[hibernate-issues] [Hibernate-JIRA] Created: (HHH-2608) allow delete-orphan cascade style in one-to-one mapping
allow delete-orphan cascade style in one-to-one mapping
-------------------------------------------------------
Key: HHH-2608
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2608
Project: Hibernate3
Issue Type: New Feature
Components: core
Affects Versions: 3.2.4
Environment: 3.2.4, DB2 v8
Reporter: Joe Kelly
Please allow the cascade-style "delete-orphan" for one-to-one relationships.
When I try to use that cascade style, I get the exception
"org.hibernate.MappingException: single-valued associations do not support orphan
delete".
I realize that the reference manual says "Note that single valued associations
(many-to-one and one-to-one associations) do not support orphan delete." But why? I
can think of many cases where you WOULD want parent-child semantics in a one-to-one
relationship.
For example, I have encountered some legacy databases where an entity has all of its
fields stored in one table EXCEPT for an optional large field (e.g. a blob field) that is
stored in another table, presumably for some performance or storage optimization reason.
In this case the two tables are joined with a one-to-one relationship, using a shared
primary key. Here are some hypothetical tables, classes and mappings that illustrate this
example:
company
(
company_id (PK)
name
)
company_extra
(
company_extra_id (PK), (FK referencing company.company_id)
some_extra_info
)
class Company
{
int companyId;
String name;
CompanyExtra companyExtra;
}
class CompanyExtra
{
int companyExtraId;
String someExtraInfo;
Company company;
}
<class name="Company" table="company">
<id name="companyId" column="company_id">
<generator class="sequence">
<param name="sequence">COMPANY_SEQ</param>
</generator>
</id>
<property name="name" column="name" />
<one-to-one name="companyExtra" class="CompanyExtra"
cascade="all, delete-orphan" />
</class>
<class name="CompanyExtra" table="company_extra">
<id name="companyExtraId" column="company_extra_id"
unsaved-value="null">
<generator class="foreign">
<param name="property">company</param>
</generator>
</id>
<property name="someExtraInfo" column="some_extra_info" />
<one-to-one name="company" class="Company"
constrained="true" />
</class>
For the purposes of this example, CompanyExtra is a child of Company and belongs to one
and only one instance of Company. It cannot be shared between Company instances and it
cannot be an orphan (i.e. it cannot exist without a parent Company). Also, CompanyExtra is
optional so you can have a Company without any associated CompanyExtra during
Company's lifecycle.
To me, it seems natural and logical that if you set Company.companyExtra to null, and save
Company, Hibernate should automatically delete the associated record in the company_extra
table if the delete-orphan cascade style is configured (which, of course, it not currently
allowed). This is what I want to do when editing an existing Company instance:
aCompany = session.load(...);
aCompany.setCompanyExtra(null);
aCompany.setName("some new name");
session.save(aCompany); // automatically deletes company_extra record
For now, I think the workaround is to explicitly delete the CompanyExtra instance in Java
code but that just doesn't seem natural to me and it isn't transparent. I do NOT
want to do this:
aCompany = session.load(...);
companyExtra = aCompany.getCompanyExtra(); // ***extra, unnatural method call
aCompany.setCompanyExtra(null);
aCompany.setName("some new name");
session.save(aCompany);
session.delete(companyExtra); // ***another extra, unnatural method call
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://opensource.atlassian.com/projects/hibernate/secure/Administrators....
-
For more information on JIRA, see: http://www.atlassian.com/software/jira