Outer Join Reference Table with Distributed Table

Based on the [documentation](http://docs.citusdata.com/en/v7.5/develop/reference_sql.html)
> Reference Tables can be used as “dimension” tables to join efficiently with large “fact” tables.

However, it turns out that we can't outer join reference table with large distributed table.

For example,I have a reference table `products` and a large distributed table `purchases`. The `purchases` table is distributed based on `customer_id` column.
Is there a plan for supporting outer join query between the reference and distributed table as follows?

```sql
select *
from products
left join purchases on products.id = purchases.product_id
where true
```

Thanks,