sql variable substitution on :joins

I would like to have substitution+sanitizing features on :joins.

class Post
  belongs_to :user
  named_scope :by_admins, {
    :joins => 'inner join users as users_for_admin_check on users_for_admin_check.id = posts.user_id'.
    :conditions => ['users_for_admin_check.admin = ?', true] }
end

Here I had to move the condition to :conditions, just to get the ? substitution. I need the substitution in this case because boolean values are handled differently on sqlite/mysql.

In this case I would have liked to keep it all in the join, since this is actually a join condition.

class Post
  belongs_to :user
  named_scope :by_admins, {
    :joins => ['inner join users as users_for_admin_check on users_for_admin_check.id = posts.user_id and users_for_admin_checking.admin = ?', true]
  }
end

I think it doesn't interfere with other stuff, since with the current behavior, it acts the same as when using symbols in an array.

at the moment: Using :joins => :symbol will try some inner join for association named :symbol Using :joins => 'string' will just put the string in the sql query. Using :joins => [:symbol, :symbol] will include inner joins for all associations Using :joins => ['string', *values] will try the same as with symbols above, which is inconsistent considering the difference between symbols and strings without the array.

Any chance this can get implemented? Thanks