get all pages which have assigned reviews submitted by a specific user

global $wpdb;

$userId = 1; // change as needed

$sql = "
    SELECT DISTINCT ap.post_id
    FROM {$wpdb->prefix}glsr_assigned_posts ap
    INNER JOIN {$wpdb->prefix}glsr_ratings r ON r.ID = ap.rating_id
    INNER JOIN {$wpdb->posts} p ON p.ID = r.review_id
    WHERE p.post_author = %d AND ap.is_published
";

$postIds = $wpdb->get_col($wpdb->prepare($sql, $userId));

$posts = new WP_Query([
    'post__in' => $postIds,
    'post_status' => 'publish',
    'post_type' => 'page',
]);