I'm using Derby (latest version) in embedded mode in a Swing application. As JPA Provider, I'm using TopLink Essentials (2.1 Build b60e-fcs).

Basically, the app grabs some data from the web and stores it in the embedded database. However, the storing process takes quite a while. Here's a code snippet:

ArrayList<Load> load_data = grabHourlyLoadForMonthAndYear(month, year);
       if (load_data.size() > 0) {
            System.out.println(load_data.size()+" objects");
        for (Load l : load_data)
       long start = System.currentTimeMillis();
       System.out.println("time: "+ ((System.currentTimeMillis()-start)/1000) + " sec"); 
grabHourlyLoadForMonthAndYear() grabs the data from the web. "em" is the EntityManager.
The entity "Load" has 5 fields (id, country, year, hourInYear, load)

A typical output looks like this:
17856 objects
time: 102 sec
16128 objects
time: 551 sec
17856 objects
time: 1200 sec

As you can see, the time increases drastically while the number of objects doesn't. From a usability standpoint, that's way too much time spent on waiting.

Has anyone seen similar slow downs while using Derby together with TopLink Essentials in a desktop application?

Best Regards