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JPA 2 Annotations

Reference (JavaDoc) of all the JPA 2 annotations, including @Entity, @Embeddable, @NamedQuery, @GeneratedValue, etc.... Object Relational Mapping (ORM) JPA providers (for mapping between a relational database and an object model and for direct SQL queries): ...


Issue with UPPER ?

Hi, Assuming those queries which are all the same except the UPPER calls: ... Rows is 100 though this returns 149!!!). The difference between this and Case (1) which works is the use of UPPER everywhere ...


Performance with large databases

When populating a large database (10s of GBs) performance drops suddenly at a certain time whenever I run the populating application.  Is there typically a database size when indexes can no longer be held fully in memory or some such issue?  The method calls that suddenly start to take the most time are those that retrieve data from the store. ... This may be explained by examining the ratio between the database size and the available RAM. As long as the ...


Many clients access same database

Hi, I have a program to manage clients of my tennis club. But we have several different computer programs open that access the database. How can I implement this topology so that there is one Persistence context for all the client programs on the different computers. For example: When I change the name of a client on 1 computer, that change has to be discovered by the other client programs as well. How is this possible? ... You cannot share a persistent context between different JVMs. You may have to refresh objects to get ...


JPA Query Structure (JPQL / Criteria)

Explains the structure of a JPQL query, which consists of 6 clauses: SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY.... are already familiar with it. The main difference between SQL and JPQL is that SQL works with relational database tables, records ...


Exporting the data out of the ObjectDB

Hi, We are currently looking at ObjectDB for high performance / high volume transaction processing system. However we want to work on one of the aspects that is the data should be able to pulled out of the ObjectDB to some sort of Big Data File system or Relation DB for reporting / analytics purpose. ... Currently, migrating data between ObjectDB and other data stores requires writing dedicated code. ...


Are Queries in ObjectDB Multithreaded ?

Greating again ObjectDB team, Will ObjectDB query engine use multithreading whenever possible ? Generally, would a single query with multiple JOINs on the same class and some filtration criteria be faster than multiple queries each with a separate thread than join them using merge functions that filters none compliances ? e.g.: searching for two words with a boolean operator AND and the filtration criteria that both are within 10 word distance Thank you indeed !... internal mechanism that can split many types of operations between threads, including operations that are part of query execution. At the ...



Determine the ordering of identity objects.(Method of javax.jdo.identity.ObjectIdentity)


High availability and other pratical questions

Hi,   I've just started developing a mobile app which will use a server side, hopefully handling a lot of processing and traffic. I was inteding to use TomEE+ with built-in OpenJPA and Postgres DB, initially on one master server but as it grows more master servers will be set (in different geo locations/data centers) using some data sync mechanism between them.   Now that i've met ObjectDB I want to check the option using it instead of postgres so I have few questions regarding it: ... geo locations/data centers) using some data sync mechanism between them.   Now that i've met ObjectDB I want to ...



This interface is implemented by listeners to be notified of clear events.(Interface of JDO)