On 12/6/22 05:57, David G. Johnston wrote:
On Mon, Dec 5, 2022 at 9:48 PM Vik Fearing <v...@postgresfriends.org> wrote:
I can imagine an optimization that would remove an ORDER BY clause
because it isn't needed for any other aggregate.
I'm referring to the query:
select any_value(v order by v) from (values (2),(1),(3)) as vals (v);
// produces 1, per the documented implementation-defined behavior.
Implementation-dependent. It is NOT implementation-defined, per spec.
We often loosen the spec rules when they don't make technical sense to
us, but I don't know of any example of when we have tightened them.
Someone writing:
select any_value(v) from (values (2),(1),(3)) as vals (v) order by v;
Is not presently, nor am I saying, promised the value 1.
I'm assuming you are thinking of the second query form, while the guarantee
only needs to apply to the first.
I am saying that a theoretical pg_aggregate.aggorderdoesnotmatter could
bestow upon ANY_VALUE the ability to make those two queries equivalent.
If you care about which value you get back, use something else.
--
Vik Fearing
