db_pager_view problem

I have a modified dimensions db_pager view.

What I am expecting that if I pass the Value of the Column with an index 'name' with a value 'currency' (Database Column Name) then it shall display the value of that column irrespective of its sequential position in the $sql query passed to db_pager

    _("Currency") => array('name'=>'currency'),

But currently I am not getting the desired result unless I bring the currency column in the same sequential position.

for e.g If in db_pager view the Currency is displayed on 3rd column then in $sql also the currency column shall be on 3rd position, otherwise it is displaying the value of any other column that is on 3rd position.

Why the 'name' index 'value' is not working? Or I am expecting something wrong?

Any Idea?