SpringBoot spring.jpa Hibernate'e Özel Ayarlar - Query Cache

Giriş

Açıklaması şöyle

Hibernate can also cache result set of a query. Hibernate Query Cache doesn’t cache the state of the actual entities in the cache; it caches only identifier values and results of value type. So it should always be used in conjunction with the second-level cache.

Açıklaması şöyle. Kullanılması tavsiye edilmiyor

Caching of query results introduces some overhead in terms of your application's normal transactional processing. For example, if you cache the results of a query against a Person, Hibernate will need to keep track of when those results should be invalidated because changes have been committed against any Person entity.

That, coupled with the fact that most applications simply gain no benefit from caching query results, leads Hibernate to disable caching of query results by default.

Açıklaması şöyle

For all tables that are queried as part of cacheable queries, Hibernate keeps last update timestamps in a separate region named org.hibernate.cache.spi.UpdateTimestampsCache. Being aware of this region is very important if we use query caching because Hibernate uses it to verify that cached query results aren't stale. The entries in this cache must not be evicted/expired as long as there are cached query results for the corresponding tables in the query results regions. It's best to turn off automatic eviction and expiration for this cache region, as it doesn't consume lots of memory anyway.

Query Cache Nerede Saklanıyor

Eskiden org.hibernate.cache.internal.StandardQueryCache diye bir sınıf içinde saklanıyormuş. Bir soru burada. Ancak sanırım Hibernate 5.3 ile bu sınıf kaldırıldı

Ayarlar

hibernate.cache.use_query_cache

collection_cache, query_cache gibi farklı cache'ler mevcut. Açıklaması şöyle

Set this to true to enable the query cache.

Kod

Örnek

Şöyle yaparız

org.hibernate.Session session = (Session) entityManager.getDelegate();

Statistics statistics = session.getSessionFactory().getStatistics();

// check these variables
// queryCacheHitCount
// queryCacheMissCount
// queryCachePutCount

Örnek - Spring Repository

Şöyle yaparız findAll() metodunun döndürdüğü her şey Hibernate Query Cache içinde saklanır

import jakarta.persistence.QueryHint;
import org.springframework.data.jpa.repository.QueryHints;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;

import static org.hibernate.jpa.HibernateHints.HINT_CACHEABLE;

@Repository
public interface BookRepository extends CrudRepository<Book, Long> {
    @Override
    @QueryHints(@QueryHint(name = HINT_CACHEABLE, value = "true"))
    Iterable<Book> findAll();
}

Örnek

Şöyle yaparız

@Repository
public interface AuthorRepository extends CrudRepository<Author, Integer> {
  @QueryHints({ @QueryHint(name = "org.hibernate.cacheable", value ="true") })
  Author findByName(String name);
}

Örnek - Spring Repository

Şöyle yaparız. Burada Query Cache için isim belirtiliyor

import org.springframework.data.jpa.repository.QueryHints;
import javax.persistence.QueryHint;

import static org.hibernate.jpa.QueryHints.HINT_CACHEABLE;
import static org.hibernate.jpa.QueryHints.HINT_CACHE_REGION;

// some code is skipped

@QueryHints({
  @QueryHint(name = HINT_CACHEABLE, value = "true"),
  @QueryHint(name = HINT_CACHE_REGION, value = "query-cache-users")
})
@Override
Iterable<User> findAll();

Örnek - EntityManager

Şöyle yaparız

TypedQuery<BookPublisherValue> q = em
  .createQuery(
    "SELECT new org.thoughts.on.java.model.BookPublisherValue(b.title, p.name) + 
    "FROM Book b JOIN b.publisher p WHERE b.id = :id",
                BookPublisherValue.class);
q.setHint(QueryHints.CACHEABLE, true);
q.setParameter("id", 1L);
BookPublisherValue value = q.getSingleResult();

EhCache

Örnek

Şöyle yaparız

spring.jpa.properties.hibernate.cache.use_query_cache=true
spring.jpa.properties.hibernate.cache.region.factory_class=org.hibernate.cache.ehcache.EhCacheRegionFactory