There are some additional offline OData features.
A built-in function that can be used in a $filter system query option to check for the existence of a related entity.
sap.entityexists takes a single parameter that is a member expression that only references navigation properties with an end cardinality of 1 or 0..1.
In the following example, each Order has a relationship to a SalesRep, and each Order either has an assigned SalesRep or it does not.
Orders?$filter=sap.entityexists( SalesRep )
Orders?$filter=not sap.entityexists( SalesRep )
odata.maxpagesize=<number greater than 0>