How do you enable batch inserts in hibernate?

To enable batching for both INSERT and UPDATE statements, you need to sett all the following Hibernate properties:

spring.jpa.properties.hibernate.jdbc.batch_size=30
spring.jpa.properties.hibernate.order_inserts=true
spring.jpa.properties.hibernate.order_updates=true

If you can use a SEQUENCE, then you should not use IDENTITY entity identifier generator, since it disables batch fetching.

If you cannot use a SEQUENCE (e.g. MySQL), then try using a separate mechanism to enable batch inserts (e.g. JDBC) instead of using the TABLE generator which does not scale and has a high-performance penalty.

Turns out what was missing in this case was:

<property name="order_inserts">true</property>

ref: https://forum.hibernate.org/viewtopic.php?p=2374413, https://stackoverflow.com/a/5240930/32453 Or possibly hibernate.order_inserts.

Now I see

 [...] cfg.SettingsFactory INFO  - Order SQL inserts for batching: enabled
 ...
 [...] Executing batch size: 2

Much more frequently (anything greater than 1 basically means it's successfully doing batch inserts).

hibernate.jdbc.batch_versioned_data may also be useful.

jdbc:mysql://localhost:3306/batch?rewriteBatchedStatements=true type connection strings might also be related somehow.

https://forum.hibernate.org/viewtopic.php?p=2374413 and also see Hibernate batch size confusion