<?php
/**
 * to import the data you do:
 *  drush migrate-import update
 * or this can be handled through the web interface at admin/content/migrate
 */
class UpdateMigration extends Migration {
  public function __construct() {
    parent::__construct();
    $this->systemOfRecord = Migration::DESTINATION;

    $options = array(
      'embedded_newlines' => TRUE,
      'header_rows' => 1
    );
    $path = drupal_get_path('module', 'my_migrate').'/migrate_ext.csv';
    $this->source = new MigrateSourceCSV($path, array(), $options);
    $this->destination = new MigrateDestinationFieldCollection('field_page_extras', array('host_entity_type' => 'node'));

    $this->map = new MigrateSQLMap($this->machineName,
      array(
        'id' => array(
          'type' => 'int',
          'unsigned' => TRUE,
          'not null' => TRUE,
        ),
       'numrow' => array(
          'type' => 'varchar',
          'length' => 16,
        )
      ),
      MigrateDestinationFieldCollection::getKeySchema()
    );

    $this->addFieldMapping('host_entity_id', 'id')
         ->sourceMigration('Extras');

    $this->addFieldMapping('field_page_extra1', 'extra1');
    $this->addFieldMapping('field_page_extra2', 'extra2');
  }
}