CODEWITHSUNDEEP
javahibernatepostgresqlorm
z0r
z0r

Reputation: 8595

Create index on column in one-to-many relationship

I have a one-to-many relationship between two classes like this:

class Parent {
    List<Child> children;
}

class Child {
    String name;
}

I'm using an .hbm.xml file to define my mapping from Java classes to tables. Something like this:

<class name="Parent" table="parent">
    <list name="children">
        <key column="parent_id" />
        <list-index column="idx" />
        <one-to-many class="Child" />
    </list>
</class>

<class name="Child" table="child">
    <property name="name" type="string" />
</class>

That works fine.

Now I want to create a column index (not a list index) on the Child.parent_id column. It seems that the <one-to-many> tag doesn't allow any nested <column> tags, so I tried adding a bidirectional association to the Child mapping like this:

<many-to-one name="parent" insert="false" update="false">
    <column name="parent_id" index="true">
</many-to-one>

But I get an exception: 

 org.hibernate.PropertyNotFoundException: Could not find a getter for parent in class Child

So, how can I create an index on the Child.parent_id column without adding a parent field to the Child class? I'm using Hibernate 3.5.6 and PostgreSQL 9.3.

Upvotes: 3

Views: 4893

Answers (1)

Petar Butkovic
Petar Butkovic

Reputation: 1910

At first I didn't get it what you are looking for, but I think I figure it out.

You defined the list-index which is used to save the index of the java.util.List and not the parent_id of the Child. So you are looking how to create real database index. That can be easy done by annotation like this;

@OneToMany(cascade = { CascadeType.ALL })
@JoinColumn(name="parent_id")
@Index(name = "idx_parent_id", columnNames = "parent_id")
private List<Child> images = new ArrayList<Child>();

And in xml configuration would look like,

  <list name="children">
   <key>
    <column index="parent_id_idx" name="parent_id"/>
   </key>
   <list-index column="idx"/>
   <one-to-many class="hr.winkme.server.model.entities.Child"/>
  </list>

Hope it helps.

Upvotes: 4

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