The Best Way To Remove Parent And Child Entities Via Bulk Deletions

Description: Commonly, deleting a parent and the associated children via CascadeType.REMOVE and/or orphanRemoval=true involved several SQL statements (e.g., each child is deleted in a dedicated DELETE statement). When the number of entities is significant, this is far from being efficient, therefore other approaches should be employed.

Consider Author and Book in a bidirectional-lazy @OneToMany association. This application exposes the best way to delete the parent(s) and the associated children in four scenarios listed below. These approaches relies on bulk deletions, therefore they are not useful if you want the deletions to take advantage of automatic optimistic locking mechanisms (e.g., via @Version):

Best way to delete author(s) and the associated books via bulk deletions when:

• One Author is in Persistent Context, no Book
• More Author are in the Persistent Context, no Book
• One Author and the associated Book are in Persistent Context
• No Author or Book is in Persistent Context

Note: The most efficient way to delete all entities via a bulk deletion can be done via the built-in deleteAllInBatch().

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