Antonin Houska <antonin.houska@gmail.com> writes:
> For example:
> SELECT *
> FROM a, b, func(a.i, b.j) as c, d
> WHERE a.i=b.j and b.j = d.k and c>1
> may become
> SELECT *
> FROM a, b, <subquery> as c, d
> WHERE a.i=b.j and b.j = d.k and c>1
> where <subquery> is
> SELECT func(a.i, b.j)
> FROM a,b
> WHERE a.i=b.j
Um ... how do you get the subquery result rows to join to only the
correct rows of the other tables? This looks like an unconstrained join
to me, which is not what I believe the SQL spec for LATERAL to be, and
it doesn't seem especially useful either. (If a subquery could do what
people wanted, we'd not be hearing all the requests for LATERAL.)
regards, tom lane