JDO 删除父行而不删除子行答案

【问题标题】：JDO Delete parent row without deleting the children rowsJDO 删除父行而不删除子行
【发布时间】：2020-03-16 09:11:07
【问题描述】：

我需要一些帮助来尝试从父表中删除一行但不删除子表。我有这张表 MyEntityA。这有 2 个表 MyEntityB 的外键，例如：

@PersistenceCapable(detachable = "true")
public class MyEntityA implements Serializable {

    private static final long serialVersionUID = 3575973891490133579L;

    /*
     * KEYS
     */
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.UUIDHEX)
    @Column(name = “Id", jdbcType = "VARCHAR", length = 32)
    private String Id;

    @Persistent(defaultFetchGroup = "true", dependent = "true")
    @Column(name = "CURRENTCLIENT", jdbcType = "VARCHAR", length = 32)
    @ForeignKey(name = “MY_ENTITY_B_FK1", deleteAction = ForeignKeyAction.RESTRICT, table = “MY_ENTITY_B", columns = {
            @Column(name = “ID") }, updateAction = ForeignKeyAction.RESTRICT)
    private MyEntityB currentClient;

    @Persistent(defaultFetchGroup = "true", dependent = "true")
    @Column(name = "RELATEDTO", jdbcType = "VARCHAR", length = 32)
    @ForeignKey(name = “MY_ENTYTY_B_FK2", deleteAction = ForeignKeyAction.RESTRICT, table = "MY_ENTITY_B", columns = {
            @Column(name = “ID") }, updateAction = ForeignKeyAction.RESTRICT)
    private MyEntityB relatedTo;


    public Relationship() {
    }


    public MyEntityB getCurrentClient() {
        return currentClient;
    }

    public void setCurrentClient(MyEntityB currentClient) {
        this.currentClient = currentClient;
    }

    public MyEntityB getRelatedTo() {
        return relatedTo;
    }

    public void setRelatedTo(MyEntityB relatedTo) {
        this.relatedTo = relatedTo;
    }

}

现在，使用 JDO，当我试图从表 MyEntityA 中删除一行时：

PersistenceManager pm = …
MyEntityA objectById = pm.getObjectById(MyEntityA.class,”abc”);
pm.deletePersistent(objectById)

或者喜欢：

PersistenceManager pm = …
MyEntityA objectById = pm.getObjectById(MyEntityA.class,”abc”);
objectById.setRelatedTo(null);
objectById.setCurrentClient(null);
pm.makePersistent(objectById);
pm.deletePersistent(objectById)

在这两种情况下，代码都会删除表 MyEntityA 中的行和表 MyEntityB 中的行，这些行在表 MyEntityA 中被引用。我希望我可以从 MyEntityA 中删除该行，但不要触摸 MyEntityB 表中的行。

有人可以帮帮我吗？

【问题讨论】：

在 JPA 中，这个问题可以通过添加 removeOrphan = false 来解决。但这是 JDO，我找不到类似的东西。

标签： mysql mysql-workbench jdo jdoql

【解决方案1】：

我找到了正确的解决方案。在我与外键的关系类中，我不得不更改行

@Persistent(defaultFetchGroup = "true", dependent = "true")
to
@Persistent(defaultFetchGroup = "true", dependent = "false")

这是启发我的帖子：Is there any method like orphanRemoval of JPA in JDO with Kodo?

另外，官方文档：https://db.apache.org/jdo/api30/apidocs/javax/jdo/annotations/Persistent.html#dependent()

【讨论】：