db4o - count number of total records in database?

Question

I am using db4o and was wondering, how can I get the total number of objects in the database? There isn't an explicit way using the API; however, I can write a query to simply count all the objects, but I was hoping for a more direct way to do it.

Walter

Answer 1

There are two ways:

The first one is to query for the type-object and then get the count:

  int numberOfObjects = container.query(Object.class).size();

However this is probably slow, because the query will construct a result list of all objects. And in a large database that can take time.

The second one is to read the meta data of all stored classes and sum up the count. This is certainly a lot faster:

    int numberOfObjects = 0;
    for(StoredClass storedClass : container.ext().storedClasses()){
        // Filter out db4o internal objects
        // and filter out object which have a parent-class, because these are in the count of the parent
        if(!storedClass.getName().startsWith("com.db4o") &&
                null==storedClass.getParentStoredClass()) {
            numberOfObjects += storedClass.instanceCount();
        }
    }
    System.out.println("Number of objects stored "+numberOfObjects);

Note here that it also report db4o internal classes. So I filter them out.