Tom Lane writes:
> > With sufficiently blurred vision one might even find SQL99's clause
> > <collection derived table> ::=
> > UNNEST <left paren> <collection value expression> <right paren>
> > applicable. Or maybe not.
>
> Hm. I'm not sure what UNNEST does, but now that you bring SQL99 into
> the picture, what about WITH? That might solve the problem, because
> (I think) WITH tables are logically determined before the main SELECT
> begins to execute.
The SQL 200x draft defines a new clause TABLE ( <collection value
expression> ) as a possible <table primary>, where the <collection value
expression> is required to be a function call. At the end this just boils
down to UNNEST, though. UNNEST is defined in terms of a hairy recursive
join subquery with a LATERAL( ) around it. LATERAL(subquery) is the same
as just (subquery) except that the scope clauses are different. So I
think this is probably what we ought to look at.
--
Peter Eisentraut peter_e@gmx.net