Re: Proposal/design feedback needed: WITHIN GROUP (sql standard ordered set aggregate functions)

Noah Misch said:
> Other aggregates based on this syntax might not desire such type unification.

Then there would have to be some way to distinguish that. Maybe those could
have -1 and the standard hypothetical set functions -2, with some flag in
CREATE AGGREGATE to sort it out.

> Having parse analysis do that distorts the character of an "any" argument.  I
> think the proper place for such processing is the first call to a transition
> function.

Except there isn't one.

> But let's not make the
> parser presume that an aggordnargs=-1 aggregate always wants its "any"
> arguments handled in the manner of the standard hypothetical set functions.

This has to happen in the parser because these are errors that should be
caught before execution:

rank(foo) within group (order by bar,baz)
rank(integercol) within group (order by textcol)

And collations have to be resolved (pairwise) before sorting can happen:

rank(textval COLLATE "C") within group (order by foo)  -- sorts in "C"
rank(textval COLLATE "C") within group (order by bar COLLATE "en_US")  -- error

(basically, in rank(x) within group (order by y) where x and y are
collatable, the collation rules apply exactly as though you were doing
(x < y), with all the implicit vs. explicit stuff included)

And this:

rank(1.1) within group (order by intcol)

should become  rank(1.1) within group (order by intcol::numeric)

-- 
Andrew (irc:RhodiumToad)