LiskMigrationIterator.php
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	<?php

	/*
	* Copyright 2012 Facebook, Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	/**
	* Iterate over every object of a given type, without holding all of them in
	* memory. This is useful for performing database migrations.
	*
	* $things = new LiskMigrationIterator(new LiskThing());
	* foreach ($things as $thing) {
	* // do something
	* }
	*
	* NOTE: This only works on objects with a normal `id` column.
	*
	* @task storage
	*/
	final class LiskMigrationIterator extends PhutilBufferedIterator {

	private $object;
	private $cursor;

	public function __construct(LiskDAO $object) {
	$this->object = $object;
	}

	protected function didRewind() {
	$this->cursor = 0;
	}

	public function key() {
	return $this->current()->getID();
	}

	protected function loadPage() {
	$results = $this->object->loadAllWhere(
	'id > %d ORDER BY id ASC LIMIT %d',
	$this->cursor,
	$this->getPageSize());
	if ($results) {
	$this->cursor = last($results)->getID();
	}
	return $results;
	}

	}