LiskMigrationIterator.php
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	<?php

	/**
	* 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;
	private $set;

	public function __construct(LiskDAO $object) {
	$this->set = new LiskDAOSet();
	$this->object = $object->putInSet($this->set);
	}

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

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

	protected function loadPage() {
	$this->set->clearSet();

	$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;
	}

	}