> ## Documentation Index
> Fetch the complete documentation index at: https://paradedb-ankitml-legacy-docs-remove.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Schema Changes

> Handle DDL/schema changes when running ParadeDB as a logical replica

<Note>
  This section assumes that you have successfully completed the [getting
  started](/deploy/self-hosted/logical-replication/getting-started) guide.
</Note>

## Schema Changes

ParadeDB leverages PostgreSQL’s built-in logical replication to provide flexible and efficient data synchronization, and is subject to the same limitations. A well-known caveat of logical replication is that schema changes (DDL commands) are not replicated. This means that any changes to the schema on the source database, such as adding new columns or tables, will not be automatically applied to the subscriber.

```sql theme={null}
-- On Publisher
ALTER TABLE mock_items ADD COLUMN num_stock;
INSERT INTO mock_items (description, category, in_stock, latest_available_time, last_updated_date, metadata, created_at, rating, num_stock)
VALUES ('Green running shoes', 'Footwear', true, '14:00:00', '2024-07-09', '{}', '2024-07-09 14:00:00', 2, 900);

-- On Subscriber
ERROR: logical replication target relation "public.mock_items" is missing some replicated columns
```

To work around this, pause the subscription on the subscriber, manually apply the schema changes, then resume the subscription:

```sql theme={null}
-- On Subscriber
ALTER SUBSCRIPTION mock_items_sub DISABLE;
ALTER TABLE entries ADD COLUMN num_stock int;
ALTER SUBSCRIPTION mock_items_sub ENABLE;
```

If new tables are added and your publication is not `FOR ALL TABLES`, add them to the publication manually:

```sql theme={null}
-- On Publisher
ALTER PUBLICATION mock_items_pub ADD TABLE newly_added_table;

-- On Subscriber
ALTER SUBSCRIPTION mock_items_sub REFRESH PUBLICATION;
```