[zengman <zengman@halodbtech.com>]

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;
```

--
regards,
Man Zeng

Attachments:

0001-Clean-up-orphaned-properties-when-dropping-a-label.patch (application/octet-stream, 3.0K) download
From 6862fcd91808602317376e8fe24f28fcfc4de063 Mon Sep 17 00:00:00 2001
From: Man Zeng <zengman@halodbtech.com>
Date: Fri, 5 Jun 2026 22:13:47 +0800
Subject: [PATCH] Clean up orphaned properties when dropping a label

The orphaned property cleanup in RemoveRelations() was missing
the drop_label case, leaving properties that no label references.
---
 src/backend/commands/propgraphcmds.c      |  2 +-
 src/test/regress/expected/graph_table.out | 18 ++++++++++++++++++
 src/test/regress/sql/graph_table.sql      | 14 ++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/backend/commands/propgraphcmds.c b/src/backend/commands/propgraphcmds.c
index cc516e27020..7c8f397afbf 100644
--- a/src/backend/commands/propgraphcmds.c
+++ b/src/backend/commands/propgraphcmds.c
@@ -1638,7 +1638,7 @@ AlterPropGraph(ParseState *pstate, const AlterPropGraphStmt *stmt)
 	}
 
 	/* Remove any orphaned pg_propgraph_property entries */
-	if (stmt->drop_properties || stmt->drop_vertex_tables || stmt->drop_edge_tables)
+	if (stmt->drop_label || stmt->drop_properties || stmt->drop_vertex_tables || stmt->drop_edge_tables)
 	{
 		foreach_oid(propoid, get_graph_property_ids(pgrelid))
 		{
diff --git a/src/test/regress/expected/graph_table.out b/src/test/regress/expected/graph_table.out
index cc6d80afd82..9617b4aa3e8 100644
--- a/src/test/regress/expected/graph_table.out
+++ b/src/test/regress/expected/graph_table.out
@@ -1044,4 +1044,22 @@ SELECT src.vname, count(*) FROM v1 AS src
  v13   |     1
 (3 rows)
 
+-- DROP LABEL should clean up orphaned properties
+CREATE TABLE v4 (a int PRIMARY KEY, b int, c int);
+INSERT INTO v4 VALUES (1, 2, 3);
+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;
+ pgpname 
+---------
+ a
+(1 row)
+
+DROP PROPERTY GRAPH g5;
+DROP TABLE v4;
 -- leave the objects behind for pg_upgrade/pg_dump tests
diff --git a/src/test/regress/sql/graph_table.sql b/src/test/regress/sql/graph_table.sql
index 0e381ec72bc..ab89bdc1553 100644
--- a/src/test/regress/sql/graph_table.sql
+++ b/src/test/regress/sql/graph_table.sql
@@ -596,4 +596,18 @@ SELECT src.vname, count(*) FROM v1 AS src
   HAVING count(*) >= (SELECT count(*) FROM GRAPH_TABLE (g1 MATCH (a IS vl1 | vl2) COLUMNS (a.vname AS n)) WHERE n = src.vname)
   ORDER BY vname;
 
+-- DROP LABEL should clean up orphaned properties
+CREATE TABLE v4 (a int PRIMARY KEY, b int, c int);
+INSERT INTO v4 VALUES (1, 2, 3);
+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;
+DROP PROPERTY GRAPH g5;
+DROP TABLE v4;
+
 -- leave the objects behind for pg_upgrade/pg_dump tests
-- 
2.45.2