Zdravím,
nebo využít vlastnost zvanou Batch Loading. Dotazy pak vypadají takto:
Hibernate: select invoice0_.id as id0_, invoice0_.created as created0_
from Invoice invoice0_
Hibernate: select invoiceent0_.INVOICE_FK as INVOICE3_1_, invoiceent0_.id as
id1_,
invoiceent0_.id as id1_0_, invoiceent0_.INVOICE_FK as INVOICE3_1_0_,
invoiceent0_.name as name1_0_
from InvoiceEntry invoiceent0_ where invoiceent0_.INVOICE_FK in (?, ?, ?)
Je to výborný kompromis mezi lazy a eager loadingem se zachováním výkonu
- nemusím mít pak dotazy typu "vrať mi zakázky a k nim jejich položky" a
"vrať mi zakázky"
přičemž obě vrací "jen" kolekci zakázek.
Jiri Mares píše v Čt 07. 06. 2007 v 09:39 +0200:
> Ahoj, asi by nebylo nezajimave zminit verzi Hibernate ...
>
> Pokud pouzivate dotaz, pak jste schopen zapisem inner join fetch nebo outer
> join fetch donutit hibernate aby to dotahla
> rovnou. Chovani Hibernate je spis to nedelat a zavisle entity tahat
> separatnimi dotazy, aby se dalo vyuzivat cachovani.
>
> Takze pro vas pripad asi neco:
>
> from Invoice as i inner join fetch i.invoiceEntries
>
> Jirka
>
> Martin Chalupa napsal(a):
> > Dobrý den, ladím rychlost hibernatu při načítání provázaných entit a
> > narazil jsem na následující věc. Mám tyto entity.
> >
> >
> >
> > @Entity
> >
> > @NamedQueries({
> >
> > @NamedQuery(name = "Invoice.all", query = "from Invoice"),
> >
> > @NamedQuery(name = "Invoice.allFetch", query = "select distinct i
> > from Invoice as i left join fetch i.invoiceEntries")
> >
> > })
> >
> > public class Invoice {
> >
> > @Id
> >
> > @GeneratedValue(strategy = GenerationType.AUTO)
> >
> > private Long id;
> >
> > @Basic
> >
> > private Date created;
> >
> > @OneToMany(cascade = CascadeType.ALL, mappedBy = "invoice)
> >
> > @Fetch(FetchMode.JOIN)
> >
> > private Set<InvoiceEntry> invoiceEntries;
> >
> > }
> >
> >
> >
> > @Entity
> >
> > public class InvoiceEntry {
> >
> > @Id
> >
> > @GeneratedValue(strategy = GenerationType.AUTO)
> >
> > private Long id;
> >
> > @Basic
> >
> > private String name;
> >
> > @ManyToOne
> >
> > @JoinColumn(name="INVOICE_FK")
> >
> > private Invoice invoice;
> >
> > }
> >
> >
> >
> > Volám tento dotaz:
> > sessionFactory.getCurrentSession().getNamedQuery("Invoice.all").list();
> >
> >
> >
> > V této konfiguraci bych očekával v logu jeden provedený dotaz který bude
> > obsahovat join, ale je tam toto:
> >
> >
> >
> > Hibernate: select invoice0_.id as id0_, invoice0_.created as created0_
> > from Invoice invoice0_
> >
> > Hibernate: select invoiceent0_.INVOICE_FK as INVOICE3_1_,
> > invoiceent0_.id as id1_, invoiceent0_.id as id1_0_,
> > invoiceent0_.INVOICE_FK as INVOICE3_1_0_, invoiceent0_.name as name1_0_
> > from InvoiceEntry invoiceent0_ where invoiceent0_.INVOICE_FK=?
> >
> > Hibernate: select invoiceent0_.INVOICE_FK as INVOICE3_1_,
> > invoiceent0_.id as id1_, invoiceent0_.id as id1_0_,
> > invoiceent0_.INVOICE_FK as INVOICE3_1_0_, invoiceent0_.name as name1_0_
> > from InvoiceEntry invoiceent0_ where invoiceent0_.INVOICE_FK=?
> >
> > Hibernate: select invoiceent0_.INVOICE_FK as INVOICE3_1_,
> > invoiceent0_.id as id1_, invoiceent0_.id as id1_0_,
> > invoiceent0_.INVOICE_FK as INVOICE3_1_0_, invoiceent0_.name as name1_0_
> > from InvoiceEntry invoiceent0_ where invoiceent0_.INVOICE_FK=?
> >
> >
> >
> > Tušíte někdo kde by mohl být problém? Nebo je toto chování normální?
> >
> > Předem děkuji za odpověď.
> >
> > Martin Chalupa
> >
>
Petr Ferschmann
SoftEU s.r.o.
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