On 21/07/2025 23:29, Matheus Alcantara wrote:
On Mon Jul 21, 2025 at 5:23 PM -03, Vik Fearing wrote:
On 21/07/2025 14:47, Matheus Alcantara wrote:
Hi all,
I'm sending a proof-of-concept patch to add support for the QUALIFY
clause in Postgres. This feature allows filtering rows after window
functions are computed, using a syntax similar to the WHERE or HAVING
clauses.
I took a very brief look at this, and I think your grammar is wrong.
The QUALIFY clause should go after the WINDOW clause, just like
FROM/WHERE and GROUP BY/HAVING.
That is what I am proposing to the standards committee, and I already
have some buy-in for that.
Thank you for the brief review and for the comments!
I'm not sure if I fully understand but please see the new attached
version.
That is my preferred grammar, thank you. I have not looked at the C
code by this can be obtained with a syntax transformation. To wit:
SELECT a, b, c
FROM tab
QUALIFY wf() OVER () = ?
can be rewritten as:
SELECT a, b, c
FROM (
SELECT a, b, c, wf() OVER () = ? AS qc
FROM tab
) AS q
WHERE qc
and then let the optimizer take over. The standard does this kind of
thing all over the place; I don't know what the postgres project's
position on doing things like this are.
--
Vik Fearing
