Views distinct option not working in drupal 7

My final goal is to show distinct list of years when nodes are created. I don't want to rewrite view and want to make it generic. So I need to build query like "SELECT DISTNICT YEAR(node.created)..."

I am porting solution to D7 for the issue http://drupal.org/node/844202 which allows to use custom date formats in SQL. I am almost done with it. And I can build following query:

SELECT DATE_FORMAT((DATE_ADD('19700101', INTERVAL node.created SECOND) + INTERVAL 10800 SECOND), '%Y') AS node_created
FROM {node} node

which returns

Post date: 2010
Post date: 2011
Post date: 2011

All I need is to make this query distinct, but when I click Distinct checkbox in the view configuration I get following query, which returns not distinct set of values:

SELECT DISTINCT node.nid AS nid, DATE_FORMAT((DATE_ADD('19700101', INTERVAL node.created SECOND) + INTERVAL 10800 SECOND), '%Y') AS node_created FROM {node} node

There is code in views_plugin_query_default.inc which have following lines:

  function query($get_count = FALSE) {
    // Check query distinct value.
    if (empty($this->no_distinct) && $this->distinct && !empty($this->fields)) {
      $base_field_alias = $this->add_field($this->base_table, $this->base_field);
      $this->add_groupby($base_field_alias);
      $distinct = TRUE;
    }
   ...

Why do we need to add group by field if we are making distinct query? Could we just delete this code and add nid field if needed manually. Other solution is to add new checkbox which will allow to set distinct granularity: "Distinct among return set", "Distinct among table items".