How To Bulk Updates

If you prefer to read it as a blog-post containing the relevant snippets of code then check this post

Description: Bulk operations (updates and deletes) are faster than batching, can benefit from indexing, but they have three main shortcomings:

• bulk updates/deletes may leave the Persistence Context in an outdated state (it's up to you to prevent this issue by flushing the Persistence Context before update/delete and close/clear it after the update/delete to avoid issues created by potentially unflushed or outdated entities)
• bulk updates/deletes don't benefit of automatic optimistic locking mechanisms (e.g., @Version is ignored), therefore the lost updates are not prevented (it is advisable to signal these updates by explicitly incrementing version (if any is present)).
• bulk deletes cannot take advantage of cascading removals (CascadeType.REMOVE) and orphanRemoval

This application provides examples of bulk updates for Author and Book entities (between Author and Book there is a bidirectional lazy @OneToMany association). Both, Author and Book, has a version field.

Key points:

• this application provide an example of bulk updates that don't involve managed entities (data is not loaded in the Persistence Context)
• this application provide an example of bulk updates that involve managed entities (data is loaded in the Persistence Context before update it via bulk operations)

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