Update README.md

Author: AnghelLeonard

HibernateSpringBootBatchDeleteOrphanRemoval/README.md

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+**[How To Batch Deletes In MySQL Via orphanRemoval=true](https://github.com/AnghelLeonard/Hibernate-SpringBoot/tree/master/HibernateSpringBootBatchDeleteOrphanRemoval)**
 
+**Description:** Batch deletes in MySQL via `orphanRemoval=true`.
+
+**Note:** Spring `deleteAllInBatch()` and `deleteInBatch()` don't use batching. The first one simply triggers a `delete from entity_name` statement, while the second one triggers a `delete from entity_name where id=? or id=? or id=? ...` statement. Rely on `delete()` method.
+
+**Key points:**\
+     - in this example, we have a `Tournament` entity and each tournament can have several `TennisPlayer` (*one-to-many*)\
+     - first, we dissociate all `TennisPlayer` from the corresponding `Tournament`\
+     - second, we explicitly (manually) flush the persistent context (this will delete in batch all `TennisPlayer` thanks to `orphanRemoval=true`; if this is set to `false`, you will obtain a bunch of updates instead of deletes)\
+     - third, we delete all `Tournament` via the `delete()` method (since we have dissaciated all `TennisPlayer`, the `Tournament` deletion will take advantage of batching as well)
+        
+**Output example:**
+
+![](https://github.com/AnghelLeonard/Hibernate-SpringBoot/blob/master/HibernateSpringBootBatchDeleteOrphanRemoval/batch_delete.png)