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A few questions on object database design

I've been trying to model a database that stores data in an MMORPG. With ObjectDB, a lot of things ... outperforms a lot of other conventional table-oriented databases, but I'm wondering ... entities, then it seems like we are back to the table-oriented databases' design principles

SELECT clause (JPQL / Criteria API)

that JPA provides for managed entity objects, including transparent navigation to other database ... The ability to retrieve managed entity objects is a major advantage of JPQL. For example, the following query returns Country objects that become managed by the EntityManager em: TypedQuery


As explained in chapter 2, entity objects can be deleted from the database by: Retrieving ... entity objects from the database. Removing entity objects from the database using a DELETE query ... all the objects in the database: DELETE FROM Object DELETE queries are executed using the executeUpdate

JPA Entity Fields

otherwise (e.g. by using the @Transient annotation). Storing an entity object in the database does not ... . When an entity object is stored in the database every persistent field must contain either null or a value ... (when stored in the database for the first time) is 1. For every transaction in which an entity object

Defining a JPA Entity Class

To be able to store Point objects in the database using JPA we need to define an entity class ... (annotated) as having the ability to represent objects in the database. Conceptually this is similar ... , and accordingly, provides the ability to store Point objects in the database and retrieve Point

Shared (L2) Entity Cache

the database and added to the shared cache. On commit - new and modified entity objects are added ... Every EntityManager owns a persistence context, which is a collection of all the entity objects ... an entity object that is already managed by the EntityManager returns the existing instance from

JPA Persistable Types

class can only be stored in the database as embedded objects, i.e. as part of a containing entity ... The term persistable types refers to data types that can be used for storing data in the database ... can be stored in the database directly. Other persistable types can be embedded in entity classes as fields

Running JPA Queries

(with getResultList) The following query retrieves all the Country objects in the database. The query ... object, which is a Long object reflecting the number of Country objects in the database ... of this assumption depends on the content of the database. If the database contains multiple Country objects


the content of specified entity objects in the database. Updating entity objects in the database using ... with the database. For example, the EntityManager may not be aware that a cached entity object in ... Existing entity objects can be updated, as explained in chapter 2, by: Retrieving the entity

Step 3: Add a Main Class

to store Point objects in the database and then retrieve them from the database. Use copy and paste ... Point objects in the database: em.getTransaction().begin(); for (int i = 0; i < 1000 ... .getTransaction().commit(); // Find the number of Point objects in the database

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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