Question

我有一个可嵌入的类定义为;

    @Embeddable
    public class Observation{

     @Column(name = "created")
      private LocalDateTime created;

     @Column(name="code")
      private string code
      ---

    }

我的实体类是;

@Entity
@Table(name = "mete_observation", uniqueConstraints = @UniqueConstraint(columnNames = "code"),
public class MeterObservation{

 @Embedded
    @AttributeOverrides({ @AttributeOverride(name = "created", column = @Column(name = "ob_created")) })
    private Observation raw = null; 
}

我想创建索引观察/创建字段和观察/代码。

创建索引的最佳方法是什么？我应该在Embeddable类中定义它们吗？或者我可以从实体类中定义它吗？我该如何定义？任何一个例子。

Answer 1

向嵌入式对象添加索引可能会有些棘手。为了使它起作用，必须使用确切的列名。
由于created列名被AttributeOverrides覆盖，因此索引的列不称为created，而是ob_created。

没有其他配置，索引看起来像这样：

@Entity
@Table(
    name = "mete_observation",
    uniqueConstraints = @UniqueConstraint(columnNames = "code"),
    indexes = {
        @Index(columnList = "ob_created", name = "idx_created"), // not 'created' but 'ob_created' as it is overwritten
        @Index(columnList = "code", name = "idx_code"),
    }
)
public class MeterObservation{
    @Embedded
    @AttributeOverrides({ @AttributeOverride(name = "created", column = @Column(name = "ob_created")) })
    private Observation raw = null; 
}

（已通过JPA 2.2.3和Hibernate 5.4.15测试。）

如果命名的隐式策略已设置为ImplicitNamingStrategyComponentPathImpl，则会增加其他复杂性。那也会改变列名。

@Entity
@Table(
    name = "mete_observation",
    uniqueConstraints = @UniqueConstraint(columnNames = "code"),
    indexes = {
        @Index(columnList = "ob_created", name = "idx_created"), // the AttributeOverride 'ob_created' beats the naming strategy
        @Index(columnList = "raw_code", name = "idx_code"), // adding 'raw_' for the naming strategy
    }
)
public class MeterObservation{
    @Embedded
    @AttributeOverrides({ @AttributeOverride(name = "created", column = @Column(name = "ob_created")) })
    private Observation raw = null; 
}

如何在Hibernate 5.2.3中为可嵌入类定义索引？

1 个答案: