Querying Instead Cache?

This is (shorter) table structure:

- id
- name
- last_date

This is code:

            $dependency = new CDbCacheDependency('SELECT MAX(last_date) FROM table WHERE id='.$id); 
            $post= Post::model()->cache(3600, $dependency)->findByPk($id);

Using CWebLogRoute I see:

02:17:50.937169 trace system.db.CDbCommand

Querying SQL: Select t.id, t.name, blabla FROM post blabla

02:17:50.937511 trace system.db.CDbCommand

select max(date) from post where id=blabla

02:17:50.938518 trace system.caching.CApcCache

Serving... bla bla (this is from cache)

Why do I have these frist system.db.CDbCommand?

Tnx