Re: Fix ALTER COLUMN ... DROP EXPRESSSION with subpartitions

Hello Alberto,

On 2026-Apr-07, Alberto Piai wrote:

> While working on [0], I noticed that DROP EXPRESSION currently refuses
> to be applied to inheritance trees of depth > 2, e.g. when there are
> subpartitions.

Yep, confirmed.

> PFA a fix for this and a test case.
>
> I added the test case to generated_stored.sql,

Looks good. I pushed your fix, with two minor changes:
1. acquiring a lock in the find_inheritance_children() call is
confusing and unnecessary, because ATSimpleRecursion already did it,
so I removed that by passing NoLock.

2. I removed the comment that suggested that the functionality could be
implemented with some effort. This was foreclosed by 8bf6ec3ba3a4,
so the comment is false and wrong.

I also moved the test to the exact spot where ALTER TABLE DROP
EXPRESSION is being tested. That gave me the perfect placement for the
corresponding test for the legacy-inheritance part of the functionality.

The backpatch was pretty straightforward (mostly because git-cherry-pick
figured out by itself that it needed to apply the generated_stored.sql
patch to generated.sql at the point where it was renamed.)

I think you didn't add a commitfest entry for this. Please don't forget
to create one for every patch that you submit; otherwise they're likely
to fall through the cracks. (Though these days the CF process seems
more and more to be a mostly useless, abandoned chore.)

Thanks!

--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
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