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<?php
/**
* Base code for update jobs that do something with some secondary
* data extracted from article.
*
* 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
*/
/**
* Abstract base class for update jobs that do something with some secondary
* data extracted from article.
*
* @note: subclasses should NOT start or commit transactions in their doUpdate() method,
* a transaction will automatically be wrapped around the update. If need be,
* subclasses can override the beginTransaction() and commitTransaction() methods.
*/
abstract class DataUpdate implements DeferrableUpdate {
/**
* Constructor
*/
public function __construct() {
# noop
}
/**
* Begin an appropriate transaction, if any.
* This default implementation does nothing.
*/
public function beginTransaction() {
//noop
}
/**
* Commit the transaction started via beginTransaction, if any.
* This default implementation does nothing.
*/
public function commitTransaction() {
//noop
}
/**
* Abort / roll back the transaction started via beginTransaction, if any.
* This default implementation does nothing.
*/
public function rollbackTransaction() {
//noop
}
/**
* Convenience method, calls doUpdate() on every DataUpdate in the array.
*
* This methods supports transactions logic by first calling beginTransaction()
* on all updates in the array, then calling doUpdate() on each, and, if all goes well,
* then calling commitTransaction() on each update. If an error occurs,
* rollbackTransaction() will be called on any update object that had beginTransaction()
* called but not yet commitTransaction().
*
* This allows for limited transactional logic across multiple backends for storing
* secondary data.
*
* @param array $updates a list of DataUpdate instances
* @throws Exception|null
*/
public static function runUpdates( $updates ) {
if ( empty( $updates ) ) return; # nothing to do
$open_transactions = array();
$exception = null;
/**
* @var $update DataUpdate
* @var $trans DataUpdate
*/
try {
// begin transactions
foreach ( $updates as $update ) {
$update->beginTransaction();
$open_transactions[] = $update;
}
// do work
foreach ( $updates as $update ) {
$update->doUpdate();
}
// commit transactions
while ( count( $open_transactions ) > 0 ) {
$trans = array_pop( $open_transactions );
$trans->commitTransaction();
}
} catch ( Exception $ex ) {
$exception = $ex;
wfDebug( "Caught exception, will rethrow after rollback: " . $ex->getMessage() );
}
// rollback remaining transactions
while ( count( $open_transactions ) > 0 ) {
$trans = array_pop( $open_transactions );
$trans->rollbackTransaction();
}
if ( $exception ) {
throw $exception; // rethrow after cleanup
}
}
}
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