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Using OneToMany or ManyToOne . A Performance issue [message #646419]

Thu, 23 December 2010 16:48

Eclipse User

I have a company entity and an employee entity

I can model it as

//Approach 1
class company
{
String id;
@OneToMany
List<Employee> employees;
}

OR as

//Approach 2
class employee
{
String id;
@ManyToOne
Company company;
}

If i am not interested in a bidirectional relationship between the entities,

Approach 1 would produce 3 Database table like this

Table : Company

Id

Table : Employee

Id

Table : Company_Employee

CompanyId EmployeeId

And if I go for approach 2 I can make it with 2 tables

Table :Company

Id

Table :Employee
Id CompanyId

Avoiding a table join means performance gain. ie, with approach 2 i get better performance at the cost of class modeling.

Is this scenario valid ? What would be your option in this context?
Please let me know

Re: Using OneToMany or ManyToOne . A Performance issue [message #647082 is a reply to message #646419]

Tue, 04 January 2011 09:28

Eclipse User

Hello,

This question is more a database design question, not an object modeling question. If you want a company to have a list of Employee's, this can be done regardless of there being a join table or not - ie you can use
@OneToMany
List<Employee> employees;

Or
@OneToMany
@JoinColumn(name="FK_COMPANY_ID")
List<Employee> employees;

The second option uses a foreign key "FK_COMPANY_ID" in the Employee table. So there is no cost to object modeling - other than when accessing the list, it will cause a query on the Employee table for associated Employees.

Best Regards,
Chris

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