class TruncateQuery in Drupal 7

General class for an abstracted TRUNCATE operation.

Hierarchy

• class \Query implements QueryPlaceholderInterface
  • class \TruncateQuery

Related topics

Database abstraction layer

Allow the use of different database servers using the same code base.

1 string reference to 'TruncateQuery'

DatabaseConnection::truncate in includes/database/database.inc

Prepares and returns a TRUNCATE query object.

File

includes/database/query.inc, line 887

Non-specific Database query code. Used by all engines.

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
      ->compiled();
  }

  /**
   * 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 = $this->connection
      ->makeComment($this->comments);

    // 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) . '} ';
    }
  }

}

Members

Name	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