Vermeulen created OPENJPA-2299:
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Summary: N+1 select when eager fetching two collection fields of
the same entity type
Key: OPENJPA-2299
URL: https://issues.apache.org/jira/browse/OPENJPA-2299
Project: OpenJPA
Issue Type: Bug
Components: jdbc, jpa, performance
Affects Versions: 2.2.1, 2.3.0
Reporter: Vermeulen
I have a ProductOrder entity that has two @OneToMany lists of
ProductOrderLines. When selecting from ProductOrder, eager fetching does not
seem to recurse into the second list so that each field of each
ProductOrderLine in the second list is fetched using a separate "load field"
operation.
The problem does not occur when there is only one List.
@Entity
public class ProductOrder {
@JoinColumn(name = "PLANNED_ORDER_ID")
@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<ProductOrderLine> plannedOrderLines = new
ArrayList<ProductOrderLine>();
@JoinColumn(name = "ACTUAL_ORDER_ID")
@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<ProductOrderLine> actualOrderLines = new
ArrayList<ProductOrderLine>();
Expected nr of queries: 1 (for Order) + 1 (for Order.plannedOrderLines) + 1
(for Order.actualOrderLines).
Actual nr of queries: same as expected + 1 query for each field of each
ProductOrderLine in Order.actualOrderLines.
Same problem exists when using @JoinTable instead of @JoinColumn (JPA 2.0 only).
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