About retrieve


Optimistic locking: prevent version increment on entity collection attribute

Hello, I have an entity E with an attribute which is a collection of entities (one to many relationship) with an optimistic locking strategy supported by a version field. Is it possible to prevent the increment of the version of entity E when entities are added to or removed from the collection? Something like the equivalent of @OptimisticLock(excluded=true) in Hibernate? Thanks, Farid ... you for your reply. I have added some code to re-retrieve the document entity in the initial call and all works fine. The ... the DB with a new EntityManager (or cleared one) should re-retrieve the original collection of readings. This is not the behaviour ...


Object DB vs EclipseLink/TopLink: Unloaded relationships in detached entities

This topic is for those considering migrating from EclipseLink JPA or TopLink to ObjectDB JPA. ... from non-tx reads still have access in their proxies to retrieve additional dettached instances. If the object was detached through ...


can't get HashMap out of the database

I'm trying to persist an Entity containing a HashMap. It stores the data in the database OK, but the map is always empty when I get the entity out of the database again. I've reproduced this problem in a simple variation of the Guestbook tutorial: Guest class: ===================== ... to the database has contact details in it, but when I retrieve it from the database it does not have contact details.  ...


Index Definition

Describes how to define indexes in JPA entity classes and explains how indexes are used in JPQL queries. 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 the iteration can be avoided and complex queries ov ...


[ODB1] Chapter 4 - JDO Metadata

Shows how to define JDO metadata for persistence capable classes. A JDO metadata file is an XML file with a '.jdo' suffix, containing information about one or more persistent classes. All the persistent classes, and only them, have to be declared in a metadata file. The metadata is used first by the JDO Enhancer, and ...


Use temporary files to enable very large transactions

We have transactions in which many objects are created. These objects are no longer needed in the current transaction after creation. Unfortunately, we will receive an OutOfMemory exception because the objects are kept in the first level cache of ObjectDB. In the forum thread http://www.objectdb.com/database/forum/921 on post #4 you wrote, that ObjectDB should support very large transactions in further version. Can you implement it that ObjectDB used temporary files? Bug Version: 1.04 Priority: Critical Status: Fixed Replies: 27 Type:  Bug ...



An instance of this class is thrown when attempting to create an object id when the object id constructor parameter is null.(Exception of JDO)


Extended mapping-definitions

The described feature is not available in any object-db I know, but possible with mapping to a relational DB, for example with Hibernate.   By default every entity of the real world (respectively its class) gets mapped to a java class. So cats get mapped to the java class 'Cat', dogs to 'Dog' and so on. In the project for which I'm evaluating objectDB, there 1.) will be hundreds of classes and 2.) not all classes are known at project start (an editor). ... of the className field with other fields in order to retrieve required data efficiently. Another idea, you can still use ...


Performance issues on aggregate query

we are using this aggregate query to collect some data: #1 2016-11-09 07:49 we are using this aggregate query to collect some data: select p3.doubleValue,c1.classIdentifier,c1.objec ...



This class represents errors in the implementation for which no user error handling is possible.(Exception of JDO)