About primary key

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JPA Primary Key

Every entity object that is stored in the database has a primary key. Once assigned, the primary ... an object database, ObjectDB supports implicit object IDs, so an explicitly defined primary key is not required. But ObjectDB also supports explicit standard JPA primary keys, including composite primary

Chapter 2 - JPA Entity Classes

Explains how to define and use JPA entity classes and other JPA persistable types.

ObjectDB Object Database Features

support of the JPA and JDO APIs. Fundamental features of relational databases (e.g. primary keys, derived ... classes. Primary Keys Support of primary keys in ObjectDB is unique compared to other Objec-Oriented Databases. Primary Key Modes Hidden - primary key is automatically managed by ObjectDB with no @Id field

JDO Predefined ID Classes

An object ID is a combination of a persistence capable class and a primary key. It provides ... for persistence capable classes with a simple single field primary key: Object IDs are used in many ... but should not be used as the type of a primary key field in a persistence capable class. For example

Auto Generated Values

generated for that field. This is primarily intended for primary key fields but ObjectDB also supports ... for entity objects with no primary key fields defined (as explained in the previous section). The same number generator is also used to generate numeric values for primary key fields annotated by

Defining a JPA Entity Class

, including which persistent types can be used for persistent fields, how to define and use a primary key ... you might have noticed that the Point entity class has no primary key (@Id) field. As an object database, ObjectDB supports implicit object IDs, so an explicitly defined primary key is not required. On the other hand

Retrieving JPA Entity Objects

of entity classes and to keep them simple as possible. Retrieval by Class and Primary Key Every entity object can be uniquely identified and retrieved by the combination of its class and its primary key ... whose primary key is 1: Employee employee = em.find(Employee.class, 1); Casting of the retrieved

2.7.3_03 Erroneous "Attempt to modify a primary key of a managed object"

key of a managed object", but my application is not trying to change the primary key.  (ObjectDB ... attached. Thanks. Could you please provide details on the primary key of JdoBlob2? Is it composite ... a combination of class + primary key and therefore it seems a bit strange to use it as the type

JPA Entity Fields

(Mapped By) fields Primary key (ID) fields Version field The first three groups (transient, persistent ... two groups (primary key and version fields) can only be used in entity classes. Primary key fields are discussed in the Primary Key section. Transient Fields Transient entity fields are fields

Index Definition

field (similar to how primary keys behave). @Index represents either an ordinary index ... can only be defined on ordinary persistent fields (not on primary key / version fields). Composite Index A composite ... the BTree's primary sort key and which field is used as a secondary sort key. If x is specified first