[474681] Add mapping strategy option to support index creation on all cross references

https://bugs.eclipse.org/bugs/show_bug.cgi?id=474681

27 files changed, 556 insertions, 54 deletions

diff --git a/features/org.eclipse.emf.cdo.server.db-feature/feature.xml b/features/org.eclipse.emf.cdo.server.db-feature/feature.xml
index d1c195260e..5e23707118 100644
--- a/features/org.eclipse.emf.cdo.server.db-feature/feature.xml
+++ b/features/org.eclipse.emf.cdo.server.db-feature/feature.xml
@@ -12,7 +12,7 @@
 <feature
       id="org.eclipse.emf.cdo.server.db"
       label="%featureName"
-      version="4.3.100.qualifier"
+      version="4.4.0.qualifier"
       provider-name="%providerName"
       license-feature="org.eclipse.emf.cdo.license"
       license-feature-version="0.0.0">
diff --git a/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/model/CDOFeatureType.java b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/model/CDOFeatureType.java
new file mode 100644
index 0000000000..4e733a45fd
--- /dev/null
+++ b/plugins/org.eclipse.emf.cdo.common/src/org/eclipse/emf/cdo/common/model/CDOFeatureType.java
@@ -0,0 +1,213 @@
+/*
+ * Copyright (c) 2004-2015 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.emf.cdo.common.model;
+
+import org.eclipse.emf.ecore.EAttribute;
+import org.eclipse.emf.ecore.EReference;
+import org.eclipse.emf.ecore.EStructuralFeature;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * @author Eike Stepper
+ * @since 4.5
+ */
+public enum CDOFeatureType
+{
+  NONE
+  {
+    @Override
+    public boolean matches(EStructuralFeature feature)
+    {
+      return false;
+    }
+  },
+
+  ALL
+  {
+    @Override
+    public boolean matches(EStructuralFeature feature)
+    {
+      return true;
+    }
+  },
+
+  ATTRIBUTE
+  {
+    @Override
+    public boolean matches(EStructuralFeature feature)
+    {
+      return feature instanceof EAttribute;
+    }
+  },
+
+  REFERENCE
+  {
+    @Override
+    public boolean matches(EStructuralFeature feature)
+    {
+      return feature instanceof EReference;
+    }
+  },
+
+  CONTAINER
+  {
+    @Override
+    public boolean matches(EStructuralFeature feature)
+    {
+      if (feature instanceof EReference)
+      {
+        EReference reference = (EReference)feature;
+        return reference.isContainer();
+      }
+
+      return false;
+    }
+  },
+
+  CONTAINMENT
+  {
+    @Override
+    public boolean matches(EStructuralFeature feature)
+    {
+      if (feature instanceof EReference)
+      {
+        EReference reference = (EReference)feature;
+        return reference.isContainment();
+      }
+
+      return false;
+    }
+  },
+
+  XREF
+  {
+    @Override
+    public boolean matches(EStructuralFeature feature)
+    {
+      if (feature instanceof EReference)
+      {
+        EReference reference = (EReference)feature;
+        return !reference.isContainer() && !reference.isContainment();
+      }
+
+      return false;
+    }
+  };
+
+  public abstract boolean matches(EStructuralFeature feature);
+
+  public static boolean matchesCombination(EStructuralFeature feature, Collection<CDOFeatureType> featureTypes)
+  {
+    if (featureTypes != null)
+    {
+      for (CDOFeatureType featureType : featureTypes)
+      {
+        if (featureType.matches(feature))
+        {
+          return true;
+        }
+      }
+    }
+
+    return false;
+  }
+
+  public static CDOFeatureType read(String str)
+  {
+    if (str != null)
+    {
+      str = str.trim().toUpperCase();
+
+      try
+      {
+        return valueOf(str);
+      }
+      catch (Exception ex)
+      {
+        //$FALL-THROUGH$
+      }
+    }
+
+    return NONE;
+  }
+
+  public static Set<CDOFeatureType> readCombination(String str)
+  {
+    if (str != null)
+    {
+      str = str.replace(' ', '|').replace(',', '|').replace(';', '|');
+
+      Set<CDOFeatureType> result = new HashSet<CDOFeatureType>();
+
+      for (String token : str.split("\\|"))
+      {
+        CDOFeatureType featureType = read(token);
+        if (featureType != NONE)
+        {
+          result.add(featureType);
+        }
+      }
+
+      return result;
+    }
+
+    return Collections.emptySet();
+  }
+
+  public static String writeCombination(Collection<CDOFeatureType> featureTypes)
+  {
+    if (featureTypes != null)
+    {
+      if (!(featureTypes instanceof Set))
+      {
+        featureTypes = new HashSet<CDOFeatureType>(featureTypes);
+      }
+
+      if (featureTypes.contains(ALL))
+      {
+        return ALL.toString();
+      }
+
+      if (featureTypes.contains(REFERENCE))
+      {
+        featureTypes.remove(CONTAINER);
+        featureTypes.remove(CONTAINMENT);
+        featureTypes.remove(XREF);
+      }
+
+      featureTypes.remove(NONE);
+
+      List<CDOFeatureType> list = new ArrayList<CDOFeatureType>(featureTypes);
+      Collections.sort(list);
+
+      StringBuilder result = new StringBuilder();
+      for (CDOFeatureType featureType : list)
+      {
+        if (result.length() != 0)
+        {
+          result.append("|");
+        }
+
+        result.append(featureType);
+      }
+
+      return result.toString();
+    }
+
+    return "";
+  }
+}
diff --git a/plugins/org.eclipse.emf.cdo.explorer/src/org/eclipse/emf/cdo/internal/explorer/checkouts/OfflineCDOCheckout.java b/plugins/org.eclipse.emf.cdo.explorer/src/org/eclipse/emf/cdo/internal/explorer/checkouts/OfflineCDOCheckout.java
index b01a1b018e..98fa3387ff 100644
--- a/plugins/org.eclipse.emf.cdo.explorer/src/org/eclipse/emf/cdo/internal/explorer/checkouts/OfflineCDOCheckout.java
+++ b/plugins/org.eclipse.emf.cdo.explorer/src/org/eclipse/emf/cdo/internal/explorer/checkouts/OfflineCDOCheckout.java
@@ -230,7 +230,7 @@ public class OfflineCDOCheckout extends CDOCheckoutImpl
     dataSource.setURL("jdbc:h2:" + dbPrefix);
 
     Map<String, String> props = new HashMap<String, String>();
-    props.put(IMappingStrategy.PROP_QUALIFIED_NAMES, "true");
+    props.put(IMappingStrategy.Props.QUALIFIED_NAMES, "true");
 
     IMappingStrategy mappingStrategy = CDODBUtil.createHorizontalMappingStrategy(true, true, false);
     mappingStrategy.setProperties(props);
diff --git a/plugins/org.eclipse.emf.cdo.explorer/src/org/eclipse/emf/cdo/internal/explorer/repositories/LocalCDORepository.java b/plugins/org.eclipse.emf.cdo.explorer/src/org/eclipse/emf/cdo/internal/explorer/repositories/LocalCDORepository.java
index 977535c7d9..6f7ba1404d 100644
--- a/plugins/org.eclipse.emf.cdo.explorer/src/org/eclipse/emf/cdo/internal/explorer/repositories/LocalCDORepository.java
+++ b/plugins/org.eclipse.emf.cdo.explorer/src/org/eclipse/emf/cdo/internal/explorer/repositories/LocalCDORepository.java
@@ -161,7 +161,7 @@ public class LocalCDORepository extends CDORepositoryImpl
   protected Map<String, String> getMappingStrategyProperties()
   {
     Map<String, String> props = new HashMap<String, String>();
-    props.put(IMappingStrategy.PROP_QUALIFIED_NAMES, "true");
+    props.put(IMappingStrategy.Props.QUALIFIED_NAMES, "true");
     props.put(CDODBUtil.PROP_COPY_ON_BRANCH, "true");
     return props;
   }
diff --git a/plugins/org.eclipse.emf.cdo.server.db/.settings/.api_filters b/plugins/org.eclipse.emf.cdo.server.db/.settings/.api_filters
index 16058e23d1..6c803d9d9c 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/.settings/.api_filters
+++ b/plugins/org.eclipse.emf.cdo.server.db/.settings/.api_filters
@@ -10,6 +10,12 @@
         <filter id="403767336">
             <message_arguments>
                 <message_argument value="org.eclipse.emf.cdo.server.db.mapping.IMappingStrategy"/>
+                <message_argument value="PROP_FORCE_INDEXES"/>
+            </message_arguments>
+        </filter>
+        <filter id="403767336">
+            <message_arguments>
+                <message_argument value="org.eclipse.emf.cdo.server.db.mapping.IMappingStrategy"/>
                 <message_argument value="PROP_TYPE_MAPPING_MODIFIER"/>
             </message_arguments>
         </filter>
diff --git a/plugins/org.eclipse.emf.cdo.server.db/META-INF/MANIFEST.MF b/plugins/org.eclipse.emf.cdo.server.db/META-INF/MANIFEST.MF
index 6f660850cf..5cef5f9c30 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/META-INF/MANIFEST.MF
+++ b/plugins/org.eclipse.emf.cdo.server.db/META-INF/MANIFEST.MF
@@ -1,7 +1,7 @@
 Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-SymbolicName: org.eclipse.emf.cdo.server.db;singleton:=true
-Bundle-Version: 4.3.100.qualifier
+Bundle-Version: 4.4.0.qualifier
 Bundle-Name: %pluginName
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin
@@ -12,10 +12,10 @@ Bundle-ClassPath: .
 Require-Bundle: org.eclipse.core.runtime;bundle-version="[3.5.0,4.0.0)",
  org.eclipse.net4j.db;bundle-version="[4.0.0,5.0.0)";visibility:=reexport,
  org.eclipse.emf.cdo.server;bundle-version="[4.0.0,5.0.0)";visibility:=reexport
-Export-Package: org.eclipse.emf.cdo.server.db;version="4.3.100",
- org.eclipse.emf.cdo.server.db.mapping;version="4.3.100",
- org.eclipse.emf.cdo.server.internal.db;version="4.3.100";x-friends:="org.eclipse.emf.cdo.tests,org.eclipse.emf.cdo.tests.db,org.eclipse.emf.cdo.explorer.ui",
- org.eclipse.emf.cdo.server.internal.db.bundle;version="4.3.100";x-internal:=true,
- org.eclipse.emf.cdo.server.internal.db.mapping;version="4.3.100";x-friends:="org.eclipse.emf.cdo.tests,org.eclipse.emf.cdo.tests.db",
- org.eclipse.emf.cdo.server.internal.db.mapping.horizontal;version="4.3.100";x-friends:="org.eclipse.emf.cdo.tests,org.eclipse.emf.cdo.tests.db",
- org.eclipse.emf.cdo.server.internal.db.messages;version="4.3.100";x-internal:=true
+Export-Package: org.eclipse.emf.cdo.server.db;version="4.4.0",
+ org.eclipse.emf.cdo.server.db.mapping;version="4.4.0",
+ org.eclipse.emf.cdo.server.internal.db;version="4.4.0";x-friends:="org.eclipse.emf.cdo.tests,org.eclipse.emf.cdo.tests.db,org.eclipse.emf.cdo.explorer.ui",
+ org.eclipse.emf.cdo.server.internal.db.bundle;version="4.4.0";x-internal:=true,
+ org.eclipse.emf.cdo.server.internal.db.mapping;version="4.4.0";x-friends:="org.eclipse.emf.cdo.tests,org.eclipse.emf.cdo.tests.db",
+ org.eclipse.emf.cdo.server.internal.db.mapping.horizontal;version="4.4.0";x-friends:="org.eclipse.emf.cdo.tests,org.eclipse.emf.cdo.tests.db",
+ org.eclipse.emf.cdo.server.internal.db.messages;version="4.4.0";x-internal:=true
diff --git a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/db/mapping/IMappingStrategy.java b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/db/mapping/IMappingStrategy.java
index a2b946ea1a..a2c9d9bc41 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/db/mapping/IMappingStrategy.java
+++ b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/db/mapping/IMappingStrategy.java
@@ -56,31 +56,46 @@ public interface IMappingStrategy
   /**
    * Name of the integer property that configures the maximum length for table names. A value of zero indicates the
    * value of the {@link IDBAdapter#getMaxTableNameLength() db adapter} to be used.
+   *
+   * @deprecated As of 4.4 use {@link Props#MAX_TABLE_NAME_LENGTH}.
    */
-  public static final String PROP_MAX_TABLE_NAME_LENGTH = "maxTableNameLength"; //$NON-NLS-1$
+  @Deprecated
+  public static final String PROP_MAX_TABLE_NAME_LENGTH = Props.MAX_TABLE_NAME_LENGTH;
 
   /**
    * Name of the integer property that configures the maximum length for column names. A value of zero indicates the
    * value of the {@link IDBAdapter#getMaxFieldNameLength() db adapter} to be used.
+   *
+   * @deprecated As of 4.4 use {@link Props#MAX_FIELD_NAME_LENGTH}.
    */
-  public static final String PROP_MAX_FIELD_NAME_LENGTH = "maxFieldNameLength"; //$NON-NLS-1$
+  @Deprecated
+  public static final String PROP_MAX_FIELD_NAME_LENGTH = Props.MAX_FIELD_NAME_LENGTH;
 
   /**
    * Name of the String property that specifies a common prefix for table names.
+   *
+   * @deprecated As of 4.4 use {@link Props#TABLE_NAME_PREFIX}.
    */
-  public static final String PROP_TABLE_NAME_PREFIX = "tableNamePrefix"; //$NON-NLS-1$
+  @Deprecated
+  public static final String PROP_TABLE_NAME_PREFIX = Props.TABLE_NAME_PREFIX;
 
   /**
    * Name of the boolean property that configures whether the table names are made of simple class names or of qualified
    * class names.
+   *
+   * @deprecated As of 4.4 use {@link Props#QUALIFIED_NAMES}.
    */
-  public static final String PROP_QUALIFIED_NAMES = "qualifiedNames"; //$NON-NLS-1$
+  @Deprecated
+  public static final String PROP_QUALIFIED_NAMES = Props.QUALIFIED_NAMES;
 
   /**
    * Name of the boolean property that configures whether table names and column names are always suffixed with the
    * internal DBID or only in cases where generated names violate the naming constraints of the underlying backend.
+   *
+   * @deprecated As of 4.4 use {@link Props#FORCE_NAMES_WITH_ID}.
    */
-  public static final String PROP_FORCE_NAMES_WITH_ID = "forceNamesWithID"; //$NON-NLS-1$
+  @Deprecated
+  public static final String PROP_FORCE_NAMES_WITH_ID = Props.FORCE_NAMES_WITH_ID;
 
   /**
    * Name of the integer property that configures the size of the object type in-memory cache. Possible configuration
@@ -93,15 +108,19 @@ public interface IMappingStrategy
    * <p>
    *
    * @since 4.0
+   * @deprecated As of 4.4 use {@link Props#OBJECT_TYPE_CACHE_SIZE}.
    */
-  public static final String PROP_OBJECT_TYPE_CACHE_SIZE = "objectTypeCacheSize"; //$NON-NLS-1$
+  @Deprecated
+  public static final String PROP_OBJECT_TYPE_CACHE_SIZE = Props.OBJECT_TYPE_CACHE_SIZE;
 
   /**
    * Name of a String property that specifies the name of a {@link ColumnTypeModifier column type modifier}.
    *
    * @since 4.2
+   * @deprecated As of 4.4 use {@link Props#COLUMN_TYPE_MODIFIER}.
    */
-  public static final String PROP_COLUMN_TYPE_MODIFIER = "columnTypeModifier"; //$NON-NLS-1$
+  @Deprecated
+  public static final String PROP_COLUMN_TYPE_MODIFIER = Props.COLUMN_TYPE_MODIFIER;
 
   /**
    * @return the store, this MappingStrategy instance belongs to.
@@ -352,4 +371,67 @@ public interface IMappingStrategy
    * @since 4.0
    */
   public String getListJoin(String attrTable, String listTable);
+
+  /**
+   * Contains symbolic constants that specifiy valid keys of {@link IMappingStrategy#getProperties() mapping strategy properties}.
+   *
+   * @author Eike Stepper
+   * @since 4.4
+   * @noimplement This interface is not intended to be implemented by clients.
+   * @noextend This interface is not intended to be extended by clients.
+   * @apiviz.exclude
+   */
+  public interface Props
+  {
+    /**
+     * Name of the integer property that configures the maximum length for table names. A value of zero indicates the
+     * value of the {@link IDBAdapter#getMaxTableNameLength() db adapter} to be used.
+     */
+    public static final String MAX_TABLE_NAME_LENGTH = "maxTableNameLength"; //$NON-NLS-1$
+
+    /**
+     * Name of the integer property that configures the maximum length for column names. A value of zero indicates the
+     * value of the {@link IDBAdapter#getMaxFieldNameLength() db adapter} to be used.
+     */
+    public static final String MAX_FIELD_NAME_LENGTH = "maxFieldNameLength"; //$NON-NLS-1$
+
+    /**
+     * Name of the String property that specifies a common prefix for table names.
+     */
+    public static final String TABLE_NAME_PREFIX = "tableNamePrefix"; //$NON-NLS-1$
+
+    /**
+     * Name of the boolean property that configures whether the table names are made of simple class names or of qualified
+     * class names.
+     */
+    public static final String QUALIFIED_NAMES = "qualifiedNames"; //$NON-NLS-1$
+
+    /**
+     * Name of the boolean property that configures whether table names and column names are always suffixed with the
+     * internal DBID or only in cases where generated names violate the naming constraints of the underlying backend.
+     */
+    public static final String FORCE_NAMES_WITH_ID = "forceNamesWithID"; //$NON-NLS-1$
+
+    /**
+     * Name of the String property that configures on what types of {@link EStructuralFeature structural features} additional
+     * indexes are to be created.
+     */
+    public static final String FORCE_INDEXES = "forceIndexes"; //$NON-NLS-1$
+
+    /**
+     * Name of the integer property that configures the size of the object type in-memory cache. Possible configuration
+     * values are:
+     * <ul>
+     * <li>0 (zero). Don't use memory caching.
+     * <li>&gt;0. Use memory caching with the cache size given.
+     * </ul>
+     * Default is a memory cache size of 10,000,000.
+     */
+    public static final String OBJECT_TYPE_CACHE_SIZE = "objectTypeCacheSize"; //$NON-NLS-1$
+
+    /**
+     * Name of a String property that specifies the name of a {@link ColumnTypeModifier column type modifier}.
+     */
+    public static final String COLUMN_TYPE_MODIFIER = "columnTypeModifier"; //$NON-NLS-1$
+  }
 }
diff --git a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/AbstractMappingStrategy.java b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/AbstractMappingStrategy.java
index 68e9d746d3..3cc751bc9c 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/AbstractMappingStrategy.java
+++ b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/AbstractMappingStrategy.java
@@ -20,6 +20,7 @@ import org.eclipse.emf.cdo.common.branch.CDOBranch;
 import org.eclipse.emf.cdo.common.branch.CDOBranchPoint;
 import org.eclipse.emf.cdo.common.id.CDOID;
 import org.eclipse.emf.cdo.common.id.CDOIDUtil;
+import org.eclipse.emf.cdo.common.model.CDOFeatureType;
 import org.eclipse.emf.cdo.common.model.CDOModelUtil;
 import org.eclipse.emf.cdo.common.model.CDOPackageRegistry;
 import org.eclipse.emf.cdo.common.model.CDOPackageUnit;
@@ -120,6 +121,8 @@ public abstract class AbstractMappingStrategy extends Lifecycle implements IMapp
 
   private SystemPackageMappingInfo systemPackageMappingInfo;
 
+  private Set<CDOFeatureType> forceIndexes;
+
   public AbstractMappingStrategy()
   {
     classMappings = new ConcurrentHashMap<EClass, IClassMapping>();
@@ -144,34 +147,44 @@ public abstract class AbstractMappingStrategy extends Lifecycle implements IMapp
 
   private int getMaxTableNameLength()
   {
-    String value = getProperties().get(PROP_MAX_TABLE_NAME_LENGTH);
+    String value = getProperties().get(Props.MAX_TABLE_NAME_LENGTH);
     return value == null ? store.getDBAdapter().getMaxTableNameLength() : Integer.valueOf(value);
   }
 
   private int getMaxFieldNameLength()
   {
-    String value = getProperties().get(PROP_MAX_FIELD_NAME_LENGTH);
+    String value = getProperties().get(Props.MAX_FIELD_NAME_LENGTH);
     return value == null ? store.getDBAdapter().getMaxFieldNameLength() : Integer.valueOf(value);
   }
 
   private boolean isQualifiedNames()
   {
-    String value = getProperties().get(PROP_QUALIFIED_NAMES);
+    String value = getProperties().get(Props.QUALIFIED_NAMES);
     return value == null ? false : Boolean.valueOf(value);
   }
 
   private boolean isForceNamesWithID()
   {
-    String value = getProperties().get(PROP_FORCE_NAMES_WITH_ID);
+    String value = getProperties().get(Props.FORCE_NAMES_WITH_ID);
     return value == null ? false : Boolean.valueOf(value);
   }
 
   private String getTableNamePrefix()
   {
-    String value = getProperties().get(PROP_TABLE_NAME_PREFIX);
+    String value = getProperties().get(Props.TABLE_NAME_PREFIX);
     return StringUtil.safe(value);
   }
 
+  public Set<CDOFeatureType> getForceIndexes()
+  {
+    if (forceIndexes == null)
+    {
+      forceIndexes = doGetForceIndexes(this);
+    }
+
+    return forceIndexes;
+  }
+
   // -- getters and setters ----------------------------------------------
 
   public final IDBStore getStore()
@@ -791,10 +804,25 @@ public abstract class AbstractMappingStrategy extends Lifecycle implements IMapp
 
   public abstract IListMapping doCreateFeatureMapMapping(EClass containingClass, EStructuralFeature feature);
 
+  private static Set<CDOFeatureType> doGetForceIndexes(IMappingStrategy mappingStrategy)
+  {
+    return CDOFeatureType.readCombination(mappingStrategy.getProperties().get(Props.FORCE_INDEXES));
+  }
+
+  public static Set<CDOFeatureType> getForceIndexes(IMappingStrategy mappingStrategy)
+  {
+    if (mappingStrategy instanceof AbstractMappingStrategy)
+    {
+      return ((AbstractMappingStrategy)mappingStrategy).getForceIndexes();
+    }
+
+    return doGetForceIndexes(mappingStrategy);
+  }
+
   /**
    * @author Eike Stepper
    */
-  private final class SystemPackageMappingInfo
+  private static final class SystemPackageMappingInfo
   {
     public boolean ecoreMapped;
 
diff --git a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/TypeMappingRegistry.java b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/TypeMappingRegistry.java
index ca297bf593..1116d42499 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/TypeMappingRegistry.java
+++ b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/TypeMappingRegistry.java
@@ -381,7 +381,7 @@ public class TypeMappingRegistry implements ITypeMapping.Registry, ITypeMapping.
 
   private ColumnTypeModifier getColumnTypeModifier(IMappingStrategy mappingStrategy)
   {
-    String factoryType = mappingStrategy.getProperties().get(IMappingStrategy.PROP_COLUMN_TYPE_MODIFIER);
+    String factoryType = mappingStrategy.getProperties().get(IMappingStrategy.Props.COLUMN_TYPE_MODIFIER);
     if (factoryType == null)
     {
       factoryType = mappingStrategy.getStore().getDBAdapter().getName();
@@ -515,7 +515,7 @@ public class TypeMappingRegistry implements ITypeMapping.Registry, ITypeMapping.
               registerFactoryType(factoryType);
             }
             else
-              // delta.getKind() == Kind.REMOVED
+            // delta.getKind() == Kind.REMOVED
             {
               // XXX Runtime removal of typeMappingFactories removal of type mappings is currently not supported.
               OM.LOG.warn(Messages.getString("TypeMappingRegistry.3"));
diff --git a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractHorizontalClassMapping.java b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractHorizontalClassMapping.java
index 8ebaa5c4c1..b83a8e41fb 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractHorizontalClassMapping.java
+++ b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractHorizontalClassMapping.java
@@ -18,6 +18,7 @@ import org.eclipse.emf.cdo.common.branch.CDOBranchManager;
 import org.eclipse.emf.cdo.common.branch.CDOBranchPoint;
 import org.eclipse.emf.cdo.common.branch.CDOBranchVersion;
 import org.eclipse.emf.cdo.common.id.CDOID;
+import org.eclipse.emf.cdo.common.model.CDOFeatureType;
 import org.eclipse.emf.cdo.common.model.CDOModelUtil;
 import org.eclipse.emf.cdo.common.revision.CDOList;
 import org.eclipse.emf.cdo.common.revision.CDORevision;
@@ -33,6 +34,7 @@ import org.eclipse.emf.cdo.server.db.mapping.IListMapping;
 import org.eclipse.emf.cdo.server.db.mapping.IMappingStrategy;
 import org.eclipse.emf.cdo.server.db.mapping.ITypeMapping;
 import org.eclipse.emf.cdo.server.internal.db.bundle.OM;
+import org.eclipse.emf.cdo.server.internal.db.mapping.AbstractMappingStrategy;
 import org.eclipse.emf.cdo.spi.common.commit.CDOChangeSetSegment;
 import org.eclipse.emf.cdo.spi.common.revision.InternalCDOList;
 import org.eclipse.emf.cdo.spi.common.revision.InternalCDORevision;
@@ -48,6 +50,7 @@ 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.ddl.InternalDBIndex;
 import org.eclipse.net4j.util.om.monitor.OMMonitor;
 import org.eclipse.net4j.util.om.monitor.OMMonitor.Async;
 import org.eclipse.net4j.util.om.trace.ContextTracer;
@@ -203,6 +206,21 @@ public abstract class AbstractHorizontalClassMapping implements IClassMapping, I
 
           valueMappings.add(mapping);
 
+          Set<CDOFeatureType> forceIndexes = AbstractMappingStrategy.getForceIndexes(mappingStrategy);
+          if (CDOFeatureType.matchesCombination(feature, forceIndexes))
+          {
+            if (field == null)
+            {
+              field = table.getField(fieldName);
+            }
+
+            if (!table.hasIndexFor(field))
+            {
+              InternalDBIndex index = (InternalDBIndex)table.addIndex(IDBIndex.Type.NON_UNIQUE, field);
+              index.setOptional(true); // Creation might fail for unsupported column type!
+            }
+          }
+
           if (feature.isUnsettable())
           {
             hasUnsettableFeatures = true;
diff --git a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractHorizontalMappingStrategy.java b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractHorizontalMappingStrategy.java
index a524387c29..8e3d98a136 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractHorizontalMappingStrategy.java
+++ b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractHorizontalMappingStrategy.java
@@ -409,7 +409,7 @@ public abstract class AbstractHorizontalMappingStrategy extends AbstractMappingS
   {
     int objectTypeCacheSize = ObjectTypeCache.DEFAULT_CACHE_CAPACITY;
 
-    Object value = getProperties().get(PROP_OBJECT_TYPE_CACHE_SIZE);
+    Object value = getProperties().get(Props.OBJECT_TYPE_CACHE_SIZE);
     if (value != null)
     {
       try
diff --git a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractListTableMapping.java b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractListTableMapping.java
index a364263f7c..b65bf0b709 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractListTableMapping.java
+++ b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/AbstractListTableMapping.java
@@ -14,6 +14,7 @@
 package org.eclipse.emf.cdo.server.internal.db.mapping.horizontal;
 
 import org.eclipse.emf.cdo.common.id.CDOID;
+import org.eclipse.emf.cdo.common.model.CDOFeatureType;
 import org.eclipse.emf.cdo.common.revision.CDOList;
 import org.eclipse.emf.cdo.common.revision.CDORevision;
 import org.eclipse.emf.cdo.server.IStoreAccessor.QueryXRefsContext;
@@ -25,6 +26,7 @@ import org.eclipse.emf.cdo.server.db.IIDHandler;
 import org.eclipse.emf.cdo.server.db.mapping.IMappingStrategy;
 import org.eclipse.emf.cdo.server.db.mapping.ITypeMapping;
 import org.eclipse.emf.cdo.server.internal.db.bundle.OM;
+import org.eclipse.emf.cdo.server.internal.db.mapping.AbstractMappingStrategy;
 import org.eclipse.emf.cdo.spi.common.revision.InternalCDORevision;
 
 import org.eclipse.net4j.db.DBException;
@@ -37,6 +39,7 @@ 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.IDBTable;
+import org.eclipse.net4j.spi.db.ddl.InternalDBIndex;
 import org.eclipse.net4j.util.collection.MoveableList;
 import org.eclipse.net4j.util.om.trace.ContextTracer;
 
@@ -51,6 +54,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
+import java.util.Set;
 
 /**
  * This abstract base class provides basic behavior needed for mapping many-valued attributes to tables.
@@ -90,10 +94,13 @@ public abstract class AbstractListTableMapping extends AbstractBasicListTableMap
 
   private void initTable()
   {
-    String tableName = getMappingStrategy().getTableName(getContainingClass(), getFeature());
-    typeMapping = getMappingStrategy().createValueMapping(getFeature());
+    IMappingStrategy mappingStrategy = getMappingStrategy();
+    EStructuralFeature feature = getFeature();
 
-    IDBDatabase database = getMappingStrategy().getStore().getDatabase();
+    String tableName = mappingStrategy.getTableName(getContainingClass(), feature);
+    typeMapping = mappingStrategy.createValueMapping(feature);
+
+    IDBDatabase database = mappingStrategy.getStore().getDatabase();
     table = database.getSchema().getTable(tableName);
     if (table == null)
     {
@@ -117,6 +124,18 @@ public abstract class AbstractListTableMapping extends AbstractBasicListTableMap
     {
       typeMapping.setDBField(table, LIST_VALUE);
     }
+
+    Set<CDOFeatureType> forceIndexes = AbstractMappingStrategy.getForceIndexes(mappingStrategy);
+    if (CDOFeatureType.matchesCombination(feature, forceIndexes))
+    {
+      IDBField field = table.getField(LIST_VALUE);
+
+      if (!table.hasIndexFor(field))
+      {
+        InternalDBIndex index = (InternalDBIndex)table.addIndex(IDBIndex.Type.NON_UNIQUE, field);
+        index.setOptional(true); // Creation might fail for unsupported column type!
+      }
+    }
   }
 
   private void initSQLStrings()
diff --git a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/HorizontalMappingStrategy.java b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/HorizontalMappingStrategy.java
index 5068ba8661..62c99da3e4 100644
--- a/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/HorizontalMappingStrategy.java
+++ b/plugins/org.eclipse.emf.cdo.server.db/src/org/eclipse/emf/cdo/server/internal/db/mapping/horizontal/HorizontalMappingStrategy.java
@@ -16,7 +16,7 @@ import org.eclipse.emf.cdo.common.model.CDOClassifierRef;
 import org.eclipse.emf.cdo.common.protocol.CDODataInput;
 import org.eclipse.emf.cdo.common.protocol.CDODataOutput;
 import org.eclipse.emf.cdo.common.revision.CDORevisionHandler;
-import org.eclipse.emf.cdo.server.IRepository.Props;
+import org.eclipse.emf.cdo.server.IRepository;
 import org.eclipse.emf.cdo.server.IStoreAccessor.QueryResourcesContext;
 import org.eclipse.emf.cdo.server.IStoreAccessor.QueryXRefsContext;
 import org.eclipse.emf.cdo.server.db.CDODBUtil;
@@ -237,8 +237,8 @@ public class HorizontalMappingStrategy extends Lifecycle implements IMappingStra
   {
     super.doActivate();
 
-    boolean auditing = getBooleanProperty(Props.SUPPORTING_AUDITS);
-    boolean branching = getBooleanProperty(Props.SUPPORTING_BRANCHES);
+    boolean auditing = getBooleanProperty(IRepository.Props.SUPPORTING_AUDITS);
+    boolean branching = getBooleanProperty(IRepository.Props.SUPPORTING_BRANCHES);
 
     boolean withRanges = false;
     if (auditing || branching)
diff --git a/plugins/org.eclipse.emf.cdo.tests.db/src/org/eclipse/emf/cdo/tests/db/DBConfig.java b/plugins/org.eclipse.emf.cdo.tests.db/src/org/eclipse/emf/cdo/tests/db/DBConfig.java
index 7f78ac3bde..90c0bf2880 100644
--- a/plugins/org.eclipse.emf.cdo.tests.db/src/org/eclipse/emf/cdo/tests/db/DBConfig.java
+++ b/plugins/org.eclipse.emf.cdo.tests.db/src/org/eclipse/emf/cdo/tests/db/DBConfig.java
@@ -136,7 +136,8 @@ public abstract class DBConfig extends RepositoryConfig
   protected Map<String, String> createMappingStrategyProperties()
   {
     Map<String, String> props = new HashMap<String, String>();
-    props.put(IMappingStrategy.PROP_QUALIFIED_NAMES, "true");
+    props.put(IMappingStrategy.Props.QUALIFIED_NAMES, "true");
+    props.put(IMappingStrategy.Props.FORCE_INDEXES, "XREF");
     props.put(CDODBUtil.PROP_COPY_ON_BRANCH, Boolean.toString(copyOnBranch));
     return props;
   }
diff --git a/plugins/org.eclipse.emf.cdo.tests.db/src/org/eclipse/emf/cdo/tests/db/offline/DBOfflineConfig.java b/plugins/org.eclipse.emf.cdo.tests.db/src/org/eclipse/emf/cdo/tests/db/offline/DBOfflineConfig.java
index 7c367c1dbd..19c6a784d4 100644
--- a/plugins/org.eclipse.emf.cdo.tests.db/src/org/eclipse/emf/cdo/tests/db/offline/DBOfflineConfig.java
+++ b/plugins/org.eclipse.emf.cdo.tests.db/src/org/eclipse/emf/cdo/tests/db/offline/DBOfflineConfig.java
@@ -102,7 +102,7 @@ public abstract class DBOfflineConfig extends OfflineConfig
   protected Map<String, String> createMappingStrategyProperties()
   {
     Map<String, String> props = new HashMap<String, String>();
-    props.put(IMappingStrategy.PROP_QUALIFIED_NAMES, "true");
+    props.put(IMappingStrategy.Props.QUALIFIED_NAMES, "true");
     props.put(CDODBUtil.PROP_COPY_ON_BRANCH, Boolean.toString(copyOnBranch));
     return props;
   }
diff --git a/plugins/org.eclipse.net4j.db/META-INF/MANIFEST.MF b/plugins/org.eclipse.net4j.db/META-INF/MANIFEST.MF
index 01089f321b..85f44d8a3c 100644
--- a/plugins/org.eclipse.net4j.db/META-INF/MANIFEST.MF
+++ b/plugins/org.eclipse.net4j.db/META-INF/MANIFEST.MF
@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.net4j.db;singleton:=true
-Bundle-Version: 4.4.100.qualifier
+Bundle-Version: 4.5.0.qualifier
 Bundle-Activator: org.eclipse.net4j.internal.db.bundle.OM$Activator
 Bundle-Vendor: %providerName
 Bundle-ClassPath: .
@@ -11,16 +11,16 @@ Bundle-RequiredExecutionEnvironment: J2SE-1.5
 Require-Bundle: org.eclipse.core.runtime;bundle-version="[3.5.0,4.0.0)",
  org.eclipse.net4j.util;bundle-version="[3.0.0,4.0.0)";visibility:=reexport,
  org.eclipse.net4j.db.jdbc;bundle-version="[4.0.0,5.0.0)"
-Export-Package: org.eclipse.net4j.db;version="4.4.100",
- org.eclipse.net4j.db.ddl;version="4.4.100",
- org.eclipse.net4j.db.ddl.delta;version="4.4.100",
- org.eclipse.net4j.db.dml;version="4.4.100",
- org.eclipse.net4j.internal.db;version="4.4.100";x-internal:=true,
- org.eclipse.net4j.internal.db.bundle;version="4.4.100";x-internal:=true,
- org.eclipse.net4j.internal.db.ddl;version="4.4.100";x-friends:="org.eclipse.emf.cdo.server.db",
- org.eclipse.net4j.internal.db.ddl.delta;version="4.4.100";x-internal:=true,
- org.eclipse.net4j.internal.db.dml;version="4.4.100";x-internal:=true,
- org.eclipse.net4j.spi.db;version="4.4.100",
- org.eclipse.net4j.spi.db.ddl;version="4.4.100"
+Export-Package: org.eclipse.net4j.db;version="4.5.0",
+ org.eclipse.net4j.db.ddl;version="4.5.0",
+ org.eclipse.net4j.db.ddl.delta;version="4.5.0",
+ org.eclipse.net4j.db.dml;version="4.5.0",
+ org.eclipse.net4j.internal.db;version="4.5.0";x-internal:=true,
+ org.eclipse.net4j.internal.db.bundle;version="4.5.0";x-internal:=true,
+ org.eclipse.net4j.internal.db.ddl;version="4.5.0";x-friends:="org.eclipse.emf.cdo.server.db",
+ org.eclipse.net4j.internal.db.ddl.delta;version="4.5.0";x-internal:=true,
+ org.eclipse.net4j.internal.db.dml;version="4.5.0";x-internal:=true,
+ org.eclipse.net4j.spi.db;version="4.5.0",
+ org.eclipse.net4j.spi.db.ddl;version="4.5.0"
 Bundle-ActivationPolicy: lazy
 Eclipse-BuddyPolicy: registered
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/IDBTable.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/IDBTable.java
index f029f12a2e..af5cfc8845 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/IDBTable.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/IDBTable.java
@@ -57,6 +57,11 @@ public interface IDBTable extends IDBSchemaElement
   public IDBField[] getFields(String... fieldNames) throws SchemaElementNotFoundException;
 
   /**
+   * @since 4.5
+   */
+  public boolean hasIndexFor(IDBField... fields);
+
+  /**
    * @since 4.2
    */
   public IDBIndex addIndex(String name, IDBIndex.Type type, IDBField... fields);
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/delta/IDBIndexDelta.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/delta/IDBIndexDelta.java
index 4e51feab0e..9162f65078 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/delta/IDBIndexDelta.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/db/ddl/delta/IDBIndexDelta.java
@@ -25,6 +25,11 @@ public interface IDBIndexDelta extends IDBDeltaWithProperties
 {
   public static final String TYPE_PROPERTY = "type";
 
+  /**
+   * @since 4.5
+   */
+  public static final String OPTIONAL_PROPERTY = "optional";
+
   public IDBTableDelta getParent();
 
   public int getIndexFieldDeltaCount();
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 0e76c53c39..3258cabbe0 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
@@ -54,6 +54,8 @@ public class DBIndex extends DBSchemaElement implements InternalDBIndex
 
   private List<IDBIndexField> indexFields = new ArrayList<IDBIndexField>();
 
+  private boolean optional;
+
   public DBIndex(IDBTable table, String name, Type type, IDBField[] fields)
   {
     super(name);
@@ -111,6 +113,16 @@ public class DBIndex extends DBSchemaElement implements InternalDBIndex
     this.type = type;
   }
 
+  public boolean isOptional()
+  {
+    return optional;
+  }
+
+  public void setOptional(boolean optional)
+  {
+    this.optional = optional;
+  }
+
   @Deprecated
   public int getPosition()
   {
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 4bb34c2778..b4349c0398 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
@@ -25,6 +25,7 @@ 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.internal.db.ddl.delta.DBSchemaDelta;
+import org.eclipse.net4j.spi.db.ddl.InternalDBIndex;
 import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
 
 import javax.sql.DataSource;
@@ -75,6 +76,8 @@ public class DBSchema extends DBSchemaElement implements InternalDBSchema
       for (IDBIndex sourceIndex : sourceTable.getIndices())
       {
         IDBIndex index = table.addIndexEmpty(sourceIndex.getName(), sourceIndex.getType());
+        ((InternalDBIndex)index).setOptional(((InternalDBIndex)sourceIndex).isOptional());
+
         for (IDBField sourceField : sourceIndex.getFields())
         {
           IDBField field = table.getField(sourceField.getPosition());
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 8b602d1e39..2502e88641 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
@@ -180,6 +180,20 @@ public class DBTable extends DBSchemaElement implements InternalDBTable
     return result.toArray(new IDBField[result.size()]);
   }
 
+  public boolean hasIndexFor(IDBField... fields)
+  {
+    for (IDBIndex index : indices)
+    {
+      IDBField[] indexFields = index.getFields();
+      if (startsWith(indexFields, fields))
+      {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
   public IDBIndex addIndex(String name, IDBIndex.Type type, IDBField... fields)
   {
     assertUnlocked();
@@ -339,4 +353,24 @@ public class DBTable extends DBSchemaElement implements InternalDBTable
   {
     ((InternalDBSchema)schema).assertUnlocked();
   }
+
+  private static boolean startsWith(IDBField[] indexFields, IDBField[] fields)
+  {
+    int length = fields.length;
+    if (length <= indexFields.length)
+    {
+      for (int i = 0; i < length; i++)
+      {
+        IDBField field = fields[i];
+        if (field != indexFields[i])
+        {
+          return false;
+        }
+      }
+
+      return true;
+    }
+
+    return false;
+  }
 }
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
index 4fb261f9de..65df3641fc 100644
--- 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
@@ -80,6 +80,16 @@ public final class DelegatingDBIndex extends DelegatingDBSchemaElement implement
     getDelegate().removeIndexField(unwrap(indexFieldToRemove));
   }
 
+  public boolean isOptional()
+  {
+    return getDelegate().isOptional();
+  }
+
+  public void setOptional(boolean optional)
+  {
+    getDelegate().setOptional(optional);
+  }
+
   @Deprecated
   public int getPosition()
   {
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
index 8b4575bba5..b3dffb2583 100644
--- 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
@@ -139,6 +139,11 @@ public final class DelegatingDBTable extends DelegatingDBSchemaElement implement
     return wrap(getDelegate().getFields(fieldNames), IDBField.class);
   }
 
+  public boolean hasIndexFor(IDBField... fields)
+  {
+    return getDelegate().hasIndexFor(unwrap(fields, IDBField.class));
+  }
+
   public IDBIndex addIndex(String name, Type type, IDBField... fields)
   {
     return wrap(getDelegate().addIndex(name, type, unwrap(fields, IDBField.class)));
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/delta/DBIndexDelta.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/delta/DBIndexDelta.java
index ec8c902e01..fcd559ec79 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/delta/DBIndexDelta.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/delta/DBIndexDelta.java
@@ -55,6 +55,14 @@ public final class DBIndexDelta extends DBDeltaWithProperties implements IDBInde
           new DBPropertyDelta<IDBIndex.Type>(this, TYPE_PROPERTY, IDBPropertyDelta.Type.STRING, type, oldType));
     }
 
+    Boolean optional = index == null ? null : ((InternalDBIndex)index).isOptional();
+    Boolean oldOptional = oldIndex == null ? null : ((InternalDBIndex)oldIndex).isOptional();
+    if (!ObjectUtil.equals(optional, oldOptional))
+    {
+      addPropertyDelta(
+          new DBPropertyDelta<Boolean>(this, OPTIONAL_PROPERTY, IDBPropertyDelta.Type.BOOLEAN, optional, oldOptional));
+    }
+
     IDBIndexField[] indexFields = index == null ? InternalDBIndex.NO_INDEX_FIELDS : index.getIndexFields();
     IDBIndexField[] oldIndexFields = oldIndex == null ? InternalDBIndex.NO_INDEX_FIELDS : oldIndex.getIndexFields();
     compare(indexFields, oldIndexFields, new SchemaElementComparator<IDBIndexField>()
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/delta/DBSchemaDelta.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/delta/DBSchemaDelta.java
index 8975ed4620..8a5b1357f3 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/delta/DBSchemaDelta.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/internal/db/ddl/delta/DBSchemaDelta.java
@@ -23,6 +23,7 @@ import org.eclipse.net4j.db.ddl.delta.IDBIndexDelta;
 import org.eclipse.net4j.db.ddl.delta.IDBIndexFieldDelta;
 import org.eclipse.net4j.db.ddl.delta.IDBSchemaDelta;
 import org.eclipse.net4j.db.ddl.delta.IDBTableDelta;
+import org.eclipse.net4j.spi.db.ddl.InternalDBIndex;
 import org.eclipse.net4j.spi.db.ddl.InternalDBSchema;
 
 import java.text.MessageFormat;
@@ -201,9 +202,11 @@ public final class DBSchemaDelta extends DBDelta implements IDBSchemaDelta
     {
       String name = delta.getName();
       IDBIndex.Type type = delta.getPropertyValue(IDBIndexDelta.TYPE_PROPERTY);
+      Boolean optional = delta.getPropertyValue(IDBIndexDelta.OPTIONAL_PROPERTY);
 
       IDBTable table = delta.getParent().getSchemaElement(schema);
-      table.addIndexEmpty(name, type);
+      InternalDBIndex index = (InternalDBIndex)table.addIndexEmpty(name, type);
+      index.setOptional(optional == Boolean.TRUE);
     }
 
     @Override
diff --git a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/DBAdapter.java b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/DBAdapter.java
index 030fa78a1d..fbd52b6c73 100644
--- a/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/DBAdapter.java
+++ b/plugins/org.eclipse.net4j.db/src/org/eclipse/net4j/spi/db/DBAdapter.java
@@ -27,6 +27,7 @@ import org.eclipse.net4j.db.ddl.delta.IDBSchemaDelta;
 import org.eclipse.net4j.db.ddl.delta.IDBTableDelta;
 import org.eclipse.net4j.internal.db.bundle.OM;
 import org.eclipse.net4j.internal.db.ddl.DBField;
+import org.eclipse.net4j.spi.db.ddl.InternalDBIndex;
 import org.eclipse.net4j.util.CheckUtil;
 import org.eclipse.net4j.util.om.trace.ContextTracer;
 
@@ -395,21 +396,41 @@ public abstract class DBAdapter implements IDBAdapter
       @Override
       public void visit(IDBIndexDelta delta)
       {
-        IDBIndex element = delta.getSchemaElement(schema);
+        InternalDBIndex index = (InternalDBIndex)delta.getSchemaElement(schema);
         ChangeKind changeKind = delta.getChangeKind();
         switch (changeKind)
         {
         case ADD:
-          createIndex(connection, element, delta);
+          try
+          {
+            createIndex(connection, index, delta);
+          }
+          catch (RuntimeException ex)
+          {
+            if (!index.isOptional())
+            {
+              throw ex;
+            }
+          }
           break;
 
         case REMOVE:
-          dropIndex(connection, element, delta);
+          dropIndex(connection, index, delta);
           break;
 
         case CHANGE:
-          dropIndex(connection, element, delta);
-          createIndex(connection, element, delta);
+          dropIndex(connection, index, delta);
+          try
+          {
+            createIndex(connection, index, delta);
+          }
+          catch (RuntimeException ex)
+          {
+            if (!index.isOptional())
+            {
+              throw ex;
+            }
+          }
           break;
 
         default:
@@ -769,7 +790,26 @@ public abstract class DBAdapter implements IDBAdapter
     IDBIndex[] indices = table.getIndices();
     for (int i = 0; i < indices.length; i++)
     {
-      createIndex(indices[i], statement, i);
+      InternalDBIndex index = (InternalDBIndex)indices[i];
+
+      try
+      {
+        createIndex(index, statement, i);
+      }
+      catch (SQLException ex)
+      {
+        if (!index.isOptional())
+        {
+          throw ex;
+        }
+      }
+      catch (RuntimeException ex)
+      {
+        if (!index.isOptional())
+        {
+          throw ex;
+        }
+      }
     }
   }
 
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 2494661b20..ff3dfafe73 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
@@ -26,4 +26,14 @@ public interface InternalDBIndex extends IDBIndex, InternalDBSchemaElement
   public IDBIndex getWrapper();
 
   public void removeIndexField(IDBIndexField indexFieldToRemove);
+
+  /**
+   * @since 4.5
+   */
+  public boolean isOptional();
+
+  /**
+   * @since 4.5
+   */
+  public void setOptional(boolean optional);
 }