Re: PostgreSQL - 'SKYLINE OF' clause added!

Shane Ambler <pgsql(at)Sheeky(dot)Biz> writes:
> If we consider this thoroughly and compile a suitable syntax that covers
> all bases it could be used as the basis of the standard definition or be
> close to what ends up in the standard.

I'll bet you a very good dinner that the word SKYLINE will never be seen
in the standard.

To me, the proposed feature seems an extremely narrow, special-purpose
thing. The SQL committee have never been into that very much, and seem
even less interested in the last couple of revisions. They like
mechanisms that can be used to solve a wide variety of problems, and
are not afraid to introduce conceptual complexity to get there.
Two examples for you: outer joins and recursive queries. Oracle's
(+) syntax is more compact than what got into the spec, but less
precise and less functional. For recursive queries, CONNECT BY is
way simpler than what got into the spec, but again doesn't cover as
much ground. The SKYLINE clause seems to me to be right about on
par with CONNECT BY ... it does something useful, but only one thing.

I think the challenge for the SKYLINE authors is to recast what they did
as a general feature --- something feeling like, say, multi-argument
aggregates or window functions. The mechanisms that they want to put
into the executor sound like they can do a whole lot more than SKYLINE;
find a way to expose that power. And the fewer bespoke keywords needed,
the better ;-)

regards, tom lane