JPA 2 Entity with composite key generates extra redundant *_KEY field in databse

Question

I'm rewriting some XML configurations to entity classes and I'm experiencing problems with hibernate generated tables.

This is my original XML config for this relation:

After strugling with @ElementCollection and composite primary keys I ended up with 2 entities in relation like this:

@Getter
@Setter
@NoArgsConstructor
@Entity
@Table(name = "article")
@ToString(callSuper = true, onlyExplicitlyIncluded = true)
public class EArticle implements Serializable {
    ... 
    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, orphanRemoval = true)
    @JoinColumn(name = "fk_article_uuid",referencedColumnName = "uuid", nullable = false)
    @MapKeyJoinColumns(value = {@MapKeyJoinColumn(name="bean_uuid"),@MapKeyJoinColumn(name="rate_type")})
    private Map rates = new HashMap<>();
    ...
}

and

@Getter
@Setter
@NoArgsConstructor
@Entity
@Table(name="article_rate")
@IdClass(EArticleRate.Id.class)
public class EArticleRate implements Serializable {

    @Getter
    @Setter
    @EqualsAndHashCode(onlyExplicitlyIncluded = true)
    public static class Id implements Serializable {

        @EqualsAndHashCode.Include
        private UUID article;
        @EqualsAndHashCode.Include
        private UUID beanUuid;
        @EqualsAndHashCode.Include
        private String rateType;

        public Id(UUID article, UUID beanUuid, String rateType) {
            this.article = article;
            this.beanUuid = beanUuid;
            this.rateType = rateType;
        }
    }

@javax.persistence.Id
@Column(name = "bean_uuid", nullable = false)
private UUID beanUuid;

@javax.persistence.Id
@Column(name = "rate_type", nullable = false)
private String rateType;

@ManyToOne
@javax.persistence.Id
@JoinColumn(name = "fk_article_uuid", foreignKey = @ForeignKey(name = "article_rate_article_uuid_fk"), insertable = false, updatable = false, nullable = false)
private EArticle article;

@Column(name = "outcome")
private Integer outcome;

@Column(name = "value")
private Float value;

@Column(name = "creator_uuid")
private UUID creatorUuid;

@Column(name = "updated")
private ZonedDateTime modified;

}

hibernate generates table that looks like:

Hibernate: 

create table article_rate (
   fk_article_uuid uuid not null,
    bean_uuid uuid not null,
    rate_type varchar(255) not null,
    creator_uuid uuid,
    updated timestamp,
    outcome int4,
    value float4,
    rates_KEY bytea,
    primary key (fk_article_uuid, bean_uuid, rate_type)
)

While the table itself looks like it's supposed to, the problem is that hibernamte generates it with redundant field rates_KEY bytea and I don't know why. Is there anything wrong with my relation, is it too complicated, can something be simplified?

Any help appreciated.

Regards
Armando
PS: as seen I also use lombok to simplify code.

user_12511566 · Answer

I've fixed it by remoivng ArticleRate.Id from ArticleRate and changed

Map

in Article entity to

Set

since I don't need map anymore.

But would still like to know why is hibernate creating redundant field.

user_3439993 · Answer

Your @OneToMany setup is a bit weird - generally for bidirectional relationship one side (@ManyToOne) does joinColumn to specify it's the owner of the relationship and has the column, while the other side uses mappedBy parameter on @OneToMany annotation. It's likely that not finding it hibernate assumed that the actual foreign key column was not specified and so it generated it from the field name (hence rates_KEY). It also possibly created a fk_article_uuid column in your article table, which you don't need.

user_12511566 · Answer

After strugling some more and since with Set I even had more problems on storing rates, I've decided to return to original solution and managed to make it work with a Map.

ArticleRate now looks like

@Getter
@Setter
@NoArgsConstructor
@Entity
@Table(name="article_rate")
public class EArticleRate implements Serializable {

    @Embeddable
    public static class RateId implements Serializable {
        private UUID beanUuid;
        private String rateType;
        private UUID articleUuid;


        public RateId() {
        }

        public RateId(UUID beanUuid, String rateType, UUID articleUuid) {
            this.beanUuid = beanUuid;
            this.rateType = rateType;
            this.articleUuid = articleUuid;
        }


        public UUID getBeanUuid() {
        return beanUuid;
        }

        public void setBeanUuid(UUID beanUuid) {
        this.beanUuid = beanUuid;
        }

        public String getRateType() {
        return rateType;
        }

        public void setRateType(String rateType) {
        this.rateType = rateType;
        }

        public UUID getArticleUuid() {
        return articleUuid;
        }

        public void setArticleUuid(UUID articleUuid) {
        this.articleUuid = articleUuid;
        }


        @Override
        public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        RateId rateId = (RateId) o;
        return beanUuid.equals(rateId.beanUuid) && rateType.equals(rateId.rateType) && articleUuid.equals(rateId.articleUuid);
        }

        @Override
        public int hashCode() {
        return Objects.hash(beanUuid, rateType, articleUuid);
        }
    }

    @EmbeddedId
    private RateId id;

    @ManyToOne
    @MapsId("articleUuid")
    @JoinColumn(name = "fk_article_uuid", foreignKey = @ForeignKey(name = "article_rate_article_uuid_fk"), insertable = false, updatable = false, nullable = false)
    private EArticle article;

    /** other fields **/
}

And relation in my Article entity now looks like:

@OneToMany(mappedBy = "article", fetch = FetchType.EAGER, cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH}, orphanRemoval = true)
@MapKey(name = "id")
private Map rates = new HashMap<>();

My db table for article rates is now correct and what I wanted

create table article_rate (
   fk_article_uuid uuid not null,
    beanUuid uuid not null,
    rateType varchar(255) not null,
    creator_uuid uuid not null,
    updated timestamp,
    outcome int4,
    value float4,
    primary key (fk_article_uuid, beanUuid, rateType)
)

I wanted to use map since I usualy know what rates I want to get out with a key, so I dont have to use .stream() or iterations to find the correct ones.

JPA 2 Entity with composite key generates extra redundant *_KEY field in databse

3 Answers