alterSubqueryCondition example

      if (isset($tables[$table_name]['condition'])) {
        $tables[$table_name]['condition'] = $this->conditionNamespace($tables[$table_name]['condition']);
      }
    }
    // Namespace fields.     foreach (array_keys($fields) as $field_name) {
      $fields[$field_name]['table'] .= $this->subquery_namespace;
      $fields[$field_name]['alias'] .= $this->subquery_namespace;
    }
    // Namespace conditions.     $where = &$subquery->conditions();
    $this->alterSubqueryCondition($subquery, $where);
    // Not sure why, but our sort order clause doesn't have a table.     // TODO: the call to addHandler() above to add the sort handler is probably     // wrong -- needs attention from someone who understands it.     // In the meantime, this works, but with a leap of faith.     $orders = &$subquery->getOrderBy();
    foreach ($orders as $order_key => $order) {
      // But if we're using a whole view, we don't know what we have!       if ($options['subquery_view']) {
        [$sort_table, $sort_field] = explode('.', $order_key);
      }
      $orders[$sort_table . $this->subquery_namespace . '.' . $sort_field] = $order;