<?php
/**
 * See docs/deferred.txt
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * Abstract base class for update jobs that put some secondary data extracted
 * from article content into the database.
 */
abstract class SecondaryDBDataUpdate extends SecondaryDataUpdate {

	/**@{{
	 * @private
	 */
	var $mDb,            //!< Database connection reference
		$mOptions;       //!< SELECT options to be used (array)
	/**@}}*/

	/**
	 * Constructor
     **/
    public function __construct( ) {
		global $wgAntiLockFlags;

        parent::__construct( );

		if ( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) {
			$this->mOptions = array();
		} else {
			$this->mOptions = array( 'FOR UPDATE' );
		}
		$this->mDb = wfGetDB( DB_MASTER );
	}

	/**
	 * Invalidate the cache of a list of pages from a single namespace
	 *
	 * @param $namespace Integer
	 * @param $dbkeys Array
	 */
	public function invalidatePages( $namespace, $dbkeys ) {
		if ( !count( $dbkeys ) ) {
			return;
		}

		/**
		 * Determine which pages need to be updated
		 * This is necessary to prevent the job queue from smashing the DB with
		 * large numbers of concurrent invalidations of the same page
		 */
		$now = $this->mDb->timestamp();
		$ids = array();
		$res = $this->mDb->select( 'page', array( 'page_id' ),
			array(
				'page_namespace' => $namespace,
				'page_title IN (' . $this->mDb->makeList( $dbkeys ) . ')',
				'page_touched < ' . $this->mDb->addQuotes( $now )
			), __METHOD__
		);
		foreach ( $res as $row ) {
			$ids[] = $row->page_id;
		}
		if ( !count( $ids ) ) {
			return;
		}

		/**
		 * Do the update
		 * We still need the page_touched condition, in case the row has changed since
		 * the non-locking select above.
		 */
		$this->mDb->update( 'page', array( 'page_touched' => $now ),
			array(
				'page_id IN (' . $this->mDb->makeList( $ids ) . ')',
				'page_touched < ' . $this->mDb->addQuotes( $now )
			), __METHOD__
		);
	}

}