First commit

includes/database/mysql/database.inc

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+<?php
+
+/**
+ * @file
+ * Database interface code for MySQL database servers.
+ */
+
+/**
+ * @addtogroup database
+ * @{
+ */
+
+class DatabaseConnection_mysql extends DatabaseConnection {
+
+  /**
+   * Flag to indicate if the cleanup function in __destruct() should run.
+   *
+   * @var boolean
+   */
+  protected $needsCleanup = FALSE;
+
+  public function __construct(array $connection_options = array()) {
+    // This driver defaults to transaction support, except if explicitly passed FALSE.
+    $this->transactionSupport = !isset($connection_options['transactions']) || ($connection_options['transactions'] !== FALSE);
+
+    // MySQL never supports transactional DDL.
+    $this->transactionalDDLSupport = FALSE;
+
+    $this->connectionOptions = $connection_options;
+
+    $charset = 'utf8';
+    // Check if the charset is overridden to utf8mb4 in settings.php.
+    if ($this->utf8mb4IsActive()) {
+      $charset = 'utf8mb4';
+    }
+
+    // The DSN should use either a socket or a host/port.
+    if (isset($connection_options['unix_socket'])) {
+      $dsn = 'mysql:unix_socket=' . $connection_options['unix_socket'];
+    }
+    else {
+      // Default to TCP connection on port 3306.
+      $dsn = 'mysql:host=' . $connection_options['host'] . ';port=' . (empty($connection_options['port']) ? 3306 : $connection_options['port']);
+    }
+    // Character set is added to dsn to ensure PDO uses the proper character
+    // set when escaping. This has security implications. See
+    // https://www.drupal.org/node/1201452 for further discussion.
+    $dsn .= ';charset=' . $charset;
+    $dsn .= ';dbname=' . $connection_options['database'];
+    // Allow PDO options to be overridden.
+    $connection_options += array(
+      'pdo' => array(),
+    );
+    $connection_options['pdo'] += array(
+      // So we don't have to mess around with cursors and unbuffered queries by default.
+      PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => TRUE,
+      // Because MySQL's prepared statements skip the query cache, because it's dumb.
+      PDO::ATTR_EMULATE_PREPARES => TRUE,
+    );
+    if (defined('PDO::MYSQL_ATTR_MULTI_STATEMENTS')) {
+      // An added connection option in PHP 5.5.21+ to optionally limit SQL to a
+      // single statement like mysqli.
+      $connection_options['pdo'] += array(PDO::MYSQL_ATTR_MULTI_STATEMENTS => FALSE);
+    }
+
+    parent::__construct($dsn, $connection_options['username'], $connection_options['password'], $connection_options['pdo']);
+
+    // Force MySQL to use the UTF-8 character set. Also set the collation, if a
+    // certain one has been set; otherwise, MySQL defaults to 'utf8_general_ci'
+    // for UTF-8.
+    if (!empty($connection_options['collation'])) {
+      $this->exec('SET NAMES ' . $charset . ' COLLATE ' . $connection_options['collation']);
+    }
+    else {
+      $this->exec('SET NAMES ' . $charset);
+    }
+
+    // Set MySQL init_commands if not already defined.  Default Drupal's MySQL
+    // behavior to conform more closely to SQL standards.  This allows Drupal
+    // to run almost seamlessly on many different kinds of database systems.
+    // These settings force MySQL to behave the same as postgresql, or sqlite
+    // in regards to syntax interpretation and invalid data handling.  See
+    // http://drupal.org/node/344575 for further discussion. Also, as MySQL 5.5
+    // changed the meaning of TRADITIONAL we need to spell out the modes one by
+    // one.
+    $connection_options += array(
+      'init_commands' => array(),
+    );
+    $connection_options['init_commands'] += array(
+      'sql_mode' => "SET sql_mode = 'REAL_AS_FLOAT,PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER'",
+    );
+    // Execute initial commands.
+    foreach ($connection_options['init_commands'] as $sql) {
+      $this->exec($sql);
+    }
+  }
+
+  public function __destruct() {
+    if ($this->needsCleanup) {
+      $this->nextIdDelete();
+    }
+  }
+
+  public function queryRange($query, $from, $count, array $args = array(), array $options = array()) {
+    return $this->query($query . ' LIMIT ' . (int) $from . ', ' . (int) $count, $args, $options);
+  }
+
+  public function queryTemporary($query, array $args = array(), array $options = array()) {
+    $tablename = $this->generateTemporaryTableName();
+    $this->query('CREATE TEMPORARY TABLE {' . $tablename . '} Engine=MEMORY ' . $query, $args, $options);
+    return $tablename;
+  }
+
+  public function driver() {
+    return 'mysql';
+  }
+
+  public function databaseType() {
+    return 'mysql';
+  }
+
+  public function mapConditionOperator($operator) {
+    // We don't want to override any of the defaults.
+    return NULL;
+  }
+
+  public function nextId($existing_id = 0) {
+    $new_id = $this->query('INSERT INTO {sequences} () VALUES ()', array(), array('return' => Database::RETURN_INSERT_ID));
+    // This should only happen after an import or similar event.
+    if ($existing_id >= $new_id) {
+      // If we INSERT a value manually into the sequences table, on the next
+      // INSERT, MySQL will generate a larger value. However, there is no way
+      // of knowing whether this value already exists in the table. MySQL
+      // provides an INSERT IGNORE which would work, but that can mask problems
+      // other than duplicate keys. Instead, we use INSERT ... ON DUPLICATE KEY
+      // UPDATE in such a way that the UPDATE does not do anything. This way,
+      // duplicate keys do not generate errors but everything else does.
+      $this->query('INSERT INTO {sequences} (value) VALUES (:value) ON DUPLICATE KEY UPDATE value = value', array(':value' => $existing_id));
+      $new_id = $this->query('INSERT INTO {sequences} () VALUES ()', array(), array('return' => Database::RETURN_INSERT_ID));
+    }
+    $this->needsCleanup = TRUE;
+    return $new_id;
+  }
+
+  public function nextIdDelete() {
+    // While we want to clean up the table to keep it up from occupying too
+    // much storage and memory, we must keep the highest value in the table
+    // because InnoDB  uses an in-memory auto-increment counter as long as the
+    // server runs. When the server is stopped and restarted, InnoDB
+    // reinitializes the counter for each table for the first INSERT to the
+    // table based solely on values from the table so deleting all values would
+    // be a problem in this case. Also, TRUNCATE resets the auto increment
+    // counter.
+    try {
+      $max_id = $this->query('SELECT MAX(value) FROM {sequences}')->fetchField();
+      // We know we are using MySQL here, no need for the slower db_delete().
+      $this->query('DELETE FROM {sequences} WHERE value < :value', array(':value' => $max_id));
+    }
+    // During testing, this function is called from shutdown with the
+    // simpletest prefix stored in $this->connection, and those tables are gone
+    // by the time shutdown is called so we need to ignore the database
+    // errors. There is no problem with completely ignoring errors here: if
+    // these queries fail, the sequence will work just fine, just use a bit
+    // more database storage and memory.
+    catch (PDOException $e) {
+    }
+  }
+
+  /**
+   * Overridden to work around issues to MySQL not supporting transactional DDL.
+   */
+  protected function popCommittableTransactions() {
+    // Commit all the committable layers.
+    foreach (array_reverse($this->transactionLayers) as $name => $active) {
+      // Stop once we found an active transaction.
+      if ($active) {
+        break;
+      }
+
+      // If there are no more layers left then we should commit.
+      unset($this->transactionLayers[$name]);
+      if (empty($this->transactionLayers)) {
+        if (!PDO::commit()) {
+          throw new DatabaseTransactionCommitFailedException();
+        }
+      }
+      else {
+        // Attempt to release this savepoint in the standard way.
+        try {
+          $this->query('RELEASE SAVEPOINT ' . $name);
+        }
+        catch (PDOException $e) {
+          // However, in MySQL (InnoDB), savepoints are automatically committed
+          // when tables are altered or created (DDL transactions are not
+          // supported). This can cause exceptions due to trying to release
+          // savepoints which no longer exist.
+          //
+          // To avoid exceptions when no actual error has occurred, we silently
+          // succeed for MySQL error code 1305 ("SAVEPOINT does not exist").
+          if ($e->errorInfo[1] == '1305') {
+            // If one SAVEPOINT was released automatically, then all were.
+            // Therefore, clean the transaction stack.
+            $this->transactionLayers = array();
+            // We also have to explain to PDO that the transaction stack has
+            // been cleaned-up.
+            PDO::commit();
+          }
+          else {
+            throw $e;
+          }
+        }
+      }
+    }
+  }
+
+  public function utf8mb4IsConfigurable() {
+    return TRUE;
+  }
+
+  public function utf8mb4IsActive() {
+    return isset($this->connectionOptions['charset']) && $this->connectionOptions['charset'] === 'utf8mb4';
+  }
+
+  public function utf8mb4IsSupported() {
+    // Ensure that the MySQL driver supports utf8mb4 encoding.
+    $version = $this->getAttribute(PDO::ATTR_CLIENT_VERSION);
+    if (strpos($version, 'mysqlnd') !== FALSE) {
+      // The mysqlnd driver supports utf8mb4 starting at version 5.0.9.
+      $version = preg_replace('/^\D+([\d.]+).*/', '$1', $version);
+      if (version_compare($version, '5.0.9', '<')) {
+        return FALSE;
+      }
+    }
+    else {
+      // The libmysqlclient driver supports utf8mb4 starting at version 5.5.3.
+      if (version_compare($version, '5.5.3', '<')) {
+        return FALSE;
+      }
+    }
+
+    // Ensure that the MySQL server supports large prefixes and utf8mb4.
+    try {
+      $this->query("CREATE TABLE {drupal_utf8mb4_test} (id VARCHAR(255), PRIMARY KEY(id(255))) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci ROW_FORMAT=DYNAMIC ENGINE=INNODB");
+    }
+    catch (Exception $e) {
+      return FALSE;
+    }
+    $this->query("DROP TABLE {drupal_utf8mb4_test}");
+    return TRUE;
+  }
+}
+
+
+/**
+ * @} End of "addtogroup database".
+ */

includes/database/mysql/install.inc

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+<?php
+
+/**
+ * @file
+ * Installation code for MySQL embedded database engine.
+ */
+
+/**
+ * Specifies installation tasks for MySQL and equivalent databases.
+ */
+class DatabaseTasks_mysql extends DatabaseTasks {
+  /**
+   * The PDO driver name for MySQL and equivalent databases.
+   *
+   * @var string
+   */
+  protected $pdoDriver = 'mysql';
+
+  /**
+   * Returns a human-readable name string for MySQL and equivalent databases.
+   */
+  public function name() {
+    return st('MySQL, MariaDB, or equivalent');
+  }
+
+  /**
+   * Returns the minimum version for MySQL.
+   */
+  public function minimumVersion() {
+    return '5.0.15';
+  }
+}
+

includes/database/mysql/query.inc

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+<?php
+
+/**
+ * @addtogroup database
+ * @{
+ */
+
+/**
+ * @file
+ * Query code for MySQL embedded database engine.
+ */
+
+
+class InsertQuery_mysql extends InsertQuery {
+
+  public function execute() {
+    if (!$this->preExecute()) {
+      return NULL;
+    }
+
+    // If we're selecting from a SelectQuery, finish building the query and
+    // pass it back, as any remaining options are irrelevant.
+    if (empty($this->fromQuery)) {
+      $max_placeholder = 0;
+      $values = array();
+      foreach ($this->insertValues as $insert_values) {
+        foreach ($insert_values as $value) {
+          $values[':db_insert_placeholder_' . $max_placeholder++] = $value;
+        }
+      }
+    }
+    else {
+      $values = $this->fromQuery->getArguments();
+    }
+
+    $last_insert_id = $this->connection->query((string) $this, $values, $this->queryOptions);
+
+    // Re-initialize the values array so that we can re-use this query.
+    $this->insertValues = array();
+
+    return $last_insert_id;
+  }
+
+  public function __toString() {
+    // Create a sanitized comment string to prepend to the query.
+    $comments = $this->connection->makeComment($this->comments);
+
+    // Default fields are always placed first for consistency.
+    $insert_fields = array_merge($this->defaultFields, $this->insertFields);
+
+    // If we're selecting from a SelectQuery, finish building the query and
+    // pass it back, as any remaining options are irrelevant.
+    if (!empty($this->fromQuery)) {
+      $insert_fields_string = $insert_fields ? ' (' . implode(', ', $insert_fields) . ') ' : ' ';
+      return $comments . 'INSERT INTO {' . $this->table . '}' . $insert_fields_string . $this->fromQuery;
+    }
+
+    $query = $comments . 'INSERT INTO {' . $this->table . '} (' . implode(', ', $insert_fields) . ') VALUES ';
+
+    $max_placeholder = 0;
+    $values = array();
+    if (count($this->insertValues)) {
+      foreach ($this->insertValues as $insert_values) {
+        $placeholders = array();
+
+        // Default fields aren't really placeholders, but this is the most convenient
+        // way to handle them.
+        $placeholders = array_pad($placeholders, count($this->defaultFields), 'default');
+
+        $new_placeholder = $max_placeholder + count($insert_values);
+        for ($i = $max_placeholder; $i < $new_placeholder; ++$i) {
+          $placeholders[] = ':db_insert_placeholder_' . $i;
+        }
+        $max_placeholder = $new_placeholder;
+        $values[] = '(' . implode(', ', $placeholders) . ')';
+      }
+    }
+    else {
+      // If there are no values, then this is a default-only query. We still need to handle that.
+      $placeholders = array_fill(0, count($this->defaultFields), 'default');
+      $values[] = '(' . implode(', ', $placeholders) . ')';
+    }
+
+    $query .= implode(', ', $values);
+
+    return $query;
+  }
+}
+
+class TruncateQuery_mysql extends TruncateQuery { }
+
+/**
+ * @} End of "addtogroup database".
+ */

includes/database/mysql/schema.inc

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+<?php
+
+/**
+ * @file
+ * Database schema code for MySQL database servers.
+ */
+
+
+/**
+ * @addtogroup schemaapi
+ * @{
+ */
+
+class DatabaseSchema_mysql extends DatabaseSchema {
+
+  /**
+   * Maximum length of a table comment in MySQL.
+   */
+  const COMMENT_MAX_TABLE = 60;
+
+  /**
+   * Maximum length of a column comment in MySQL.
+   */
+  const COMMENT_MAX_COLUMN = 255;
+
+  /**
+   * Get information about the table and database name from the prefix.
+   *
+   * @return
+   *   A keyed array with information about the database, table name and prefix.
+   */
+  protected function getPrefixInfo($table = 'default', $add_prefix = TRUE) {
+    $info = array('prefix' => $this->connection->tablePrefix($table));
+    if ($add_prefix) {
+      $table = $info['prefix'] . $table;
+    }
+    if (($pos = strpos($table, '.')) !== FALSE) {
+      $info['database'] = substr($table, 0, $pos);
+      $info['table'] = substr($table, ++$pos);
+    }
+    else {
+      $db_info = $this->connection->getConnectionOptions();
+      $info['database'] = $db_info['database'];
+      $info['table'] = $table;
+    }
+    return $info;
+  }
+
+  /**
+   * Build a condition to match a table name against a standard information_schema.
+   *
+   * MySQL uses databases like schemas rather than catalogs so when we build
+   * a condition to query the information_schema.tables, we set the default
+   * database as the schema unless specified otherwise, and exclude table_catalog
+   * from the condition criteria.
+   */
+  protected function buildTableNameCondition($table_name, $operator = '=', $add_prefix = TRUE) {
+    $info = $this->connection->getConnectionOptions();
+
+    $table_info = $this->getPrefixInfo($table_name, $add_prefix);
+
+    $condition = new DatabaseCondition('AND');
+    $condition->condition('table_schema', $table_info['database']);
+    $condition->condition('table_name', $table_info['table'], $operator);
+    return $condition;
+  }
+
+  /**
+   * Generate SQL to create a new table from a Drupal schema definition.
+   *
+   * @param $name
+   *   The name of the table to create.
+   * @param $table
+   *   A Schema API table definition array.
+   * @return
+   *   An array of SQL statements to create the table.
+   */
+  protected function createTableSql($name, $table) {
+    $info = $this->connection->getConnectionOptions();
+
+    // Provide defaults if needed.
+    $table += array(
+      'mysql_engine' => 'InnoDB',
+      // Allow the default charset to be overridden in settings.php.
+      'mysql_character_set' => $this->connection->utf8mb4IsActive() ? 'utf8mb4' : 'utf8',
+    );
+
+    $sql = "CREATE TABLE {" . $name . "} (\n";
+
+    // Add the SQL statement for each field.
+    foreach ($table['fields'] as $field_name => $field) {
+      $sql .= $this->createFieldSql($field_name, $this->processField($field)) . ", \n";
+    }
+
+    // Process keys & indexes.
+    $keys = $this->createKeysSql($table);
+    if (count($keys)) {
+      $sql .= implode(", \n", $keys) . ", \n";
+    }
+
+    // Remove the last comma and space.
+    $sql = substr($sql, 0, -3) . "\n) ";
+
+    $sql .= 'ENGINE = ' . $table['mysql_engine'] . ' DEFAULT CHARACTER SET ' . $table['mysql_character_set'];
+    // By default, MySQL uses the default collation for new tables, which is
+    // 'utf8_general_ci' for utf8. If an alternate collation has been set, it
+    // needs to be explicitly specified.
+    // @see DatabaseConnection_mysql
+    if (!empty($info['collation'])) {
+      $sql .= ' COLLATE ' . $info['collation'];
+    }
+
+    // The row format needs to be either DYNAMIC or COMPRESSED in order to allow
+    // for the innodb_large_prefix setting to take effect, see
+    // https://dev.mysql.com/doc/refman/5.6/en/create-table.html
+    if ($this->connection->utf8mb4IsActive()) {
+      $sql .= ' ROW_FORMAT=DYNAMIC';
+    }
+
+    // Add table comment.
+    if (!empty($table['description'])) {
+      $sql .= ' COMMENT ' . $this->prepareComment($table['description'], self::COMMENT_MAX_TABLE);
+    }
+
+    return array($sql);
+  }
+
+  /**
+   * Create an SQL string for a field to be used in table creation or alteration.
+   *
+   * Before passing a field out of a schema definition into this function it has
+   * to be processed by _db_process_field().
+   *
+   * @param $name
+   *   Name of the field.
+   * @param $spec
+   *   The field specification, as per the schema data structure format.
+   */
+  protected function createFieldSql($name, $spec) {
+    $sql = "`" . $name . "` " . $spec['mysql_type'];
+
+    if (in_array($spec['mysql_type'], array('VARCHAR', 'CHAR', 'TINYTEXT', 'MEDIUMTEXT', 'LONGTEXT', 'TEXT'))) {
+      if (isset($spec['length'])) {
+        $sql .= '(' . $spec['length'] . ')';
+      }
+      if (!empty($spec['binary'])) {
+        $sql .= ' BINARY';
+      }
+    }
+    elseif (isset($spec['precision']) && isset($spec['scale'])) {
+      $sql .= '(' . $spec['precision'] . ', ' . $spec['scale'] . ')';
+    }
+
+    if (!empty($spec['unsigned'])) {
+      $sql .= ' unsigned';
+    }
+
+    if (isset($spec['not null'])) {
+      if ($spec['not null']) {
+        $sql .= ' NOT NULL';
+      }
+      else {
+        $sql .= ' NULL';
+      }
+    }
+
+    if (!empty($spec['auto_increment'])) {
+      $sql .= ' auto_increment';
+    }
+
+    // $spec['default'] can be NULL, so we explicitly check for the key here.
+    if (array_key_exists('default', $spec)) {
+      if (is_string($spec['default'])) {
+        $spec['default'] = "'" . $spec['default'] . "'";
+      }
+      elseif (!isset($spec['default'])) {
+        $spec['default'] = 'NULL';
+      }
+      $sql .= ' DEFAULT ' . $spec['default'];
+    }
+
+    if (empty($spec['not null']) && !isset($spec['default'])) {
+      $sql .= ' DEFAULT NULL';
+    }
+
+    // Add column comment.
+    if (!empty($spec['description'])) {
+      $sql .= ' COMMENT ' . $this->prepareComment($spec['description'], self::COMMENT_MAX_COLUMN);
+    }
+
+    return $sql;
+  }
+
+  /**
+   * Set database-engine specific properties for a field.
+   *
+   * @param $field
+   *   A field description array, as specified in the schema documentation.
+   */
+  protected function processField($field) {
+
+    if (!isset($field['size'])) {
+      $field['size'] = 'normal';
+    }
+
+    // Set the correct database-engine specific datatype.
+    // In case one is already provided, force it to uppercase.
+    if (isset($field['mysql_type'])) {
+      $field['mysql_type'] = drupal_strtoupper($field['mysql_type']);
+    }
+    else {
+      $map = $this->getFieldTypeMap();
+      $field['mysql_type'] = $map[$field['type'] . ':' . $field['size']];
+    }
+
+    if (isset($field['type']) && $field['type'] == 'serial') {
+      $field['auto_increment'] = TRUE;
+    }
+
+    return $field;
+  }
+
+  public function getFieldTypeMap() {
+    // Put :normal last so it gets preserved by array_flip. This makes
+    // it much easier for modules (such as schema.module) to map
+    // database types back into schema types.
+    // $map does not use drupal_static as its value never changes.
+    static $map = array(
+      'varchar:normal'  => 'VARCHAR',
+      'char:normal'     => 'CHAR',
+
+      'text:tiny'       => 'TINYTEXT',
+      'text:small'      => 'TINYTEXT',
+      'text:medium'     => 'MEDIUMTEXT',
+      'text:big'        => 'LONGTEXT',
+      'text:normal'     => 'TEXT',
+
+      'serial:tiny'     => 'TINYINT',
+      'serial:small'    => 'SMALLINT',
+      'serial:medium'   => 'MEDIUMINT',
+      'serial:big'      => 'BIGINT',
+      'serial:normal'   => 'INT',
+
+      'int:tiny'        => 'TINYINT',
+      'int:small'       => 'SMALLINT',
+      'int:medium'      => 'MEDIUMINT',
+      'int:big'         => 'BIGINT',
+      'int:normal'      => 'INT',
+
+      'float:tiny'      => 'FLOAT',
+      'float:small'     => 'FLOAT',
+      'float:medium'    => 'FLOAT',
+      'float:big'       => 'DOUBLE',
+      'float:normal'    => 'FLOAT',
+
+      'numeric:normal'  => 'DECIMAL',
+
+      'blob:big'        => 'LONGBLOB',
+      'blob:normal'     => 'BLOB',
+    );
+    return $map;
+  }
+
+  protected function createKeysSql($spec) {
+    $keys = array();
+
+    if (!empty($spec['primary key'])) {
+      $keys[] = 'PRIMARY KEY (' . $this->createKeysSqlHelper($spec['primary key']) . ')';
+    }
+    if (!empty($spec['unique keys'])) {
+      foreach ($spec['unique keys'] as $key => $fields) {
+        $keys[] = 'UNIQUE KEY `' . $key . '` (' . $this->createKeysSqlHelper($fields) . ')';
+      }
+    }
+    if (!empty($spec['indexes'])) {
+      foreach ($spec['indexes'] as $index => $fields) {
+        $keys[] = 'INDEX `' . $index . '` (' . $this->createKeysSqlHelper($fields) . ')';
+      }
+    }
+
+    return $keys;
+  }
+
+  protected function createKeySql($fields) {
+    $return = array();
+    foreach ($fields as $field) {
+      if (is_array($field)) {
+        $return[] = '`' . $field[0] . '`(' . $field[1] . ')';
+      }
+      else {
+        $return[] = '`' . $field . '`';
+      }
+    }
+    return implode(', ', $return);
+  }
+
+  protected function createKeysSqlHelper($fields) {
+    $return = array();
+    foreach ($fields as $field) {
+      if (is_array($field)) {
+        $return[] = '`' . $field[0] . '`(' . $field[1] . ')';
+      }
+      else {
+        $return[] = '`' . $field . '`';
+      }
+    }
+    return implode(', ', $return);
+  }
+
+  public function renameTable($table, $new_name) {
+    if (!$this->tableExists($table)) {
+      throw new DatabaseSchemaObjectDoesNotExistException(t("Cannot rename @table to @table_new: table @table doesn't exist.", array('@table' => $table, '@table_new' => $new_name)));
+    }
+    if ($this->tableExists($new_name)) {
+      throw new DatabaseSchemaObjectExistsException(t("Cannot rename @table to @table_new: table @table_new already exists.", array('@table' => $table, '@table_new' => $new_name)));
+    }
+
+    $info = $this->getPrefixInfo($new_name);
+    return $this->connection->query('ALTER TABLE {' . $table . '} RENAME TO `' . $info['table'] . '`');
+  }
+
+  public function dropTable($table) {
+    if (!$this->tableExists($table)) {
+      return FALSE;
+    }
+
+    $this->connection->query('DROP TABLE {' . $table . '}');
+    return TRUE;
+  }
+
+  public function addField($table, $field, $spec, $keys_new = array()) {
+    if (!$this->tableExists($table)) {
+      throw new DatabaseSchemaObjectDoesNotExistException(t("Cannot add field @table.@field: table doesn't exist.", array('@field' => $field, '@table' => $table)));
+    }
+    if ($this->fieldExists($table, $field)) {
+      throw new DatabaseSchemaObjectExistsException(t("Cannot add field @table.@field: field already exists.", array('@field' => $field, '@table' => $table)));
+    }
+
+    $fixnull = FALSE;
+    if (!empty($spec['not null']) && !isset($spec['default'])) {
+      $fixnull = TRUE;
+      $spec['not null'] = FALSE;
+    }
+    $query = 'ALTER TABLE {' . $table . '} ADD ';
+    $query .= $this->createFieldSql($field, $this->processField($spec));
+    if ($keys_sql = $this->createKeysSql($keys_new)) {
+      $query .= ', ADD ' . implode(', ADD ', $keys_sql);
+    }
+    $this->connection->query($query);
+    if (isset($spec['initial'])) {
+      $this->connection->update($table)
+        ->fields(array($field => $spec['initial']))
+        ->execute();
+    }
+    if ($fixnull) {
+      $spec['not null'] = TRUE;
+      $this->changeField($table, $field, $field, $spec);
+    }
+  }
+
+  public function dropField($table, $field) {
+    if (!$this->fieldExists($table, $field)) {
+      return FALSE;
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} DROP `' . $field . '`');
+    return TRUE;
+  }
+
+  public function fieldSetDefault($table, $field, $default) {
+    if (!$this->fieldExists($table, $field)) {
+      throw new DatabaseSchemaObjectDoesNotExistException(t("Cannot set default value of field @table.@field: field doesn't exist.", array('@table' => $table, '@field' => $field)));
+    }
+
+    if (!isset($default)) {
+      $default = 'NULL';
+    }
+    else {
+      $default = is_string($default) ? "'$default'" : $default;
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} ALTER COLUMN `' . $field . '` SET DEFAULT ' . $default);
+  }
+
+  public function fieldSetNoDefault($table, $field) {
+    if (!$this->fieldExists($table, $field)) {
+      throw new DatabaseSchemaObjectDoesNotExistException(t("Cannot remove default value of field @table.@field: field doesn't exist.", array('@table' => $table, '@field' => $field)));
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} ALTER COLUMN `' . $field . '` DROP DEFAULT');
+  }
+
+  public function indexExists($table, $name) {
+    // Returns one row for each column in the index. Result is string or FALSE.
+    // Details at http://dev.mysql.com/doc/refman/5.0/en/show-index.html
+    $row = $this->connection->query('SHOW INDEX FROM {' . $table . "} WHERE key_name = '$name'")->fetchAssoc();
+    return isset($row['Key_name']);
+  }
+
+  public function addPrimaryKey($table, $fields) {
+    if (!$this->tableExists($table)) {
+      throw new DatabaseSchemaObjectDoesNotExistException(t("Cannot add primary key to table @table: table doesn't exist.", array('@table' => $table)));
+    }
+    if ($this->indexExists($table, 'PRIMARY')) {
+      throw new DatabaseSchemaObjectExistsException(t("Cannot add primary key to table @table: primary key already exists.", array('@table' => $table)));
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} ADD PRIMARY KEY (' . $this->createKeySql($fields) . ')');
+  }
+
+  public function dropPrimaryKey($table) {
+    if (!$this->indexExists($table, 'PRIMARY')) {
+      return FALSE;
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} DROP PRIMARY KEY');
+    return TRUE;
+  }
+
+  public function addUniqueKey($table, $name, $fields) {
+    if (!$this->tableExists($table)) {
+      throw new DatabaseSchemaObjectDoesNotExistException(t("Cannot add unique key @name to table @table: table doesn't exist.", array('@table' => $table, '@name' => $name)));
+    }
+    if ($this->indexExists($table, $name)) {
+      throw new DatabaseSchemaObjectExistsException(t("Cannot add unique key @name to table @table: unique key already exists.", array('@table' => $table, '@name' => $name)));
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} ADD UNIQUE KEY `' . $name . '` (' . $this->createKeySql($fields) . ')');
+  }
+
+  public function dropUniqueKey($table, $name) {
+    if (!$this->indexExists($table, $name)) {
+      return FALSE;
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} DROP KEY `' . $name . '`');
+    return TRUE;
+  }
+
+  public function addIndex($table, $name, $fields) {
+    if (!$this->tableExists($table)) {
+      throw new DatabaseSchemaObjectDoesNotExistException(t("Cannot add index @name to table @table: table doesn't exist.", array('@table' => $table, '@name' => $name)));
+    }
+    if ($this->indexExists($table, $name)) {
+      throw new DatabaseSchemaObjectExistsException(t("Cannot add index @name to table @table: index already exists.", array('@table' => $table, '@name' => $name)));
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} ADD INDEX `' . $name . '` (' . $this->createKeySql($fields) . ')');
+  }
+
+  public function dropIndex($table, $name) {
+    if (!$this->indexExists($table, $name)) {
+      return FALSE;
+    }
+
+    $this->connection->query('ALTER TABLE {' . $table . '} DROP INDEX `' . $name . '`');
+    return TRUE;
+  }
+
+  public function changeField($table, $field, $field_new, $spec, $keys_new = array()) {
+    if (!$this->fieldExists($table, $field)) {
+      throw new DatabaseSchemaObjectDoesNotExistException(t("Cannot change the definition of field @table.@name: field doesn't exist.", array('@table' => $table, '@name' => $field)));
+    }
+    if (($field != $field_new) && $this->fieldExists($table, $field_new)) {
+      throw new DatabaseSchemaObjectExistsException(t("Cannot rename field @table.@name to @name_new: target field already exists.", array('@table' => $table, '@name' => $field, '@name_new' => $field_new)));
+    }
+
+    $sql = 'ALTER TABLE {' . $table . '} CHANGE `' . $field . '` ' . $this->createFieldSql($field_new, $this->processField($spec));
+    if ($keys_sql = $this->createKeysSql($keys_new)) {
+      $sql .= ', ADD ' . implode(', ADD ', $keys_sql);
+    }
+    $this->connection->query($sql);
+  }
+
+  public function prepareComment($comment, $length = NULL) {
+    // Work around a bug in some versions of PDO, see http://bugs.php.net/bug.php?id=41125
+    $comment = str_replace("'", '’', $comment);
+
+    // Truncate comment to maximum comment length.
+    if (isset($length)) {
+      // Add table prefixes before truncating.
+      $comment = truncate_utf8($this->connection->prefixTables($comment), $length, TRUE, TRUE);
+    }
+
+    return $this->connection->quote($comment);
+  }
+
+  /**
+   * Retrieve a table or column comment.
+   */
+  public function getComment($table, $column = NULL) {
+    $condition = $this->buildTableNameCondition($table);
+    if (isset($column)) {
+      $condition->condition('column_name', $column);
+      $condition->compile($this->connection, $this);
+      // Don't use {} around information_schema.columns table.
+      return $this->connection->query("SELECT column_comment FROM information_schema.columns WHERE " . (string) $condition, $condition->arguments())->fetchField();
+    }
+    $condition->compile($this->connection, $this);
+    // Don't use {} around information_schema.tables table.
+    $comment = $this->connection->query("SELECT table_comment FROM information_schema.tables WHERE " . (string) $condition, $condition->arguments())->fetchField();
+    // Work-around for MySQL 5.0 bug http://bugs.mysql.com/bug.php?id=11379
+    return preg_replace('/; InnoDB free:.*$/', '', $comment);
+  }
+
+  public function tableExists($table) {
+    // The information_schema table is very slow to query under MySQL 5.0.
+    // Instead, we try to select from the table in question.  If it fails,
+    // the most likely reason is that it does not exist. That is dramatically
+    // faster than using information_schema.
+    // @link http://bugs.mysql.com/bug.php?id=19588
+    // @todo: This override should be removed once we require a version of MySQL
+    // that has that bug fixed.
+    try {
+      $this->connection->queryRange("SELECT 1 FROM {" . $table . "}", 0, 1);
+      return TRUE;
+    }
+    catch (Exception $e) {
+      return FALSE;
+    }
+  }
+
+  public function fieldExists($table, $column) {
+    // The information_schema table is very slow to query under MySQL 5.0.
+    // Instead, we try to select from the table and field in question. If it
+    // fails, the most likely reason is that it does not exist. That is
+    // dramatically faster than using information_schema.
+    // @link http://bugs.mysql.com/bug.php?id=19588
+    // @todo: This override should be removed once we require a version of MySQL
+    // that has that bug fixed.
+    try {
+      $this->connection->queryRange("SELECT $column FROM {" . $table . "}", 0, 1);
+      return TRUE;
+    }
+    catch (Exception $e) {
+      return FALSE;
+    }
+  }
+
+}
+
+/**
+ * @} End of "addtogroup schemaapi".
+ */