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Subject: Re: CheckAttributeType() forgot to recurse into multiranges
From: Chao Li <li.evan.chao@gmail.com>
In-Reply-To: <93ce56cd-02a6-4db1-8224-c8999372facc@iki.fi>
Date: Thu, 23 Apr 2026 11:24:26 +0800
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
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Message-Id: <0B5FC478-013D-45D1-876A-AD3FE0C21E7C@gmail.com>
References: <93ce56cd-02a6-4db1-8224-c8999372facc@iki.fi>
To: Heikki Linnakangas <hlinnaka@iki.fi>
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 <https://www.postgresql.org/message-id/0B5FC478-013D-45D1-876A-AD3FE0C21E7C%40gmail.com>
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> On Apr 23, 2026, at 04:56, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>=20
> Happened to spot this little bug:
>=20
> create type two_ints as (a int, b int);
> create type two_ints_range as range (subtype =3D two_ints);
>=20
> -- CheckAttributeType() forbids this:
> alter type two_ints add attribute c two_ints_range;
> ERROR:  composite type two_ints cannot be made a member of itself
>=20
> -- But the same with a multirange is allowed:
> alter type two_ints add attribute c two_ints_multirange;
> ALTER TYPE
>=20
> That looks like a straightforward oversight in CheckAttributeType(). =
When multiranges were introduced, it didn't get the memo.
>=20
> Fix attached. Assuming no objections, I'll commit and backpatch that.
>=20
> While working on the fix, I noticed that in case of dropped columns, =
CheckAttributeType() is called with InvalidOid. It tolerates that, but =
it seems accidental and it performs a bunch of futile syscache lookups =
with InvalidOid, so it would be better to not do that. The second patch =
fixes that.
>=20
> - Heikki
> =
<0001-Don-t-allow-composite-type-to-be-member-of-itself-vi.patch><0002-Don=
-t-call-CheckAttributeType-with-InvalidOid-on-dro.patch>

I traced this patch set, 0002 looks good, but I have a suspicion about =
0001.

```
+	else if (att_typtype =3D=3D TYPTYPE_MULTIRANGE)
+	{
+		/*
+		 * If it's a multirange, recurse to check its plain =
range type.
+		 */
+		CheckAttributeType(attname, =
get_multirange_range(atttypid),
+						   =
get_range_collation(atttypid),
+						   containing_rowtypes,
+						   flags);
+	}
```

Looking at get_range_collation(), it only searches for RANGETYPE, so =
get_range_collation(atttypid) here will always return InvalidOid. This =
does not seem to cause a problem, because CheckAttributeType() will =
recurse into the TYPTYPE_RANGE path, and the collation will be evaluated =
there.

But to make the logic clearer, I think we could just pass InvalidOid as =
the collation OID in the TYPTYPE_MULTIRANGE case. If we really want to =
pass the actual collation OID here, I think it would need to be done =
more like this:

```
	else if (att_typtype =3D=3D TYPTYPE_MULTIRANGE)
	{
		Oid multirange_range_typid =3D =
get_multirange_range(atttypid);
		Oid collation =3D =
get_range_collation(multirange_range_typid);
		/*
		 * If it's a multirange, recurse to check its plain =
range type.
		 */
		CheckAttributeType(attname, multirange_range_typid,
						   collation,
						   containing_rowtypes,
						   flags);
	}
```

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