Describe the bug

After upgrading to Quarkus >= 3.14.0, some save operations started to fail with the following error:

Caused by: org.hibernate.FetchNotFoundException: Entity `com.x.y.entity` with identifier value `2` does not exist
        at org.hibernate.sql.results.graph.entity.internal.EntityInitializerImpl.setMissing(EntityInitializerImpl.java:661)
        at org.hibernate.sql.results.graph.entity.internal.EntityInitializerImpl.resolveFromPreviousRow(EntityInitializerImpl.java:674)
        at org.hibernate.sql.results.graph.entity.internal.EntityInitializerImpl.resolveFromPreviousRow(EntityInitializerImpl.java:94)

Check also this comment #42902 (comment)

The error is also happening with quarkus.hibernate-orm.flush.mode=always

This seems to be related to the Hibernate 6.6 update.

Expected behavior

Save correctly, as previous Quarkus versions. It is working in <= 3.13.3

Actual behavior

No response

How to Reproduce?

https://github.com/fabrii/quarkus-playground/tree/FetchNotFoundException

It has something to do with detached entities, and optional = false annotation.

For example,

In Module class,

@ManyToOne(optional = false)
@JoinColumn(name = "sistema_id")
private System system;

if the optional=false tag is removed, the test works.

This reproducer works correctly on Quarkus <= 3.13.3

Output of uname -a or ver

No response

Output of java -version

openjdk version "21.0.2"

Quarkus version or git rev

= 3.14.0

Build tool (ie. output of mvnw --version or gradlew --version)

No response

Additional information

No response