diff -r 000000000000 -r bb6990c0dd1a org/sonews/storage/AggregatedGroup.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org/sonews/storage/AggregatedGroup.java	Thu Aug 20 14:31:19 2009 +0200
@@ -0,0 +1,260 @@
+/*
+ *   SONEWS News Server
+ *   see AUTHORS for the list of contributors
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.sonews.storage;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import org.sonews.util.Pair;
+
+/**
+ * An aggregated group is a group consisting of several "real" group.
+ * @author Christian Lins
+ * @since sonews/1.0
+ */
+class AggregatedGroup extends Channel
+{
+
+  static class GroupElement
+  {
+    private Group group;
+    private long  offsetStart, offsetEnd;
+    
+    public GroupElement(Group group, long offsetStart, long offsetEnd)
+    {
+      this.group       = group;
+      this.offsetEnd   = offsetEnd;
+      this.offsetStart = offsetStart;
+    }
+  }
+
+  public static List<Channel> getAll()
+  {
+    List<Channel> all = new ArrayList<Channel>();
+    all.add(getByName("agg.test"));
+    return all;
+  }
+
+  public static AggregatedGroup getByName(String name)
+  {
+    if("agg.test".equals(name))
+    {
+      AggregatedGroup agroup = new AggregatedGroup(name);
+      agroup.addGroup(Group.getByName("agg.test0"), 0, 1000);
+      agroup.addGroup(Group.getByName("agg.test1"), 2000, 4000);
+      return agroup;
+    }
+    else
+      return null;
+  }
+
+  private GroupElement[] groups = new GroupElement[2];
+  private String         name;
+
+  public AggregatedGroup(String name)
+  {
+    this.name = name;
+  }
+
+  private long aggIdxToIdx(long aggIdx)
+    throws StorageBackendException
+  {
+    assert groups != null && groups.length == 2;
+    assert groups[0] != null;
+    assert groups[1] != null;
+
+    // Search in indices of group one
+    List<Long> idxs0 = groups[0].group.getArticleNumbers();
+    Collections.sort(idxs0);
+    for(long idx : idxs0)
+    {
+      if(idx == aggIdx)
+      {
+        return idx;
+      }
+    }
+
+    // Given aggIdx must be an index of group two
+    List<Long> idxs1 = groups[1].group.getArticleNumbers();
+    return 0;
+  }
+  
+  private long idxToAggIdx(long idx)
+  {
+    return 0;
+  }
+
+  /**
+   * Adds the given group to this aggregated set.
+   * @param group
+   * @param offsetStart Lower limit for the article ids range
+   */
+  public void addGroup(Group group, long offsetStart, long offsetEnd)
+  {
+    this.groups[groups[0] == null ? 0 : 1]
+      = new GroupElement(group, offsetStart, offsetEnd);
+  }
+
+  @Override
+  public Article getArticle(long idx)
+    throws StorageBackendException
+  {
+    Article article = null;
+
+    for(GroupElement groupEl : groups)
+    {
+      if(groupEl.offsetStart <= idx && groupEl.offsetEnd >= idx)
+      {
+        article = groupEl.group.getArticle(idx - groupEl.offsetStart);
+        break;
+      }
+    }
+
+    return article;
+  }
+
+  @Override
+  public List<Pair<Long, ArticleHead>> getArticleHeads(
+    final long first, final long last)
+    throws StorageBackendException
+  {
+    List<Pair<Long, ArticleHead>> heads = new ArrayList<Pair<Long, ArticleHead>>();
+    
+    for(GroupElement groupEl : groups)
+    {
+      List<Pair<Long, ArticleHead>> partHeads = new ArrayList<Pair<Long, ArticleHead>>();
+      if(groupEl.offsetStart <= first && groupEl.offsetEnd >= first)
+      {
+        long end = Math.min(groupEl.offsetEnd, last);
+        partHeads = groupEl.group.getArticleHeads
+          (first - groupEl.offsetStart, end - groupEl.offsetStart);
+      }
+      else if(groupEl.offsetStart <= last && groupEl.offsetEnd >= last)
+      {
+        long start = Math.max(groupEl.offsetStart, first);
+        partHeads = groupEl.group.getArticleHeads
+          (start - groupEl.offsetStart, last - groupEl.offsetStart);
+      }
+
+      for(Pair<Long, ArticleHead> partHead : partHeads)
+      {
+        heads.add(new Pair<Long, ArticleHead>(
+          partHead.getA() + groupEl.offsetStart, partHead.getB()));
+      }
+    }
+
+    return heads;
+  }
+
+  @Override
+  public List<Long> getArticleNumbers()
+    throws StorageBackendException
+  {
+    List<Long> articleNumbers = new ArrayList<Long>();
+    
+    for(GroupElement groupEl : groups)
+    {
+      List<Long> partNums = groupEl.group.getArticleNumbers();
+      for(Long partNum : partNums)
+      {
+        articleNumbers.add(partNum + groupEl.offsetStart);
+      }
+    }
+
+    return articleNumbers;
+  }
+
+  @Override
+  public long getIndexOf(Article art)
+    throws StorageBackendException
+  {
+    for(GroupElement groupEl : groups)
+    {
+      long idx = groupEl.group.getIndexOf(art);
+      if(idx > 0)
+      {
+        return idx;
+      }
+    }
+    return -1;
+  }
+
+  public long getInternalID()
+  {
+    return -1;
+  }
+
+  @Override
+  public String getName()
+  {
+    return this.name;
+  }
+
+  @Override
+  public long getFirstArticleNumber()
+    throws StorageBackendException
+  {
+    long first = Long.MAX_VALUE;
+
+    for(GroupElement groupEl : groups)
+    {
+      first = Math.min(first, groupEl.group.getFirstArticleNumber() + groupEl.offsetStart);
+    }
+
+    return first;
+  }
+
+  @Override
+  public long getLastArticleNumber()
+    throws StorageBackendException
+  {
+    long last = 1;
+
+    for(GroupElement groupEl : groups)
+    {
+      last = Math.max(last, groupEl.group.getLastArticleNumber() + groupEl.offsetStart);
+    }
+
+    return last + getPostingsCount(); // This is a hack
+  }
+  
+  public long getPostingsCount()
+    throws StorageBackendException
+  {
+    long postings = 0;
+
+    for(GroupElement groupEl : groups)
+    {
+      postings += groupEl.group.getPostingsCount();
+    }
+
+    return postings;
+  }
+
+  public boolean isDeleted()
+  {
+    return false;
+  }
+
+  public boolean isWriteable()
+  {
+    return false;
+  }
+
+}