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LiskMigrationIterator.php
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Thu, Apr 24, 13:43

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 implements Iterator {
private $object;
private $cursor;
private $data;
public function __construct(LiskDAO $object) {
$this->object = $object;
}
public function rewind() {
$this->cursor = 0;
$this->data = array();
$this->next();
}
public function valid() {
if (!$this->data) {
$this->next();
}
return (bool)$this->data;
}
public function current() {
return end($this->data);
}
public function key() {
return $this->current()->getID();
}
public function next() {
if ($this->data) {
return array_pop($this->data);
}
$this->data = $this->object->loadAllWhere(
'id > %d ORDER BY id ASC LIMIT %d',
$this->cursor,
100);
if ($this->data) {
$this->cursor = last($this->data)->getID();
$this->data = array_reverse($this->data);
}
}
}

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