Condition.php

<?php

namespace Drupal\Core\Entity\Query\Null;

use Drupal\Core\Entity\Query\ConditionBase;

/**
 * Defines the condition class for the null entity query.
 */
class Condition extends ConditionBase {
    
    /**
     * {@inheritdoc}
     */
    public function compile($query) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function exists($field, $langcode = NULL) {
        return $this->condition($field, NULL, 'IS NOT NULL', $langcode);
    }
    
    /**
     * {@inheritdoc}
     */
    public function notExists($field, $langcode = NULL) {
        return $this->condition($field, NULL, 'IS NULL', $langcode);
    }

}