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Difference between revisions of "EclipseLink/UserGuide/JPA/Advanced JPA Development/Schema Generation/Index"

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  <td>'''<tt>name</tt>'''</td>
 
  <td>'''<tt>name</tt>'''</td>
 
  <td>The name of the INDEX.</td>
 
  <td>The name of the INDEX.</td>
  <td><code><table>_<column>_INDEX</code> (but a name should be provided)</td>
+
  <td><tt>&lt;table&gt;_<column>_INDEX</tt> (but a name should be provided)</td>
 
  <td>No</td>
 
  <td>No</td>
 
</tr>
 
</tr>

Revision as of 16:34, 1 February 2011

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@Index Annotation and <index> XML

>>>>>>THIS PAGE IS IN PROGRESS. PLEASE SEE DISCUSSION PAGE.<<<<<<

An index is a database structure defined for a table, to improve query and look-up performance for a set of columns. Use the @Index annotation in code or the <index> element in the orm.xml descriptor to create an index on a table.

An index can be defined on an Entity or on an attribute. For the Entity it must define a set of columns to index.

Index creation is database specific, some databases may not support indexes. Most databases auto index primary key and foriegn key columns. Some databases support advanced index DDL options. To create more advanced index DDL and DDL script or native query can be used.

Index Attributes
Attribute Description Default Required?
catalog The catalog of the INDEX. Default catalog No
columnNames Specify the set of columns to define the index on. For an Entity , the table. For an attribute, the table and column. Not required when annotated on a field or method.
name The name of the INDEX. <table>_<column>_INDEX (but a name should be provided) No
schema The schema of the INDEX. Default schema No
table The table to define the index on, defaults to entities primary table. The entity's primary table. No
unique Specify whether the index is unique or non-unique. false No

Configuration File

Create an index in orm.xml using <index>, as follows:

<index name="EMP_NAME_INDEX" table="EMPLOYEE" unique="true">
    <column>F_NAME</column>
    <column>L_NAME</column>
</index>

Usage of @Index Annotation

 
@Entity
@Index(name="EMP_NAME_INDEX", columns={"F_NAME","L_NAME"})
public class Employee{
    @Id
    private long id;
    @Index
    @Column(name="F_NAME")
    private String firstName;
    @Index
    @Column(name="L_NAME")
    private String lastName;
    ...
}

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