JPQL 多重连接获取 returns 错误 "cannot simultaneously fetch multiple bags"

Question

我正在学习 Spring Data JPA。

我在处理 JPQL 时遇到问题。我神三个实体。

public class Cheat implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "cheat_seq", length = 10)
    private Long cheatSeq;

    @OneToMany(mappedBy = "cheat", fetch=FetchType.LAZY)
    private List<CheatGoodVote> goodVote;

    @OneToMany(mappedBy = "cheat", fetch=FetchType.LAZY)
    private List<CheatBadVote> badVote;

    // skipped.
}

和其他是映射到上述实体的实体。

public class CheatGoodVote {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="vote_seq", length=10)
    private Long voteSeq;

    @ManyToOne(cascade=CascadeType.ALL)
    @JoinColumn(name="cheat_fk", referencedColumnName="cheat_seq")
    public Cheat cheat;

    // ..skipped
}

两个实体彼此几乎相同。

public class CheatBadVote {    
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="vote_seq", length=10)
    private Long voteSeq;

    @Column(name="ip_address", nullable=false)
    private String ipAddress;

    @Column(name="reg_date", nullable=false)
    private Date regDate;

    @ManyToOne(cascade=CascadeType.ALL)
    @JoinColumn(name="cheat_fk", referencedColumnName="cheat_seq")
    public Cheat cheat;

}

当我调用 JPQL 时 "@Query("SELECT c FROM Cheat c JOIN FETCH c.goodVote JOIN FETCH c.badVote WHERE SIZE(c.goodVote) <= :voteCnt")",

它returns错误：

Caused by: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags: [com.aibiigae1221.skyQuiz.data.entity.Cheat.goodVote, com.aibiigae1221.skyQuiz.data.entity.Cheat.badVote]
    at org.hibernate.loader.BasicLoader.postInstantiate(BasicLoader.java:75) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.loader.hql.QueryLoader.<init>(QueryLoader.java:106) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:210) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:141) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:115) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:77) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:153) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.getQueryPlan(AbstractSharedSessionContract.java:553) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:662) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    ... 103 common frames omitted

我想把 Cheat、CheatGoodVote、CheatBadVote 实体放在一起。错误来自jpql问题吗？或者我的实体映射有误？

Answer 1

这似乎是框架相关的错误。取决于您的休眠版本。

考虑一下这个问题，看起来像你的问题LINK

笛卡尔积

请注意，加入获取两个集合最终会得到 cartesian product of both. For more information about problem itself and solutions go HERE

JPQL 多重连接获取 returns 错误 "cannot simultaneously fetch multiple bags"

JPQL multiple join fetch returns error "cannot simultaneously fetch multiple bags"

hibernate

jpa

jpql

笛卡尔积