Removing a reference to an array in a schema evolution results in a corrupted database. Please follow these steps to reproduce the problem. Sample output of corrupted data is attached below.

// Needed just as a simple value holder, not relevant any further
public class SimpleObject {

String name;

public SimpleObject(String name) {
this.name = name;
}

public String toString() {
return name;
}
}


// Base-Class storing a date which gets corrupted later on
import java.util.Date;

public class Base {
Date date;
}


// Main Class (extending Base) which holds the array and is going to be schema evoluted... later on the status field gets corrupted.
import java.util.Date;

public class ExtendedBase extends Base {

String name;

// Please comment out for schema-evolution test after first run
SimpleObject[] array;

boolean status;

public ExtendedBase() {

}

public ExtendedBase(String name, boolean status, SimpleObject[] array) {
this.date = new Date();
this.name = name;
this.status = status;
// Please comment out for schema-evolution after first run
this.array = array;
}

public String toString() {
return new StringBuilder().append(name).append("\t").append(status)
.append("\t").append(date).toString();
}
}


// And here's the TestRun
// 1. Run it the first time without any changes to ExtendedBase, so a database is populated.
// 2. Simulate the schema evolution: Comment out all references to the array in ExtendedBase (see comments) and rerun TestRun (database is reused if it exists).

import java.io.File;

import com.db4o.Db4o;
import com.db4o.ObjectContainer;

public class TestRun {

static String YAP_FILE = "test.yap";

public static void createDb() {
if (!new File(YAP_FILE).exists()) {
System.out.println("Creating database: " + Db4o.version());
ObjectContainer oc = Db4o.openFile(YAP_FILE);
for (int i = 0; i < 1000; i++) {
SimpleObject[] array = new SimpleObject[10];
for (int j = 0; j < 10; j++) {
array[j] = new SimpleObject("" + j + i);
}
oc.set(new ExtendedBase("" + i, i % 2 == 0, array));
}
oc.commit();
oc.close();
}
}

public static void logDb() {
ObjectContainer oc = Db4o.openFile(YAP_FILE);
for (Object obj : oc.get(ExtendedBase.class)) {
System.out.println(obj);
}
oc.close();
}

public static void main(String[] args) {
createDb();
logDb();
}
}


---------------------------------------
Output of TestRun (first time)
---------------------------------------

Creating database: db4o 6.1.602
0 true Wed Jul 25 08:47:00 CEST 2007
1 false Wed Jul 25 08:47:00 CEST 2007
2 true Wed Jul 25 08:47:00 CEST 2007
3 false Wed Jul 25 08:47:00 CEST 2007
...

After schema evolution (removing array reference in ExtendedBase):


--------------------------------------------
Output of TestRun (second time)
---------------------------------------------

0 false Thu Feb 19 18:02:47 CET 1970
1 false Thu Feb 19 18:02:47 CET 1970
2 false Thu Feb 19 18:02:47 CET 1970
3 false Thu Feb 19 18:02:47 CET 1970
...