StatisticsLastCommentName.php

<?php

namespace Drupal\comment\Plugin\views\sort;

use Drupal\views\Plugin\views\sort\SortPluginBase;

/**
 * Sort handler to sort by last comment name which might be in 2 different
 * fields.
 *
 * @ingroup views_sort_handlers
 *
 * @ViewsSort("comment_ces_last_comment_name")
 */
class StatisticsLastCommentName extends SortPluginBase {
    public function query() {
        $this->ensureMyTable();
        $definition = [
            'table' => 'users_field_data',
            'field' => 'uid',
            'left_table' => 'comment_entity_statistics',
            'left_field' => 'last_comment_uid',
        ];
        $join = \Drupal::service('plugin.manager.views.join')->createInstance('standard', $definition);
        // @todo this might be safer if we had an ensure_relationship rather than guessing
        // the table alias. Though if we did that we'd be guessing the relationship name
        // so that doesn't matter that much.
        $this->user_table = $this->query
            ->ensureTable('ces_users', $this->relationship, $join);
        $this->user_field = $this->query
            ->addField($this->user_table, 'name');
        // Add the field.
        $this->query
            ->addOrderBy(NULL, "LOWER(COALESCE({$this->user_table}.name, {$this->tableAlias}.{$this->field}))", $this->options['order'], $this->tableAlias . '_' . $this->field);
    }

}