diff --git a/jdo/rdbms/src/java/org/datanucleus/samples/rdbms/scostore/ListElement.java b/jdo/rdbms/src/java/org/datanucleus/samples/rdbms/scostore/ListElement.java
new file mode 100644
index 00000000..65738522
--- /dev/null
+++ b/jdo/rdbms/src/java/org/datanucleus/samples/rdbms/scostore/ListElement.java
@@ -0,0 +1,42 @@
+/**********************************************************************
+Copyright (c) 2026 Contributors. All rights reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+Contributors:
+    ...
+**********************************************************************/
+package org.datanucleus.samples.rdbms.scostore;
+
+import javax.jdo.annotations.DatastoreIdentity;
+import javax.jdo.annotations.IdGeneratorStrategy;
+import javax.jdo.annotations.PersistenceCapable;
+
+/**
+ * Element class for join-table List, for testing bulk shift ordering.
+ */
+@PersistenceCapable
+@DatastoreIdentity(strategy = IdGeneratorStrategy.IDENTITY)
+public class ListElement
+{
+    String value;
+
+    public ListElement(String value)
+    {
+        this.value = value;
+    }
+
+    public String getValue()
+    {
+        return value;
+    }
+}
diff --git a/jdo/rdbms/src/java/org/datanucleus/samples/rdbms/scostore/ListHolder.java b/jdo/rdbms/src/java/org/datanucleus/samples/rdbms/scostore/ListHolder.java
new file mode 100644
index 00000000..959e71e4
--- /dev/null
+++ b/jdo/rdbms/src/java/org/datanucleus/samples/rdbms/scostore/ListHolder.java
@@ -0,0 +1,54 @@
+/**********************************************************************
+Copyright (c) 2026 Contributors. All rights reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+Contributors:
+    ...
+**********************************************************************/
+package org.datanucleus.samples.rdbms.scostore;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.jdo.annotations.DatastoreIdentity;
+import javax.jdo.annotations.IdGeneratorStrategy;
+import javax.jdo.annotations.Join;
+import javax.jdo.annotations.PersistenceCapable;
+
+/**
+ * Owner class with a join-table List of elements, for testing bulk shift ordering.
+ */
+@PersistenceCapable
+@DatastoreIdentity(strategy = IdGeneratorStrategy.IDENTITY)
+public class ListHolder
+{
+    String name;
+
+    @Join
+    List<ListElement> items = new ArrayList<>();
+
+    public ListHolder(String name)
+    {
+        this.name = name;
+    }
+
+    public String getName()
+    {
+        return name;
+    }
+
+    public List<ListElement> getItems()
+    {
+        return items;
+    }
+}
diff --git a/jdo/rdbms/src/test/org/datanucleus/tests/BulkShiftListTest.java b/jdo/rdbms/src/test/org/datanucleus/tests/BulkShiftListTest.java
new file mode 100644
index 00000000..2376cdff
--- /dev/null
+++ b/jdo/rdbms/src/test/org/datanucleus/tests/BulkShiftListTest.java
@@ -0,0 +1,212 @@
+/**********************************************************************
+Copyright (c) 2026 Contributors. All rights reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+Contributors:
+    ...
+**********************************************************************/
+package org.datanucleus.tests;
+
+import java.util.List;
+
+import javax.jdo.PersistenceManager;
+import javax.jdo.Transaction;
+
+import org.datanucleus.samples.rdbms.scostore.ListElement;
+import org.datanucleus.samples.rdbms.scostore.ListHolder;
+
+/**
+ * Tests for List bulk shift operations using join tables.
+ * Verifies that positional insertion (add at index) works correctly when
+ * existing elements need their indices shifted upward.
+ * Regression test for https://github.com/datanucleus/datanucleus-rdbms/issues/464
+ */
+public class BulkShiftListTest extends JDOPersistenceTestCase
+{
+    private static boolean initialised = false;
+
+    public BulkShiftListTest(String name)
+    {
+        super(name);
+
+        if (!initialised)
+        {
+            addClassesToSchema(new Class[] { ListHolder.class, ListElement.class });
+            initialised = true;
+        }
+    }
+
+    /**
+     * Test inserting an element at the start of a join-table List.
+     * This requires all existing indices to shift up by 1, which on MySQL
+     * can cause duplicate key violations if the bulk UPDATE processes rows
+     * in ascending index order (issue #464).
+     */
+    public void testAddAtStart()
+    throws Exception
+    {
+        PersistenceManager pm = pmf.getPersistenceManager();
+        Transaction tx = pm.currentTransaction();
+        Object holderId = null;
+        try
+        {
+            // Create a list with 5 elements
+            tx.begin();
+            ListHolder holder = new ListHolder("holder1");
+            for (int i = 0; i < 5; i++)
+            {
+                holder.getItems().add(new ListElement("element-" + i));
+            }
+            pm.makePersistent(holder);
+            holderId = pm.getObjectId(holder);
+            tx.commit();
+        }
+        finally
+        {
+            if (tx.isActive())
+            {
+                tx.rollback();
+            }
+            pm.close();
+        }
+
+        // Insert at position 0 - forces all indices to shift up
+        pm = pmf.getPersistenceManager();
+        tx = pm.currentTransaction();
+        try
+        {
+            tx.begin();
+            ListHolder holder = (ListHolder) pm.getObjectById(holderId);
+            holder.getItems().add(0, new ListElement("inserted-at-0"));
+            tx.commit();
+        }
+        finally
+        {
+            if (tx.isActive())
+            {
+                tx.rollback();
+            }
+            pm.close();
+        }
+
+        // Verify the list order is correct
+        pm = pmf.getPersistenceManager();
+        tx = pm.currentTransaction();
+        try
+        {
+            tx.begin();
+            ListHolder holder = (ListHolder) pm.getObjectById(holderId);
+            List<ListElement> items = holder.getItems();
+
+            assertEquals("List should have 6 elements", 6, items.size());
+            assertEquals("First element should be the inserted one", "inserted-at-0", items.get(0).getValue());
+            assertEquals("Second element should be original first", "element-0", items.get(1).getValue());
+            assertEquals("Last element should be original last", "element-4", items.get(5).getValue());
+
+            tx.commit();
+        }
+        finally
+        {
+            if (tx.isActive())
+            {
+                tx.rollback();
+            }
+            pm.close();
+        }
+
+        // Clean up
+        clean(ListHolder.class);
+        clean(ListElement.class);
+    }
+
+    /**
+     * Test inserting an element in the middle of a join-table List.
+     */
+    public void testAddAtMiddle()
+    throws Exception
+    {
+        PersistenceManager pm = pmf.getPersistenceManager();
+        Transaction tx = pm.currentTransaction();
+        Object holderId = null;
+        try
+        {
+            tx.begin();
+            ListHolder holder = new ListHolder("holder2");
+            for (int i = 0; i < 5; i++)
+            {
+                holder.getItems().add(new ListElement("element-" + i));
+            }
+            pm.makePersistent(holder);
+            holderId = pm.getObjectId(holder);
+            tx.commit();
+        }
+        finally
+        {
+            if (tx.isActive())
+            {
+                tx.rollback();
+            }
+            pm.close();
+        }
+
+        // Insert at position 2 - forces indices 2,3,4 to shift up
+        pm = pmf.getPersistenceManager();
+        tx = pm.currentTransaction();
+        try
+        {
+            tx.begin();
+            ListHolder holder = (ListHolder) pm.getObjectById(holderId);
+            holder.getItems().add(2, new ListElement("inserted-at-2"));
+            tx.commit();
+        }
+        finally
+        {
+            if (tx.isActive())
+            {
+                tx.rollback();
+            }
+            pm.close();
+        }
+
+        // Verify the list order is correct
+        pm = pmf.getPersistenceManager();
+        tx = pm.currentTransaction();
+        try
+        {
+            tx.begin();
+            ListHolder holder = (ListHolder) pm.getObjectById(holderId);
+            List<ListElement> items = holder.getItems();
+
+            assertEquals("List should have 6 elements", 6, items.size());
+            assertEquals("Element at 0 should be unchanged", "element-0", items.get(0).getValue());
+            assertEquals("Element at 1 should be unchanged", "element-1", items.get(1).getValue());
+            assertEquals("Element at 2 should be the inserted one", "inserted-at-2", items.get(2).getValue());
+            assertEquals("Element at 3 should be original element-2", "element-2", items.get(3).getValue());
+            assertEquals("Element at 5 should be original element-4", "element-4", items.get(5).getValue());
+
+            tx.commit();
+        }
+        finally
+        {
+            if (tx.isActive())
+            {
+                tx.rollback();
+            }
+            pm.close();
+        }
+
+        // Clean up
+        clean(ListHolder.class);
+        clean(ListElement.class);
+    }
+}