[401763] Make CDO Server more robust against data dictionary changes

https://bugs.eclipse.org/bugs/show_bug.cgi?id=401763

30 files changed, 1134 insertions, 156 deletions

diff --git a/plugins/org.eclipse.emf.cdo.common.db/src/org/eclipse/emf/cdo/common/internal/db/cache/DBRevisionCacheSchema.java b/plugins/org.eclipse.emf.cdo.common.db/src/org/eclipse/emf/cdo/common/internal/db/cache/DBRevisionCacheSchema.java
index 8126370e4b..8c604e6c93 100644
--- a/plugins/org.eclipse.emf.cdo.common.db/src/org/eclipse/emf/cdo/common/internal/db/cache/DBRevisionCacheSchema.java
+++ b/plugins/org.eclipse.emf.cdo.common.db/src/org/eclipse/emf/cdo/common/internal/db/cache/DBRevisionCacheSchema.java
@@ -12,19 +12,19 @@
 package org.eclipse.emf.cdo.common.internal.db.cache;
 
 import org.eclipse.net4j.db.DBType;
+import org.eclipse.net4j.db.DBUtil;
 import org.eclipse.net4j.db.ddl.IDBField;
 import org.eclipse.net4j.db.ddl.IDBIndex;
+import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.IDBTable;
-import org.eclipse.net4j.spi.db.DBSchema;
+import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
 
 /**
  * @author Andre Dietisheim
  */
-public class DBRevisionCacheSchema extends DBSchema
+public class DBRevisionCacheSchema
 {
-  public static final DBRevisionCacheSchema INSTANCE = new DBRevisionCacheSchema();
-
-  private static final long serialVersionUID = 1L;
+  public static final IDBSchema INSTANCE = DBUtil.createSchema("DBRevisionCache");
 
   /**
    * DBTable dbrevisioncache_revisions.
@@ -69,13 +69,8 @@ public class DBRevisionCacheSchema extends DBSchema
   public static final IDBIndex INDEX_REVISIONS_CONTAINERID = //
   REVISIONS.addIndex(IDBIndex.Type.NON_UNIQUE, REVISIONS_CONTAINERID);
 
-  private DBRevisionCacheSchema()
-  {
-    super("DBRevisionCache");
-  }
-
   static
   {
-    INSTANCE.lock();
+    ((InternalDBSchema)INSTANCE).lock();
   }
 }
diff --git a/plugins/org.eclipse.emf.cdo.server.lissome/src/org/eclipse/emf/cdo/server/internal/lissome/db/Index.java b/plugins/org.eclipse.emf.cdo.server.lissome/src/org/eclipse/emf/cdo/server/internal/lissome/db/Index.java
index 5719c214c0..57f2854c7c 100644
--- a/plugins/org.eclipse.emf.cdo.server.lissome/src/org/eclipse/emf/cdo/server/internal/lissome/db/Index.java
+++ b/plugins/org.eclipse.emf.cdo.server.lissome/src/org/eclipse/emf/cdo/server/internal/lissome/db/Index.java
@@ -17,11 +17,13 @@ import org.eclipse.emf.cdo.server.internal.lissome.LissomeStore;
 import org.eclipse.emf.cdo.spi.server.InternalRepository;
 
 import org.eclipse.net4j.db.DBException;
+import org.eclipse.net4j.db.DBUtil;
 import org.eclipse.net4j.db.IDBAdapter;
 import org.eclipse.net4j.db.IDBConnectionProvider;
+import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.h2.H2Adapter;
 import org.eclipse.net4j.spi.db.DBAdapter;
-import org.eclipse.net4j.spi.db.DBSchema;
+import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
 import org.eclipse.net4j.util.io.IOUtil;
 import org.eclipse.net4j.util.om.trace.ContextTracer;
 
@@ -38,7 +40,7 @@ import java.sql.SQLException;
 /**
  * @author Eike Stepper
  */
-public class Index extends DBSchema implements IDBConnectionProvider
+public class Index implements IDBConnectionProvider
 {
   public static final long NULL_POINTER = 0; // A pointer value that has no meaning in the vob.
 
@@ -46,10 +48,10 @@ public class Index extends DBSchema implements IDBConnectionProvider
 
   private static final String INDENT = "       ";
 
-  private static final long serialVersionUID = 1L;
-
   private LissomeStore store;
 
+  private IDBSchema schema = DBUtil.createSchema(LissomeStore.TYPE);
+
   private IDBAdapter adapter;
 
   private DataSource dataSource;
@@ -64,7 +66,6 @@ public class Index extends DBSchema implements IDBConnectionProvider
 
   public Index(LissomeStore store)
   {
-    super(LissomeStore.TYPE);
     this.store = store;
 
     adapter = createAdapter();
@@ -78,7 +79,7 @@ public class Index extends DBSchema implements IDBConnectionProvider
       branches = new BranchesTable(this);
     }
 
-    lock();
+    ((InternalDBSchema)schema).lock();
   }
 
   public LissomeStore getStore()
@@ -161,7 +162,12 @@ public class Index extends DBSchema implements IDBConnectionProvider
   public void createTables()
   {
     Connection connection = writer.getConnection();
-    create(adapter, connection);
+    schema.create(adapter, connection);
+  }
+
+  public IDBSchema getSchema()
+  {
+    return schema;
   }
 
   public Connection getConnection()
diff --git a/plugins/org.eclipse.emf.cdo.server.lissome/src/org/eclipse/emf/cdo/server/internal/lissome/db/Table.java b/plugins/org.eclipse.emf.cdo.server.lissome/src/org/eclipse/emf/cdo/server/internal/lissome/db/Table.java
index 55654dc21e..051c78d0ed 100644
--- a/plugins/org.eclipse.emf.cdo.server.lissome/src/org/eclipse/emf/cdo/server/internal/lissome/db/Table.java
+++ b/plugins/org.eclipse.emf.cdo.server.lissome/src/org/eclipse/emf/cdo/server/internal/lissome/db/Table.java
@@ -30,7 +30,7 @@ public class Table
   public Table(Index index, String name)
   {
     this.index = index;
-    table = index.addTable(name);
+    table = index.getSchema().addTable(name);
   }
 
   public Index getIndex()
diff --git a/plugins/org.eclipse.net4j.db.tests/src/org/eclipse/net4j/db/tests/TestSchema.java b/plugins/org.eclipse.net4j.db.tests/src/org/eclipse/net4j/db/tests/TestSchema.java
index f62eb9bf55..4f93f5a193 100644
--- a/plugins/org.eclipse.net4j.db.tests/src/org/eclipse/net4j/db/tests/TestSchema.java
+++ b/plugins/org.eclipse.net4j.db.tests/src/org/eclipse/net4j/db/tests/TestSchema.java
@@ -11,19 +11,19 @@
 package org.eclipse.net4j.db.tests;
 
 import org.eclipse.net4j.db.DBType;
+import org.eclipse.net4j.db.DBUtil;
 import org.eclipse.net4j.db.ddl.IDBField;
 import org.eclipse.net4j.db.ddl.IDBIndex;
+import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.IDBTable;
-import org.eclipse.net4j.spi.db.DBSchema;
+import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
 
 /**
  * @author Eike Stepper
  */
-public class TestSchema extends DBSchema
+public class TestSchema
 {
-  public static final TestSchema INSTANCE = new TestSchema();
-
-  private static final long serialVersionUID = 1L;
+  public static final IDBSchema INSTANCE = DBUtil.createSchema("CDO");
 
   /**
    * DBTable cdo_repository
@@ -195,13 +195,8 @@ public class TestSchema extends DBSchema
 
   public static final String REFERENCES_TARGET = "cdo_target";
 
-  private TestSchema()
-  {
-    super("CDO");
-  }
-
   static
   {
-    INSTANCE.lock();
+    ((InternalDBSchema)INSTANCE).lock();
   }
 }
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/IDBDatabase.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/IDBDatabase.java
index 928180ccea..3b0448d1cc 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/IDBDatabase.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/IDBDatabase.java
@@ -11,8 +11,6 @@
 package org.eclipse.net4j.db;
 
 import org.eclipse.net4j.db.ddl.IDBSchema;
-import org.eclipse.net4j.db.ddl.IDBSchemaElement;
-import org.eclipse.net4j.db.ddl.IDBTable;
 import org.eclipse.net4j.db.ddl.delta.IDBSchemaDelta;
 import org.eclipse.net4j.util.collection.Closeable;
 import org.eclipse.net4j.util.container.IContainer;
@@ -38,12 +36,7 @@ public interface IDBDatabase extends IContainer<IDBTransaction>, Closeable
 
   public IDBSchemaTransaction getSchemaTransaction();
 
-  public void ensureSchemaElement(RunnableWithSchema updateRunnable, RunnableWithSchema commitRunnable);
-
-  public <T extends IDBSchemaElement, P extends IDBSchemaElement> T ensureSchemaElement(P parent, Class<T> type,
-      String name, RunnableWithSchemaElement<T, P> runnable);
-
-  public IDBTable ensureTable(String name, RunnableWithTable runnable);
+  public void updateSchema(RunnableWithSchema runnable);
 
   public IDBTransaction openTransaction();
 
@@ -70,20 +63,4 @@ public interface IDBDatabase extends IContainer<IDBTransaction>, Closeable
   {
     public void run(IDBSchema schema);
   }
-
-  /**
-   * @author Eike Stepper
-   */
-  public interface RunnableWithSchemaElement<T extends IDBSchemaElement, P extends IDBSchemaElement>
-  {
-    public T run(P parent, String name);
-  }
-
-  /**
-   * @author Eike Stepper
-   */
-  public interface RunnableWithTable
-  {
-    public void run(IDBTable table);
-  }
 }
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/IDBSchemaElement.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/IDBSchemaElement.java
index ac45e373ee..527cd9352d 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/IDBSchemaElement.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/IDBSchemaElement.java
@@ -12,8 +12,6 @@ package org.eclipse.net4j.db.ddl;
 
 import org.eclipse.net4j.util.container.IContainer;
 
-import java.io.Serializable;
-
 /**
  * Specifies a hierachical namespace for elements in a {@link IDBSchema DB schema}.
  *
@@ -21,8 +19,7 @@ import java.io.Serializable;
  * @noimplement This interface is not intended to be implemented by clients.
  * @noextend This interface is not intended to be extended by clients.
  */
-public interface IDBSchemaElement extends IDBNamedElement, IContainer<IDBSchemaElement>, Comparable<IDBSchemaElement>,
-    Serializable
+public interface IDBSchemaElement extends IDBNamedElement, IContainer<IDBSchemaElement>, Comparable<IDBSchemaElement>
 {
   /**
    * @since 4.2
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/delta/IDBDelta.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/delta/IDBDelta.java
index 578946ab91..b8cb44251f 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/delta/IDBDelta.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/delta/IDBDelta.java
@@ -15,15 +15,13 @@ import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.IDBSchemaElement;
 import org.eclipse.net4j.util.container.IContainer;
 
-import java.io.Serializable;
-
 /**
  * @since 4.2
  * @author Eike Stepper
  * @noextend This interface is not intended to be extended by clients.
  * @noimplement This interface is not intended to be implemented by clients.
  */
-public interface IDBDelta extends IDBNamedElement, IContainer<IDBDelta>, Comparable<IDBDelta>, Serializable
+public interface IDBDelta extends IDBNamedElement, IContainer<IDBDelta>, Comparable<IDBDelta>
 {
   public DeltaType getDeltaType();
 
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/DBDatabase.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/DBDatabase.java
index 2f3541b593..09f7973580 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/DBDatabase.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/DBDatabase.java
@@ -16,8 +16,6 @@ import org.eclipse.net4j.db.IDBConnectionProvider;
 import org.eclipse.net4j.db.IDBDatabase;
 import org.eclipse.net4j.db.IDBTransaction;
 import org.eclipse.net4j.db.ddl.IDBSchema;
-import org.eclipse.net4j.db.ddl.IDBSchemaElement;
-import org.eclipse.net4j.db.ddl.IDBTable;
 import org.eclipse.net4j.db.ddl.delta.IDBSchemaDelta;
 import org.eclipse.net4j.internal.db.ddl.delta.DBSchemaDelta;
 import org.eclipse.net4j.spi.db.DBAdapter;
@@ -25,8 +23,6 @@ import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
 import org.eclipse.net4j.util.WrappedException;
 import org.eclipse.net4j.util.container.SetContainer;
 import org.eclipse.net4j.util.event.Event;
-import org.eclipse.net4j.util.event.IEvent;
-import org.eclipse.net4j.util.event.IListener;
 
 import java.sql.Connection;
 import java.sql.SQLException;
@@ -114,80 +110,22 @@ public final class DBDatabase extends SetContainer<IDBTransaction> implements ID
     return schemaTransaction;
   }
 
-  public void ensureSchemaElement(RunnableWithSchema updateRunnable, final RunnableWithSchema commitRunnable)
+  public void updateSchema(RunnableWithSchema runnable)
   {
-    if (schemaTransaction != null)
+    DBSchemaTransaction schemaTransaction = openSchemaTransaction();
+
+    try
     {
       IDBSchema workingCopy = schemaTransaction.getWorkingCopy();
-      updateRunnable.run(workingCopy);
-
-      if (commitRunnable != null)
-      {
-        addListener(new IListener()
-        {
-          public void notifyEvent(IEvent event)
-          {
-            if (event instanceof SchemaChangedEvent)
-            {
-              commitRunnable.run(schema);
-              removeListener(this);
-            }
-          }
-        });
-      }
+      runnable.run(workingCopy);
+      schemaTransaction.commit();
     }
-    else
+    finally
     {
-      if (commitRunnable != null)
-      {
-        commitRunnable.run(schema);
-      }
+      schemaTransaction.close();
     }
   }
 
-  public <T extends IDBSchemaElement, P extends IDBSchemaElement> T ensureSchemaElement(P parent, Class<T> type,
-      String name, RunnableWithSchemaElement<T, P> runnable)
-  {
-    T element = parent.getElement(type, name);
-    if (element == null)
-    {
-      DBSchemaTransaction schemaTransaction = openSchemaTransaction();
-
-      try
-      {
-        IDBSchema workingCopy = schemaTransaction.getWorkingCopy();
-        P parentCopy = workingCopy.findElement(parent);
-
-        T elementCopy = runnable.run(parentCopy, name);
-
-        schemaTransaction.commit();
-        if (elementCopy != null)
-        {
-          element = parent.getSchema().findElement(elementCopy);
-        }
-      }
-      finally
-      {
-        schemaTransaction.close();
-      }
-    }
-
-    return element;
-  }
-
-  public IDBTable ensureTable(String name, final RunnableWithTable runnable)
-  {
-    return ensureSchemaElement(schema, IDBTable.class, name, new RunnableWithSchemaElement<IDBTable, IDBSchema>()
-    {
-      public IDBTable run(IDBSchema parent, String name)
-      {
-        IDBTable table = parent.addTable(name);
-        runnable.run(table);
-        return table;
-      }
-    });
-  }
-
   public DBTransaction openTransaction()
   {
     DBTransaction transaction = new DBTransaction(this);
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/DBSchemaTransaction.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/DBSchemaTransaction.java
index 22b14e0b56..2e14a1c846 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/DBSchemaTransaction.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/DBSchemaTransaction.java
@@ -17,6 +17,8 @@ import org.eclipse.net4j.db.IDBSchemaTransaction;
 import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.delta.IDBDeltaVisitor;
 import org.eclipse.net4j.db.ddl.delta.IDBSchemaDelta;
+import org.eclipse.net4j.internal.db.ddl.DelegatingDBSchema;
+import org.eclipse.net4j.internal.db.ddl.DelegatingDBSchemaElement;
 import org.eclipse.net4j.internal.db.ddl.delta.DBSchemaDelta;
 import org.eclipse.net4j.spi.db.DBAdapter;
 import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
@@ -42,7 +44,8 @@ public final class DBSchemaTransaction implements IDBSchemaTransaction, Runnable
     this.database = database;
 
     oldSchema = database.getSchema();
-    workingCopy = DBUtil.copySchema(oldSchema);
+    IDBSchema copy = DBUtil.copySchema(oldSchema);
+    workingCopy = DelegatingDBSchemaElement.wrap(copy);
   }
 
   public DBDatabase getDatabase()
@@ -117,6 +120,8 @@ public final class DBSchemaTransaction implements IDBSchemaTransaction, Runnable
 
       DBAdapter adapter = database.getAdapter();
       adapter.updateSchema(connection, oldSchema, delta);
+
+      ((DelegatingDBSchema)workingCopy).setDelegate(oldSchema);
     }
     finally
     {
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBField.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBField.java
index 9fc5ef8cf4..e2414bcfd3 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBField.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBField.java
@@ -11,6 +11,7 @@
 package org.eclipse.net4j.internal.db.ddl;
 
 import org.eclipse.net4j.db.DBType;
+import org.eclipse.net4j.db.ddl.IDBField;
 import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.IDBSchemaElement;
 import org.eclipse.net4j.db.ddl.IDBSchemaVisitor;
@@ -100,6 +101,12 @@ public class DBField extends DBSchemaElement implements InternalDBField
   {
   }
 
+  @Override
+  public IDBField getWrapper()
+  {
+    return (IDBField)super.getWrapper();
+  }
+
   public SchemaElementType getSchemaElementType()
   {
     return SchemaElementType.FIELD;
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBIndex.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBIndex.java
index 1c385c8faf..239c3e90d5 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBIndex.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBIndex.java
@@ -64,6 +64,12 @@ public class DBIndex extends DBSchemaElement implements InternalDBIndex
   {
   }
 
+  @Override
+  public IDBIndex getWrapper()
+  {
+    return (IDBIndex)super.getWrapper();
+  }
+
   public SchemaElementType getSchemaElementType()
   {
     return SchemaElementType.INDEX;
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBIndexField.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBIndexField.java
index f961eead99..09ea2a2c23 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBIndexField.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBIndexField.java
@@ -12,6 +12,7 @@ package org.eclipse.net4j.internal.db.ddl;
 
 import org.eclipse.net4j.db.ddl.IDBField;
 import org.eclipse.net4j.db.ddl.IDBIndex;
+import org.eclipse.net4j.db.ddl.IDBIndexField;
 import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.IDBSchemaElement;
 import org.eclipse.net4j.db.ddl.IDBSchemaVisitor;
@@ -49,6 +50,12 @@ public class DBIndexField extends DBSchemaElement implements InternalDBIndexFiel
   {
   }
 
+  @Override
+  public IDBIndexField getWrapper()
+  {
+    return (IDBIndexField)super.getWrapper();
+  }
+
   public SchemaElementType getSchemaElementType()
   {
     return SchemaElementType.INDEX_FIELD;
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBNamedElement.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBNamedElement.java
index d903aba5b8..1920bf2637 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBNamedElement.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBNamedElement.java
@@ -52,7 +52,7 @@ public abstract class DBNamedElement extends DBElement implements InternalDBName
   }
 
   @Override
-  public final boolean equals(Object obj)
+  public boolean equals(Object obj)
   {
     if (obj == this)
     {
@@ -69,7 +69,7 @@ public abstract class DBNamedElement extends DBElement implements InternalDBName
   }
 
   @Override
-  public final int hashCode()
+  public int hashCode()
   {
     return name.hashCode();
   }
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBSchema.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBSchema.java
index 23b7d35797..ac3c7c35bc 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBSchema.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBSchema.java
@@ -93,6 +93,12 @@ public class DBSchema extends DBSchemaElement implements InternalDBSchema
   {
   }
 
+  @Override
+  public IDBSchema getWrapper()
+  {
+    return (IDBSchema)super.getWrapper();
+  }
+
   /**
    * @since 4.2
    */
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBSchemaElement.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBSchemaElement.java
index ca8a67bc73..ee998d872c 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBSchemaElement.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBSchemaElement.java
@@ -35,6 +35,8 @@ public abstract class DBSchemaElement extends DBNamedElement implements Internal
 
   private transient IDBSchemaElement[] elements;
 
+  private transient IDBSchemaElement wrapper;
+
   public DBSchemaElement(String name)
   {
     super(name);
@@ -47,6 +49,33 @@ public abstract class DBSchemaElement extends DBNamedElement implements Internal
   {
   }
 
+  public IDBSchemaElement getWrapper()
+  {
+    return wrapper;
+  }
+
+  public final void setWrapper(IDBSchemaElement wrapper)
+  {
+    this.wrapper = wrapper;
+  }
+
+  @Override
+  public final boolean equals(Object obj)
+  {
+    if (super.equals(obj))
+    {
+      return getSchemaElementType() == ((IDBSchemaElement)obj).getSchemaElementType();
+    }
+
+    return false;
+  }
+
+  @Override
+  public final int hashCode()
+  {
+    return super.hashCode() ^ getSchemaElementType().hashCode();
+  }
+
   public final int compareTo(IDBSchemaElement element2)
   {
     int result = getSchemaElementType().compareTo(element2.getSchemaElementType());
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBTable.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBTable.java
index 6adb743e1a..c41339d3b6 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBTable.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DBTable.java
@@ -17,6 +17,7 @@ import org.eclipse.net4j.db.ddl.IDBIndex;
 import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.IDBSchemaElement;
 import org.eclipse.net4j.db.ddl.IDBSchemaVisitor;
+import org.eclipse.net4j.db.ddl.IDBTable;
 import org.eclipse.net4j.db.ddl.SchemaElementNotFoundException;
 import org.eclipse.net4j.spi.db.ddl.InternalDBField;
 import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
@@ -52,6 +53,12 @@ public class DBTable extends DBSchemaElement implements InternalDBTable
   {
   }
 
+  @Override
+  public IDBTable getWrapper()
+  {
+    return (IDBTable)super.getWrapper();
+  }
+
   public SchemaElementType getSchemaElementType()
   {
     return SchemaElementType.TABLE;
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBField.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBField.java
new file mode 100644
index 0000000000..da565560f2
--- /dev/null
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBField.java
@@ -0,0 +1,114 @@
+/*
+ * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.net4j.internal.db.ddl;
+
+import org.eclipse.net4j.db.DBType;
+import org.eclipse.net4j.db.ddl.IDBField;
+import org.eclipse.net4j.db.ddl.IDBTable;
+import org.eclipse.net4j.spi.db.ddl.InternalDBField;
+
+/**
+ * @author Eike Stepper
+ */
+public final class DelegatingDBField extends DelegatingDBSchemaElement implements InternalDBField
+{
+  DelegatingDBField(InternalDBField delegate)
+  {
+    super(delegate);
+  }
+
+  @Override
+  public InternalDBField getDelegate()
+  {
+    return (InternalDBField)super.getDelegate();
+  }
+
+  public IDBField getWrapper()
+  {
+    return this;
+  }
+
+  public int getPosition()
+  {
+    return getDelegate().getPosition();
+  }
+
+  public void setPosition(int position)
+  {
+    getDelegate().setPosition(position);
+  }
+
+  public Exception getConstructionStackTrace()
+  {
+    return getDelegate().getConstructionStackTrace();
+  }
+
+  @Override
+  public IDBTable getParent()
+  {
+    return wrap(getDelegate().getParent());
+  }
+
+  public IDBTable getTable()
+  {
+    return wrap(getDelegate().getTable());
+  }
+
+  public DBType getType()
+  {
+    return getDelegate().getType();
+  }
+
+  public void setType(DBType type)
+  {
+    getDelegate().setType(type);
+  }
+
+  public int getPrecision()
+  {
+    return getDelegate().getPrecision();
+  }
+
+  public void setPrecision(int precision)
+  {
+    getDelegate().setPrecision(precision);
+  }
+
+  public int getScale()
+  {
+    return getDelegate().getScale();
+  }
+
+  public void setScale(int scale)
+  {
+    getDelegate().setScale(scale);
+  }
+
+  public boolean isNotNull()
+  {
+    return getDelegate().isNotNull();
+  }
+
+  public void setNotNull(boolean notNull)
+  {
+    getDelegate().setNotNull(notNull);
+  }
+
+  public String formatPrecision()
+  {
+    return getDelegate().formatPrecision();
+  }
+
+  public String formatPrecisionAndScale()
+  {
+    return getDelegate().formatPrecisionAndScale();
+  }
+}
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBIndex.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBIndex.java
new file mode 100644
index 0000000000..d70721d5fc
--- /dev/null
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBIndex.java
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.net4j.internal.db.ddl;
+
+import org.eclipse.net4j.db.ddl.IDBField;
+import org.eclipse.net4j.db.ddl.IDBIndex;
+import org.eclipse.net4j.db.ddl.IDBIndexField;
+import org.eclipse.net4j.db.ddl.IDBSchemaElement;
+import org.eclipse.net4j.db.ddl.IDBTable;
+import org.eclipse.net4j.db.ddl.SchemaElementNotFoundException;
+import org.eclipse.net4j.spi.db.ddl.InternalDBIndex;
+
+/**
+ * @author Eike Stepper
+ */
+public final class DelegatingDBIndex extends DelegatingDBSchemaElement implements InternalDBIndex
+{
+  DelegatingDBIndex(InternalDBIndex delegate)
+  {
+    super(delegate);
+  }
+
+  @Override
+  public InternalDBIndex getDelegate()
+  {
+    return (InternalDBIndex)super.getDelegate();
+  }
+
+  @Override
+  public void setDelegate(IDBSchemaElement delegate)
+  {
+    IDBIndexField[] wrapperIndexFields = getIndexFields();
+
+    IDBIndex delegateIndex = (IDBIndex)delegate;
+    super.setDelegate(delegateIndex);
+
+    for (IDBIndexField wrapperIndexField : wrapperIndexFields)
+    {
+      IDBIndexField delegateIndexField = delegateIndex.getIndexField(wrapperIndexField.getName());
+      ((DelegatingDBSchemaElement)wrapperIndexField).setDelegate(delegateIndexField);
+    }
+  }
+
+  public IDBIndex getWrapper()
+  {
+    return this;
+  }
+
+  @Override
+  public IDBTable getParent()
+  {
+    return wrap(getDelegate().getParent());
+  }
+
+  public IDBTable getTable()
+  {
+    return wrap(getDelegate().getTable());
+  }
+
+  public Type getType()
+  {
+    return getDelegate().getType();
+  }
+
+  public void setType(Type type)
+  {
+    getDelegate().setType(type);
+  }
+
+  public void removeIndexField(IDBIndexField indexFieldToRemove)
+  {
+    getDelegate().removeIndexField(unwrap(indexFieldToRemove));
+  }
+
+  @Deprecated
+  public int getPosition()
+  {
+    return getDelegate().getPosition();
+  }
+
+  public IDBIndexField addIndexField(IDBField field)
+  {
+    return wrap(getDelegate().addIndexField(unwrap(field)));
+  }
+
+  public IDBIndexField addIndexField(String name) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().addIndexField(name));
+  }
+
+  public IDBIndexField getIndexFieldSafe(String name) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().getIndexFieldSafe(name));
+  }
+
+  public IDBIndexField getIndexField(String name)
+  {
+    return wrap(getDelegate().getIndexField(name));
+  }
+
+  public IDBIndexField getIndexField(int position)
+  {
+    return wrap(getDelegate().getIndexField(position));
+  }
+
+  public IDBField getFieldSafe(String name) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().getFieldSafe(name));
+  }
+
+  public IDBField getField(String name)
+  {
+    return wrap(getDelegate().getField(name));
+  }
+
+  public IDBField getField(int position)
+  {
+    return wrap(getDelegate().getField(position));
+  }
+
+  public int getFieldCount()
+  {
+    return getDelegate().getFieldCount();
+  }
+
+  public IDBIndexField[] getIndexFields()
+  {
+    return wrap(getDelegate().getIndexFields(), IDBIndexField.class);
+  }
+
+  public IDBField[] getFields()
+  {
+    return wrap(getDelegate().getFields(), IDBField.class);
+  }
+}
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBIndexField.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBIndexField.java
new file mode 100644
index 0000000000..b688f2de66
--- /dev/null
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBIndexField.java
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.net4j.internal.db.ddl;
+
+import org.eclipse.net4j.db.ddl.IDBField;
+import org.eclipse.net4j.db.ddl.IDBIndex;
+import org.eclipse.net4j.db.ddl.IDBIndexField;
+import org.eclipse.net4j.spi.db.ddl.InternalDBIndexField;
+
+/**
+ * @author Eike Stepper
+ */
+public final class DelegatingDBIndexField extends DelegatingDBSchemaElement implements InternalDBIndexField
+{
+  DelegatingDBIndexField(InternalDBIndexField delegate)
+  {
+    super(delegate);
+  }
+
+  @Override
+  public InternalDBIndexField getDelegate()
+  {
+    return (InternalDBIndexField)super.getDelegate();
+  }
+
+  public IDBIndexField getWrapper()
+  {
+    return this;
+  }
+
+  public int getPosition()
+  {
+    return getDelegate().getPosition();
+  }
+
+  public void setPosition(int position)
+  {
+    getDelegate().setPosition(position);
+  }
+
+  @Override
+  public IDBIndex getParent()
+  {
+    return wrap(getDelegate().getParent());
+  }
+
+  public IDBIndex getIndex()
+  {
+    return wrap(getDelegate().getIndex());
+  }
+
+  public IDBField getField()
+  {
+    return wrap(getDelegate().getField());
+  }
+}
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBSchema.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBSchema.java
new file mode 100644
index 0000000000..8934d240a3
--- /dev/null
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBSchema.java
@@ -0,0 +1,191 @@
+/*
+ * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.net4j.internal.db.ddl;
+
+import org.eclipse.net4j.db.DBException;
+import org.eclipse.net4j.db.IDBAdapter;
+import org.eclipse.net4j.db.IDBConnectionProvider;
+import org.eclipse.net4j.db.ddl.IDBField;
+import org.eclipse.net4j.db.ddl.IDBIndex.Type;
+import org.eclipse.net4j.db.ddl.IDBSchema;
+import org.eclipse.net4j.db.ddl.IDBSchemaElement;
+import org.eclipse.net4j.db.ddl.IDBTable;
+import org.eclipse.net4j.db.ddl.SchemaElementNotFoundException;
+import org.eclipse.net4j.db.ddl.delta.IDBSchemaDelta;
+import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
+
+import javax.sql.DataSource;
+
+import java.io.PrintStream;
+import java.sql.Connection;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * @author Eike Stepper
+ */
+public final class DelegatingDBSchema extends DelegatingDBSchemaElement implements InternalDBSchema
+{
+  DelegatingDBSchema(InternalDBSchema delegate)
+  {
+    super(delegate);
+  }
+
+  @Override
+  public InternalDBSchema getDelegate()
+  {
+    return (InternalDBSchema)super.getDelegate();
+  }
+
+  @Override
+  public void setDelegate(IDBSchemaElement delegate)
+  {
+    IDBTable[] wrapperTables = getTables();
+
+    IDBSchema delegateSchema = (IDBSchema)delegate;
+    super.setDelegate(delegateSchema);
+
+    for (IDBTable wrapperTable : wrapperTables)
+    {
+      ((DelegatingDBSchemaElement)wrapperTable).setDelegate(delegateSchema.getTable(wrapperTable.getName()));
+    }
+  }
+
+  public IDBSchema getWrapper()
+  {
+    return this;
+  }
+
+  @Override
+  public IDBSchemaElement getParent()
+  {
+    return wrap(getDelegate().getParent());
+  }
+
+  public IDBTable addTable(String name)
+  {
+    return wrap(getDelegate().addTable(name));
+  }
+
+  public IDBTable removeTable(String name)
+  {
+    return wrap(getDelegate().removeTable(name));
+  }
+
+  public String createIndexName(IDBTable table, Type type, IDBField[] fields, int position)
+  {
+    return getDelegate().createIndexName(unwrap(table), type, fields, position);
+  }
+
+  public boolean isLocked()
+  {
+    return getDelegate().isLocked();
+  }
+
+  public boolean lock()
+  {
+    return getDelegate().lock();
+  }
+
+  @SuppressWarnings("unchecked")
+  public <T extends IDBSchemaElement> T findElement(IDBSchemaElement prototype)
+  {
+    T unwrapped = (T)unwrap(prototype);
+    return (T)wrap(getDelegate().findElement(unwrapped));
+  }
+
+  public boolean unlock()
+  {
+    return getDelegate().unlock();
+  }
+
+  public void assertUnlocked() throws DBException
+  {
+    getDelegate().assertUnlocked();
+  }
+
+  public IDBTable getTableSafe(String name) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().getTableSafe(name));
+  }
+
+  public IDBTable getTable(String name)
+  {
+    return wrap(getDelegate().getTable(name));
+  }
+
+  public IDBTable[] getTables()
+  {
+    IDBTable[] tables = getDelegate().getTables();
+    IDBTable[] wrappers = new IDBTable[tables.length];
+    for (int i = 0; i < tables.length; i++)
+    {
+      wrappers[i] = wrap(tables[i]);
+    }
+
+    return wrappers;
+  }
+
+  public Set<IDBTable> create(IDBAdapter dbAdapter, Connection connection) throws DBException
+  {
+    return wrap(getDelegate().create(dbAdapter, connection));
+  }
+
+  public Set<IDBTable> create(IDBAdapter dbAdapter, DataSource dataSource) throws DBException
+  {
+    return wrap(getDelegate().create(dbAdapter, dataSource));
+  }
+
+  public Set<IDBTable> create(IDBAdapter dbAdapter, IDBConnectionProvider connectionProvider) throws DBException
+  {
+    return wrap(getDelegate().create(dbAdapter, connectionProvider));
+  }
+
+  public void drop(IDBAdapter dbAdapter, Connection connection) throws DBException
+  {
+    getDelegate().drop(dbAdapter, connection);
+  }
+
+  public void drop(IDBAdapter dbAdapter, DataSource dataSource) throws DBException
+  {
+    getDelegate().drop(dbAdapter, dataSource);
+  }
+
+  public void drop(IDBAdapter dbAdapter, IDBConnectionProvider connectionProvider) throws DBException
+  {
+    getDelegate().drop(dbAdapter, connectionProvider);
+  }
+
+  public void export(Connection connection, PrintStream out) throws DBException
+  {
+    getDelegate().export(connection, out);
+  }
+
+  public void export(DataSource dataSource, PrintStream out) throws DBException
+  {
+    getDelegate().export(dataSource, out);
+  }
+
+  public void export(IDBConnectionProvider connectionProvider, PrintStream out) throws DBException
+  {
+    getDelegate().export(connectionProvider, out);
+  }
+
+  public IDBSchemaDelta compare(IDBSchema oldSchema)
+  {
+    return getDelegate().compare(unwrap(oldSchema));
+  }
+
+  private static Set<IDBTable> wrap(Set<IDBTable> tables)
+  {
+    return wrap(tables, new HashSet<IDBTable>());
+  }
+}
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBSchemaElement.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBSchemaElement.java
new file mode 100644
index 0000000000..667b4e8bc2
--- /dev/null
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBSchemaElement.java
@@ -0,0 +1,284 @@
+/*
+ * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.net4j.internal.db.ddl;
+
+import org.eclipse.net4j.db.ddl.IDBSchema;
+import org.eclipse.net4j.db.ddl.IDBSchemaElement;
+import org.eclipse.net4j.db.ddl.IDBSchemaVisitor;
+import org.eclipse.net4j.spi.db.ddl.InternalDBField;
+import org.eclipse.net4j.spi.db.ddl.InternalDBIndex;
+import org.eclipse.net4j.spi.db.ddl.InternalDBIndexField;
+import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
+import org.eclipse.net4j.spi.db.ddl.InternalDBSchemaElement;
+import org.eclipse.net4j.spi.db.ddl.InternalDBTable;
+import org.eclipse.net4j.util.event.IListener;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.util.Properties;
+import java.util.Set;
+
+/**
+ * @author Eike Stepper
+ */
+public abstract class DelegatingDBSchemaElement implements InternalDBSchemaElement
+{
+  private InternalDBSchemaElement delegate;
+
+  DelegatingDBSchemaElement(InternalDBSchemaElement delegate)
+  {
+    this.delegate = delegate;
+  }
+
+  public InternalDBSchemaElement getDelegate()
+  {
+    return delegate;
+  }
+
+  public void setDelegate(IDBSchemaElement delegate)
+  {
+    if (this.delegate != null)
+    {
+      this.delegate.setWrapper(null);
+    }
+
+    this.delegate = (InternalDBSchemaElement)delegate;
+
+    if (this.delegate != null)
+    {
+      this.delegate.setWrapper(this);
+    }
+  }
+
+  public final void setWrapper(IDBSchemaElement wrapper)
+  {
+    throw new UnsupportedOperationException();
+  }
+
+  public IDBSchemaElement getParent()
+  {
+    return wrap(getDelegate().getParent());
+  }
+
+  public final String getName()
+  {
+    return getDelegate().getName();
+  }
+
+  @Deprecated
+  public final void setName(String name)
+  {
+    getDelegate().setName(name);
+  }
+
+  public final <T extends IDBSchemaElement> T getElement(Class<T> type, String name)
+  {
+    return getDelegate().getElement(type, name);
+  }
+
+  public final String getFullName()
+  {
+    return getDelegate().getFullName();
+  }
+
+  public final IDBSchema getSchema()
+  {
+    return wrap(getDelegate().getSchema());
+  }
+
+  public final Properties getProperties()
+  {
+    return getDelegate().getProperties();
+  }
+
+  public final String dumpToString()
+  {
+    return getDelegate().dumpToString();
+  }
+
+  public final void dump()
+  {
+    getDelegate().dump();
+  }
+
+  public final void dump(Writer writer) throws IOException
+  {
+    getDelegate().dump(writer);
+  }
+
+  public final SchemaElementType getSchemaElementType()
+  {
+    return getDelegate().getSchemaElementType();
+  }
+
+  public final boolean isEmpty()
+  {
+    return getDelegate().isEmpty();
+  }
+
+  public final IDBSchemaElement[] getElements()
+  {
+    IDBSchemaElement[] elements = getDelegate().getElements();
+    IDBSchemaElement[] wrappers = new IDBSchemaElement[elements.length];
+    for (int i = 0; i < elements.length; i++)
+    {
+      wrappers[i] = wrap(elements[i]);
+    }
+
+    return wrappers;
+  }
+
+  public final void accept(IDBSchemaVisitor visitor)
+  {
+    getDelegate().accept(visitor);
+  }
+
+  public final void remove()
+  {
+    getDelegate().remove();
+  }
+
+  public final void addListener(IListener listener)
+  {
+    getDelegate().addListener(listener);
+  }
+
+  public final IListener[] getListeners()
+  {
+    return getDelegate().getListeners();
+  }
+
+  public final boolean hasListeners()
+  {
+    return getDelegate().hasListeners();
+  }
+
+  public final void removeListener(IListener listener)
+  {
+    getDelegate().removeListener(listener);
+  }
+
+  @Override
+  public int hashCode()
+  {
+    return getDelegate().hashCode();
+  }
+
+  @Override
+  public boolean equals(Object obj)
+  {
+    return getDelegate().equals(obj);
+  }
+
+  public final int compareTo(IDBSchemaElement o)
+  {
+    return getDelegate().compareTo(unwrap(o));
+  }
+
+  @Override
+  public String toString()
+  {
+    return getDelegate().toString();
+  }
+
+  public static <T extends IDBSchemaElement> T wrap(T delegate)
+  {
+    if (delegate == null || delegate instanceof DelegatingDBSchemaElement)
+    {
+      return delegate;
+    }
+
+    InternalDBSchemaElement internalDelegate = (InternalDBSchemaElement)delegate;
+    IDBSchemaElement wrapper = internalDelegate.getWrapper();
+    if (wrapper == null)
+    {
+      SchemaElementType schemaElementType = internalDelegate.getSchemaElementType();
+      switch (schemaElementType)
+      {
+      case SCHEMA:
+        wrapper = new DelegatingDBSchema((InternalDBSchema)internalDelegate);
+        break;
+
+      case TABLE:
+        wrapper = new DelegatingDBTable((InternalDBTable)internalDelegate);
+        break;
+
+      case FIELD:
+        wrapper = new DelegatingDBField((InternalDBField)internalDelegate);
+        break;
+
+      case INDEX:
+        wrapper = new DelegatingDBIndex((InternalDBIndex)internalDelegate);
+        break;
+
+      case INDEX_FIELD:
+        wrapper = new DelegatingDBIndexField((InternalDBIndexField)internalDelegate);
+        break;
+
+      default:
+        throw new IllegalStateException("Illegal schema element type: " + schemaElementType);
+      }
+
+      internalDelegate.setWrapper(wrapper);
+    }
+
+    @SuppressWarnings("unchecked")
+    T result = (T)wrapper;
+    return result;
+  }
+
+  public static <T extends IDBSchemaElement> T[] wrap(T[] delegates, Class<T> type)
+  {
+    @SuppressWarnings("unchecked")
+    T[] wrappers = (T[])java.lang.reflect.Array.newInstance(type, delegates.length);
+    for (int i = 0; i < delegates.length; i++)
+    {
+      T wrapper = wrap(delegates[i]);
+      wrappers[i] = wrapper;
+    }
+
+    return wrappers;
+  }
+
+  public static <T extends IDBSchemaElement> Set<T> wrap(Set<T> delegates, Set<T> wrappers)
+  {
+    for (T delegate : delegates)
+    {
+      wrappers.add(wrap(delegate));
+    }
+
+    return wrappers;
+  }
+
+  public static <T extends IDBSchemaElement> T unwrap(T wrapper)
+  {
+    if (wrapper instanceof DelegatingDBSchemaElement)
+    {
+      @SuppressWarnings("unchecked")
+      T delegate = (T)((DelegatingDBSchemaElement)wrapper).getDelegate();
+      return delegate;
+    }
+
+    return wrapper;
+  }
+
+  public static <T extends IDBSchemaElement> T[] unwrap(T[] wrappers, Class<T> type)
+  {
+    @SuppressWarnings("unchecked")
+    T[] delegates = (T[])java.lang.reflect.Array.newInstance(type, wrappers.length);
+    for (int i = 0; i < wrappers.length; i++)
+    {
+      delegates[i] = unwrap(wrappers[i]);
+    }
+
+    return delegates;
+  }
+}
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBTable.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBTable.java
new file mode 100644
index 0000000000..7fa91fac9a
--- /dev/null
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/DelegatingDBTable.java
@@ -0,0 +1,206 @@
+/*
+ * Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.net4j.internal.db.ddl;
+
+import org.eclipse.net4j.db.DBType;
+import org.eclipse.net4j.db.ddl.IDBField;
+import org.eclipse.net4j.db.ddl.IDBIndex;
+import org.eclipse.net4j.db.ddl.IDBIndex.Type;
+import org.eclipse.net4j.db.ddl.IDBSchema;
+import org.eclipse.net4j.db.ddl.IDBSchemaElement;
+import org.eclipse.net4j.db.ddl.IDBTable;
+import org.eclipse.net4j.db.ddl.SchemaElementNotFoundException;
+import org.eclipse.net4j.spi.db.ddl.InternalDBTable;
+
+/**
+ * @author Eike Stepper
+ */
+public final class DelegatingDBTable extends DelegatingDBSchemaElement implements InternalDBTable
+{
+  DelegatingDBTable(InternalDBTable delegate)
+  {
+    super(delegate);
+  }
+
+  @Override
+  public InternalDBTable getDelegate()
+  {
+    return (InternalDBTable)super.getDelegate();
+  }
+
+  @Override
+  public void setDelegate(IDBSchemaElement delegate)
+  {
+    IDBField[] wrapperFields = getFields();
+    IDBIndex[] wrapperIndices = getIndices();
+
+    IDBTable delegateTable = (IDBTable)delegate;
+    super.setDelegate(delegateTable);
+
+    for (IDBField wrapperField : wrapperFields)
+    {
+      IDBField delegateField = delegateTable.getField(wrapperField.getName());
+      ((DelegatingDBSchemaElement)wrapperField).setDelegate(delegateField);
+    }
+
+    for (IDBIndex wrapperIndex : wrapperIndices)
+    {
+      IDBIndex delegateIndex = delegateTable.getIndex(wrapperIndex.getName());
+      ((DelegatingDBSchemaElement)wrapperIndex).setDelegate(delegateIndex);
+    }
+  }
+
+  public IDBTable getWrapper()
+  {
+    return this;
+  }
+
+  @Override
+  public IDBSchema getParent()
+  {
+    return wrap(getDelegate().getParent());
+  }
+
+  public IDBField addField(String name, DBType type)
+  {
+    return wrap(getDelegate().addField(name, type));
+  }
+
+  public IDBField addField(String name, DBType type, boolean notNull)
+  {
+    return wrap(getDelegate().addField(name, type, notNull));
+  }
+
+  public void removeField(IDBField fieldToRemove)
+  {
+    getDelegate().removeField(unwrap(fieldToRemove));
+  }
+
+  public IDBField addField(String name, DBType type, int precision)
+  {
+    return wrap(getDelegate().addField(name, type, precision));
+  }
+
+  public void removeIndex(IDBIndex indexToRemove)
+  {
+    getDelegate().removeIndex(unwrap(indexToRemove));
+  }
+
+  public IDBField addField(String name, DBType type, int precision, boolean notNull)
+  {
+    return wrap(getDelegate().addField(name, type, precision, notNull));
+  }
+
+  public IDBField addField(String name, DBType type, int precision, int scale)
+  {
+    return wrap(getDelegate().addField(name, type, precision, scale));
+  }
+
+  public IDBField addField(String name, DBType type, int precision, int scale, boolean notNull)
+  {
+    return wrap(getDelegate().addField(name, type, precision, scale, notNull));
+  }
+
+  public IDBField getFieldSafe(String name) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().getFieldSafe(name));
+  }
+
+  public IDBField getField(String name)
+  {
+    return wrap(getDelegate().getField(name));
+  }
+
+  public IDBField getField(int position)
+  {
+    return wrap(getDelegate().getField(position));
+  }
+
+  public int getFieldCount()
+  {
+    return getDelegate().getFieldCount();
+  }
+
+  public IDBField[] getFields()
+  {
+    return wrap(getDelegate().getFields(), IDBField.class);
+  }
+
+  public IDBField[] getFields(String... fieldNames) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().getFields(fieldNames), IDBField.class);
+  }
+
+  public IDBIndex addIndex(String name, Type type, IDBField... fields)
+  {
+    return wrap(getDelegate().addIndex(name, type, unwrap(fields, IDBField.class)));
+  }
+
+  public IDBIndex addIndex(String name, Type type, String... fieldNames) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().addIndex(name, type, fieldNames));
+  }
+
+  public IDBIndex addIndexEmpty(String name, Type type)
+  {
+    return wrap(getDelegate().addIndexEmpty(name, type));
+  }
+
+  public IDBIndex addIndex(Type type, IDBField... fields)
+  {
+    return wrap(getDelegate().addIndex(type, unwrap(fields, IDBField.class)));
+  }
+
+  public IDBIndex addIndex(Type type, String... fieldNames) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().addIndex(type, fieldNames));
+  }
+
+  public IDBIndex addIndexEmpty(Type type)
+  {
+    return wrap(getDelegate().addIndexEmpty(type));
+  }
+
+  public IDBIndex getIndexSafe(String name) throws SchemaElementNotFoundException
+  {
+    return wrap(getDelegate().getIndexSafe(name));
+  }
+
+  public IDBIndex getIndex(String name)
+  {
+    return wrap(getDelegate().getIndex(name));
+  }
+
+  public IDBIndex getIndex(int position)
+  {
+    return wrap(getDelegate().getIndex(position));
+  }
+
+  public int getIndexCount()
+  {
+    return getDelegate().getIndexCount();
+  }
+
+  public IDBIndex[] getIndices()
+  {
+    return wrap(getDelegate().getIndices(), IDBIndex.class);
+  }
+
+  public IDBIndex getPrimaryKeyIndex()
+  {
+    return wrap(getDelegate().getPrimaryKeyIndex());
+  }
+
+  public String sqlInsert()
+  {
+    return getDelegate().sqlInsert();
+  }
+}
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBField.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBField.java
index 9a72c3f2b4..3916c1f244 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBField.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBField.java
@@ -20,6 +20,8 @@ import org.eclipse.net4j.db.ddl.IDBField;
  */
 public interface InternalDBField extends IDBField, InternalDBSchemaElement
 {
+  public IDBField getWrapper();
+
   public void setPosition(int position);
 
   public Exception getConstructionStackTrace();
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBIndex.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBIndex.java
index 062351b33e..6feadf6ac9 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBIndex.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBIndex.java
@@ -23,5 +23,7 @@ public interface InternalDBIndex extends IDBIndex, InternalDBSchemaElement
 {
   public static final IDBIndexField[] NO_INDEX_FIELDS = {};
 
+  public IDBIndex getWrapper();
+
   public void removeIndexField(IDBIndexField indexFieldToRemove);
 }
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBIndexField.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBIndexField.java
index 28bd2dfff5..310c9e87c9 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBIndexField.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBIndexField.java
@@ -20,5 +20,7 @@ import org.eclipse.net4j.db.ddl.IDBIndexField;
  */
 public interface InternalDBIndexField extends IDBIndexField, InternalDBSchemaElement
 {
+  public IDBIndexField getWrapper();
+
   public void setPosition(int position);
 }
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBSchema.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBSchema.java
index 12720dabfc..7a694bffc3 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBSchema.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBSchema.java
@@ -26,6 +26,8 @@ public interface InternalDBSchema extends IDBSchema, InternalDBSchemaElement
 {
   public static final IDBTable[] NO_TABLES = {};
 
+  public IDBSchema getWrapper();
+
   public IDBTable addTable(String name);
 
   public IDBTable removeTable(String name);
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBSchemaElement.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBSchemaElement.java
index e560758d9f..f7e3570b46 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBSchemaElement.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBSchemaElement.java
@@ -20,4 +20,7 @@ import org.eclipse.net4j.db.ddl.IDBSchemaElement;
  */
 public interface InternalDBSchemaElement extends IDBSchemaElement, InternalDBNamedElement
 {
+  public IDBSchemaElement getWrapper();
+
+  public void setWrapper(IDBSchemaElement wrapper);
 }
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBTable.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBTable.java
index 9456789f9b..89e1eeaf15 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBTable.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/ddl/InternalDBTable.java
@@ -26,6 +26,8 @@ public interface InternalDBTable extends IDBTable, InternalDBSchemaElement
 
   public static final IDBIndex[] NO_INDICES = {};
 
+  public IDBTable getWrapper();
+
   public void removeField(IDBField fieldToRemove);
 
   public void removeIndex(IDBIndex indexToRemove);
diff --git a/plugins/org.eclipse.net4j.examples.installer/examples/org.eclipse.net4j.jms.server.jdbc/src/org/eclipse/net4j/jms/server/internal/jdbc/JMSSchema.java b/plugins/org.eclipse.net4j.examples.installer/examples/org.eclipse.net4j.jms.server.jdbc/src/org/eclipse/net4j/jms/server/internal/jdbc/JMSSchema.java
index c3e9ea82bc..1fd4ae6de6 100644
--- a/plugins/org.eclipse.net4j.examples.installer/examples/org.eclipse.net4j.jms.server.jdbc/src/org/eclipse/net4j/jms/server/internal/jdbc/JMSSchema.java
+++ b/plugins/org.eclipse.net4j.examples.installer/examples/org.eclipse.net4j.jms.server.jdbc/src/org/eclipse/net4j/jms/server/internal/jdbc/JMSSchema.java
@@ -11,19 +11,19 @@
 package org.eclipse.net4j.jms.server.internal.jdbc;
 
 import org.eclipse.net4j.db.DBType;
+import org.eclipse.net4j.db.DBUtil;
 import org.eclipse.net4j.db.ddl.IDBField;
 import org.eclipse.net4j.db.ddl.IDBIndex;
+import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.IDBTable;
-import org.eclipse.net4j.spi.db.DBSchema;
+import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
 
 /**
  * @author Eike Stepper
  */
-public class JMSSchema extends DBSchema
+public class JMSSchema
 {
-  public static final JMSSchema INSTANCE = new JMSSchema();
-
-  private static final long serialVersionUID = 1L;
+  public static final IDBSchema INSTANCE = DBUtil.createSchema("JMS");
 
   /**
    * DBTable Destinations
@@ -63,13 +63,8 @@ public class JMSSchema extends DBSchema
       + " FROM " + DESTINATIONS + ", " + MESSAGES + " WHERE " + DESTINATIONS_NAME + "=" + MESSAGES_DESTINATION //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
       + " AND " + DESTINATIONS_NAME + "=?"; //$NON-NLS-1$ //$NON-NLS-2$
 
-  private JMSSchema()
-  {
-    super("JMS"); //$NON-NLS-1$
-  }
-
   static
   {
-    INSTANCE.lock();
+    ((InternalDBSchema)INSTANCE).lock();
   }
 }
diff --git a/plugins/org.eclipse.net4j.jms.server.jdbc/src/org/eclipse/net4j/jms/server/internal/jdbc/JMSSchema.java b/plugins/org.eclipse.net4j.jms.server.jdbc/src/org/eclipse/net4j/jms/server/internal/jdbc/JMSSchema.java
index c3e9ea82bc..1fd4ae6de6 100644
--- a/plugins/org.eclipse.net4j.jms.server.jdbc/src/org/eclipse/net4j/jms/server/internal/jdbc/JMSSchema.java
+++ b/plugins/org.eclipse.net4j.jms.server.jdbc/src/org/eclipse/net4j/jms/server/internal/jdbc/JMSSchema.java
@@ -11,19 +11,19 @@
 package org.eclipse.net4j.jms.server.internal.jdbc;
 
 import org.eclipse.net4j.db.DBType;
+import org.eclipse.net4j.db.DBUtil;
 import org.eclipse.net4j.db.ddl.IDBField;
 import org.eclipse.net4j.db.ddl.IDBIndex;
+import org.eclipse.net4j.db.ddl.IDBSchema;
 import org.eclipse.net4j.db.ddl.IDBTable;
-import org.eclipse.net4j.spi.db.DBSchema;
+import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
 
 /**
  * @author Eike Stepper
  */
-public class JMSSchema extends DBSchema
+public class JMSSchema
 {
-  public static final JMSSchema INSTANCE = new JMSSchema();
-
-  private static final long serialVersionUID = 1L;
+  public static final IDBSchema INSTANCE = DBUtil.createSchema("JMS");
 
   /**
    * DBTable Destinations
@@ -63,13 +63,8 @@ public class JMSSchema extends DBSchema
       + " FROM " + DESTINATIONS + ", " + MESSAGES + " WHERE " + DESTINATIONS_NAME + "=" + MESSAGES_DESTINATION //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
       + " AND " + DESTINATIONS_NAME + "=?"; //$NON-NLS-1$ //$NON-NLS-2$
 
-  private JMSSchema()
-  {
-    super("JMS"); //$NON-NLS-1$
-  }
-
   static
   {
-    INSTANCE.lock();
+    ((InternalDBSchema)INSTANCE).lock();
   }
 }