Hibernate version: 2.1.8

Problem description:
I have a problem concerning a "one-to-one" association. I have not been able to figure out how to tell Hibernate to load the association along with the owner objects, i.e. I want to make an eager load of the association using a left join fetch. Debugging through Hibernate, I see that the SQL is as I would suppose, and it loads both my owner object and the associated object. However - when I reach the method <code>initializeEntitiesAndCollections</code> on Loader.java for the main object - Hibernate makes a new sql on the relating table. This it does for each row in the resultset, i.e. for 10 owner objects it would result in 11 sql-statements.

What am I doing wrong here ??

Mapping documents:

Main class:
<class
name="dk.mlon.appmoduler.medarbejder.impl.MedarbejderAkkordDO"
schema="h7805"
table="medarb"
dynamic-insert="true"
dynamic-update="true"
>

<one-to-one
name="fritvalg"
class="dk.mlon.appmoduler.medarbejder.impl.FritvalgDO"
property-ref="medarbejder"
outer-join="false"
constrained="true"
cascade="all"/>
</class>

Associated class:

<class
name="dk.mlon.appmoduler.medarbejder.impl.FritvalgDO"
schema="h7805"
table="fritvalg"
dynamic-insert="true"
dynamic-update="true"
lazy="true"
>

<many-to-one
name="medarbejder"
class="dk.mlon.appmoduler.medarbejder.impl.MedarbejderAkkordDO"
outer-join="false"
column="m25medarbide"/>



Name and version of the database you are using: DB2 for Z-os version 8.

The generated SQL (show_sql=true):

In the example below, I select one owning object and along with that the associated object. However it results in 2 sql-statements.

Hibernate: select medarbejde0_.m20objektid as m20objek1_0_, fritvalgdo1_.m25objektid as m25objek1_1_, medarbejde0_.m20opdtv as m20opdtv0_, medarbejde0_.m20samleobjid as m20samle3_0_, medarbejde0_.m20edb as m20edb0_, medarbejde0_.m20arb as m20arb0_, medarbejde0_.m20versionsid as m20versi6_0_, medarbejde0_.m20erudgaet as m20erudg7_0_, medarbejde0_.m20prod as m20prod0_, medarbejde0_.m20titel as m20titel0_, medarbejde0_.m20conavn as m20conavn0_, medarbejde0_.m20navn as m20navn0_, medarbejde0_.m20gade as m20gade0_, medarbejde0_.m20postnr as m20postnr0_, medarbejde0_.m20by as m20by0_, medarbejde0_.m20natadresse as m20nata15_0_, medarbejde0_.m20cprnr as m20cprnr0_, medarbejde0_.m20fodsdato as m20fods17_0_, medarbejde0_.m20cprlobenr as m20cprl18_0_, medarbejde0_.m20tlfnr as m20tlfnr0_, medarbejde0_.m20mobiltlf as m20mobi20_0_, medarbejde0_.m20emailadr as m20emai21_0_, medarbejde0_.m20bank1 as m20bank10_, medarbejde0_.m20kontonr1 as m20kont23_0_, medarbejde0_.m20bank2 as m20bank20_, medarbejde0_.m20kontonr2 as m20kont25_0_, medarbejde0_.m20pensionkd as m20pens26_0_, medarbejde0_.m20ancidato as m20anci27_0_, medarbejde0_.m20datoaranc as m20dato28_0_, medarbejde0_.m20til0fratr as m20til029_0_, medarbejde0_.m20afspads as m20afspads0_, medarbejde0_.m20modetid as m20modetid0_, medarbejde0_.m20longrp as m20longrp0_, medarbejde0_.m20udbetsted as m20udbe33_0_, medarbejde0_.m20organisa as m20orga34_0_, medarbejde0_.m20arbsted as m20arbsted0_, medarbejde0_.m20hel0del as m20hel0del0_, medarbejde0_.m20skfthold as m20skft37_0_, medarbejde0_.m20morgenpa as m20morg38_0_, medarbejde0_.m20kommune as m20kommune0_, medarbejde0_.m20grpliv as m20grpliv0_, medarbejde0_.m20sh0opspa as m20sh0o41_0_, medarbejde0_.m20atp as m20atp0_, medarbejde0_.m20timelont as m20time43_0_, medarbejde0_.m20normalti as m20norm44_0_, medarbejde0_.m20belob as m20belob0_, medarbejde0_.m20indi0time as m20indi46_0_, medarbejde0_.m20fast0lon as m20fast47_0_, medarbejde0_.m20kapp0pct as m20kapp48_0_, medarbejde0_.m20kapp0kr as m20kapp0kr0_, medarbejde0_.m20pct0supen as m20pct050_0_, medarbejde0_.m20nationalitet as m20nati51_0_, medarbejde0_.m20anvferiekort as m20anvf52_0_, medarbejde0_.m20ambfritag as m20ambf53_0_, medarbejde0_.m20deltid as m20deltid0_, medarbejde0_.m20fridafri as m20frid55_0_, medarbejde0_.m20landekd as m20landekd0_, medarbejde0_.m20arbstedund as m20arbs57_0_, medarbejde0_.m20logon as m20logon0_, medarbejde0_.m20retdato as m20retdato0_, fritvalgdo1_.m25opdtv as m25opdtv1_, fritvalgdo1_.m25edb as m25edb1_, fritvalgdo1_.m25prod as m25prod1_, fritvalgdo1_.m25udbetandel as m25udbet5_1_, fritvalgdo1_.m25pensionandel as m25pensi6_1_, fritvalgdo1_.m25fridagandel as m25frida7_1_, fritvalgdo1_.m25glordn as m25glordn1_, fritvalgdo1_.m25medarbide as m25medar9_1_ from h7805.medarb medarbejde0_ left outer join h7805.fritvalg fritvalgdo1_ on medarbejde0_.m20objektid=fritvalgdo1_.m25medarbide where (medarbejde0_.m20edb=999 )and(medarbejde0_.m20prod=2304 )and(medarbejde0_.m20arb=10 )

Hibernate: select fritvalgdo0_.m25objektid as m25objek1_0_, fritvalgdo0_.m25opdtv as m25opdtv0_, fritvalgdo0_.m25edb as m25edb0_, fritvalgdo0_.m25prod as m25prod0_, fritvalgdo0_.m25udbetandel as m25udbet5_0_, fritvalgdo0_.m25pensionandel as m25pensi6_0_, fritvalgdo0_.m25fridagandel as m25frida7_0_, fritvalgdo0_.m25glordn as m25glordn0_, fritvalgdo0_.m25medarbide as m25medar9_0_ from h7805.fritvalg fritvalgdo0_ where fritvalgdo0_.m25medarbide=?

Hi tmc, I had the same problem. Remove the lazy="true" and it will eagerly load.

No - I already tried lazy="true" (see mapping above).

Set lazy="false".

Sorry - didn't see you said "remove"....

However - I just tries this, and it still results in two SQL-statements. Even though it is set to lazy="true" it ought to be possible to load it eagerly by using "left join fetch".

But no matter how I declare the mapping, I can not seem to make it work.

Sorry tmc, I don't know enough about how Hibernate works. Setting lazy=false resolved the problem though, no?

No, it did not solve the problem.

In your mapping try:

<one-to-one
.....
outer-join="true"
lazy="false"
>

If that works, please let me know :)

If the Main Class has a one-to-one relationship with Associated class, why does the Associated class have a many-to-one relationship back ? Shouldn't they both be one-to-one ?

Also, the class-level lazy=true might be effecting this.

Just an FYI. In Hibernate version 2 Lazy defaults to "false". When you move to Hibernate version 3 Lazy defaults to "true". Remember this becasue what ever you do here to correct this problem, my may have to come back to it after upgrading.

To clark98108:

<one-to-one
.....
outer-join="true"
lazy="false"
>

This does not solve the problem.

To pksiv:

Logically it should be a "one-to-one" association both ways. However - to do this - Hibernate demands that both ends have the same object-id. This is not the case for us. Therefore we map one end as a "many-to-one" (which is also described in the documentation).