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Subject: Re: Fix bug of CHECK constraint enforceability recursion
From: Chao Li <li.evan.chao@gmail.com>
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Date: Wed, 3 Jun 2026 09:54:01 +0800
Cc: pgsql-hackers@lists.postgresql.org
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To: Zsolt Parragi <zsolt.parragi@percona.com>
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> On Jun 3, 2026, at 04:56, Zsolt Parragi <zsolt.parragi@percona.com> =
wrote:
>=20
> Hello
>=20
> + * During recursion, another parent outside this ALTER may still =
enforce
> + * the same constraint. In that case, keep the child constraint =
ENFORCED
> + * so that its merged enforceability still reflects the remaining =
enforced
> + * parent.
> + */
> + if (!cmdcon->is_enforced)
> + {
>=20
> This means once is_enforced is set to true, it will never be
> rechecked. See the following example which showcases an issue with
> this:
>=20
> create table g(a int constraint k check(a > 0) enforced);
> create table o(a int constraint k check(a > 0) enforced);
> create table s1() inherits(g);
> create table s2() inherits(g, o);
> create table s3() inherits(g);
> alter table g alter constraint k not enforced;
> select conrelid::regclass as tbl, conenforced
> from   pg_constraint
> where  conname =3D 'k' and contype =3D 'c'
> order  by conrelid::regclass::text collate "C";
> insert into s1 values (-1);
> insert into s3 values (-1);   -- bug: ERRORs out, but shouldn't
>=20

Hi Zsolt,

Thanks for your view.

I just tried your test with v6, but didn't see the bug you mentioned:
```
evantest=3D# create table g(a int constraint k check(a > 0) enforced);
CREATE TABLE
evantest=3D# create table o(a int constraint k check(a > 0) enforced);
CREATE TABLE
evantest=3D# create table s1() inherits(g);
CREATE TABLE
evantest=3D# create table s2() inherits(g, o);
NOTICE:  merging multiple inherited definitions of column "a"
CREATE TABLE
evantest=3D# create table s3() inherits(g);
CREATE TABLE
evantest=3D# alter table g alter constraint k not enforced;
ALTER TABLE
evantest=3D# select conrelid::regclass as tbl, conenforced
evantest-# from   pg_constraint
evantest-# where  conname =3D 'k';
 tbl | conenforced
-----+-------------
 o   | t
 s2  | t
 g   | f
 s1  | f
 s3  | f
(5 rows)

evantest=3D# insert into s1 values (-1);
INSERT 0 1
evantest=3D# insert into s3 values (-1);
INSERT 0 1
```

Here, both s1 and s3 are the direct child of g, thus when g is set to =
=E2=80=9Cnot enforced=E2=80=9D, s1 and s3 is set to =E2=80=9Cnot =
enforced" as well. While s2 is a child of both g and o, as o is still =
enforced, s2 remains enforced. The test result is right as expected.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/