Batch update existing menus

Hello,
the main reason I (and I suppose most of the user) searched for something like Menu Attributes is because along the development of the website a new need appeared. In my case targeting the menu links with "_top".

Installed the module; no problem.
Configuration; easy.
Set value; ok.
See result.... NO RESULTS!!!¿?¿?

Right!..... "for new menu items"..... What if you already have more than 2000??? No batch option??

Tried to look in the database to see if search and replace could do some good, but not found the table/field....
This is actually a GENERIC DRUPAL ISSUE, all Modules should include a list of referenced database tables and/or fields for the specific module, this would avoid hours of needless searching, trying and sometimes not finding, like in this case.

How could I, at least, manually try to set target="_top" for all existing menus through the database?

thanks.