Hibernate: @OneToMany with @JoinColumn deletes and reinserts the whole collection

A unidirectional @OneToMany owns the foreign key from the wrong side. Hibernate cannot express 'remove one child', so it nulls out every FK and writes them all back - N deletes and N inserts to remove one row.

• Hibernate: getReference hands back a proxy that throws after the session closes
• Hibernate: without @Version, the last write silently wins
• Hibernate: orphanRemoval and CascadeType.REMOVE are different rules
• Hibernate: equals/hashCode on a generated id breaks HashSet membership
• Hibernate: the first-level cache means a re-query never sees another transaction's update
• Hibernate: merge returns a copy, and the object you passed in stays detached

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Published 2026-08-25

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