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From "Vermeulen (JIRA)" <j...@apache.org>
Subject [jira] [Created] (OPENJPA-2299) N+1 select when eager fetching two collection fields of the same entity type
Date Wed, 21 Nov 2012 12:57:58 GMT
Vermeulen created OPENJPA-2299:
----------------------------------

             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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