It seems I'm having the same issue. Although the answer of @Emmanuel_Gonzalez might be helpful it is not a solution in all cases. I definitely have a 1:N relation, but it does not work.
I have an old GW Service with an Entity Order and a 1:N relation to the Entity OrderItems. When I call the service with /Orders('1234567890')/OrderItems then IT_FILTER_SELECT_OPTIONS is empty and IT_KEY_TAB has the one key of the dependent entity from the referential constraints. Also, if I create a new service + include the old service there I can still call the same /Orders('1234567890')/OrderItems from the new service which gives me exactly the same result as above (IT_KEY_TAB is filled). Of course in both cases the method ORDERITEMS_GET_ENTITYSET is called. This is exactly what I axpected.
However, when I create a new entity, let's say OrderTwo, and model a 1:N relation to the OrderItems from the included service (of course, I created also the correct referential constraints) + call /OrderTwoSet('1234567890')/OrderItems then IT_FILTER_SELECT_OPTIONS is filled while IT_KEY_TAB is empty (why that???????):
Consider also the blog Make your SAP Gateway Work Smarter not Harder – Part 1.2 ) Search Patterns and Service inclusion of Leigh Mason and there scroll down to the section "Limitations / Gotchas" (by the way - the first part of his blog is also great!).
Is there anyone who can explain this? I'm sure I have modeled the referential constraints correctly in the new service, or is that the limitation which Leigh Mason mentioned?
Thanks,
Nabi
ps thi is what we have:
