Maciej Walkowiak | @maciejwalkowiak Performance Oriented Spring Data JPA & Hibernate

Maciej Walkowiak | @maciejwalkowiak Why so slow?

Maciej Walkowiak | @maciejwalkowiak Why so slow? • Poor database connection management • Too many queries • Slow queries • Wrong JPA mappings • Fetching more than needed

Don’t guess

Maciej Walkowiak | @maciejwalkowiak

Maciej Walkowiak | @maciejwalkowiak

Database Connection Management

Maciej Walkowiak | @maciejwalkowiak Database JDBC Driver DataSource Application Database JDBC Driver DataSource Application get connection get connection get connection connection connection connection Network

Maciej Walkowiak | @maciejwalkowiak Database JDBC Driver DataSource Application Database JDBC Driver DataSource Application get connection get connection get connection connection connection connection Network • TCP Handshake • TLS negotiation • Authentication

Maciej Walkowiak | @maciejwalkowiak On the Database side (Postgres) • Each connection sparks a new OS process • Consumes 5-10MB of RAM • CPU context switching

3ms to execute query, 100ms to establish connection

Maciej Walkowiak | @maciejwalkowiak Connection Pooling

Maciej Walkowiak | @maciejwalkowiak • On application startup, creates a pool of physical connections • Reuses already open connections • Creates more connections, when pool is exhausted Connection Pooling

Maciej Walkowiak | @maciejwalkowiak Connection Pool DataSource Application Connection Pool DataSource Application get connection acquire connection connection connection

How big is your pool?

Maciej Walkowiak | @maciejwalkowiak • Tomcat handles requests with 200 threads • HikariCP default pool size is 10 How big is your pool?

If you have 10,000 front-end users, having a connection pool of 10,000 would be shear insanity. 1000 still horrible. Even 100 connections, overkill. You want a small pool of a few dozen connections at most, and you want the rest of the application threads blocked on the pool awaiting connections. https://github.com/brettwooldridge/HikariCP/wiki/About-Pool-Sizing

No content

When is connection acquired? When is connection released?

Artur Havliukovskyi Vlad Mihalcea

Maciej Walkowiak | @maciejwalkowiak Demo 🔥

Maciej Walkowiak | @maciejwalkowiak • Turn off `spring.jpa.open-in-view` • Call external services outside of database transaction • Turn off auto-commit • Be very careful with @Transactional(propagation = REQUIRES_NEW) • Use TransactionTemplate when you need more control Summary

Maciej Walkowiak | @maciejwalkowiak Summary • Avoid select on insert with @Version or implement Persistable • Use Repository#getReferenceById when you need … references • Always use FetchType.LAZY on @ManyToOne, @ManyToMany • Explicitly fetch associations with fetch join or @EntityGraph • Use @DynamicUpdate for table with large number of columns

Maciej Walkowiak | @maciejwalkowiak How to bulletproof mappings?

Vlad Mihalcea Jean Bisutti

Maciej Walkowiak | @maciejwalkowiak Entities - goods and bads • Fetching more data than needed (even with LAZY fetch types) - 😢 • Loaded entities are stored in JPA Persistence Context - memory 🥺 • Dirty Tracking - CPU 😡 • The risk of N+1 - Database 😱 • Handles business logic and enforces invariants

Maciej Walkowiak | @maciejwalkowiak Fetch entity with an intention to modify it.

Maciej Walkowiak | @maciejwalkowiak Fetch projection for reading.

Maciej Walkowiak | @maciejwalkowiak @Entity public class Account { @Id private String id; private String iban; private String firstName; private String lastName; @ElementCollection @CollectionTable( name = "phone_number", joinColumns = @JoinColumn(name = “account_id") ) private List phoneNumbers; } {"id":"sender-id","firstName":"John","lastName":"Doe"} Expected Response: record NamesOnly(String id, String firstName, String lastName) {} Projection Class

Maciej Walkowiak | @maciejwalkowiak record NamesOnly(String id, String firstName, String lastName) {} Projection Class public interface AccountRepository extends JpaRepository { NamesOnly findNamesOnlyById(String id); } Repository

Maciej Walkowiak | @maciejwalkowiak NamesOnly findNamesOnlyById(String id); Columns to select where clause

Maciej Walkowiak | @maciejwalkowiak @Query("select new NamesOnly(a.id, a.firstName, a.lastName) from Account a where a.id = :id") NamesOnly findNamesOnlyById(String id);

Maciej Walkowiak | @maciejwalkowiak @Query(value = "select id, first_name, last_name from account where id = :id", nativeQuery = true) NamesOnly findNamesOnlyById(String id); interface NamesOnly { String getId(); String getFirstName(); String getLastName(); } 😳

Maciej Walkowiak | @maciejwalkowiak public interface AccountRepository extends JpaRepository { NamesOnly findNamesOnlyById(String id); }

Maciej Walkowiak | @maciejwalkowiak public interface AccountRepository extends JpaRepository { NamesOnly findNamesOnlyById(String id); AccountWithState findAccountWithStateById(String id); }

Maciej Walkowiak | @maciejwalkowiak public interface AccountRepository extends JpaRepository { NamesOnly findNamesOnlyById(String id); AccountWithState findAccountWithStateById(String id); AccountDTO findAccountDtoById(String id); }

Maciej Walkowiak | @maciejwalkowiak public interface AccountRepository extends JpaRepository { NamesOnly findNamesOnlyById(String id); AccountWithState findAccountWithStateById(String id); AccountDTO findAccountDtoById(String id); AccountLight findLightAccountById(String id); } 😳

Maciej Walkowiak | @maciejwalkowiak public interface AccountRepository extends JpaRepository { T findById(String id, Class clazz); } 😎

Maciej Walkowiak | @maciejwalkowiak public interface AccountRepository extends JpaRepository { T findById(String id, Class clazz); } 🥴 … but no custom query

Maciej Walkowiak | @maciejwalkowiak Just use SQL

Maciej Walkowiak | @maciejwalkowiak Takeaways • JPA & Hibernate are NOT easy • Get connections management right • Log queries during development • Consider getting Hibernate Optimiser from Vlad or using QuickPerf for testing • Use projections for reading data

Maciej Walkowiak | @maciejwalkowiak Vlad Mihalcea Thorben Janssen

Maciej Walkowiak | @maciejwalkowiak Thank you!