(SQL/PGQ) Clean up orphaned properties when dropping a label

On Fri, Jun 5, 2026 at 7:59 PM zengman <zengman@halodbtech.com> wrote:

Hi all,

I noticed that ALTER PROPERTY GRAPH ... DROP LABEL doesn't clean up
orphaned pg_propgraph_property entries. The cleanup condition in
RemoveRelations() only checks for drop_properties,
drop_vertex_tables, and drop_edge_tables, but not drop_label.

Before fix:

```sql
postgres@zxm-VMware-Virtual-Platform:~/code/postgres$ psql
psql (19beta1)
Type "help" for help.

postgres=# CREATE TABLE v4 (a int PRIMARY KEY, b int, c int);
CREATE TABLE
postgres=# CREATE PROPERTY GRAPH g5
VERTEX TABLES (
v4 LABEL l1 PROPERTIES (a, b, c)
LABEL l2 PROPERTIES (a)
);
CREATE PROPERTY GRAPH
postgres=# ALTER PROPERTY GRAPH g5 ALTER VERTEX TABLE v4 DROP LABEL l1;
ALTER PROPERTY GRAPH
postgres=# SELECT pgpname FROM pg_propgraph_property
WHERE pgppgid = 'g5'::regclass ORDER BY pgpname;
pgpname
---------
a
b
c
(3 rows)
```

After fix:
```sql
postgres@zxm-VMware-Virtual-Platform:~/code/postgres$ psql
psql (19beta1)
Type "help" for help.

postgres=# CREATE TABLE v4 (a int PRIMARY KEY, b int, c int);
CREATE TABLE
postgres=# CREATE PROPERTY GRAPH g5
VERTEX TABLES (
v4 LABEL l1 PROPERTIES (a, b, c)
LABEL l2 PROPERTIES (a)
);
CREATE PROPERTY GRAPH
postgres=# ALTER PROPERTY GRAPH g5 ALTER VERTEX TABLE v4 DROP LABEL l1;
ALTER PROPERTY GRAPH
postgres=# SELECT pgpname FROM pg_propgraph_property
WHERE pgppgid = 'g5'::regclass ORDER BY pgpname;
pgpname
---------
a
(1 row)
```

```sql
CREATE TABLE v4 (a int PRIMARY KEY, b int, c int);
CREATE PROPERTY GRAPH g5
VERTEX TABLES (
v4 LABEL l1 PROPERTIES (a, b, c)
LABEL l2 PROPERTIES (a)
);
ALTER PROPERTY GRAPH g5 ALTER VERTEX TABLE v4 DROP LABEL l1;
SELECT pgpname FROM pg_propgraph_property
WHERE pgppgid = 'g5'::regclass ORDER BY pgpname;
```

Thanks for the report and the patch. The fix is on the right track. I
changed a few things as follows
a. we usually add operands to the same operator at the end, not at the
beginning.
b. create_property_graph.sql, which tests all property graph DDLs, is
the right place to add these tests. graph_table.sql tests graph query.

I have used an existing property graph in create_property_graph.sql in
the test. It removes a label from the property graph which has two
properties associated with it, one that gets orphaned and one that
doesn't. We can verify that the orphaned property gets dropped from
the property graph but not the other one by information schema query
outputs later. So didn't add any separate verification step after the
DDL.

Attached patch with those changes.

--
Best Wishes,
Ashutosh Bapat

Thanks for the report and the patch. The fix is on the right track. I
changed a few things as follows
a. we usually add operands to the same operator at the end, not at the
beginning.
b. create_property_graph.sql, which tests all property graph DDLs, is
the right place to add these tests. graph_table.sql tests graph query.

I have used an existing property graph in create_property_graph.sql in
the test. It removes a label from the property graph which has two
properties associated with it, one that gets orphaned and one that
doesn't. We can verify that the orphaned property gets dropped from
the property graph but not the other one by information schema query
outputs later. So didn't add any separate verification step after the
DDL.

Attached patch with those changes.

Hi Ashutosh,

Thank you for your assistance. This looks better. There is a small problem that

https://commitfest.postgresql.org/patch/6848/

It seems that a 'rebase' is needed to conduct the test normally. Could you please make some adjustments again?

--
regards,
Man Zeng

On 12.06.26 03:36, zengman wrote:

Thanks for the report and the patch. The fix is on the right track. I
changed a few things as follows
a. we usually add operands to the same operator at the end, not at the
beginning.
b. create_property_graph.sql, which tests all property graph DDLs, is
the right place to add these tests. graph_table.sql tests graph query.

I have used an existing property graph in create_property_graph.sql in
the test. It removes a label from the property graph which has two
properties associated with it, one that gets orphaned and one that
doesn't. We can verify that the orphaned property gets dropped from
the property graph but not the other one by information schema query
outputs later. So didn't add any separate verification step after the
DDL.

Attached patch with those changes.

Hi Ashutosh,

Thank you for your assistance. This looks better. There is a small problem that

https://commitfest.postgresql.org/patch/6848/

It seems that a 'rebase' is needed to conduct the test normally. Could you please make some adjustments again?

The most recently posted patch does not apply, and if I apply it
manually, the code change does not appear to cause any changes in the
test output. Seemingly, this depends on that some other patches that
are not shown here? Please clarify.