// create composite dataset
RandomAccessDataset<Map<String, SpecificRecord>> ds = repo.load(tableName + ".SubEntity1.SubEntity2");
// Construct entities
SubEntity1 subEntity1 = SubEntity1.newBuilder().setPart1("1").setPart2("1")
.setField1("field1_1").setField2("field1_2").build();
SubEntity2 subEntity2 = SubEntity2.newBuilder().setPart1("1").setPart2("1")
.setField1("field2_1").setField2("field2_2").build();
Map<String, SpecificRecord> compositeEntity = new HashMap<String, SpecificRecord>();