Hibernate generates multiple select queries even for FETCHMODE.JOIN

Question

I get multiple select queries ('1' for parent and 'n' select queries for n child records) while fetching child parent entities based on the provided parent Id.

To overcome this I put @Fetch(FetchMode.JOIN) on both parent and child entities. But that didn't help. Parent (MessageDetails) and child (MessageHits) entities I used are as below

 @Entity
    @Table(name = "Scantit_msg_dtls")
    public class ScanitMessageDetails implements DomainObject{
 private String icgreference;
 private Long messageId;
private Set<ScanitMessageHit> scanitMessageHits = new HashSet<ScanitMessageHit>();

     @Id
@Column(name = "ICGREFERENCE")
public String getIcgreference() {
    return icgreference;
}

        @Column(name = "PK_MRS_MESSAGE")
    public Long getMessageId() {
        return messageId;
    }

@OneToMany(mappedBy="scanitMessageDetails", orphanRemoval = true, 
    cascade = { javax.persistence.CascadeType.ALL }, fetch=FetchType.EAGER)

        @Fetch(FetchMode.JOIN)
    public Set<ScanitMessageHit> getScanitMessageHits() {
        return scanitMessageHits;
    }

     }

and the child entity is

@Entity
@Table(name = "Scanit_msg_hit")

public class ScanitMessageHit implements DomainObject {

    private static final long serialVersionUID = 1L;
    private Long hitId;
private ScanitMessageDetails scanitMessageDetails;

@Id
    @Column(name = "PK_MRS_HIT")
    public Long getHitId() {
        return hitId;
    }

    public void setHitId(Long hitId) {
        this.hitId = hitId;
    }

    @ManyToOne(cascade = { javax.persistence.CascadeType.ALL }, fetch=FetchType.EAGER)
    @Fetch(FetchMode.JOIN)
    @JoinColumn(name="FK_MRS_MESSAGE",referencedColumnName="PK_MRS_MESSAGE")
    public ScanitMessageDetails getScanitMessageDetails() {
        return scanitMessageDetails;
    }

    public void setScanitMessageDetails(ScanitMessageDetails scanitMessageDetails) {
        this.scanitMessageDetails = scanitMessageDetails;
}
}

Though I am using join fetching strategy, I still get multiple (n+1) select queries while fetching data. This is hampering the application performance.

KINDLY SUGGEST IF I HAVE MADE ANY MISTAKE HERE OR IF THERE IS ANY OTHER WAY TO OVERCOME THIS ISSUE. REALLY APPRECIATE IF YOU CAN HELP ME ON THAT.THANKS IN ADVANCE

Rishi

Ahmed Ashour · Accepted Answer · 2017-11-30 17:58:39Z

4

can you try same after removing fetching strategy from class ScanitMessageHit kindly remove fetch=FetchType.EAGER hope fully it will work. please change your mapping as below.

@OneToMany(mappedBy="scanitMessageDetails", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
public Set<ScanitMessageHit> getScanitMessageHits() {
    return scanitMessageHits;
}

@ManyToOne
@JoinColumn(name="FK_MRS_MESSAGE",referencedColumnName="PK_MRS_MESSAGE")
    public ScanitMessageDetails getScanitMessageDetails() {
    return scanitMessageDetails;
}

edited Nov 30, 2017 at 17:58

Ahmed Ashour

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answered Aug 5, 2014 at 12:31

Arjun Prajapati

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1 Comment

user3730042 Over a year ago

Thanks Arjun,I tried that but it did not work.Still it generates n+1 select statments:( Is there any other thing I need to do?

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