Many Java developers use ORM in their projects but most of them don’t do deep dive into configuration, settings and tuning to achieve really good performance. What is worse most of them even don’t know what options do they have to improve performance. In this talk we will review them on practical samples and give concrete recommendations how to make your Hibernate work much better in real projects. Code samples can be found here: https://github.com/xpinjection/hibernate-performance .

1. Hibernate performance
tuning
Mikalai Alimenkou/Igor Dmitriev
http://xpinjection.com
@xpinjection

5. Disclaimer
This is only my
personal experience

6. You could follow code samples
https://github.com/xpinjection/hibernate-performance

7. What Hibernate really does?

8. Full execution chain

9. How to measure
• Hibernate statistics with
• Benchmarks with JMH:
– http://openjdk.java.net/projects/code-tools/jmh/

10. How to understand and trace
• Datasource proxy:
– https://github.com/ttddyy/datasource-proxy
– https://github.com/p6spy/p6spy
• Queries counting interceptor:
– https://github.com/vladmihalcea/db-util
• Log and format SQL statements

12. Demo database schema

14. JDBC tuning
• Use good implementation of connection pool
• Batching, fetching
• Switch to native queries where performance is
critical
• Do direct JDBC stuff with Session doWork

15. N + 1, lazy loading issues
• Eager load
• Entity graphs
• Fetch modes
• Fetch profiles
• Query batching

17. Operations batching
• Flush Session state to avoid memory issues
• Use JDBC batching options
in order to mix statements for different tables
• Deletes are batched only for the same table

19. Second level cache

20. Cache providers and strategies

21. Query cache

23. Mark lightweight requests
• Read-only flag for transactions
• Choose appropriate transaction isolation level
• Annotate entity as immutable if it is not
updated anywhere
• Use StatelessSession for some operations

25. Don’t use entities everywhere
• ResultTransformer and Transformers
• Fields map instead of object
• @SqlResultSetMapping
• Direct mapping on DTO

27. Don’t update all columns
• Dynamic insert, update
• Update only changed columns
• Be careful with number of PreparedStatement

29. Slow ID generation
• Id generator mapping
• Don’t use GenerationType.AUTO, use
GenerationType.SEQUENCE instead
• Try to generate ID/PK in the
code, not delegate to Hibernate

30. Other advices
• Use native queries if really helpful:
– “ORDER BY NULL” or “DELETE with JOIN” in
MySQL
– Effective data removal
• Don’t use lists, arrays and ordering in
Hibernate

31. Start thinking in CQRS way

32. When we really need to use ORM?

34. Resources
• https://vladmihalcea.com/presentations/
• https://vladmihalcea.com/tutorials/hibernate/
• http://jeeconf.com/archive/jeeconf-
2012/materials/hibernate-performance/
• https://docs.jboss.org/hibernate/orm/5.0/manual/en-
US/html_single/#performance
• http://jeeconf.com/program/hibernate-how-the-magic-
is-really-done/
• http://jeeconf.com/program/hibernate-performance-
tuning/

35. Books to read

36. @xpinjection
http://xpinjection.com
mikalai.alimenkou@xpinjection.com
ihor.dmitriiev@gmail.com