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Index Definition

Querying without indexes requires iteration over entity objects in the database one by one. This may take a significant amount of time if many entity objects have to be examined. Using proper indexes ... . Index management introduces overhead in terms of maintenance time and storage space, so deciding


Method javax.persistence.criteria.ListJoin Expression<Integer> index() Create an expression that corresponds to the index of the object in the referenced association or element collection ... for which an order column has been defined. Returns: expression denoting the index Since: JPA 2.0

JDO Annotations for Index Definition

The following annotations are used to define indexes on persistent fields: The Index Definition section of the ObjectDB manual explains these annotations in details.

[ODB1] Chapter 4 - JDO Metadata

identity supported by ObjectDB. To enforce unique values in a field you can define a unique index as ... only in index declarations, as explained in the next section. 4.5 Index Definition Querying a large extent without indexes may take a significant amount of time because it requires iteration


javax.jdo.annotations Annotation Index Target: Classes and fields (including property get methods) Annotation for a database index. Used for database schema generation to create indexes. Corresponds to the xml element "index". Since: JDO 2.1 Column[] columns Columns that compose this index. Columns


Annotation Element javax.jdo.annotations.Index String table Table for the index. This is needed iff annotating a type where the index is not defined on the primary table for the type. Returns: the table on which the index is defined Default value: "" Since: JDO 2.1


Annotation Element javax.jdo.annotations.Discriminator String indexed Whether the discriminator is indexed. Returns: whether the discriminator is indexed Default value: "" Since: JDO 2.1


Annotation Element javax.jdo.annotations.Index String[] members Member (field and property) names that compose this index. Returns: member names that compose this index Default value: {} Since: JDO 2.1


Annotation Element javax.jdo.annotations.Index Column[] columns Columns that compose this index. Returns: columns that compose this index Default value: {} Since: JDO 2.1


Annotation Element javax.jdo.annotations.Version String indexed Whether the version column(s) is(are) indexed. Returns: whether the version column(s) is(are) indexed Default value: "" Since: JDO 2.1

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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