在休眠统计中，加载和获取之间有什么区别

Question

Im mainly looking at the EntityStatics ( http://www.hibernate.org/hib_docs/v3/api/org/hibernate/stat/EntityStatistics.html ). I can see a lot of fetch, loads and updates and i cant find anywhere that says what the difference between them are.

Answer 1

Working backward through the code, the fetch counter only gets incremented when the entity is retrieved from the datasource (as opposed to any caches) -

    protected Object loadFromDatasource(
        final LoadEvent event,
        final EntityPersister persister,
        final EntityKey keyToLoad,
        final LoadEventListener.LoadType options) {
    final SessionImplementor source = event.getSession();
    Object entity = persister.load(
            event.getEntityId(),
            event.getInstanceToLoad(),
            event.getLockMode(),
            source
    );

    if ( event.isAssociationFetch() && source.getFactory().getStatistics().isStatisticsEnabled() ) {
        source.getFactory().getStatisticsImplementor().fetchEntity( event.getEntityClassName() );
    }

    return entity;
}

The load counter was called from too many places to track them all down, but it looks like it gets incremented any time the entity gets loaded, whether from the datasource or the caches.

Answer 2

https://vladmihalcea.com/hibernate-statistics/ This article contains explicit difference between fetch and load counts:

long getEntityLoadCount() It gives you the total number of entities that were loaded (including the one fetched from the first or second-level cache or the database) by the current EntityManagerFactory or SessionFactory. long getEntityFetchCount() It gives you the total number of entities that were fetched from the database by the current EntityManagerFactory or SessionFactory.