Mastering JPA Performance
Speaker: Thomas Broll
@speakjava

For more blog posts, see The Oracle Code One table of contents

Problem

• Users complain
• With microservices more important beause more calls

General

• Apache lang has ImmutableTriple class

Techniques

• Monior – number sql statemtenrs, cpu, i/o
• hibernate.show_sql = true
• run jstack while transaction running to see where stuck
• Check JDBC driver batch size

Create – Performance improvements

Scenario: writing large amounts of data

• Use table generator (vs sequence generator) where gt batch of ids so not a roud trip to get it each time. Even better to use external UUID generator
• JPA only supports one open batch. But goes to database if do a query or persist a different entity. So faster if persist by entity

Read – Performance improvements

• 1+N problem. One statement in code. Executes more statement to get relationships. All, XToOne are eagerly loaded
• Can provide hints to eagerly or lazy load
• fetch query to get data actually needed – can put it in the JQL query
• Can get Hibernate statistics for number of queries/loads/fetches
• Cal setFirstResult() and setMaxResults() on query object

Update – Performance improvements

• Auto flushes are caused by transaction commit, insert/delete, query or explicitly flush()
• Performance cost due to dirty checks and actual updates. Cost also depends on size of persistence context
• Call getReference() to get empty proxy. This allows saving without changing in database?

Delete – Performance improvements

• Remove() requires persistent entities, requires loading reference
• Delete by query could be more efficient

Cloud

• Two orders of maginude worse when database on different continent.
• 35 minutes to do 5 second run when database on a different continent

My take: It’s been a while since I look at this topic. It was a good mix of review and things I never knew. Not having a physical network between the machine and database really hanges the numbers. It would have been nice to use a cloud database to get those numbers [scratch that; he did at the very end. I would have liked to see it earlier]