src/infrastructure/storage/lisk/LiskMigrationIterator.php

   1 <?php
   2
   3 /**
   4  * Iterate over every object of a given type, without holding all of them in
   5  * memory. This is useful for performing database migrations.
   6  *
   7  *   $things = new LiskMigrationIterator(new LiskThing());
   8  *   foreach ($things as $thing) {
   9  *     // do something
  10  *   }
  11  *
  12  * NOTE: This only works on objects with a normal `id` column.
  13  *
  14  * @task storage
  15  */
  16 final class LiskMigrationIterator extends PhutilBufferedIterator {
  17
  18   private $object;
  19   private $cursor;
  20
  21   public function __construct(LiskDAO $object) {
  22     $this->object = $object;
  23   }
  24
  25   protected function didRewind() {
  26     $this->cursor = 0;
  27   }
  28
  29   public function key() {
  30     return $this->current()->getID();
  31   }
  32
  33   protected function loadPage() {
  34     $results = $this->object->loadAllWhere(
  35       'id > %d ORDER BY id ASC LIMIT %d',
  36       $this->cursor,
  37       $this->getPageSize());
  38
  39     if ($results) {
  40       $this->cursor = last($results)->getID();
  41     }
  42
  43     return $results;
  44   }
  45
  46 }