Difference in environment since last close.

Question

Hallo developers.
We got a strange problem.
When we close the application its store and the environment we make a dump of the databases present in the environment and we count N databases; this number is not the same as we would expect. After we restart the application and opening again the environment we see that that size of the jdb files is grown and that the number of databases too (and is the same as we would expect the first time). We think that this is a strange behaviour.
Is it a bug or is it a feature?
Kind regards
Massimo

Answer 1

When you say "dump of the databases" what do you mean? A list of the DB names returned by >Environment.getDatabaseNames()? Or a dump of everything in the log files using DbPrintLog? Or a >dump of your specific databases using DbDump?Dump using DbDump.
If you are using DbDump or DbPrintLog while the application is running, the information that is >dumped may not be 100% complete. These utilities read the log files. The log files are written when >the log buffers fill up, when a transaction is committed (unless WriteNoSync is used), and when a >checkpoint is performed.To count the number of databases we stop the application, then we run DbDump and we count N databases.
Our test is made like this:
We got a bean Person with a relation 1:N with Animal:
@Entity(version=1)
public class Person {
     @PrimaryKey
     private String name;
     @SecondaryKey(relate = Relationship.MANY_TO_ONE)
     private String surname;
     private String address;
     @SecondaryKey(relate = Relationship.ONE_TO_ONE)
     private String job;
     @SecondaryKey(relate = Relationship.MANY_TO_ONE)
     private String age;
     @SecondaryKey(relate=Relationship.ONE_TO_MANY, relatedEntity=Animal.class, onRelatedEntityDelete=DeleteAction.NULLIFY)
     private Collection<String> cats = new ArrayList<String>();
     @SecondaryKey(relate=Relationship.ONE_TO_MANY, relatedEntity=Animal.class,onRelatedEntityDelete=DeleteAction.ABORT)
     private Collection<String> dogs = new ArrayList<String>();
Animal
@Entity
public class Animal {
     @PrimaryKey
     private String name;
And a bean Cat:
@Persistent(version=0)
public class Cat extends Animal{
     private String color;
     @SecondaryKey(relate=Relationship.MANY_TO_ONE, relatedEntity=Person.class, onRelatedEntityDelete=DeleteAction.NULLIFY)     
     private String owner;
Our test is very simple:
// Create and add an Animal of type Cat
Animal cat = new Cat("cat");
cat.setOwner("max");
dataAccessor.getCatByName().put(cat);
// Create and add an Animal of type Dog
Dog dog = new Dog("dog");
dataAccessor.getDogByName().put(dog);
// Create a person and add it 2 Animals
Person person = new Person("max");
person.setAge("29");
person.addCat(cat.getName());
person.addDog(dog.getName());
// add a Person
dataAccessor.getPersonByName().put(person);
person = dataAccessor.getPersonByName().get("max");                                        
System.out.println("Record added....");
When i close the application and run the DbDump this is the databases list:
persist#store#com.sleepycat.persist.formats
persist#store#dpl.beans.Animal
persist#store#dpl.beans.Person
persist#store#dpl.beans.Person#age
persist#store#dpl.beans.Person#cats
persist#store#dpl.beans.Person#dogs
persist#store#dpl.beans.Person#job
persist#store#dpl.beans.Person#surname
Notice that i haven't the database for the Cat's attribute owner.
When i run again the example showing the Person after this code line
personByName = entityStore.getPrimaryIndex(String.class, Person.class);
I obtain this databases list:
persist#store#com.sleepycat.persist.formats
persist#store#dpl.beans.Animal
persist#store#dpl.beans.Animal#owner
persist#store#dpl.beans.Person
persist#store#dpl.beans.Person#age
persist#store#dpl.beans.Person#cats
persist#store#dpl.beans.Person#dogs
persist#store#dpl.beans.Person#job
persist#store#dpl.beans.Person#surname
Now as you can see i got a new database, persist#store#dpl.beans.Animal#owner.
What is going on?
I got the example in a eclipse project if you want to check the code.
Kind regards
Massimo