DeferredUpdates.php

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<?php
interface DeferrableUpdate {
    function doUpdate();
}

class DeferredUpdates {
    private static $updates = array();

    public static function addUpdate( DeferrableUpdate $update ) {
        array_push( self::$updates, $update );
    }

    public static function addHTMLCacheUpdate( $title, $table ) {
        self::addUpdate( new HTMLCacheUpdate( $title, $table ) );
    }

    public static function addCallableUpdate( $callable ) {
        self::addUpdate( new MWCallableUpdate( $callable ) );
    }

    public static function doUpdates( $commit = '' ) {
        global $wgDeferredUpdateList;

        wfProfileIn( __METHOD__ );

        $updates = array_merge( $wgDeferredUpdateList, self::$updates );

        // No need to get master connections in case of empty updates array
        if ( !count( $updates ) ) {
            wfProfileOut( __METHOD__ );

            return;
        }

        $dbw = false;
        $doCommit = $commit == 'commit';
        if ( $doCommit ) {
            $dbw = wfGetDB( DB_MASTER );
        }

        while ( $updates ) {
            self::clearPendingUpdates();

            foreach ( $updates as $update ) {
                try {
                    $update->doUpdate();

                    if ( $doCommit && $dbw->trxLevel() ) {
                        $dbw->commit( __METHOD__, 'flush' );
                    }
                } catch ( MWException $e ) {
                    // We don't want exceptions thrown during deferred updates to
                    // be reported to the user since the output is already sent.
                    // Instead we just log them.
                    if ( !$e instanceof ErrorPageError ) {
                        MWExceptionHandler::logException( $e );
                    }
                }
            }
            $updates = array_merge( $wgDeferredUpdateList, self::$updates );
        }

        wfProfileOut( __METHOD__ );
    }

    public static function clearPendingUpdates() {
        global $wgDeferredUpdateList;
        $wgDeferredUpdateList = self::$updates = array();
    }
}