EclipseLink/UserGuide/JPA/Advanced JPA Development/Schema Generation/Index

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@Index Annotation and <index> XML

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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.

 
@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;
    ...
}

@Index Attributes

Attribute	Description	Default	Required?
catalog	The catalog of the INDEX.	?	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.	_<column>_INDEX (but a name should be provided)	No
schema	The schema of the INDEX.	?	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>

Version: 2.2.0 DRAFT
Other versions...

@CascadeOnDelete	Schema Generation	Performance
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