class TruncateQuery

General class for an abstracted TRUNCATE operation.


Expanded class hierarchy of TruncateQuery

Related topics

1 string reference to 'TruncateQuery'
DatabaseConnection::truncate in drupal/includes/database/
Prepares and returns a TRUNCATE query object.


drupal/includes/database/, line 887
Non-specific Database query code. Used by all engines.

View source
class TruncateQuery extends Query {

   * The table to truncate.
   * @var string
  protected $table;

   * Constructs a TruncateQuery object.
   * @param DatabaseConnection $connection
   *   A DatabaseConnection object.
   * @param string $table
   *   Name of the table to associate with this query.
   * @param array $options
   *   Array of database options.
  public function __construct(DatabaseConnection $connection, $table, array $options = array()) {
    $options['return'] = Database::RETURN_AFFECTED;
    parent::__construct($connection, $options);
    $this->table = $table;

   * Implements QueryConditionInterface::compile().
  public function compile(DatabaseConnection $connection, QueryPlaceholderInterface $queryPlaceholder) {
    return $this->condition
      ->compile($connection, $queryPlaceholder);

   * Implements QueryConditionInterface::compiled().
  public function compiled() {
    return $this->condition

   * Executes the TRUNCATE query.
   * @return
   *   Return value is dependent on the database type.
  public function execute() {
    return $this->connection
      ->query((string) $this, array(), $this->queryOptions);

   * Implements PHP magic __toString method to convert the query to a string.
   * @return string
   *   The prepared statement.
  public function __toString() {

    // Create a sanitized comment string to prepend to the query.
    $comments = $this->connection

    // In most cases, TRUNCATE is not a transaction safe statement as it is a
    // DDL statement which results in an implicit COMMIT. When we are in a
    // transaction, fallback to the slower, but transactional, DELETE.
    // PostgreSQL also locks the entire table for a TRUNCATE strongly reducing
    // the concurrency with other transactions.
    if ($this->connection
      ->inTransaction()) {
      return $comments . 'DELETE FROM {' . $this->connection
        ->escapeTable($this->table) . '}';
    else {
      return $comments . 'TRUNCATE {' . $this->connection
        ->escapeTable($this->table) . '} ';



Namesort descending Modifiers Type Description Overrides
Query::$comments protected property An array of comments that can be prepended to a query.
Query::$connection protected property The connection object on which to run this query.
Query::$connectionKey protected property The key of the connection object.
Query::$connectionTarget protected property The target of the connection object.
Query::$nextPlaceholder protected property The placeholder counter.
Query::$queryOptions protected property The query options to pass on to the connection object.
Query::$uniqueIdentifier protected property A unique identifier for this query object.
Query::comment public function Adds a comment to the query.
Query::getComments public function Returns a reference to the comments array for the query.
Query::nextPlaceholder public function Gets the next placeholder value for this query object. Overrides QueryPlaceholderInterface::nextPlaceholder
Query::uniqueIdentifier public function Returns a unique identifier for this object. Overrides QueryPlaceholderInterface::uniqueIdentifier
Query::__clone public function Implements the magic __clone function. 1
Query::__sleep public function Implements the magic __sleep function to disconnect from the database.
Query::__wakeup public function Implements the magic __wakeup function to reconnect to the database.
TruncateQuery::$table protected property The table to truncate.
TruncateQuery::compile public function Implements QueryConditionInterface::compile().
TruncateQuery::compiled public function Implements QueryConditionInterface::compiled().
TruncateQuery::execute public function Executes the TRUNCATE query. Overrides Query::execute
TruncateQuery::__construct public function Constructs a TruncateQuery object. Overrides Query::__construct
TruncateQuery::__toString public function Implements PHP magic __toString method to convert the query to a string. Overrides Query::__toString 1