UrlAliasBase.php

<?php

namespace Drupal\path\Plugin\migrate\source;

use Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase;

/**
 * Base class for the url_alias source plugins.
 */
abstract class UrlAliasBase extends DrupalSqlBase {
    
    /**
     * {@inheritdoc}
     */
    public function query() {
        // The order of the migration is significant since
        // \Drupal\path_alias\AliasRepository::lookupPathAlias() orders by pid
        // before returning a result. Postgres does not automatically order by
        // primary key therefore we need to add a specific order by.
        return $this->select('url_alias', 'ua')
            ->fields('ua')
            ->orderBy('pid');
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        return [
            'pid' => $this->t('The numeric identifier of the path alias.'),
            'language' => $this->t('The language code of the URL alias.'),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        $ids['pid']['type'] = 'integer';
        return $ids;
    }

}