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@Repository | |
public interface UserRepository extends JpaRepository<User, Long> { | |
@EntityGraph(attributePaths = {"messages"}) | |
List<User> findTop5By(); | |
// JPQL does not support LIMIT | |
// We need to use Pageable to set the number of ids we want | |
@Query("SELECT id " + | |
"FROM User ") | |
List<Long> findIds(Pageable pageable); |
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List<Message> getAllBy() { | |
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder(); | |
CriteriaQuery<Message> query = criteriaBuilder.createQuery(Message.class); | |
Root<Message> message = query.from(Message.class); | |
// Add fetching of the author field | |
message.fetch(Message_.author, JoinType.LEFT); | |
query.select(message); | |
TypedQuery<Message> typedQuery = entityManager.createQuery(query); |
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@Query("SELECT * | |
FROM Message m | |
LEFT JOIN FETCH m.author") | |
List<Message> getAllBy(); |
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@EntityGraph(attributePaths = {"author"}) | |
List<Message> getAllBy(); |
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@RunWith(SpringRunner.class) | |
@SpringBootTest("hibernate.query.interceptor.error-level=ERROR") | |
@Transactional | |
class NPlusOneQueriesLoggingTest { | |
... | |
} |
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@RunWith(MockitoJUnitRunner.class) | |
@SpringBootTest | |
@Transactional | |
class NPlusOneQueriesLoggingTest { | |
@Autowired | |
private MessageRepository messageRepository; | |
@Test | |
void nPlusOneQueriesDetection_isLoggingWhenDetectingNPlusOneQueries() { |
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... | |
import com.yannbriancon.interceptor.HibernateQueryCountInterceptor; | |
@RunWith(SpringRunner.class) | |
@SpringBootTest | |
@Transactional | |
public class NotificationResourceIntTest { | |
@Autowired | |
private HibernateQueryCountInterceptor hibernateQueryCountInterceptor; |
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<dependency> | |
<groupId>com.yannbriancon</groupId> | |
<artifactId>spring-hibernate-query-utils</artifactId> | |
<version>1.0.3</version> | |
</dependency> |
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void logMessages() { | |
// Get all the messages from the database | |
// -> Triggers 1 query | |
Set<Message> messages = messageDao.findAll(); | |
// Map through the N messages to create the DTO with the author display name | |
// -> Triggers 1 query to fetch each author so N queries! | |
messages.stream.map( | |
message -> logger.info( | |
message.getAuthor().getName() + ": " + message.getText() |
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class Message { | |
... | |
@ManyToOne(fetch = FetchType.LAZY) | |
@JoinColumn(name = "author_id") | |
private User author; | |
} |
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