Question

I have a class, Location. Location contains a List of BorderPoint objects, but it can be a HUGE list (20,000 is not impossible). The tables for this are LOCATION and BORDERPOINT.

I initially populate Location via an import from an ESRI Shapefile. Here’s a code snip:

        try {
            while (featureIterator.hasNext()) {
                Location location = new Location();

                SimpleFeatureImpl feature = (SimpleFeatureImpl) featureIterator.next();

                // set the information in location based on stuff in the feature, lets me clean up this
                // method a bit
                setLocationInfo(location, feature);

                List<BorderPoint> borderPointList = getBorderPoints(feature, location);
                //saveBorderPoints(location, feature);
                location.setBorderPointList(borderPointList);

                try {
                    locationRepository.persist(location);
                } catch (RepositoryException e) {
                    throw new ServiceException("processShapefile() threw RepositoryException", e);
                }
            }
        } finally {
            featureIterator.close();
        }

Since there are so many BorderPoint objects in the List, but I am only saving them by calling persist on the Location object, can I automatically set some sort of batch size for persisting the BorderPoints?

Answer 1

I don’t know OpenJPA, but I have used Hibernate a lot. You probably have to control the transaction size yourself. If you change the code a little this should be easy:

1. Create and persist the Location. You should probably also commit the database transaction.
2. Persist BorderPoints into the database, making sure that you have set their parent Location. This implies that the parent Location is mapped on BorderPoint. You probably want to commit every 100 BorderPoints or so.
3. Query the Location from the database and access its BorderPoints. All persisted BorderPoints should be there.