function DatabaseConnection_mysql::nextId

File

includes/database/mysql/database.inc, line 488

Class

DatabaseConnection_mysql

Code

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;
}