB/QueryBuilder/ExpressionBuilder/MySqlExpressionBuilder.php
+++ b/lib/private/DB/QueryBuilder/ExpressionBuilder/MySqlExpressionBuilder.php
@@ -24,9 +24,8 @@
 
 namespace OC\DB\QueryBuilder\ExpressionBuilder;
 
-use OC\DB\Connection;
+use OC\DB\ConnectionAdapter;
 use OCP\DB\QueryBuilder\IQueryBuilder;
-use OCP\IDBConnection;
 
 class MySqlExpressionBuilder extends ExpressionBuilder {
 
@@ -34,13 +33,13 @@ class MySqlExpressionBuilder extends ExpressionBuilder {
 	protected $charset;
 
 	/**
-	 * @param \OCP\IDBConnection|Connection $connection
+	 * @param ConnectionAdapter $connection
 	 * @param IQueryBuilder $queryBuilder
 	 */
-	public function __construct(IDBConnection $connection, IQueryBuilder $queryBuilder) {
+	public function __construct(ConnectionAdapter $connection, IQueryBuilder $queryBuilder) {
 		parent::__construct($connection, $queryBuilder);
 
-		$params = $connection->getParams();
+		$params = $connection->getInner()->getParams();
 		$this->charset = isset($params['charset']) ? $params['charset'] : 'utf8';
 	}
 
diff --git a/lib/private/DB/QueryBuilder/QueryBuilder.php b/lib/private/DB/QueryBuilder/QueryBuilder.php
index 2d5fe6ce575..657e52e54bc 100644
--- a/lib/private/DB/QueryBuilder/QueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/QueryBuilder.php
@@ -30,11 +30,12 @@
 
 namespace OC\DB\QueryBuilder;
 
-use Doctrine\DBAL\Platforms\MySqlPlatform;
-use Doctrine\DBAL\Platforms\PostgreSqlPlatform;
+use Doctrine\DBAL\Platforms\MySQLPlatform;
+use Doctrine\DBAL\Platforms\OraclePlatform;
+use Doctrine\DBAL\Platforms\PostgreSQL94Platform;
 use Doctrine\DBAL\Platforms\SqlitePlatform;
 use Doctrine\DBAL\Query\QueryException;
-use OC\DB\OracleConnection;
+use OC\DB\ConnectionAdapter;
 use OC\DB\QueryBuilder\ExpressionBuilder\ExpressionBuilder;
 use OC\DB\QueryBuilder\ExpressionBuilder\MySqlExpressionBuilder;
 use OC\DB\QueryBuilder\ExpressionBuilder\OCIExpressionBuilder;
@@ -44,17 +45,18 @@ use OC\DB\QueryBuilder\FunctionBuilder\FunctionBuilder;
 use OC\DB\QueryBuilder\FunctionBuilder\OCIFunctionBuilder;
 use OC\DB\QueryBuilder\FunctionBuilder\PgSqlFunctionBuilder;
 use OC\DB\QueryBuilder\FunctionBuilder\SqliteFunctionBuilder;
+use OC\DB\ResultAdapter;
 use OC\SystemConfig;
+use OCP\DB\IResult;
 use OCP\DB\QueryBuilder\ILiteral;
 use OCP\DB\QueryBuilder\IParameter;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\DB\QueryBuilder\IQueryFunction;
-use OCP\IDBConnection;
 use OCP\ILogger;
 
 class QueryBuilder implements IQueryBuilder {
 
-	/** @var \OCP\IDBConnection */
+	/** @var ConnectionAdapter */
 	private $connection;
 
 	/** @var SystemConfig */
@@ -78,15 +80,15 @@ class QueryBuilder implements IQueryBuilder {
 	/**
 	 * Initializes a new QueryBuilder.
 	 *
-	 * @param IDBConnection $connection
+	 * @param ConnectionAdapter $connection
 	 * @param SystemConfig $systemConfig
 	 * @param ILogger $logger
 	 */
-	public function __construct(IDBConnection $connection, SystemConfig $systemConfig, ILogger $logger) {
+	public function __construct(ConnectionAdapter $connection, SystemConfig $systemConfig, ILogger $logger) {
 		$this->connection = $connection;
 		$this->systemConfig = $systemConfig;
 		$this->logger = $logger;
-		$this->queryBuilder = new \Doctrine\DBAL\Query\QueryBuilder($this->connection);
+		$this->queryBuilder = new \Doctrine\DBAL\Query\QueryBuilder($this->connection->getInner());
 		$this->helper = new QuoteHelper();
 	}
 
@@ -118,17 +120,20 @@ class QueryBuilder implements IQueryBuilder {
 	 * @return \OCP\DB\QueryBuilder\IExpressionBuilder
 	 */
 	public function expr() {
-		if ($this->connection instanceof OracleConnection) {
+		if ($this->connection->getDatabasePlatform() instanceof OraclePlatform) {
 			return new OCIExpressionBuilder($this->connection, $this);
-		} elseif ($this->connection->getDatabasePlatform() instanceof PostgreSqlPlatform) {
+		}
+		if ($this->connection->getDatabasePlatform() instanceof PostgreSQL94Platform) {
 			return new PgSqlExpressionBuilder($this->connection, $this);
-		} elseif ($this->connection->getDatabasePlatform() instanceof MySqlPlatform) {
+		}
+		if ($this->connection->getDatabasePlatform() instanceof MySQLPlatform) {
 			return new MySqlExpressionBuilder($this->connection, $this);
-		} elseif ($this->connection->getDatabasePlatform() instanceof SqlitePlatform) {
+		}
+		if ($this->connection->getDatabasePlatform() instanceof SqlitePlatform) {
 			return new SqliteExpressionBuilder($this->connection, $this);
-		} else {
-			return new ExpressionBuilder($this->connection, $this);
 		}
+
+		return new ExpressionBuilder($this->connection, $this);
 	}
 
 	/**
@@ -148,15 +153,17 @@ class QueryBuilder implements IQueryBuilder {
 	 * @return \OCP\DB\QueryBuilder\IFunctionBuilder
 	 */
 	public function func() {
-		if ($this->connection instanceof OracleConnection) {
+		if ($this->connection->getDatabasePlatform() instanceof OraclePlatform) {
 			return new OCIFunctionBuilder($this->helper);
-		} elseif ($this->connection->getDatabasePlatform() instanceof SqlitePlatform) {
+		}
+		if ($this->connection->getDatabasePlatform() instanceof SqlitePlatform) {
 			return new SqliteFunctionBuilder($this->helper);
-		} elseif ($this->connection->getDatabasePlatform() instanceof PostgreSqlPlatform) {
+		}
+		if ($this->connection->getDatabasePlatform() instanceof PostgreSQL94Platform) {
 			return new PgSqlFunctionBuilder($this->helper);
-		} else {
-			return new FunctionBuilder($this->helper);
 		}
+
+		return new FunctionBuilder($this->helper);
 	}
 
 	/**
@@ -192,7 +199,7 @@ class QueryBuilder implements IQueryBuilder {
 	 * Uses {@see Connection::executeQuery} for select statements and {@see Connection::executeUpdate}
 	 * for insert, update and delete statements.
 	 *
-	 * @return \Doctrine\DBAL\Driver\Statement|int
+	 * @return IResult|int
 	 */
 	public function execute() {
 		if ($this->systemConfig->getValue('log_query', false)) {
@@ -246,7 +253,11 @@ class QueryBuilder implements IQueryBuilder {
 			}
 		}
 
-		return $this->queryBuilder->execute();
+		$result = $this->queryBuilder->execute();
+		if (is_int($result)) {
+			return $result;
+		}
+		return new ResultAdapter($result);
 	}
 
 	/**
diff --git a/lib/private/DB/ReconnectWrapper.php b/lib/private/DB/ReconnectWrapper.php
index 9599d6b0fe6..a0170152862 100644
--- a/lib/private/DB/ReconnectWrapper.php
+++ b/lib/private/DB/ReconnectWrapper.php
@@ -44,12 +44,12 @@ class ReconnectWrapper extends \Doctrine\DBAL\Connection {
 
 		if ($this->lastConnectionCheck > $checkTime || $this->isTransactionActive()) {
 			return parent::connect();
-		} else {
-			$this->lastConnectionCheck = $now;
-			if (!$this->ping()) {
-				$this->close();
-			}
-			return parent::connect();
 		}
+
+		$this->lastConnectionCheck = $now;
+		if (!$this->isConnected()) {
+			$this->close();
+		}
+		return parent::connect();
 	}
 }
diff --git a/lib/private/DB/ResultAdapter.php b/lib/private/DB/ResultAdapter.php
new file mode 100644
index 00000000000..176de5b45ea
--- /dev/null
+++ b/lib/private/DB/ResultAdapter.php
@@ -0,0 +1,71 @@
+<?php
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @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/>.
+ */
+
+declare(strict_types=1);
+
+namespace OC\DB;
+
+use Doctrine\DBAL\Result;
+use OCP\DB\IResult;
+use PDO;
+
+/**
+ * Adapts DBAL 2.6 API for DBAL 3.x for backwards compatibility of a leaked type
+ */
+class ResultAdapter implements IResult {
+
+	/** @var Result */
+	private $inner;
+
+	public function __construct(Result $inner) {
+		$this->inner = $inner;
+	}
+
+	public function closeCursor(): bool {
+		$this->inner->free();
+
+		return true;
+	}
+
+	public function fetch(int $fetchMode = PDO::FETCH_ASSOC) {
+		return $this->inner->fetch($fetchMode);
+	}
+
+	public function fetchAll(int $fetchMode = PDO::FETCH_ASSOC): array {
+		if ($fetchMode !== PDO::FETCH_ASSOC && $fetchMode !== PDO::FETCH_NUM && $fetchMode !== PDO::FETCH_COLUMN) {
+			throw new \Exception('Fetch mode needs to be assoc, num or column.');
+		}
+		return $this->inner->fetchAll($fetchMode);
+	}
+
+	public function fetchColumn($columnIndex = 0) {
+		return $this->inner->fetchOne();
+	}
+
+	public function fetchOne() {
+		return $this->inner->fetchOne();
+	}
+
+	public function rowCount(): int {
+		return $this->inner->rowCount();
+	}
+}
diff --git a/lib/private/DB/SQLiteMigrator.php b/lib/private/DB/SQLiteMigrator.php
index 16f18be135e..24b6c02b31c 100644
--- a/lib/private/DB/SQLiteMigrator.php
+++ b/lib/private/DB/SQLiteMigrator.php
@@ -26,7 +26,6 @@
 
 namespace OC\DB;
 
-use Doctrine\DBAL\DBALException;
 use Doctrine\DBAL\Schema\Schema;
 use Doctrine\DBAL\Types\BigIntType;
 use Doctrine\DBAL\Types\Type;
@@ -34,42 +33,6 @@ use Doctrine\DBAL\Types\Type;
 class SQLiteMigrator extends Migrator {
 
 	/**
-	 * @param \Doctrine\DBAL\Schema\Schema $targetSchema
-	 * @throws \OC\DB\MigrationException
-	 *
-	 * For sqlite we simple make a copy of the entire database, and test the migration on that
-	 */
-	public function checkMigrate(\Doctrine\DBAL\Schema\Schema $targetSchema) {
-		$dbFile = $this->connection->getDatabase();
-		$tmpFile = $this->buildTempDatabase();
-		copy($dbFile, $tmpFile);
-
-		$connectionParams = [
-			'path' => $tmpFile,
-			'driver' => 'pdo_sqlite',
-		];
-		$conn = \Doctrine\DBAL\DriverManager::getConnection($connectionParams);
-		try {
-			$this->applySchema($targetSchema, $conn);
-			$conn->close();
-			unlink($tmpFile);
-		} catch (DBALException $e) {
-			$conn->close();
-			unlink($tmpFile);
-			throw new MigrationException('', $e->getMessage());
-		}
-	}
-
-	/**
-	 * @return string
-	 */
-	private function buildTempDatabase() {
-		$dataDir = $this->config->getSystemValue("datadirectory", \OC::$SERVERROOT . '/data');
-		$tmpFile = uniqid("oc_");
-		return "$dataDir/$tmpFile.db";
-	}
-
-	/**
 	 * @param Schema $targetSchema
 	 * @param \Doctrine\DBAL\Connection $connection
 	 * @return \Doctrine\DBAL\Schema\SchemaDiff
diff --git a/lib/private/DB/SQLiteSessionInit.php b/lib/private/DB/SQLiteSessionInit.php
index 0c53a0587f0..924a3b2758c 100644
--- a/lib/private/DB/SQLiteSessionInit.php
+++ b/lib/private/DB/SQLiteSessionInit.php
@@ -60,8 +60,9 @@ class SQLiteSessionInit implements EventSubscriber {
 		$sensitive = $this->caseSensitiveLike ? 'true' : 'false';
 		$args->getConnection()->executeUpdate('PRAGMA case_sensitive_like = ' . $sensitive);
 		$args->getConnection()->executeUpdate('PRAGMA journal_mode = ' . $this->journalMode);
-		/** @var \PDO $pdo */
-		$pdo = $args->getConnection()->getWrappedConnection();
+		/** @var \Doctrine\DBAL\Driver\PDO\Connection $connection */
+		$connection = $args->getConnection()->getWrappedConnection();
+		$pdo = $connection->getWrappedConnection();
 		$pdo->sqliteCreateFunction('md5', 'md5', 1);
 	}
 
diff --git a/lib/private/DB/SchemaWrapper.php b/lib/private/DB/SchemaWrapper.php
index 440008d35b3..20ae5b6faa6 100644
--- a/lib/private/DB/SchemaWrapper.php
+++ b/lib/private/DB/SchemaWrapper.php
@@ -26,11 +26,10 @@ namespace OC\DB;
 
 use Doctrine\DBAL\Schema\Schema;
 use OCP\DB\ISchemaWrapper;
-use OCP\IDBConnection;
 
 class SchemaWrapper implements ISchemaWrapper {
 
-	/** @var IDBConnection|Connection */
+	/** @var Connection */
 	protected $connection;
 
 	/** @var Schema */
@@ -39,10 +38,7 @@ class SchemaWrapper implements ISchemaWrapper {
 	/** @var array */
 	protected $tablesToDelete = [];
 
-	/**
-	 * @param IDBConnection $connection
-	 */
-	public function __construct(IDBConnection $connection) {
+	public function __construct(Connection $connection) {
 		$this->connection = $connection;
 		$this->schema = $this->connection->createSchema();
 	}