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From: Chao Li <[email protected]>
To: Heikki Linnakangas <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: CheckAttributeType() forgot to recurse into multiranges
Date: Thu, 23 Apr 2026 11:24:26 +0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>



> On Apr 23, 2026, at 04:56, Heikki Linnakangas <[email protected]> wrote:
> 
> Happened to spot this little bug:
> 
> create type two_ints as (a int, b int);
> create type two_ints_range as range (subtype = two_ints);
> 
> -- 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
> 
> -- But the same with a multirange is allowed:
> alter type two_ints add attribute c two_ints_multirange;
> ALTER TYPE
> 
> That looks like a straightforward oversight in CheckAttributeType(). When multiranges were introduced, it didn't get the memo.
> 
> Fix attached. Assuming no objections, I'll commit and backpatch that.
> 
> 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.
> 
> - 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 == 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 == TYPTYPE_MULTIRANGE)
	{
		Oid multirange_range_typid = get_multirange_range(atttypid);
		Oid collation = 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/

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