Decibel! <decibel@decibel.org> writes:
> On Aug 8, 2008, at 3:23 PM, Tom Lane wrote:
>> * has no set operations (UNION etc), grouping, set-returning functions
>> in the SELECT list, LIMIT, or a few other funny cases
> Couldn't union/union all be treated as
> EXISTS(a)
> OR EXISTS(b)
Perhaps, but that would end up defeating the optimization anyway,
because as soon as the EXISTS is underneath an OR, it's no longer
representing a potential join clause.
regards, tom lane
