<?php
/**
 * Base code for update jobs that put some secondary data extracted
 * from article content into the database.
 *
 * 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
 *
 * @file
 */
class PurgeJobUtils {
	/**
	 * Invalidate the cache of a list of pages from a single namespace.
	 * This is intended for use by subclasses.
	 *
	 * @param IDatabase $dbw
	 * @param int $namespace Namespace number
	 * @param array $dbkeys
	 */
	public static function invalidatePages( IDatabase $dbw, $namespace, array $dbkeys ) {
		if ( $dbkeys === [] ) {
			return;
		}

		$dbw->onTransactionPreCommitOrIdle( function() use ( $dbw, $namespace, $dbkeys ) {
			// 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 = $dbw->timestamp();
			$ids = $dbw->selectFieldValues(
				'page',
				'page_id',
				[
					'page_namespace' => $namespace,
					'page_title' => $dbkeys,
					'page_touched < ' . $dbw->addQuotes( $now )
				],
				__METHOD__
			);

			if ( $ids === [] ) {
				return;
			}

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