I wrote:
> Lastly, for a simple aggregate used with an OVER clause, the current
> patch seems to define the aggregate as being taken over the frame
> rather than the partition, but I cannot find anything in SQL2008 that
> lends any support to *either* definition.
Never mind that --- I found it in 10.9 syntax rule 4.b.
But what this seems to boil down to is that LEAD() and LAST_VALUE()
are completely useless unless you're allowed to specify a nondefault
framing clause ... and don't mind ignoring the clearly-insane
restriction of 6.10 syntax rule 6.b.
The minimum extra functionality needed to make these functions useful
would seem to be to allow UNBOUNDED FOLLOWING ...
regards, tom lane