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Hibernate version: 3.0.5

Mapping documents:


I save two Person objects A and B, with one being the spouse of other and vice versa.

When I load the object A, the spouse reference is not being proxied but loaded when not-foun set to ignore for the many-to-one association. But if I remove it then it is proxied as expected.
Is this related to foreign key constraint or something like that? like one-to-one needs to have constraint=true otherwise the reference is initialized instead of proxied.

Can any one help?

Thanks,
Prasad

Upon further inspection, when not-found is set true, ManyToOneType.isNullable() is returning true thus selecting LoadEvenListener.INTERNAL_LOAD_NULLABLE. But this type do not allow creation of proxies. Any idea why this restriction exists? Basically this means that not-found=ignore can't be used with lazy fetching strategy. Is that right?

The code is from 3.0.5 version.
EntityType.java:261


SessionImpl.java:651

Yes, that is correct.

(Well, lazy="proxy" can't be used. lazy="true" can be.)

Thanks Gavin for the quick response. I have tried with the following combinations to understand completely when proxying is enabled and when not.

1. <many-to-one name="Spouse" class="Person" not-null="true" not-found="ignore" lazy="true" access="property"/> -->proxying is disabled


2. <many-to-one name="Spouse" class="Person" not-null="true" access="property"/> -->proxying is enabled


3. <many-to-one name="Spouse" class="Person" not-null="true" lazy="true" access="property"/> -->proxying is disabled


4. <many-to-one name="Spouse" class="Person" not-null="false" access="property"/> -->proxying is enabled


5. <many-to-one name="Spouse" class="Person" not-null="false" lazy="true" access="property"/> -->proxying is disabled


What is the difference between laze="true" or lazy="proxy"? Even with lazy=true and not-found=ignore, proxying is disabled. Can you please clarify?

How about reading the documentation about lazy="true"? Among other things, it tells you you need the bytecode enhancer.

By the way, it should be very obvious why lazy="proxy" does not work with not-found="ignore". Think about it.

Actually, I apologise, I gave you bad advice. We have removed lazy="true" from the <many-to-one> mapping in 3.1 'cos it had some problems.

There is no way to use lazy fetching with not-found="ignore".

gavin, this post helped me solve an almost identical problem I've been having. Let me ask you, though, you mentioned above that

>>it should be very obvious why lazy="proxy" does not work with not-found="ignore"

Is that because the proxy object that serves as a place holder can't be null?
Can you elaborate on the rationale for that, please? To the uninitiated like myself, it would seem that you could leave those as null, but I am sure there's a good reason why not. (and, yes, I read the documentation about proxying, unless there's some place you can point to that I should have read more carefully).
Thanks so much,
Alex

and being that there isn't a way to have lazy fetching with not-found="ignore", is the only way to avoid multiple selects in that case is to do a fetch outer join?

To determine if the object should be built with a proxy instance or with a null, you have to hit the other database table. In which case you may as well just load the object on the other side.

aha, ok, now it makes sense - thanks for your lightning-fast response. so my only option to avoid n+1 selects, then, is fetch outer join, ha?

shucks, left outer join doesn't seem to help here either. I searched high and low through the documentation, but I couldn't see anything that said that left outer join solution to the n+1 problem would not work where not-found="ignore". Please help. Thanks so much.

btw, when I say it doesn't work I mean I still get multiple selects. Let me know if it's not supposed to work in this case, or if it's meant to work, in which case I will post my code.

I haven't received a response. Is that because I should post this as a separate topic? Yet, this strongly appears to be an issue with not-found="ignore". I tried everything and yet I still get the multiple selects issue, with join="fetch" being ignored. Now, in the past what appeared to me as a bug turned out to be a hibernate feature or an oversight on my part, but this one certainly looks a lot like a bug. If I am wrong, I apologize.

What is the code and mapping that causes the multiple selects? You have not given enough information.

Thanks for your willingness to help, gavin

Here are the mappings (just to eliminate all factors, I resorted to specifying left outer join in three different ways: outer-join="true" fetch="join" and in hql)





Here's the code I'm running:



And here's what I get:


Hibernate: select buyermgr0_.BUYER_CODE as BUYER1_1_0_, buyermgr0_.SEC_GROUP_CD as SEC2_1_0_, buyermgr0_.SOURCE_SYSTEM as SOURCE3_1_0_, useridenti1_.USER_ID as USER1_8_1_, buyermgr0_.BUYER_NAME as BUYER4_1_0_, buyermgr0_.BUYER_USER_ID as BUYER5_1_0_, buyermgr0_.BUYER_USER_ID as formula0_0_, useridenti1_.FIRST_NAME as FIRST2_8_1_, useridenti1_.LAST_NAME as LAST3_8_1_, useridenti1_.TIMESTAMP as TIMESTAMP8_1_ from V_BUYER_MGR buyermgr0_ left outer join T32_USER_IDENTITY_REF useridenti1_ on buyermgr0_.BUYER_USER_ID=useridenti1_.USER_ID
Hibernate: select useridenti0_.USER_ID as USER1_8_0_, useridenti0_.FIRST_NAME as FIRST2_8_0_, useridenti0_.LAST_NAME as LAST3_8_0_, useridenti0_.TIMESTAMP as TIMESTAMP8_0_ from T32_USER_IDENTITY_REF useridenti0_ where useridenti0_.USER_ID=?
Hibernate: select useridenti0_.USER_ID as USER1_8_0_, useridenti0_.FIRST_NAME as FIRST2_8_0_, useridenti0_.LAST_NAME as LAST3_8_0_, useridenti0_.TIMESTAMP as TIMESTAMP8_0_ from T32_USER_IDENTITY_REF useridenti0_ where useridenti0_.USER_ID=?
Hibernate: select useridenti0_.USER_ID as USER1_8_0_, useridenti0_.FIRST_NAME as FIRST2_8_0_, useridenti0_.LAST_NAME as LAST3_8_0_, useridenti0_.TIMESTAMP as TIMESTAMP8_0_ from T32_USER_IDENTITY_REF useridenti0_ where useridenti0_.USER_ID=? and then a whole bunch of these identical selects