How "lazy=proxy" impacts final SQL for many-to-one?
I have done build-time bytecode instrumentation. I also add lazy="true" to joined side
I known many-to-one is the formal solution for foreign key. In most cases, we expect lazy loading foreign table.
How ever, I found no matter what is laze attribute value, final generated SQL keep no change.

I have two classes: Topic and Company. Topic has a field named company:


My tested HQL: select id, company from Topic
My expected SQL: select id, company from DT_TOPIC.
The actual Hibernate tools generated SQL:

This SQL has two weakness:
1. join foreign table
2. select all fields in foreign tables.

Why lazy loading does not effect?

I have done build-time bytecode instrumentation and try all configurations on lazy. The problem remains!

I have done build-time bytecode instrumentation and try all configurations on lazy. The problem remains!

I have done build-time bytecode instrumentation and try all configurations on lazy. The problem remains!

How it imagines that hibernate can give back the Company object that is in select if it does not do join against the corresponding table?

What "join against " mean?
You mean I should write the hql as this?


I have defined such relationship in O/R mapping. It is terrible if join all foreign reference tables.

If your HQL query includes the company object in the select clause, is logical that corresponding SQL query includes a JOIN against the corresponding table.
Sorry for my English, is not my natural idiom.

I think when you write

select id, company from Topic in HQL,

hibernate interprets it as that you want id and the Company object corresponding to each Topic and hence it joins company table and select all columns.

Have a look at the result set, I am sure that it will be returning the company object instead of its id.

I have found two ways to active lazy loading even without byte code instrument.
1. select id, company.id from Topic
2. from Topic

Obviously, Hibernate love the HQL without select sub clause very much. I just wonder why Hibernate request byte code instrument.