Function iter_schema_items 

fn iter_schema_items<F, T>(
    session: &Arc<SessionImpl>,
    schema: &Option<Ident>,
    reader: &ArcRwLockReadGuard<RawRwLock, Catalog>,
    current_user: &UserCatalog,
    f: F,
) -> Vec<T>
where
    F: FnMut(&SchemaCatalog) -> Vec<T>,