Re: [hibernate-dev] Composite IDs with a null property/field

> I think in the past we argued the same for attributes of a composite id, > like you said, if one of the element can be nul, why is it in the id > property in the first place. As an example you might Imagine someone wants to put internationalization properties into a database and having a table structure like this (this might be an old legacy application that doesn't have a PK column): BUNDLE_NAME (not nullable) KEY (not nullable) LOCALE (nullable) VALUE (not nullable) The first 3 (BUNDLE_NAME, KEY, LOCALE) are the CompositeKey and there's a unique constraint on the database on these columns. It is fine to have the LOCALE as <null>, as in this case the systems default locale would be used, but for each BUNDLE_NAME/KEY combination you could only have a single composite key with a <null> LOCALE. Hibernate should be (must be?) able to handle this scenario, what do you think? Joerg On Wed, Dec 11, 2019 at 10:18 AM Emmanuel Bernard <emmanuel(a)hibernate.org&gt; wrote: > Just talking about simple id, even if we allow the column to be > nullable > (if the DB even allows that), I don't think Hibernate allows null to > be > a valid id value. Because null means I don't know or not applicable. > I think in the past we argued the same for attributes of a composite > id, > like you said, if one of the element can be nul, why is it in the id > property in the first place. > > As for whether there is a strong implementation detail reason to not > allow it, I don't know but I assume the null checking assuming "not > an > id" is pretty much all over the place. > > Emmanuel > > On 11 Dec 2019, at 3:37, Gail Badner wrote: > >> Currently, there is no way to load an entity that exists in the >> database >> with a composite ID, if one of the composite ID columns is null. >> >> This behavior is due to this code in ComponentType#hydrate: >> > https://github.com/hibernate/hibernate-orm/blob/master/hibernate-core/src... >> >> Basically, if any field/property in a composite ID is null, >> Hibernate >> assumes the entire ID is null. An entity cannot have a null ID, so >> it >> returns null for the entity result. >> >> I believe that Hibernate does allow a primary key column to be >> nullable. >> >> TBH, it seems strange to have a property in a composite ID that can >> be >> null. If it can be null, it seems that the property could be removed >> from >> the composite key. >> >> I don't see anything in the spec about a requirement that all >> composite ID >> fields/properties must be non-null. Am I missing something? >> >> The code I referenced above is 13 years old. Does anyone have >> insight >> into >> why Hibernate does this? >> >> Thanks, >> Gail >> _______________________________________________ >> hibernate-dev mailing list >> hibernate-dev(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/hibernate-dev > > _______________________________________________ > hibernate-dev mailing list > hibernate-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/hibernate-dev > > -- JOERG BAESNER SENIOR SOFTWARE MAINTENANCE ENGINEER Red Hat <https://www.redhat.com/> jbaesner(a)redhat.com T: +49-211-95439691 <https://red.ht/sig> TRIED. TESTED. TRUSTED. <https://redhat.com/trusted>