One of the benefits of using JPA and Hibernate is that it provides an abstraction of database-specific dialects and features. So, in theory, you can implement an application, connect it to one of the supported databases and it will run without any code changes.

Hibernate does that really well. But let’s be honest, you didn’t expect that your application will run perfectly with every supported database, did you?

Hibernate handles the most important things. But if you want your application to perform well, you still need to know which database(s) you want to use and adjust your configuration and code accordingly.

In one of the previous posts, I talked about 6 things you need to know if you want to use Hibernate with a PostgreSQL database. And today I want to have a closer look at the MySQL database.

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Introduction Dealing with time zones is always challenging. As a rule of thumb, it’s much easier if all date/time values are stored in the UTC format, and, if necessary, dealing with time zone conversations in the UI only. This article is going to demonstrate how you can accomplish this task with JDBC and the awesome … Continue reading How to store date, time, and timestamps in UTC time zone with JDBC and Hibernate →

Introduction As I already mentioned, you should never use the TABLE identifier generator since it does not scale properly. In this post, I’ll show you why you should not rely on the AUTO GenerationType strategy if you’re Hibernate application uses MySQL. Prior to Hibernate 5 On Hibernate 4, if you had the following entity mapping: … Continue reading Why should not use the AUTO JPA GenerationType with MySQL and Hibernate →

Introduction I read a very interesting article by Krešimir Nesek regarding MySQL result set streaming when it comes to reducing memory usage. Mark Paluch, from Spring Data, asked if we could turn the MySQL result set streaming by default whenever we are using Query#stream or Query#scroll. That being said, the HHH-11260 issue was created, and … Continue reading How does MySQL result set streaming perform vs fetching the whole JDBC ResultSet at once →

Introduction This article is part of a series of posts related to calling various relational database systems stored procedures and database functions from Hibernate. The reason for writing this down is because there are many peculiarities related to the underlying JDBC driver support and not every JPA or Hibernate feature is supported on every relational … Continue reading How to call MySQL stored procedures and functions with JPA and Hibernate →

Recent Tips and News on Java, Java EE 6, GlassFish & more :

“I believe that one should benchmark before making any technology decisions.” An interview with Pieter van Zyl creator of the OO7J benchmark. In August last year, I published an interesting resource in ODBMS.ORG, the dissertation of Pieter van Zyl, from the University of Pretoria:“Performance investigation into selected object persistence stores”. The dissertation presented the OO7J [...]

Not so long ago, in a galaxy not very far away... a middle-aged programmer battled to free memory from the dark side of the hibernate query cache.  He was successful, or so it seemed. For the query cache memory problems had risen from the ashes -- stronger and more bloated than ever...

What's With All This Garbage?
We hit a case at work (again), where the java server process came to a grinding halt.  It wasn't dead, it just wasn't making much forward progress either.  A quick look at the heap stats showed we were nearly at capacity and that garbage collection was eating all CPU time, thus not allowing any real work to happen.  Looks like it is time to whip out the ol' memory profiler.  This time I went with Eclipse's Memory Analysis Tool .  …

Red Hat increases its service levels. Linux Foundation appoints Ted Ts’o CTO. Sun delivers VirtualBox update. Novell cancels BrainShare. BBC enables iPlayer for Linux. And more.

Note: This is the last 451 CAOS Links post of 2008. We’ll be back with a bumper holiday special on January 2. Happy holidays!

Official announcements
Red Hat Increases Service Levels and Reduces Costs for Customers with Extended Update Support Red Hat

Linux Foundation Appoints Ted Ts’o to Position of Chief Technology Officer Linux Foundation

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You Mean, Memory Is Not Infinite? We're working hard getting MySQL Enterprise Monitor 2.0, featuring Query Analyzer, ready for release. As part of that, we started really ramping up the number of MySQL servers reporting in query data to see how we could scale. Not surprising (to me, anyway), the first efforts did not go so well. My old friend OutOfMemoryError reared its ugly head once again.
Query Cache -- It's More Than Just Results! We're big (ab)users of hibernate query caching, and more importantly to us the natural id optimized query cache. Firing up the profiler, I was not shocked to see that the second level (let's call it L2) and query caches were hogging the majority of memory. But, something didn't smell right...

What I was seeing was tons of …