CDS Custom Entity not working with Multilevel Expand

[catalinfeidi]

Hi there,

We have been experimenting CDS Custom Entity in order to keep the legacy code clean but we do have a corner case to load full BO which custom entity is not supporting.

We need to retrieve parent entity -> children entity -> grandchildren entity, all together as follows:

Parent(entity: parent)

-Child1(entity:_children)

--GrandChild1forChild1(entity: _grandchildren)

--GrandChild2forChild2(entity: _grandchildren)

Child2(entity:_children)

--GrandChild1forChild2(entity: _grandchildren)

--GrandChild2forChild2(entity: _grandchildren)

Our OData call:

/parent?$filter=((key1 eq 'something1')and(key2 eq 'something2'))&$expand=_child($expand=_grandchildren)

When we want to get the navigation keys inside of _grandchildren query implementation class as doing get_filter()->get_as_ranges(), it is short-dumping when method is being called, because there are 2 children for the Parent(Child1 and Child2). It doesn't work with multiple parents for that respective entity.

This seems to be a limitation of Custom Entity, not supporting the expand of associations on entities that have more entries.

[dominik_ee]

As mentioned in the documentation, it is not possible to express all types of filters as ranges:

https://help.sap.com/docs/btp/sap-abap-restful-application-programming-model/implementing-filtering-...

and

https://help.sap.com/docs/btp/sap-abap-restful-application-programming-model/interface-if-rap-query-...

[Andre_Fischer]

Hi Catalin,

as Dominik wrote the root cause is that the filter statement cannot be translated into a ranges table.

As a result an exception is thrown when calling the get_as_ranges( ) method.

And if this is not catched you get a dump because raising exceptions is not allowed within the RAP framework.

If you surround the call of the method get_as_ranges() with a TRY CATCH block you will probably see an exception of type CX_RAP_QUERY_FILTER_NO_RANGE.

Or if you catch it into cx_root the exception message should be something like that the filter condition could not be translated to a ranges table.

CATCH cx_root INTO DATA(exception).   

DATA(exception_message) = cl_message_helper=>get_latest_t100_exception( exception )->if_message~get_longtext( ).

I have built a sample with three entities as well and got the following filter string on grandchild level (root has one key field "SALESORDERID", child has two key fields "SALESORDERID" and "ITEMPOSITION")

( SALESORDERID = ' 2' AND ITEMPOSITION = ' 2' OR SALESORDERID = ' 2' AND ITEMPOSITION = ' 1' )

So you can try to retrieve the filter as string or in newer releases as filter tree.

DATA(filter_string) =   io_request->get_filter( )->get_as_sql_string(  ).  

DATA(filter_tree) =   io_request->get_filter( )->get_as_tree(  ).

Hope this helps.

Kind regards,

Andre