Subquery with OR

There are various reasons why Oracle is sometimes unable to unnest a subquery. Here’s one example of a fairly common problem:

select
	count(small_vc)
from
	t1
where
	t1.mod_15 > 10
and	(    t1.modded = 0
	  or exists (
		select	null
		from	t2
		where	t2.id = t1.id
		)
	)
;