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OneToOne optimization

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deeeed

Post subject: OneToOne optimization

Posted: Fri Apr 18, 2008 2:04 pm

Newbie

Joined: Sun Dec 24, 2006 10:23 pm
Posts: 11

Hi,
I'm trying to understand how to optimize OneToOne relationship between entities. In several of my code I can see that hibernate treat a property as EAGER even if I specified manually the LAZY into my mapping.
For example with the following code, we can see that the same entity SimEntity is fetched twice before the sql update, so I would like it to be only fetched once. any idea how to do this ?
Off course I could use session.update instead of session.merge but I think it doesn't deal very good with @Version..

Hibernate version: 3.2
Name and version of the database you are using: Postgresql 8.2
Mapping documents:

Code:

@Entity
public class SimEntity {
   private Integer simId;
   private String phoneNumber;
   private PhoneEntity phone;
   private Integer version;

   public SimEntity() {
   }

   @Id
   @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sim_seq")
   @SequenceGenerator(name = "sim_seq", sequenceName = "sim_seq")
   public Integer getSimId() {
      return simId;
   }

   public void setSimId(Integer simId) {
      this.simId = simId;
   }

   public String getPhoneNumber() {
      return phoneNumber;
   }

   public void setPhoneNumber(String phoneNumber) {
      this.phoneNumber = phoneNumber;
   }

   @OneToOne(optional = true)
   @JoinColumn(name = "`phoneId`", nullable = true)
   public PhoneEntity getPhone() {
      return phone;
   }

   public void setPhone(PhoneEntity phone) {
      this.phone = phone;
   }
   
   @Version
   @Column(name = "`OPTLOCK`")
   public Integer getVersion() {
      return version;
   }

   public void setVersion(Integer version) {
      this.version = version;
   }
}

Code:

@Entity
public class PhoneEntity {
   private Integer phoneId;
   private String color;
   private SimEntity sim;
   private Integer version;

   public PhoneEntity() {
   }

   @Id
   @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "phone_seq")
   @SequenceGenerator(name = "phone_seq", sequenceName = "phone_seq")
   public Integer getPhoneId() {
      return phoneId;
   }

   public void setPhoneId(Integer phoneId) {
      this.phoneId = phoneId;
   }

   public String getColor() {
      return color;
   }

   public void setColor(String color) {
      this.color = color;
   }

   @OneToOne(mappedBy = "phone", fetch = FetchType.LAZY, optional = true)
   public SimEntity getSim() {
      return sim;
   }

   public void setSim(SimEntity sim) {
      this.sim = sim;
   }
   
   @Version
   @Column(name = "`OPTLOCK`")
   public Integer getVersion() {
      return version;
   }

   public void setVersion(Integer version) {
      this.version = version;
   }
}

Code:

SimEntity sim1 = new SimEntity();
      sim1.setPhoneNumber("3333");
      simDAO.save(sim1);
      PhoneEntity p1 = new PhoneEntity();
      p1.setColor("blue");
      p1.setSim(sim1);
      phoneDAO.save(p1);
      System.out.println("saved phone: "+p1.getPhoneId());
      
      sim1.setPhone(p1);
      sim1 = simDAO.merge(sim1);

The generated SQL (show_sql=true):

Quote:

Hibernate:
select
nextval ('sim_seq')
Hibernate:
/* insert hibernate.SimEntity
*/ insert
into
SimEntity
("phoneId", phoneNumber, "OPTLOCK", simId)
values
(?, ?, ?, ?)
Hibernate:
select
nextval ('phone_seq')
Hibernate:
/* insert hibernate.PhoneEntity
*/ insert
into
PhoneEntity
(color, "OPTLOCK", phoneId)
values
(?, ?, ?)
saved phone: 50
Hibernate:
/* load hibernate.SimEntity */ select
simentity0_.simId as simId3_0_,
simentity0_."phoneId" as phoneId4_3_0_,
simentity0_.phoneNumber as phoneNum2_3_0_,
simentity0_."OPTLOCK" as OPTLOCK3_3_0_
from
SimEntity simentity0_
where
simentity0_.simId=?
Hibernate:
/* load hibernate.PhoneEntity */ select
phoneentit0_.phoneId as phoneId2_0_,
phoneentit0_.color as color2_0_,
phoneentit0_."OPTLOCK" as OPTLOCK3_2_0_
from
PhoneEntity phoneentit0_
where
phoneentit0_.phoneId=?
Hibernate:
/* load hibernate.SimEntity */ select
simentity0_.simId as simId3_1_,
simentity0_."phoneId" as phoneId4_3_1_,
simentity0_.phoneNumber as phoneNum2_3_1_,
simentity0_."OPTLOCK" as OPTLOCK3_3_1_,
phoneentit1_.phoneId as phoneId2_0_,
phoneentit1_.color as color2_0_,
phoneentit1_."OPTLOCK" as OPTLOCK3_2_0_
from
SimEntity simentity0_
left outer join
PhoneEntity phoneentit1_
on simentity0_."phoneId"=phoneentit1_.phoneId
where
simentity0_."phoneId"=?
Hibernate:
/* update
hibernate.SimEntity */ update
SimEntity
set
"phoneId"=?,
phoneNumber=?,
"OPTLOCK"=?
where
simId=?
and "OPTLOCK"=?

Code:

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deeeed

Post subject:

Posted: Mon Apr 21, 2008 12:23 pm

Newbie

Joined: Sun Dec 24, 2006 10:23 pm
Posts: 11

After a few search, I found some possible solution.
I would now need your help to know what is the best to implement.
So after reading http://www.hibernate.org/315.html I can see that it is possible to have a OneToOne lazy by using optional=false.
So I tried it, but in my case it doesn't work...
Let's take a simple example, I have a VehicleEntity which has dependency to many other entities, VehicleStatusEntity, VehicleModelEntity, VehicleCharacteristicsEntity, etc... All these relations are @OneToOne.

So in my VehicleEntity I did:

Code:

@OneToOne(mappedBy = "vehicle", fetch = FetchType.LAZY, optional = false)

That line is the same on all the getCharacteristics(), getVehicleStatus(), ...

On the other side (on vehicleStatus, vehicleCharacteristics, etc) I have:

Code:

@OneToOne(fetch = FetchType.LAZY, optional = false)
   @JoinColumn(name = "`vehicle_id`", nullable = false)
   public VehicleEntity getVehicle() {

Then I create a query which retrieve a single VehicleEntity in my vehicleDAO, as I defined my OneToOne with optional=false it shouldn't load all the status,characteristics,model entities.

Code:

          Criteria criteria = session
                     .createCriteria(VehicleEntity.class);
               criteria.add(Restrictions.idEq(1));
               VehicleEntity vehicle = (VehicleEntity) criteria
                     .uniqueResult();

Here is the generated query:

Quote:

/* criteria query */ select
this_."vehicle_id" as vehicle1_18_0_,
...
from
config."Vehicle" this_
where
this_."vehicle_id"=?
/* load model.VehicleCharacteristicsEntity */ select
vehiclecha0_."vehicleCharacteristics_id" as vehicleC1_21_1_,
...
vehicleent1_."vehicle_id" as vehicle1_18_0_,
...
from
config."VehicleCharacteristics" vehiclecha0_
inner join
config."Vehicle" vehicleent1_
on vehiclecha0_."vehicle_id"=vehicleent1_."vehicle_id"
where
vehiclecha0_."vehicle_id"=?
/* load model.VehicleModelEntity */ select
vehiclemod0_."vehicleModel_id" as vehicleM1_20_1_,
...
vehicleent1_."vehicle_id" as vehicle1_18_0_,
...
from
config."VehicleModel" vehiclemod0_
left outer join
config."Vehicle" vehicleent1_
on vehiclemod0_."vehicle_id"=vehicleent1_."vehicle_id"
where
vehiclemod0_."vehicle_id"=?
...

As you can see this can result as a performance nightmare...
So I would really need any feedback on how to really use this optional=false and why it doesn't work on my case;)

The possible way to solve these problems are:
1) Simulate a @ManyToOne with unique="true":
as described in the comment of http://www.hibernate.org/162.html.
but I don't like this solution because @ManyToOne is simply not supposed to be a OneToOne...
2) Using a JoinColumn on both side of the relation and make it nullable="true":
@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "`vehicleStatus_id`", nullable = true)
but I don't like this solution because I don't want to add a foreign key to all my tables.. When there are many relation and then a foreign key for each of them it will end with a lot of column on my table which i'd prefer to avoid...
3) Using a common JoinTable for all OneToOne association:
for example I could have the fields: vehicle_id, vehicleStatus_id, vehicleCharacteristics_id, etc.. in this table.
I think this can be a good solution but only when there are many relation on the table so sometimes I just don't want a join table and then I'm back to the original problem.

So here I would like to know what you think about these solution, and what would be best practise ?

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