php: construct

gistfile1.txt

<?php

namespace Core\Db;

/**
 * Helps to iterate over huge data collection.
 * It loads records by small chunks
 * 
 * Example:
 * <pre>
 *      $collection = $app['mongo.default']->sample;
 *      $loader = new ChunkLoader($collection, 50);
 *      foreach($loader as $row) {
 *          var_dump($row);
 *      }
 * </pre>
 */
class ChunkLoader implements \Iterator
{
    /**
     * @var MongoCollection
     */
    protected $collection;

    /**
     * @var int how many items to load per one query
     */
    protected $chunkSize;

    /**
     * @var array current chunk data from mongo
     */
    protected $chunkData;

    /**
     * @var int how many rows to skip
     */
    protected $skip = 0;

    /**
     * @var int cursor position in current chunk
     */
    protected $position = 0;

    public function __construct($collection, $chunkSize=100)
    {
        $this->collection = $collection;
        $this->chunkSize = $chunkSize;
        $this->total = $this->collection->count();
    }

    protected function load()
    {
        $this->chunkData = iterator_to_array($this->collection
            ->find()
            ->skip($this->skip)
            ->limit($this->chunkSize)
        , false);
    }

    public function current()
    {
        return $this->chunkData[$this->position];
    }

    public function next()
    {
        ++$this->position;
        if ($this->position <= $this->total && $this->position >= $this->chunkSize) {
            $this->skip += $this->chunkSize;
            $this->position = 0;
            $this->load();
        }
    }

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

    public function valid()
    {
        return isset($this->chunkData[$this->position]);
    }

    public function rewind()
    {
        $this->skip = 0;
        $this->position = 0;
        $this->load();
    }
}