Re: ALTER COLUMN SET EXPRESSION on partitions not work in case of constraint dependencies

On Sat Aug 1, 2026 at 7:57 AM CEST, jian he wrote:
> Hi.
>
> Reproducer:
>
> drop table if exists t;
> CREATE TABLE t (
> a int,
> b int GENERATED ALWAYS AS (NULLIF(a, 1)) STORED NOT NULL,
> constraint cc check (b > 0)) PARTITION BY RANGE (a);
> CREATE TABLE tp_0_1 PARTITION OF t FOR VALUES FROM (10) TO (20);
> ALTER TABLE tp_0_1 ALTER COLUMN b SET EXPRESSION AS (a);
>
> -- expect two row, now nothing
> select conname, contype from pg_constraint where conrelid = 'tp_0_1'::regclass;

It's admittedly a long shot, since I'm still studying all of this, but:
what if, when we RememberConstraintForRebuilding() a constraint with
conislocal=false, we also RememberConstraintForRebuilding() its
corresponding parent constraint?

I have not fully considered the implications of this and I'm only
thinking about CHECK and NN constraints.

The attached patch is not meant for code-review, but just to illustrate
the idea and get the conversation started. What do you think?

Regards,

Alberto

--
Alberto Piai
Sensational AG
Zürich, Switzerland