Add postmeta to all blog posts

Post meta entries are in your wordpress database, in the wp_postmeta table.

I am just a newbie, not sure if this is right, but something I can think of that might help you in the right direction. Hope this helps.

function wordpress_custom_post_meta_bulk()
   {
      $posts = get_posts(array('numberposts' => -1) );
      foreach($posts as $p) :  
         $meta += array('_key' => '';
                        '_value' => '';);
         update_post_meta($p->ID, 'meta',true);
      endforeach; 
   }