		while ( $blockStart <= $end ) {
			$this->output( "...doing rev_id from $blockStart to $blockEnd\n" );
			$cond = "rev_id BETWEEN $blockStart AND $blockEnd";
			$res = $db->select( 'revision',
				[ 'rev_id', 'rev_page', 'rev_timestamp', 'rev_parent_id' ],
				[ $cond, 'rev_parent_id' => null ], __METHOD__ );
			# Go through and update rev_parent_id from these rows.
			# Assume that the previous revision of the title was
			# the original previous revision of the title when the
			# edit was made...
			foreach ( $res as $row ) {
				# First, check rows with the same timestamp other than this one