Edit Question - KnowledgeHub

Title Body

we have a n+1 select problem with Hibernate 3.3. For simplicity's sake, I'll just do a short abstract example. Suppose we have the following simple classes: class MainEntity { @Id public Long id; //we have a table generator create this id @OneToOne ( mappedBy ="main" ) public SubEntity subEntity; } class SubEntity { @Id @Column( name = "mainId" ) //note that this is the same column as the join column below public Long mainId; //in order to have the exact same id as the corresponding MainEntity @OneToOne ( fetch = FetchType.LAZY ) @JoinColumn ( name = "mainId", insertable = false, updatable = false, nullable = false ) public MainEntity main; //this is used for navigation and queries (" ... subentity.main = :x") } So as you can see SubEntity has a relation to MainEntity that is expressed by two properties, where the mainId property is the one responsible for managing the relation/foreign key. This works quite well and perfectly fits our needs. However, there's one problem with eagerly loading the SubEntity along with the MainEntity . Suppose I have a query that returns a collection of MainEntity . With the current setup, Hibernate will issue n + 1 selects: the query itself + n selects for each SubEntity . Of course I could add a join fetch to the query, but I'd rather like Hibernate to do that automatically. Thus I tried adding @Fetch( FetchMode.JOIN ) , but that didn't do anything. I would also have no problem using @Fetch( FetchMode.SUBSELECT ) , which should reduce the select statements to 2 - the original query and a select for the sub entities (at least that's what happens on another property annotated with @CollectionOfElements and @Fetch( FetchMode.SUBSELECT ) ). So the question is: how woul

Tags (comma-separated) Cancel