About entities

forum_thread

Performance Questions...

Greetings ObjectDB team, All below questions assume a very large database (~1,000,000,000 objects) Q1: Two queries with a big overlap between their result sets. If I query the first and hold them in memory somehow, would that speed up the execution of the second query since many of its result objects already created and reside in memory ? Q2: Do I need to manually use strong references to such cached result objects ? or do ObjectDB exploits frequency of querying such objects and keep them in memory longer automatically somehow before GC takes place ? #1 2011-01-01 08:18 Greetings ObjectDB team, The below questions assume a very large database (~1,000,000,000 objects): Q1: If m ...

 
issue

UnexpectedException on query

Hi, I'm getting the following exception when trying to query an Entity type by id using googlecode generic dao.   Bug Version: 1.04 Priority: Normal Status: Fixed Replies: 2 Type:  Bug ...

 
forum_thread

Level 2 cache not hit in @ManyToOne

Hi! I have 2 entities: User and Item, both @Cacheable. Item has @ManyToOne private User user. Level 2 JPA cache is activated and it works ok for find by id (tested by changing data in explorer and reading in my app). Problem 1: find by id on Item it's good, it hits the cache, but not for its field "user". "user" is loaded each time from the DB (tested by changing data in explorer and reading in my app). "user" should also be taken from L2 cache, shouldn't it? Otherwise...it's a huge performance hit. ... Hi! I have 2 entities: User and Item, both @Cacheable. Item has @ManyToOne private User ...

 
api-jpa

javax.persistence.NamedQuery

Specifies a static, named query in the Java Persistence query language.(Annotation of JPA)

 
api-jpa

OneToMany.targetEntity

(Optional) The entity class that is the target of the association.(Annotation Element of javax.persistence.OneToMany)

 
api-jpa

getCriteriaBuilder()

Return an instance of CriteriaBuilder for the creation of CriteriaQuery objects.(Method of javax.persistence.EntityManager)

 
api-jpa

PersistenceUnitTransactionType.JTA

JTA entity managers will be created.(Enum Constant of javax.persistence.spi.PersistenceUnitTransactionType)

 
forum_thread

Attempt to begin a new transaction when a transaction is active

The code I have a RecordDao stateless java bean :  #1 2013-06-17 15:02 The code I have a RecordDao stateless java bean :  @ Stateless public cl ...

 
forum_thread

Cache configuration of database file pages, query programs, query results

Are there some possibilities to configure following caches in order to keep cache data for only some important entity types and for the entire life cycle of the EntityManagerFactory. Cache of database file pages. Cache of query programs. Cache of query execution results. #1 2016-06-22 08:04 Are there some possibilities to configure following caches in order to keep cache data for only some important en ...

 
forum_thread

Best practice: Database update/migration of embedded databases in products

Hello Support, what experience do you have for data migration within a product? An example: There are three versions of a product (v1.0; v1.1, v2.0). In each version, the entities have been modified. Attributes added, removed and renamed. If attributes were removed, then only because the data is now held otherwise. ... of a product (v1.0; v1.1, v2.0). In each version, the entities have been modified. Attributes added, removed and renamed. If ...