|R| = 10000 tuples,  10 tuples with  a=5, R is indexed on a

-- Cost of execution 

   for rec in
      select * from R
   loop
      if (rec.a = 5) then
         ...
      end if;
   end loop;

#iterations = 10000

   for rec in
      select * from R where a = 5
   loop
      ...
   end loop;

#queries = 10