Allowing DESC for a PRIMARY KEY column

Hi!

I have the same problem as [1]. I have table something like:

CREATE TABLE values (
id int NOT NULL,
revision int NOT NULL,
data jsonb NOT NULL,
PRIMARY KEY (id, revision)
)

And I would like to be able to specify PRIMARY KEY (id, revision DESC)
because the most common query I am making is:

SELECT data FROM values WHERE id=123 ORDER BY revision DESC LIMIT 1

My understanding, based on [2], is that the primary key index cannot
help here, unless it is defined with DESC on revision. But this does
not seem to be possible. Would you entertain a patch adding this
feature? It seems pretty straightforward?

Mitar

[1] https://stackoverflow.com/questions/45597101/primary-key-with-asc-or-desc-ordering
[2] https://www.postgresql.org/docs/16/indexes-ordering.html

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