Re: Property graph: fix error handling when dropping non-existent label property

> On Apr 24, 2026, at 20:38, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
>
> On Fri, Apr 24, 2026 at 1:03 PM Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> wrote:
>>
>> Hi,
>>
>> I am testing graph tables today and noticed an improper error message when dropping a property.
>>
>> Here is a simple repro:
>> ```
>> evantest=# CREATE TABLE t1 (a int PRIMARY KEY, b int);
>> CREATE TABLE
>> evantest=#
>> evantest=# CREATE PROPERTY GRAPH g
>> evantest-# VERTEX TABLES (
>> evantest(# t1
>> evantest(# LABEL l1 PROPERTIES (a AS p1)
>> evantest(# LABEL l2 PROPERTIES (b AS p2)
>> evantest(# );
>> CREATE PROPERTY GRAPH
>> evantest=#
>> evantest=# ALTER PROPERTY GRAPH g
>> evantest-# ALTER VERTEX TABLE t1
>> evantest-# ALTER LABEL l1 DROP PROPERTIES (p2);
>> ERROR: could not find tuple for label property 0
>> ```
>>
>> This does not look like a normal user-facing SQL error message.
>>
>> Looking into the code, AlterPropGraph() checks whether the property exists in the graph, but does not check if label property exists. As a result, InvalidOid can be passed to ObjectAddressSet() and then to performDeletion().
>>
>> The fix is simple, just check the label-property OID before trying to delete it. I also added a regress test.
>>
>> With the patch, the error becomes:
>> ```
>> evantest=# ALTER PROPERTY GRAPH g
>> evantest-# ALTER VERTEX TABLE t1
>> evantest-# ALTER LABEL l1 DROP PROPERTIES (p2);
>> ERROR: property graph "g" element "t1" label "l1" has no property "p2"
>> ```
>
> Thanks for the report. Agree that we need to provide a correct error
> message. The code changes look good to me.

Cool! Thanks for reviewing and confirming.

> However, the way you have
> written this code is different from similar code earlier in the
> function. Either your code should match that style or that code should
> be changed to your style. I like your way - reduces code a bit and
> does not repeat ereport. I also noticed that the code to fetch the
> element label oid from element_alias and label name is repeated along
> with the ereport in a few places. I think we could instead write a
> function to do that and call that function in those places. When
> writing the function, we could change that code to use your style.

I updated the nearby code to align with my style. PFA v2.

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