Prevent GET_EXPANDED_ENTITYSET from calling multiple time?

I have a OData Gateway Service with nested entities (say Entity A can be expanded with Entities B ;navigation properties "nv" ).

Now I redefined GET_EXPANDED_ENTITYSET and call in there a method that fills the complete return structure (including the expanded entities).

i have written call to call RFC that will provide me data for A and B.

A= Sales Order

B= Item Data

i konw that structure of the output entity set should have a field with Name same as Navigation Property Name.

i also kow that i need to append the Navigation Property Name in exporting parameter ET_EXPANDED_TECH_CLAUSES , which will tell the gate way framework that the child entity has already been expanded and there is no need to call the child entity set.

Now Problem is that GET_EXPANDED_ENTITYSET is called multiple time and so is my RFC. i am getting all required data in first call.

Prevent GET_EXPANDED_ENTITYSET  from calling multiple time.