Add a mechanism to try the database migration on a copy of the tables before running it on the "real" data

1 files changed, 139 insertions, 0 deletions

diff --git a/lib/private/db/migrator.php b/lib/private/db/migrator.php
new file mode 100644
index 00000000000..91060663f87
--- /dev/null
+++ b/lib/private/db/migrator.php
@@ -0,0 +1,139 @@
+<?php
+/**
+ * Copyright (c) 2014 Robin Appelman <icewind@owncloud.com>
+ * This file is licensed under the Affero General Public License version 3 or
+ * later.
+ * See the COPYING-README file.
+ */
+
+namespace OC\DB;
+
+use \Doctrine\DBAL\DBALException;
+use \Doctrine\DBAL\Schema\Table;
+use \Doctrine\DBAL\Schema\Schema;
+use \Doctrine\DBAL\Schema\SchemaConfig;
+
+class Migrator {
+	/**
+	 * @var \Doctrine\DBAL\Connection $connection
+	 */
+	protected $connection;
+
+	/**
+	 * @param \Doctrine\DBAL\Connection $connection
+	 */
+	public function __construct(\Doctrine\DBAL\Connection $connection) {
+		$this->connection = $connection;
+	}
+
+	/**
+	 * @param \Doctrine\DBAL\Schema\Schema $targetSchema
+	 */
+	public function migrate(Schema $targetSchema) {
+		$this->applySchema($targetSchema);
+	}
+
+	/**
+	 * @param Schema $targetSchema
+	 */
+	public function checkMigrate(Schema $targetSchema) {
+		/**
+		 * @var \Doctrine\DBAL\Schema\Table[] $tables
+		 */
+		$tables = $targetSchema->getTables();
+
+		$existingTables = $this->connection->getSchemaManager()->listTableNames();
+
+		foreach ($tables as $table) {
+			// don't need to check for new tables
+			list(, $tableName) = explode('.', $table->getName());
+			if (array_search($tableName, $existingTables) !== false) {
+				$this->checkTableMigrate($table);
+			}
+		}
+	}
+
+	/**
+	 * Check the migration of a table on a copy so we can detect errors before messing with the real table
+	 *
+	 * @param \Doctrine\DBAL\Schema\Table $table
+	 */
+	protected function checkTableMigrate(Table $table) {
+		$name = $table->getName();
+		$tmpName = $name . '_copy_' . uniqid();
+
+		$this->copyTable($name, $tmpName);
+
+		//create the migration schema for the temporary table
+		$tmpTable = new Table($tmpName, $table->getColumns(), $table->getIndexes(), $table->getForeignKeys(), $table->_idGeneratorType, $table->getOptions());
+		$schemaConfig = new SchemaConfig();
+		$schemaConfig->setName($this->connection->getDatabase());
+		$schema = new Schema(array($tmpTable), array(), $schemaConfig);
+
+		try {
+			$this->applySchema($schema);
+			$this->dropTable($tmpName);
+		} catch (DBALException $e) {
+			$this->dropTable($tmpName);
+			throw new MigrationException($table->getName(), $e->getMessage());
+		}
+	}
+
+	/**
+	 * @param \Doctrine\DBAL\Schema\Schema $targetSchema
+	 * @param \Doctrine\DBAL\Connection $connection
+	 */
+	protected function applySchema(Schema $targetSchema, \Doctrine\DBAL\Connection $connection = null) {
+		if (is_null($connection)) {
+			$connection = $this->connection;
+		}
+
+		$sourceSchema = $this->connection->getSchemaManager()->createSchema();
+
+		// remove tables we don't know about
+		/** @var $table \Doctrine\DBAL\Schema\Table */
+		foreach ($sourceSchema->getTables() as $table) {
+			if (!$targetSchema->hasTable($table->getName())) {
+				$sourceSchema->dropTable($table->getName());
+			}
+		}
+		// remove sequences we don't know about
+		foreach ($sourceSchema->getSequences() as $table) {
+			if (!$targetSchema->hasSequence($table->getName())) {
+				$sourceSchema->dropSequence($table->getName());
+			}
+		}
+
+		$comparator = new \Doctrine\DBAL\Schema\Comparator();
+		$schemaDiff = $comparator->compare($sourceSchema, $targetSchema);
+
+		foreach ($schemaDiff->changedTables as $tableDiff) {
+			$tableDiff->name = $this->connection->quoteIdentifier($tableDiff->name);
+		}
+
+		$connection->beginTransaction();
+		foreach ($schemaDiff->toSql($connection->getDatabasePlatform()) as $sql) {
+			$connection->query($sql);
+		}
+		$connection->commit();
+	}
+
+	/**
+	 * @param string $sourceName
+	 * @param string $targetName
+	 */
+	protected function copyTable($sourceName, $targetName) {
+		$quotedSource = $this->connection->quoteIdentifier($sourceName);
+		$quotedTarget = $this->connection->quoteIdentifier($targetName);
+
+		$this->connection->exec('CREATE TABLE ' . $quotedTarget . ' LIKE ' . $quotedSource);
+		$this->connection->exec('INSERT INTO ' . $quotedTarget . ' SELECT * FROM ' . $quotedSource);
+	}
+
+	/**
+	 * @param string $name
+	 */
+	protected function dropTable($name) {
+		$this->connection->exec('DROP TABLE ' . $this->connection->quoteIdentifier($name));
+	}
+}