select SUM(abs(CAST(rev1.rev_len as signed)-if(rev1.rev_parent_id=0,0,CAST(parent1.rev_len as signed)))) from revision rev1

     JOIN revision parent1

    ON parent1.rev_id = rev1.rev_parent_id

     JOIN page p1

    ON p1.page_id = rev1.rev_page

     join actor actor1 ON actor1.actor_id = rev1.rev_actor 

    WHERE  

     p1.page_namespace = 0

    and rev1.rev_actor="Chaduvari"

    and parent1.rev_page in (select rev_page from revision rev11 where rev11.rev_actor=rev1.rev_actor)

     group by rev1.rev_actor;