Joined-subclass useability margins

bbones · **Joined:** Fri Nov 07, 2008 7:04 am **Posts:** 1

In our legacy system we have 4 level hierarchy of objects with dozen of entities. In root entity we generate id and use hierarchically organized integer discriminator. Application level based on Oracle editable view with instead-of triggers.

The question is how applicable joined subclass approach without discriminator for our data. I think joining altogether underlying tables as in your Animal example is rather expensive.

Subclass approach with discriminator doesn't accept more then 2 levels of hierarchy.

What is the best practice in our case?

Hibernate version: 3.2

Mapping documents:Animal.hbm.xml from standard package test

The generated SQL (show_sql=true):

Generated by from Animal query

Code:

select 
 animal0_.id as id163_, 
 animal0_.description as descript2_163_, 
 animal0_.body_weight as body3_163_, 
 animal0_.mother_id as mother4_163_, 
 animal0_.father_id as father5_163_, 
 animal0_.zoo_id as zoo6_163_, 
 animal0_.serialNumber as serialNu7_163_, 
 animal0_1_.bodyTemperature as bodyTemp2_164_, 
 animal0_3_.pregnant as pregnant166_, 
 animal0_3_.birthdate as birthdate166_, 
 animal0_4_.owner as owner167_, 
 animal0_7_.name_first as name2_170_, 
 animal0_7_.name_initial as name3_170_, 
 animal0_7_.name_last as name4_170_, 
 animal0_7_.nickName as nickName170_, 
 animal0_7_.height as height170_, 
 animal0_7_.intValue as intValue170_, 
 animal0_7_.floatValue as floatValue170_, 
 animal0_7_.bigDecimalValue as bigDecim9_170_, 
 animal0_7_.bigIntegerValue as bigInte10_170_, 
case 
 when animal0_2_.reptile is not null then 2 
 when animal0_5_.mammal is not null then 5 
 when animal0_6_.mammal is not null then 6 
 when animal0_4_.mammal is not null then 4 
 when animal0_7_.mammal is not null then 7 
 when animal0_1_.animal is not null then 1 
 when animal0_3_.animal is not null then 3 
 when animal0_.id is not null then 0 end as clazz_ 
from Animal animal0_ 
 left outer join Reptile animal0_1_ on animal0_.id=animal0_1_.animal 
 left outer join Lizard animal0_2_ on animal0_.id=animal0_2_.reptile 
 left outer join Mammal animal0_3_ on animal0_.id=animal0_3_.animal 
 left outer join DomesticAnimal animal0_4_ on animal0_.id=animal0_4_.mammal 
 left outer join Cat animal0_5_ on animal0_.id=animal0_5_.mammal 
 left outer join Dog animal0_6_ on animal0_.id=animal0_6_.mammal 
 left outer join Human animal0_7_ on animal0_.id=animal0_7_.mammal]