Force hibernate to insert batch data in single insert in MySQL

Question

We are facing problems with how hibernate handles multiple inserts.

First, We have several instances of a class where the primary key is not auto-generated. We save them in a loop then call flush. But hibernate creates separate insert queries as shown in hibernate log (show_sql). Is this normal? Can we make it use a single insert rather than multiple ones?

Second, Look at the following code:

public void saveCourse() {
    Course course = new Course();
    List<Student> studentList = new ArraryList();
    studentList.add(getStudentService().save(new Student(“hasan”,”askari”)));
    studentList.add(getStudentService().save(new Student(“ali”,”alavi”)));
    studentList.add(getStudentService().save(Student(“reza”,”rezaei”)));
    course.setStudents(studentList);
    getCourseService().save(course);    
}

When the course object is being saved hibernate create separate inserts for table course_student. Why?

Here are our classes:

@Entity
@Table(name = "student ")
public class Student {
    private Long id;
    private String name;
    private String family;
    ….
}    

@Entity
@Table(name = "course ")
public class Course {
    private Long id;
    private List<Student> students;

    @OneToMany
    @JoinTable(name = "course_student")
   public List<Student> getStudents() {
        return students;
    }
    public void setStudents(List<Student> students) {
        this.students = students;
    }
}

Jdbc batch size is made: hibernate.jdbc.batch_size=100 and we flush the session after every 100 saves.

If I understood right, that is the correct behavior. Hibernate is going to insert records on the JoinTable when you persist Course. Otherwise, Courses would be persisted without any Student. — Rafa
– Rafa, Commented Sep 7, 2013 at 19:56
The problem is that why 10 inserts is done for a course with 10 students? why hibernate does not handle it with one insert? — rabolfazl
– rabolfazl, Commented Sep 9, 2013 at 12:34

askari88 · Accepted Answer · 2013-09-11 08:05:35Z

2

You must add this option to hibernate connection URL: rewriteBatchedStatements=true

<property name="hibernate.connection.url">jdbc:mysql://localhost/hibernateTest?rewriteBatchedStatements=true</property>

Note that this does not change anything in hibernate log (generated by setting show_sql=true). It shown separate inserts even after adding this option to jdbc url. To ensure it really works you should check mysql log.

edited Sep 11, 2013 at 8:05

answered Sep 10, 2013 at 8:55

askari88

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