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JPA and querying the RIGHT data

Some JPA performance tips Ted Vinke

This repository contains 2 projects:

  • jpa-examples - The Spring Boot application containing Ted's JPA examples. This is a Gradle project.
  • spring-petclinic - The Spring Petclinic application, slightly modified for the workshop exercises. This contains both the Maven and Gradle build frameworks, so you can choose. See spring-petclinic/README.md for more details.

Workshop exercises

Enable JPA logging

We need some query logging so we can see what happens under the hood.

  • Modify application.properties to enable JPA logging.
  • Possibly restart the application.

Too many owners

The "Find owners" button shows an overview of all available owners and their pets.

But - it looks like some owners are shown more than once e.g. Eduardo Rodriquez

  • Fix the overview of owners so each owner is shown just once. Hint: it's in the data, not in the view.

Veterinarian blowout!

The Veterinarians overview shows world-famous experts on animal care. But they list grows too big - and the database becomes very slow!

Prevent showing all veterinarians all at once!

  • Please add pagination and show them in pages of 5 records at a time.

Specialty of the day

When you open the Veterinarians overview, go see the various queries under the hood!

We surely can improve this by fetching specialties in a single query!

Try to update the collections Vet.specialties to FetchType.LAZY, restart the application and see what happens when you navigate the Veterinarians overview.

The application probably crashes with

failed to lazily initialize a collection of role: org.springframework.samples.petclinic.vet.Vet.specialties
  • Can you fix the overview by querying differently (and in a single query)?

Bonus!

  • Can you make sure the Owners overview used DTO-based projection instead of Owner entities?
  • Can you add an additional search option to find owner by (part of their) pet name?
  • Can you improve other queries?
  • Explore how the Open Session in View works
  • Explore how the cache works
  • Can you enable Hibernate statistics?
  • Can you add Spring Sleuth and use P6spy to see the actual queries (including bound parameters?)