Index: lucene/contrib/instantiated/src/java/org/apache/lucene/store/instantiated/InstantiatedIndexReader.java
===================================================================
--- lucene/contrib/instantiated/src/java/org/apache/lucene/store/instantiated/InstantiatedIndexReader.java	(revision 1054582)
+++ lucene/contrib/instantiated/src/java/org/apache/lucene/store/instantiated/InstantiatedIndexReader.java	(working copy)
@@ -31,6 +31,7 @@
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.FieldSelector;
 import org.apache.lucene.index.*;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.BitVector;
 import org.apache.lucene.util.BytesRef;
@@ -45,6 +46,8 @@
 public class InstantiatedIndexReader extends IndexReader {
 
   private final InstantiatedIndex index;
+  private ReaderContext context = new AtomicContext(this);
+
 
   public InstantiatedIndexReader(InstantiatedIndex index) {
     super();
@@ -424,6 +427,11 @@
       }
     };
   }
+  
+  @Override
+  public ReaderContext topLevelReaderContext() {
+    return context;
+  }
 
   @Override
   public TermFreqVector[] getTermFreqVectors(int docNumber) throws IOException {
Index: lucene/contrib/memory/src/java/org/apache/lucene/index/memory/MemoryIndex.java
===================================================================
--- lucene/contrib/memory/src/java/org/apache/lucene/index/memory/MemoryIndex.java	(revision 1054582)
+++ lucene/contrib/memory/src/java/org/apache/lucene/index/memory/MemoryIndex.java	(working copy)
@@ -48,6 +48,7 @@
 import org.apache.lucene.index.TermPositionVector;
 import org.apache.lucene.index.TermVectorMapper;
 import org.apache.lucene.index.FieldInvertState;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.Collector;
 import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.Query;
@@ -739,6 +740,7 @@
   private final class MemoryIndexReader extends IndexReader {
     
     private Searcher searcher; // needed to find searcher.getSimilarity() 
+    private final ReaderContext readerInfos = new AtomicContext(this);
     
     private MemoryIndexReader() {
       super(); // avoid as much superclass baggage as possible
@@ -765,6 +767,11 @@
       if (DEBUG) System.err.println("MemoryIndexReader.docFreq: " + term + ", freq:" + freq);
       return freq;
     }
+    
+    @Override
+    public ReaderContext topLevelReaderContext() {
+      return readerInfos;
+    }
   
     @Override
     public Fields fields() {
Index: lucene/contrib/queries/src/java/org/apache/lucene/search/BooleanFilter.java
===================================================================
--- lucene/contrib/queries/src/java/org/apache/lucene/search/BooleanFilter.java	(revision 1054582)
+++ lucene/contrib/queries/src/java/org/apache/lucene/search/BooleanFilter.java	(working copy)
@@ -21,6 +21,7 @@
 import java.util.ArrayList;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.BooleanClause.Occur;
 import org.apache.lucene.util.OpenBitSet;
 import org.apache.lucene.util.OpenBitSetDISI;
@@ -41,10 +42,10 @@
   ArrayList<Filter> notFilters = null;
   ArrayList<Filter> mustFilters = null;
   
-  private DocIdSetIterator getDISI(ArrayList<Filter> filters, int index, IndexReader reader)
+  private DocIdSetIterator getDISI(ArrayList<Filter> filters, int index, ReaderContext info)
   throws IOException
   {
-    return filters.get(index).getDocIdSet(reader).iterator();
+    return filters.get(index).getDocIdSet(info).iterator();
   }
 
   /**
@@ -52,21 +53,21 @@
    * of the filters that have been added.
    */
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException
   {
     OpenBitSetDISI res = null;
-  
+    final IndexReader reader = info.reader;
     if (shouldFilters != null) {
       for (int i = 0; i < shouldFilters.size(); i++) {
         if (res == null) {
-          res = new OpenBitSetDISI(getDISI(shouldFilters, i, reader), reader.maxDoc());
+          res = new OpenBitSetDISI(getDISI(shouldFilters, i, info), reader.maxDoc());
         } else { 
-          DocIdSet dis = shouldFilters.get(i).getDocIdSet(reader);
+          DocIdSet dis = shouldFilters.get(i).getDocIdSet(info);
           if(dis instanceof OpenBitSet) {
             // optimized case for OpenBitSets
             res.or((OpenBitSet) dis);
           } else {
-            res.inPlaceOr(getDISI(shouldFilters, i, reader));
+            res.inPlaceOr(getDISI(shouldFilters, i, info));
           }
         }
       }
@@ -75,15 +76,15 @@
     if (notFilters!=null) {
       for (int i = 0; i < notFilters.size(); i++) {
         if (res == null) {
-          res = new OpenBitSetDISI(getDISI(notFilters, i, reader), reader.maxDoc());
+          res = new OpenBitSetDISI(getDISI(notFilters, i, info), reader.maxDoc());
           res.flip(0, reader.maxDoc()); // NOTE: may set bits on deleted docs
         } else {
-          DocIdSet dis = notFilters.get(i).getDocIdSet(reader);
+          DocIdSet dis = notFilters.get(i).getDocIdSet(info);
           if(dis instanceof OpenBitSet) {
             // optimized case for OpenBitSets
             res.andNot((OpenBitSet) dis);
           } else {
-            res.inPlaceNot(getDISI(notFilters, i, reader));
+            res.inPlaceNot(getDISI(notFilters, i, info));
           }
         }
       }
@@ -92,14 +93,14 @@
     if (mustFilters!=null) {
       for (int i = 0; i < mustFilters.size(); i++) {
         if (res == null) {
-          res = new OpenBitSetDISI(getDISI(mustFilters, i, reader), reader.maxDoc());
+          res = new OpenBitSetDISI(getDISI(mustFilters, i, info), reader.maxDoc());
         } else {
-          DocIdSet dis = mustFilters.get(i).getDocIdSet(reader);
+          DocIdSet dis = mustFilters.get(i).getDocIdSet(info);
           if(dis instanceof OpenBitSet) {
             // optimized case for OpenBitSets
             res.and((OpenBitSet) dis);
           } else {
-            res.inPlaceAnd(getDISI(mustFilters, i, reader));
+            res.inPlaceAnd(getDISI(mustFilters, i, info));
           }
         }
       }
Index: lucene/contrib/queries/src/java/org/apache/lucene/search/ChainedFilter.java
===================================================================
--- lucene/contrib/queries/src/java/org/apache/lucene/search/ChainedFilter.java	(revision 1054582)
+++ lucene/contrib/queries/src/java/org/apache/lucene/search/ChainedFilter.java	(working copy)
@@ -20,6 +20,7 @@
 import java.io.IOException;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.DocIdSetIterator;
 import org.apache.lucene.search.Filter;
@@ -96,21 +97,21 @@
      * {@link Filter#getDocIdSet}.
      */
     @Override
-    public DocIdSet getDocIdSet(IndexReader reader) throws IOException
+    public DocIdSet getDocIdSet(ReaderContext info) throws IOException
     {
         int[] index = new int[1]; // use array as reference to modifiable int; 
         index[0] = 0;             // an object attribute would not be thread safe.
         if (logic != -1)
-            return getDocIdSet(reader, logic, index);
+            return getDocIdSet(info, logic, index);
         else if (logicArray != null)
-            return getDocIdSet(reader, logicArray, index);
+            return getDocIdSet(info, logicArray, index);
         else
-            return getDocIdSet(reader, DEFAULT, index);
+            return getDocIdSet(info, DEFAULT, index);
     }
 
-    private DocIdSetIterator getDISI(Filter filter, IndexReader reader)
+    private DocIdSetIterator getDISI(Filter filter, ReaderContext info)
     throws IOException {
-        DocIdSet docIdSet = filter.getDocIdSet(reader);
+        DocIdSet docIdSet = filter.getDocIdSet(info);
         if (docIdSet == null) {
           return DocIdSet.EMPTY_DOCIDSET.iterator();
         } else {
@@ -123,9 +124,10 @@
         }
     }
 
-    private OpenBitSetDISI initialResult(IndexReader reader, int logic, int[] index)
+    private OpenBitSetDISI initialResult(ReaderContext info, int logic, int[] index)
     throws IOException
     {
+        IndexReader reader = info.reader;
         OpenBitSetDISI result;
         /**
          * First AND operation takes place against a completely false
@@ -133,12 +135,12 @@
          */
         if (logic == AND)
         {
-            result = new OpenBitSetDISI(getDISI(chain[index[0]], reader), reader.maxDoc());
+            result = new OpenBitSetDISI(getDISI(chain[index[0]], info), reader.maxDoc());
             ++index[0];
         }
         else if (logic == ANDNOT)
         {
-            result = new OpenBitSetDISI(getDISI(chain[index[0]], reader), reader.maxDoc());
+            result = new OpenBitSetDISI(getDISI(chain[index[0]], info), reader.maxDoc());
             result.flip(0,reader.maxDoc()); // NOTE: may set bits for deleted docs.
             ++index[0];
         }
@@ -155,13 +157,13 @@
      * @param logic Logical operation
      * @return DocIdSet
      */
-    private DocIdSet getDocIdSet(IndexReader reader, int logic, int[] index)
+    private DocIdSet getDocIdSet(ReaderContext info, int logic, int[] index)
     throws IOException
     {
-        OpenBitSetDISI result = initialResult(reader, logic, index);
+        OpenBitSetDISI result = initialResult(info, logic, index);
         for (; index[0] < chain.length; index[0]++)
         {
-            doChain(result, logic, chain[index[0]].getDocIdSet(reader));
+            doChain(result, logic, chain[index[0]].getDocIdSet(info));
         }
         return result;
     }
@@ -172,16 +174,16 @@
      * @param logic Logical operation
      * @return DocIdSet
      */
-    private DocIdSet getDocIdSet(IndexReader reader, int[] logic, int[] index)
+    private DocIdSet getDocIdSet(ReaderContext info, int[] logic, int[] index)
     throws IOException
     {
         if (logic.length != chain.length)
             throw new IllegalArgumentException("Invalid number of elements in logic array");
 
-        OpenBitSetDISI result = initialResult(reader, logic[0], index);
+        OpenBitSetDISI result = initialResult(info, logic[0], index);
         for (; index[0] < chain.length; index[0]++)
         {
-            doChain(result, logic[index[0]], chain[index[0]].getDocIdSet(reader));
+            doChain(result, logic[index[0]], chain[index[0]].getDocIdSet(info));
         }
         return result;
     }
Index: lucene/contrib/queries/src/java/org/apache/lucene/search/DuplicateFilter.java
===================================================================
--- lucene/contrib/queries/src/java/org/apache/lucene/search/DuplicateFilter.java	(revision 1054582)
+++ lucene/contrib/queries/src/java/org/apache/lucene/search/DuplicateFilter.java	(working copy)
@@ -19,6 +19,7 @@
 
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Terms;
 import org.apache.lucene.index.DocsEnum;
 import org.apache.lucene.index.TermsEnum;
@@ -27,7 +28,8 @@
 import org.apache.lucene.util.Bits;
 
 public class DuplicateFilter extends Filter
-{
+{ // TODO: make duplicate filter aware of ReaderContext such that we can 
+  // filter duplicates across segments
 	
 	String fieldName;
 	
@@ -70,15 +72,15 @@
 	}
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException
 	{
 		if(processingMode==PM_FAST_INVALIDATION)
 		{
-			return fastBits(reader);
+			return fastBits(info.reader);
 		}
 		else
 		{
-			return correctBits(reader);
+			return correctBits(info.reader);
 		}
 	}
 	
@@ -96,7 +98,7 @@
         } else {
           docs = termsEnum.docs(delDocs, docs);
           int doc = docs.nextDoc();
-          if (doc != docs.NO_MORE_DOCS) {
+          if (doc != DocsEnum.NO_MORE_DOCS) {
             if (keepMode == KM_USE_FIRST_OCCURRENCE) {
               bits.set(doc);
             } else {
@@ -104,7 +106,7 @@
               while (true) {
                 lastDoc = doc;
                 doc = docs.nextDoc();
-                if (doc == docs.NO_MORE_DOCS) {
+                if (doc == DocsEnum.NO_MORE_DOCS) {
                   break;
                 }
               }
@@ -136,7 +138,7 @@
             // unset potential duplicates
             docs = termsEnum.docs(delDocs, docs);
             int doc = docs.nextDoc();
-            if (doc != docs.NO_MORE_DOCS) {
+            if (doc != DocsEnum.NO_MORE_DOCS) {
               if (keepMode == KM_USE_FIRST_OCCURRENCE) {
                 doc = docs.nextDoc();
               }
@@ -147,7 +149,7 @@
               lastDoc = doc;
               bits.clear(lastDoc);
               doc = docs.nextDoc();
-              if (doc == docs.NO_MORE_DOCS) {
+              if (doc == DocsEnum.NO_MORE_DOCS) {
                 break;
               }
             }
Index: lucene/contrib/queries/src/java/org/apache/lucene/search/TermsFilter.java
===================================================================
--- lucene/contrib/queries/src/java/org/apache/lucene/search/TermsFilter.java	(revision 1054582)
+++ lucene/contrib/queries/src/java/org/apache/lucene/search/TermsFilter.java	(working copy)
@@ -23,6 +23,7 @@
 import java.util.TreeSet;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.DocsEnum;
 import org.apache.lucene.index.Terms;
@@ -57,7 +58,8 @@
    * @see org.apache.lucene.search.Filter#getDocIdSet(org.apache.lucene.index.IndexReader)
 	 */
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+    IndexReader reader = info.reader;
     OpenBitSet result=new OpenBitSet(reader.maxDoc());
     Fields fields = reader.fields();
     BytesRef br = new BytesRef();
Index: lucene/contrib/queries/src/test/org/apache/lucene/search/BooleanFilterTest.java
===================================================================
--- lucene/contrib/queries/src/test/org/apache/lucene/search/BooleanFilterTest.java	(revision 1054582)
+++ lucene/contrib/queries/src/test/org/apache/lucene/search/BooleanFilterTest.java	(working copy)
@@ -24,6 +24,7 @@
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.index.SlowMultiReaderWrapper;
 import org.apache.lucene.index.Term;
@@ -83,7 +84,7 @@
         private void tstFilterCard(String mes, int expected, Filter filt)
         throws Throwable
         {
-          DocIdSetIterator disi = filt.getDocIdSet(reader).iterator();
+          DocIdSetIterator disi = filt.getDocIdSet(new AtomicContext(reader)).iterator();
           int actual = 0;
           while (disi.nextDoc() != DocIdSetIterator.NO_MORE_DOCS) {
             actual++;
Index: lucene/contrib/queries/src/test/org/apache/lucene/search/TermsFilterTest.java
===================================================================
--- lucene/contrib/queries/src/test/org/apache/lucene/search/TermsFilterTest.java	(revision 1054582)
+++ lucene/contrib/queries/src/test/org/apache/lucene/search/TermsFilterTest.java	(working copy)
@@ -21,6 +21,7 @@
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.store.Directory;
@@ -59,23 +60,25 @@
 			w.addDocument(doc);			
 		}
 		IndexReader reader = new SlowMultiReaderWrapper(w.getReader());
+		ReaderContext context = reader.topLevelReaderContext();
+		assertTrue(context.isAtomic);
 		w.close();
 		
 		TermsFilter tf=new TermsFilter();
 		tf.addTerm(new Term(fieldName,"19"));
-		OpenBitSet bits = (OpenBitSet)tf.getDocIdSet(reader);
+		OpenBitSet bits = (OpenBitSet)tf.getDocIdSet(context);
 		assertEquals("Must match nothing", 0, bits.cardinality());
 
 		tf.addTerm(new Term(fieldName,"20"));
-		bits = (OpenBitSet)tf.getDocIdSet(reader);
+		bits = (OpenBitSet)tf.getDocIdSet(context);
 		assertEquals("Must match 1", 1, bits.cardinality());
 		
 		tf.addTerm(new Term(fieldName,"10"));
-		bits = (OpenBitSet)tf.getDocIdSet(reader);
+		bits = (OpenBitSet)tf.getDocIdSet(context);
 		assertEquals("Must match 2", 2, bits.cardinality());
 		
 		tf.addTerm(new Term(fieldName,"00"));
-		bits = (OpenBitSet)tf.getDocIdSet(reader);
+		bits = (OpenBitSet)tf.getDocIdSet(context);
 		assertEquals("Must match 2", 2, bits.cardinality());
 		
 		reader.close();
Index: lucene/contrib/remote/src/java/org/apache/lucene/search/RemoteCachingWrapperFilter.java
===================================================================
--- lucene/contrib/remote/src/java/org/apache/lucene/search/RemoteCachingWrapperFilter.java	(revision 1054582)
+++ lucene/contrib/remote/src/java/org/apache/lucene/search/RemoteCachingWrapperFilter.java	(working copy)
@@ -20,6 +20,7 @@
 import java.io.IOException;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 /**
  * Provides caching of {@link org.apache.lucene.search.Filter}s themselves on the remote end of an RMI connection.
@@ -50,8 +51,8 @@
    * @return the DocIdSet
    */
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
     Filter cachedFilter = FilterManager.getInstance().getFilter(filter);
-    return cachedFilter.getDocIdSet(reader);
+    return cachedFilter.getDocIdSet(info);
   }
 }
Index: lucene/contrib/remote/src/test/org/apache/lucene/search/RemoteCachingWrapperFilterHelper.java
===================================================================
--- lucene/contrib/remote/src/test/org/apache/lucene/search/RemoteCachingWrapperFilterHelper.java	(revision 1054582)
+++ lucene/contrib/remote/src/test/org/apache/lucene/search/RemoteCachingWrapperFilterHelper.java	(working copy)
@@ -22,6 +22,7 @@
 import junit.framework.Assert;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 /**
  * A unit test helper class to help with RemoteCachingWrapperFilter testing and
@@ -41,7 +42,7 @@
   }
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
     Filter cachedFilter = FilterManager.getInstance().getFilter(filter);
     
     Assert.assertNotNull("Filter should not be null", cachedFilter);
@@ -54,6 +55,6 @@
     if (filter instanceof CachingWrapperFilterHelper) {
       ((CachingWrapperFilterHelper)cachedFilter).setShouldHaveCache(shouldHaveCache);
     }
-    return cachedFilter.getDocIdSet(reader);
+    return cachedFilter.getDocIdSet(info);
   }
 }
Index: lucene/contrib/spatial/src/java/org/apache/lucene/spatial/geohash/GeoHashDistanceFilter.java
===================================================================
--- lucene/contrib/spatial/src/java/org/apache/lucene/spatial/geohash/GeoHashDistanceFilter.java	(revision 1054582)
+++ lucene/contrib/spatial/src/java/org/apache/lucene/spatial/geohash/GeoHashDistanceFilter.java	(working copy)
@@ -19,7 +19,7 @@
 
 import java.io.IOException;
 
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.FieldCache;
 import org.apache.lucene.search.FieldCache.DocTerms;
 import org.apache.lucene.search.Filter;
@@ -62,15 +62,15 @@
   }
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
 
-    final DocTerms geoHashValues = FieldCache.DEFAULT.getTerms(reader, geoHashField);
+    final DocTerms geoHashValues = FieldCache.DEFAULT.getTerms(info.reader, geoHashField);
     final BytesRef br = new BytesRef();
 
     final int docBase = nextDocBase;
-    nextDocBase += reader.maxDoc();
+    nextDocBase += info.reader.maxDoc();
 
-    return new FilteredDocIdSet(startingFilter.getDocIdSet(reader)) {
+    return new FilteredDocIdSet(startingFilter.getDocIdSet(info)) {
       @Override
       public boolean match(int doc) {
 
Index: lucene/contrib/spatial/src/java/org/apache/lucene/spatial/tier/CartesianShapeFilter.java
===================================================================
--- lucene/contrib/spatial/src/java/org/apache/lucene/spatial/tier/CartesianShapeFilter.java	(revision 1054582)
+++ lucene/contrib/spatial/src/java/org/apache/lucene/spatial/tier/CartesianShapeFilter.java	(working copy)
@@ -20,7 +20,7 @@
 import java.util.List;
 
 import org.apache.lucene.index.DocsEnum;
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.Filter;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.DocIdSetIterator;
@@ -45,8 +45,8 @@
   }
   
   @Override
-  public DocIdSet getDocIdSet(final IndexReader reader) throws IOException {
-    final Bits delDocs = reader.getDeletedDocs();
+  public DocIdSet getDocIdSet(final ReaderContext info) throws IOException {
+    final Bits delDocs = info.reader.getDeletedDocs();
     final List<Double> area = shape.getArea();
     final int sz = area.size();
     
@@ -58,7 +58,7 @@
       return new DocIdSet() {
         @Override
         public DocIdSetIterator iterator() throws IOException {
-          return reader.termDocsEnum(delDocs, fieldName, bytesRef);
+          return info.reader.termDocsEnum(delDocs, fieldName, bytesRef);
         }
         
         @Override
@@ -67,11 +67,11 @@
         }
       };
     } else {
-      final OpenBitSet bits = new OpenBitSet(reader.maxDoc());
+      final OpenBitSet bits = new OpenBitSet(info.reader.maxDoc());
       for (int i =0; i< sz; i++) {
         double boxId = area.get(i).doubleValue();
         NumericUtils.longToPrefixCoded(NumericUtils.doubleToSortableLong(boxId), 0, bytesRef);
-        final DocsEnum docsEnum = reader.termDocsEnum(delDocs, fieldName, bytesRef);
+        final DocsEnum docsEnum = info.reader.termDocsEnum(delDocs, fieldName, bytesRef);
         if (docsEnum == null) continue;
         // iterate through all documents
         // which have this boxId
Index: lucene/contrib/spatial/src/java/org/apache/lucene/spatial/tier/LatLongDistanceFilter.java
===================================================================
--- lucene/contrib/spatial/src/java/org/apache/lucene/spatial/tier/LatLongDistanceFilter.java	(revision 1054582)
+++ lucene/contrib/spatial/src/java/org/apache/lucene/spatial/tier/LatLongDistanceFilter.java	(working copy)
@@ -18,7 +18,8 @@
 package org.apache.lucene.spatial.tier;
 
 import java.io.IOException;
-import org.apache.lucene.index.IndexReader;
+
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.FilteredDocIdSet;
 import org.apache.lucene.search.FieldCache;
 import org.apache.lucene.search.Filter;
@@ -64,15 +65,15 @@
   }
   
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
 
-    final double[] latIndex = FieldCache.DEFAULT.getDoubles(reader, latField);
-    final double[] lngIndex = FieldCache.DEFAULT.getDoubles(reader, lngField);
+    final double[] latIndex = FieldCache.DEFAULT.getDoubles(info.reader, latField);
+    final double[] lngIndex = FieldCache.DEFAULT.getDoubles(info.reader, lngField);
 
     final int docBase = nextDocBase;
-    nextDocBase += reader.maxDoc();
+    nextDocBase += info.reader.maxDoc();
 
-    return new FilteredDocIdSet(startingFilter.getDocIdSet(reader)) {
+    return new FilteredDocIdSet(startingFilter.getDocIdSet(info)) {
       @Override
       protected boolean match(int doc) {
         double x = latIndex[doc];
Index: lucene/contrib/spatial/src/test/org/apache/lucene/spatial/tier/TestDistance.java
===================================================================
--- lucene/contrib/spatial/src/test/org/apache/lucene/spatial/tier/TestDistance.java	(revision 1054582)
+++ lucene/contrib/spatial/src/test/org/apache/lucene/spatial/tier/TestDistance.java	(working copy)
@@ -25,11 +25,13 @@
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
 import org.apache.lucene.search.QueryWrapperFilter;
 import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.store.Directory;
 
+
 public class TestDistance extends LuceneTestCase {
   
   private Directory directory;
@@ -100,9 +102,9 @@
     LatLongDistanceFilter f = new LatLongDistanceFilter(new QueryWrapperFilter(new MatchAllDocsQuery()),
                                                         lat, lng, 1.0, latField, lngField);
 
-    IndexReader[] readers = r.getSequentialSubReaders();
-    for(int i=0;i<readers.length;i++) {
-      f.getDocIdSet(readers[i]);
+    AtomicContext[] leafs = r.topLevelReaderContext().leafs();
+    for (int i = 0; i < leafs.length; i++) {
+      f.getDocIdSet(leafs[i]);
     }
     r.close();
   }
Index: lucene/contrib/xml-query-parser/src/java/org/apache/lucene/xmlparser/builders/NumericRangeFilterBuilder.java
===================================================================
--- lucene/contrib/xml-query-parser/src/java/org/apache/lucene/xmlparser/builders/NumericRangeFilterBuilder.java	(revision 1054582)
+++ lucene/contrib/xml-query-parser/src/java/org/apache/lucene/xmlparser/builders/NumericRangeFilterBuilder.java	(working copy)
@@ -19,7 +19,7 @@
 
 import java.io.IOException;
 
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.Filter;
 import org.apache.lucene.search.NumericRangeFilter;
@@ -157,7 +157,7 @@
 		private static final long serialVersionUID = 1L;
 
 		@Override
-		public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+		public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
 			return null;
 		}
 
Index: lucene/contrib/xml-query-parser/src/test/org/apache/lucene/xmlparser/builders/TestNumericRangeFilterBuilder.java
===================================================================
--- lucene/contrib/xml-query-parser/src/test/org/apache/lucene/xmlparser/builders/TestNumericRangeFilterBuilder.java	(revision 1054582)
+++ lucene/contrib/xml-query-parser/src/test/org/apache/lucene/xmlparser/builders/TestNumericRangeFilterBuilder.java	(working copy)
@@ -67,7 +67,7 @@
 			IndexReader reader = IndexReader.open(ramDir, true);
 			try
 			{
-				assertNull(filter.getDocIdSet(reader));
+				assertNull(filter.getDocIdSet(reader.topLevelReaderContext()));
 			}
 			finally
 			{
Index: lucene/src/java/org/apache/lucene/index/BufferedDeletes.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/BufferedDeletes.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/index/BufferedDeletes.java	(working copy)
@@ -26,6 +26,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.Scorer;
@@ -364,12 +365,16 @@
     // Delete by query
     if (deletes.queries.size() > 0) {
       IndexSearcher searcher = new IndexSearcher(reader);
+      
+      final ReaderContext readerContext = searcher.topLevelReaderContext();
+      assert readerContext.isAtomic;
       try {
         for (Entry<Query, Integer> entry : deletes.queries.entrySet()) {
           Query query = entry.getKey();
           int limit = entry.getValue().intValue();
           Weight weight = query.weight(searcher);
-          Scorer scorer = weight.scorer(reader, true, false);
+          
+          Scorer scorer = weight.scorer(readerContext, true, false);
           if (scorer != null) {
             while(true)  {
               int doc = scorer.nextDoc();
Index: lucene/src/java/org/apache/lucene/index/DirectoryReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/DirectoryReader.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/index/DirectoryReader.java	(working copy)
@@ -37,7 +37,6 @@
 import org.apache.lucene.store.LockObtainFailedException;
 import org.apache.lucene.index.codecs.CodecProvider;
 import org.apache.lucene.util.Bits;
-import org.apache.lucene.util.ReaderUtil;
 import org.apache.lucene.util.BytesRef;
 
 import org.apache.lucene.search.FieldCache; // not great (circular); used only to purge FieldCache entry on close
@@ -61,9 +60,9 @@
 
   private boolean rollbackHasChanges;
 
+  private ReaderContext topLevelReaderContext;
   private SegmentReader[] subReaders;
   private int[] starts;                           // 1st docno for each segment
-  private final Map<SegmentReader,ReaderUtil.Slice> subReaderToSlice = new HashMap<SegmentReader,ReaderUtil.Slice>();
   private Map<String,byte[]> normsCache = new HashMap<String,byte[]>();
   private int maxDoc = 0;
   private int numDocs = -1;
@@ -335,25 +334,22 @@
   private void initialize(SegmentReader[] subReaders) throws IOException {
     this.subReaders = subReaders;
     starts = new int[subReaders.length + 1];    // build starts array
-
+    final AtomicContext[] subReaderCtx = new AtomicContext[subReaders.length];
+    topLevelReaderContext = new CompositeContext(this, subReaderCtx, subReaderCtx);
     final List<Fields> subFields = new ArrayList<Fields>();
-    final List<ReaderUtil.Slice> fieldSlices = new ArrayList<ReaderUtil.Slice>();
-
+    
     for (int i = 0; i < subReaders.length; i++) {
       starts[i] = maxDoc;
+      subReaderCtx[i] = new AtomicContext(topLevelReaderContext, subReaders[i], i, maxDoc, i, maxDoc);
       maxDoc += subReaders[i].maxDoc();      // compute maxDocs
 
       if (subReaders[i].hasDeletions()) {
         hasDeletions = true;
       }
-
-      final ReaderUtil.Slice slice = new ReaderUtil.Slice(starts[i], subReaders[i].maxDoc(), i);
-      subReaderToSlice.put(subReaders[i], slice);
-
+      
       final Fields f = subReaders[i].fields();
       if (f != null) {
         subFields.add(f);
-        fieldSlices.add(slice);
       }
     }
     starts[subReaders.length] = maxDoc;
@@ -903,16 +899,16 @@
       fieldSet.addAll(names);
     }
     return fieldSet;
-  } 
+  }
   
   @Override
-  public IndexReader[] getSequentialSubReaders() {
-    return subReaders;
+  public ReaderContext topLevelReaderContext() {
+    return topLevelReaderContext;
   }
-
+  
   @Override
-  public int getSubReaderDocBase(IndexReader subReader) {
-    return subReaderToSlice.get(subReader).start;
+  public IndexReader[] getSequentialSubReaders() {
+    return subReaders;
   }
 
   /** Returns the directory this index resides in. */
Index: lucene/src/java/org/apache/lucene/index/FilterIndexReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/FilterIndexReader.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/index/FilterIndexReader.java	(working copy)
@@ -19,6 +19,7 @@
 
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.FieldSelector;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.Bits;
 import org.apache.lucene.search.FieldCache; // not great (circular); used only to purge FieldCache entry on close
@@ -417,6 +418,11 @@
   public IndexReader[] getSequentialSubReaders() {
     return in.getSequentialSubReaders();
   }
+  
+  @Override
+  public ReaderContext topLevelReaderContext() {
+    return in.topLevelReaderContext();
+  }
 
   @Override
   public Fields fields() throws IOException {
Index: lucene/src/java/org/apache/lucene/index/IndexReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/IndexReader.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/index/IndexReader.java	(working copy)
@@ -1126,7 +1126,7 @@
     if (docs == null) return 0;
     int n = 0;
     int doc;
-    while ((doc = docs.nextDoc()) != docs.NO_MORE_DOCS) {
+    while ((doc = docs.nextDoc()) != DocsEnum.NO_MORE_DOCS) {
       deleteDocument(doc);
       n++;
     }
@@ -1374,12 +1374,6 @@
     return null;
   }
 
-
-  /** Expert: returns the docID base for this subReader. */
-  public int getSubReaderDocBase(IndexReader subReader) {
-    throw new UnsupportedOperationException();
-  }
-
   /** Expert */
   public Object getCoreCacheKey() {
     return this;
@@ -1431,4 +1425,136 @@
   Fields retrieveFields() {
     return fields;
   }
+  
+
+  // nocommit - add JAVADOC
+  // this could maybe replace sequential subreaders as well as its docBase relative.
+  public ReaderContext topLevelReaderContext() {
+    throw new UnsupportedOperationException("This reader does not support this method.");
+  }
+
+
+
+  /**
+   * A struct like class that represents a hierarchical relationship between
+   * {@link IndexReader} instances. 
+   */
+  public static abstract class ReaderContext {
+    /** The reader context for this reader's immediate parent, or null if none */
+    public final ReaderContext parent;
+    /** The actual reader */
+    public final IndexReader reader;
+    /** <code>true</code> iff the reader is an atomic reader */
+    public final boolean isAtomic;
+    /** <code>true</code> if this context struct represents the top level reader within the hierarchical context */
+    public final boolean isTopLevel;
+    /** the doc base for this reader in the parent, <tt>0</tt> if parent is null */
+    public final int docbaseInParent;
+    /** the ord for this reader in the parent, <tt>0</tt> if parent is null */
+    public final int ordInParent;
+    
+    ReaderContext(ReaderContext parent, IndexReader reader,
+        boolean isAtomic, boolean isTopLevel, int ordInParent, int docbaseInParent) {
+      this.parent = parent;
+      this.reader = reader;
+      this.isAtomic = isAtomic;
+      this.docbaseInParent = docbaseInParent;
+      this.ordInParent = ordInParent;
+      this.isTopLevel = isTopLevel;
+    }
+    
+    /**
+     * Returns the leaf contexts for this context if this reader is a top-level reader otherwise <code>null</code>.
+     * <p>
+     * Note: this is convenience method since leafs can always be obtained by walking the
+     * context tree.
+     */
+    public AtomicContext[] leafs() {
+      return null;
+    }
+    
+    /**
+     * Returns the leaf contexts for this context if this reader is either an
+     * atomic reader or a top-level reader. If this context is an
+     * {@link AtomicContext} this method will return an array with this instance
+     * as the only element in the array.
+     * <p>
+     * Note: this is convenience method since leafs can always be obtained by
+     * walking the context tree.
+     */
+    public AtomicContext[] forceLeafs() {
+      if (leafs() == null) {
+        assert this.isAtomic; // nocommit - this is kind of hacky workaround for QueryWrapperFilter internal hacks
+        return new AtomicContext[] { (AtomicContext) this };
+      }
+      return leafs();
+    }
+  }
+  
+  /**
+   * {@link ReaderContext} for composite {@link IndexReader} instance
+   */
+  public static final class CompositeContext extends ReaderContext {
+    /** the composite readers immediate children */
+    public final ReaderContext[] children;
+    /** the composite readers leaf reader contexts if this is the top level reader in this context */
+    public final AtomicContext[] leafs;
+
+    /**
+     * Creates a {@link CompositeContext} for intermediate readers that aren't
+     * not top-level readers in the current context
+     */
+    public CompositeContext(ReaderContext parent, IndexReader reader,
+        int ordInParent, int docbaseInParent, ReaderContext[] children) {
+      this(parent, reader, ordInParent, docbaseInParent, children, null);
+    }
+    
+    /**
+     * Creates a {@link CompositeContext} for top-level readers with parent set to <code>null</code>
+     */
+    public CompositeContext(IndexReader reader, ReaderContext[] children, AtomicContext[] leafs) {
+      this(null, reader, 0, 0, children, leafs);
+    }
+    
+    private CompositeContext(ReaderContext parent, IndexReader reader,
+        int ordInParent, int docbaseInParent, ReaderContext[] children,
+        AtomicContext[] leafs) {
+      super(parent, reader, false, leafs != null, ordInParent, docbaseInParent);
+      this.children = children;
+      this.leafs = leafs;
+    }
+
+    @Override
+    public AtomicContext[] leafs() {
+      return this.leafs;
+    }
+  }
+  
+  /**
+   * {@link ReaderContext} for atomic {@link IndexReader} instances
+   */
+  public static final class AtomicContext extends ReaderContext {
+    /** The readers ord in the top-level's leafs array */
+    public final int ord;
+    /** The readers absolute doc base */
+    public final int docBase;
+    /**
+     * Creates a new {@link AtomicContext} 
+     */
+    public AtomicContext(ReaderContext parent, IndexReader reader,
+        int ord, int docBase, int leafOrd, int leafDocBase) {
+      super(parent, reader, true, false,  ord, docBase);
+      assert reader.getSequentialSubReaders() == null : "Atomic readers must not have subreaders";
+      this.ord = leafOrd;
+      this.docBase = leafDocBase;
+    }
+    
+    /**
+     * Creates a new {@link AtomicContext} for a atomic reader without an immediate
+     * parent.
+     */
+    public AtomicContext(IndexReader atomicReader) {
+      this(null, atomicReader, 0, 0, 0, 0);
+    }
+  }
 }
Index: lucene/src/java/org/apache/lucene/index/MultiReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/MultiReader.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/index/MultiReader.java	(working copy)
@@ -36,12 +36,12 @@
 public class MultiReader extends IndexReader implements Cloneable {
   protected IndexReader[] subReaders;
   private int[] starts;                           // 1st docno for each segment
-  private final Map<IndexReader,ReaderUtil.Slice> subReaderToSlice = new HashMap<IndexReader,ReaderUtil.Slice>();
   private boolean[] decrefOnClose;                // remember which subreaders to decRef on close
   private Map<String,byte[]> normsCache = new HashMap<String,byte[]>();
   private int maxDoc = 0;
   private int numDocs = -1;
   private boolean hasDeletions = false;
+  private final ReaderContext topLevelContext;
   
  /**
   * <p>Construct a MultiReader aggregating the named set of (sub)readers.
@@ -51,7 +51,7 @@
   * @param subReaders set of (sub)readers
   */
   public MultiReader(IndexReader... subReaders) throws IOException {
-    initialize(subReaders, true);
+    topLevelContext = initialize(subReaders, true);
   }
 
   /**
@@ -63,14 +63,13 @@
    * @param subReaders set of (sub)readers
    */
   public MultiReader(IndexReader[] subReaders, boolean closeSubReaders) throws IOException {
-    initialize(subReaders, closeSubReaders);
+    topLevelContext = initialize(subReaders, closeSubReaders);
   }
   
-  private void initialize(IndexReader[] subReaders, boolean closeSubReaders) throws IOException {
+  private ReaderContext initialize(IndexReader[] subReaders, boolean closeSubReaders) throws IOException {
     this.subReaders =  subReaders.clone();
     starts = new int[subReaders.length + 1];    // build starts array
     decrefOnClose = new boolean[subReaders.length];
-
     for (int i = 0; i < subReaders.length; i++) {
       starts[i] = maxDoc;
       maxDoc += subReaders[i].maxDoc();      // compute maxDocs
@@ -85,14 +84,9 @@
       if (subReaders[i].hasDeletions()) {
         hasDeletions = true;
       }
-
-      final ReaderUtil.Slice slice = new ReaderUtil.Slice(starts[i],
-                                                          subReaders[i].maxDoc(),
-                                                          i);
-      subReaderToSlice.put(subReaders[i], slice);
     }
-
     starts[subReaders.length] = maxDoc;
+    return ReaderUtil.buildReaderContext(this);
   }
 
   @Override
@@ -101,11 +95,6 @@
   }
 
   @Override
-  public int getSubReaderDocBase(IndexReader subReader) {
-    return subReaderToSlice.get(subReader).start;
-  }
-
-  @Override
   public Fields fields() throws IOException {
     throw new UnsupportedOperationException("please use MultiFields.getFields, or wrap your IndexReader with SlowMultiReaderWrapper, if you really need a top level Fields");
   }
@@ -433,4 +422,8 @@
   public IndexReader[] getSequentialSubReaders() {
     return subReaders;
   }
+  
+  public ReaderContext topLevelReaderContext() {
+    return topLevelContext;
+  }
 }
Index: lucene/src/java/org/apache/lucene/index/ParallelReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/ParallelReader.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/index/ParallelReader.java	(working copy)
@@ -21,7 +21,9 @@
 import org.apache.lucene.document.FieldSelector;
 import org.apache.lucene.document.FieldSelectorResult;
 import org.apache.lucene.document.Fieldable;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.util.Bits;
+import org.apache.lucene.util.ReaderUtil;
 import org.apache.lucene.search.FieldCache; // not great (circular); used only to purge FieldCache entry on close
 import org.apache.lucene.util.BytesRef;
 
@@ -53,6 +55,7 @@
   private SortedMap<String,IndexReader> fieldToReader = new TreeMap<String,IndexReader>();
   private Map<IndexReader,Collection<String>> readerToFields = new HashMap<IndexReader,Collection<String>>();
   private List<IndexReader> storedFieldReaders = new ArrayList<IndexReader>();
+  private ReaderContext topLevelReaderContext = new AtomicContext(this);
 
   private int maxDoc;
   private int numDocs;
@@ -88,7 +91,7 @@
     buffer.append(')');
     return buffer.toString();
   }
-
+  
  /** Add an IndexReader.
   * @throws IOException if there is a low-level IO error
   */
@@ -529,6 +532,11 @@
     }
     return fieldSet;
   }
+  @Override
+  public ReaderContext topLevelReaderContext() {
+    return topLevelReaderContext;
+  }
+
 }
 
 
Index: lucene/src/java/org/apache/lucene/index/SegmentReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/SegmentReader.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/index/SegmentReader.java	(working copy)
@@ -51,7 +51,7 @@
 
   private SegmentInfo si;
   private int readBufferSize;
-
+  private final ReaderContext readerContext = new AtomicContext(this);
   CloseableThreadLocal<FieldsReader> fieldsReaderLocal = new FieldsReaderLocal();
   CloseableThreadLocal<TermVectorsReader> termVectorsLocal = new CloseableThreadLocal<TermVectorsReader>();
 
@@ -1183,6 +1183,11 @@
     buffer.append(si.toString(core.dir, pendingDeleteCount));
     return buffer.toString();
   }
+  
+  @Override
+  public ReaderContext topLevelReaderContext() {
+    return readerContext;
+  }
 
   /**
    * Return the name of the segment this reader is reading.
Index: lucene/src/java/org/apache/lucene/index/SlowMultiReaderWrapper.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/SlowMultiReaderWrapper.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/index/SlowMultiReaderWrapper.java	(working copy)
@@ -23,6 +23,7 @@
 
 import org.apache.lucene.index.DirectoryReader; // javadoc
 import org.apache.lucene.index.MultiReader; // javadoc
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 /**
  * This class forces a composite reader (eg a {@link
@@ -47,9 +48,10 @@
  */
 
 public final class SlowMultiReaderWrapper extends FilterIndexReader {
-
+  private final ReaderContext readerContext;
   public SlowMultiReaderWrapper(IndexReader other) {
     super(other);
+    readerContext = new AtomicContext(this); // emulate atomic reader!
   }
 
   @Override
@@ -67,4 +69,9 @@
     return null;
   }
   
+  @Override
+  public ReaderContext topLevelReaderContext() {
+    return readerContext;
+  }
+  
 }
Index: lucene/src/java/org/apache/lucene/search/BooleanQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/BooleanQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/BooleanQuery.java	(working copy)
@@ -18,6 +18,7 @@
  */
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.util.ToStringUtils;
 import org.apache.lucene.search.BooleanClause.Occur;
@@ -223,7 +224,7 @@
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc)
+    public Explanation explain(ReaderContext context, int doc)
       throws IOException {
       final int minShouldMatch =
         BooleanQuery.this.getMinimumNumberShouldMatch();
@@ -237,7 +238,7 @@
       for (Iterator<Weight> wIter = weights.iterator(); wIter.hasNext();) {
         Weight w = wIter.next();
         BooleanClause c = cIter.next();
-        if (w.scorer(reader, true, true) == null) {
+        if (w.scorer(context, true, true) == null) {
           if (c.isRequired()) {
             fail = true;
             Explanation r = new Explanation(0.0f, "no match on required clause (" + c.getQuery().toString() + ")");
@@ -245,7 +246,7 @@
           }
           continue;
         }
-        Explanation e = w.explain(reader, doc);
+        Explanation e = w.explain(context, doc);
         if (e.isMatch()) {
           if (!c.isProhibited()) {
             sumExpl.addDetail(e);
@@ -299,7 +300,7 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer)
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer)
         throws IOException {
       List<Scorer> required = new ArrayList<Scorer>();
       List<Scorer> prohibited = new ArrayList<Scorer>();
@@ -307,7 +308,7 @@
       Iterator<BooleanClause> cIter = clauses.iterator();
       for (Weight w  : weights) {
         BooleanClause c =  cIter.next();
-        Scorer subScorer = w.scorer(reader, true, false);
+        Scorer subScorer = w.scorer(context, true, false);
         if (subScorer == null) {
           if (c.isRequired()) {
             return null;
Index: lucene/src/java/org/apache/lucene/search/CachingSpanFilter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/CachingSpanFilter.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/CachingSpanFilter.java	(working copy)
@@ -17,6 +17,7 @@
 
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.MultiFields;
 import org.apache.lucene.util.Bits;
 
@@ -61,8 +62,8 @@
   }
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-    SpanFilterResult result = getCachedResult(reader);
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+    SpanFilterResult result = getCachedResult(info.reader);
     return result != null ? result.getDocIdSet() : null;
   }
   
Index: lucene/src/java/org/apache/lucene/search/CachingWrapperFilter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/CachingWrapperFilter.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/CachingWrapperFilter.java	(working copy)
@@ -23,6 +23,7 @@
 import java.util.WeakHashMap;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.MultiFields;
 import org.apache.lucene.util.OpenBitSetDISI;
 import org.apache.lucene.util.Bits;
@@ -38,6 +39,9 @@
  * {@link DeletesMode#DYNAMIC}).
  */
 public class CachingWrapperFilter extends Filter {
+  // TODO: make this filter aware of ReaderContext. a cached filter could 
+  // specify the actual readers key or something similar to indicate on which
+  // level of the readers hierarchy it should be cached.
   Filter filter;
 
   /**
@@ -192,8 +196,8 @@
   int hitCount, missCount;
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+    final IndexReader reader = info.reader;
     final Object coreKey = reader.getCoreCacheKey();
     final Object delCoreKey = reader.hasDeletions() ? MultiFields.getDeletedDocs(reader) : coreKey;
 
@@ -206,7 +210,7 @@
     missCount++;
 
     // cache miss
-    docIdSet = docIdSetToCache(filter.getDocIdSet(reader), reader);
+    docIdSet = docIdSetToCache(filter.getDocIdSet(info), reader);
 
     if (docIdSet != null) {
       cache.put(coreKey, delCoreKey, docIdSet);
Index: lucene/src/java/org/apache/lucene/search/ConstantScoreQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/ConstantScoreQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/ConstantScoreQuery.java	(working copy)
@@ -18,6 +18,7 @@
  */
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.util.ToStringUtils;
 
@@ -132,18 +133,18 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+    public Scorer scorer(ReaderContext context,  boolean scoreDocsInOrder, boolean topScorer) throws IOException {
       final DocIdSetIterator disi;
       if (filter != null) {
         assert query == null;
-        final DocIdSet dis = filter.getDocIdSet(reader);
+        final DocIdSet dis = filter.getDocIdSet(context);
         if (dis == null)
           return null;
         disi = dis.iterator();
       } else {
         assert query != null && innerWeight != null;
         disi =
-          innerWeight.scorer(reader, scoreDocsInOrder, topScorer);
+          innerWeight.scorer(context, scoreDocsInOrder, topScorer);
       }
       if (disi == null)
         return null;
@@ -156,8 +157,8 @@
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
-      final Scorer cs = scorer(reader, true, false);
+    public Explanation explain(ReaderContext context, int doc) throws IOException {
+      final Scorer cs = scorer(context, true, false);
       final boolean exists = (cs != null && cs.advance(doc) == doc);
 
       final ComplexExplanation result = new ComplexExplanation();
Index: lucene/src/java/org/apache/lucene/search/DisjunctionMaxQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/DisjunctionMaxQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/DisjunctionMaxQuery.java	(working copy)
@@ -23,6 +23,7 @@
 import java.util.Set;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 
 /**
@@ -141,12 +142,12 @@
 
     /* Create the scorer used to score our associated DisjunctionMaxQuery */
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder,
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder,
         boolean topScorer) throws IOException {
       Scorer[] scorers = new Scorer[weights.size()];
       int idx = 0;
       for (Weight w : weights) {
-        Scorer subScorer = w.scorer(reader, true, false);
+        Scorer subScorer = w.scorer(context, true, false);
         if (subScorer != null && subScorer.nextDoc() != DocIdSetIterator.NO_MORE_DOCS) {
           scorers[idx++] = subScorer;
         }
@@ -158,13 +159,13 @@
 
     /* Explain the score we computed for doc */
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
-      if (disjuncts.size() == 1) return weights.get(0).explain(reader,doc);
+    public Explanation explain(ReaderContext context, int doc) throws IOException {
+      if (disjuncts.size() == 1) return weights.get(0).explain(context,doc);
       ComplexExplanation result = new ComplexExplanation();
       float max = 0.0f, sum = 0.0f;
       result.setDescription(tieBreakerMultiplier == 0.0f ? "max of:" : "max plus " + tieBreakerMultiplier + " times others of:");
       for (Weight wt : weights) {
-        Explanation e = wt.explain(reader, doc);
+        Explanation e = wt.explain(context, doc);
         if (e.isMatch()) {
           result.setMatch(Boolean.TRUE);
           result.addDetail(e);
Index: lucene/src/java/org/apache/lucene/search/FieldCacheRangeFilter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/FieldCacheRangeFilter.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/FieldCacheRangeFilter.java	(working copy)
@@ -19,6 +19,7 @@
 import java.io.IOException;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.MultiFields;
 import org.apache.lucene.util.NumericUtils;
 import org.apache.lucene.util.Bits;
@@ -73,7 +74,7 @@
   
   /** This method is implemented for each data type */
   @Override
-  public abstract DocIdSet getDocIdSet(IndexReader reader) throws IOException;
+  public abstract DocIdSet getDocIdSet(ReaderContext info) throws IOException;
 
   /**
    * Creates a string range filter using {@link FieldCache#getTermsIndex}. This works with all
@@ -83,8 +84,8 @@
   public static FieldCacheRangeFilter<String> newStringRange(String field, String lowerVal, String upperVal, boolean includeLower, boolean includeUpper) {
     return new FieldCacheRangeFilter<String>(field, null, lowerVal, upperVal, includeLower, includeUpper) {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-        final FieldCache.DocTermsIndex fcsi = FieldCache.DEFAULT.getTermsIndex(reader, field);
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+        final FieldCache.DocTermsIndex fcsi = FieldCache.DEFAULT.getTermsIndex(info.reader, field);
         final BytesRef spare = new BytesRef();
         final int lowerPoint = fcsi.binarySearchLookup(lowerVal == null ? null : new BytesRef(lowerVal), spare);
         final int upperPoint = fcsi.binarySearchLookup(upperVal == null ? null : new BytesRef(upperVal), spare);
@@ -124,7 +125,7 @@
         
         // for this DocIdSet, we can ignore deleted docs
         // because deleted docs have an order of 0 (null entry in StringIndex)
-        return new FieldCacheDocIdSet(reader, true) {
+        return new FieldCacheDocIdSet(info.reader, true) {
           @Override
           final boolean matchDoc(int doc) {
             final int docOrd = fcsi.getOrd(doc);
@@ -152,7 +153,7 @@
   public static FieldCacheRangeFilter<Byte> newByteRange(String field, FieldCache.ByteParser parser, Byte lowerVal, Byte upperVal, boolean includeLower, boolean includeUpper) {
     return new FieldCacheRangeFilter<Byte>(field, parser, lowerVal, upperVal, includeLower, includeUpper) {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
         final byte inclusiveLowerPoint, inclusiveUpperPoint;
         if (lowerVal != null) {
           final byte i = lowerVal.byteValue();
@@ -174,9 +175,9 @@
         if (inclusiveLowerPoint > inclusiveUpperPoint)
           return DocIdSet.EMPTY_DOCIDSET;
         
-        final byte[] values = FieldCache.DEFAULT.getBytes(reader, field, (FieldCache.ByteParser) parser);
+        final byte[] values = FieldCache.DEFAULT.getBytes(info.reader, field, (FieldCache.ByteParser) parser);
         // we only respect deleted docs if the range contains 0
-        return new FieldCacheDocIdSet(reader, !(inclusiveLowerPoint <= 0 && inclusiveUpperPoint >= 0)) {
+        return new FieldCacheDocIdSet(info.reader, !(inclusiveLowerPoint <= 0 && inclusiveUpperPoint >= 0)) {
           @Override
           boolean matchDoc(int doc) {
             return values[doc] >= inclusiveLowerPoint && values[doc] <= inclusiveUpperPoint;
@@ -203,7 +204,7 @@
   public static FieldCacheRangeFilter<Short> newShortRange(String field, FieldCache.ShortParser parser, Short lowerVal, Short upperVal, boolean includeLower, boolean includeUpper) {
     return new FieldCacheRangeFilter<Short>(field, parser, lowerVal, upperVal, includeLower, includeUpper) {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
         final short inclusiveLowerPoint, inclusiveUpperPoint;
         if (lowerVal != null) {
           short i = lowerVal.shortValue();
@@ -225,9 +226,9 @@
         if (inclusiveLowerPoint > inclusiveUpperPoint)
           return DocIdSet.EMPTY_DOCIDSET;
         
-        final short[] values = FieldCache.DEFAULT.getShorts(reader, field, (FieldCache.ShortParser) parser);
+        final short[] values = FieldCache.DEFAULT.getShorts(info.reader, field, (FieldCache.ShortParser) parser);
         // ignore deleted docs if range doesn't contain 0
-        return new FieldCacheDocIdSet(reader, !(inclusiveLowerPoint <= 0 && inclusiveUpperPoint >= 0)) {
+        return new FieldCacheDocIdSet(info.reader, !(inclusiveLowerPoint <= 0 && inclusiveUpperPoint >= 0)) {
           @Override
           boolean matchDoc(int doc) {
             return values[doc] >= inclusiveLowerPoint && values[doc] <= inclusiveUpperPoint;
@@ -254,7 +255,7 @@
   public static FieldCacheRangeFilter<Integer> newIntRange(String field, FieldCache.IntParser parser, Integer lowerVal, Integer upperVal, boolean includeLower, boolean includeUpper) {
     return new FieldCacheRangeFilter<Integer>(field, parser, lowerVal, upperVal, includeLower, includeUpper) {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
         final int inclusiveLowerPoint, inclusiveUpperPoint;
         if (lowerVal != null) {
           int i = lowerVal.intValue();
@@ -276,9 +277,9 @@
         if (inclusiveLowerPoint > inclusiveUpperPoint)
           return DocIdSet.EMPTY_DOCIDSET;
         
-        final int[] values = FieldCache.DEFAULT.getInts(reader, field, (FieldCache.IntParser) parser);
+        final int[] values = FieldCache.DEFAULT.getInts(info.reader, field, (FieldCache.IntParser) parser);
         // ignore deleted docs if range doesn't contain 0
-        return new FieldCacheDocIdSet(reader, !(inclusiveLowerPoint <= 0 && inclusiveUpperPoint >= 0)) {
+        return new FieldCacheDocIdSet(info.reader, !(inclusiveLowerPoint <= 0 && inclusiveUpperPoint >= 0)) {
           @Override
           boolean matchDoc(int doc) {
             return values[doc] >= inclusiveLowerPoint && values[doc] <= inclusiveUpperPoint;
@@ -305,7 +306,7 @@
   public static FieldCacheRangeFilter<Long> newLongRange(String field, FieldCache.LongParser parser, Long lowerVal, Long upperVal, boolean includeLower, boolean includeUpper) {
     return new FieldCacheRangeFilter<Long>(field, parser, lowerVal, upperVal, includeLower, includeUpper) {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
         final long inclusiveLowerPoint, inclusiveUpperPoint;
         if (lowerVal != null) {
           long i = lowerVal.longValue();
@@ -327,9 +328,9 @@
         if (inclusiveLowerPoint > inclusiveUpperPoint)
           return DocIdSet.EMPTY_DOCIDSET;
         
-        final long[] values = FieldCache.DEFAULT.getLongs(reader, field, (FieldCache.LongParser) parser);
+        final long[] values = FieldCache.DEFAULT.getLongs(info.reader, field, (FieldCache.LongParser) parser);
         // ignore deleted docs if range doesn't contain 0
-        return new FieldCacheDocIdSet(reader, !(inclusiveLowerPoint <= 0L && inclusiveUpperPoint >= 0L)) {
+        return new FieldCacheDocIdSet(info.reader, !(inclusiveLowerPoint <= 0L && inclusiveUpperPoint >= 0L)) {
           @Override
           boolean matchDoc(int doc) {
             return values[doc] >= inclusiveLowerPoint && values[doc] <= inclusiveUpperPoint;
@@ -356,7 +357,7 @@
   public static FieldCacheRangeFilter<Float> newFloatRange(String field, FieldCache.FloatParser parser, Float lowerVal, Float upperVal, boolean includeLower, boolean includeUpper) {
     return new FieldCacheRangeFilter<Float>(field, parser, lowerVal, upperVal, includeLower, includeUpper) {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
         // we transform the floating point numbers to sortable integers
         // using NumericUtils to easier find the next bigger/lower value
         final float inclusiveLowerPoint, inclusiveUpperPoint;
@@ -382,9 +383,9 @@
         if (inclusiveLowerPoint > inclusiveUpperPoint)
           return DocIdSet.EMPTY_DOCIDSET;
         
-        final float[] values = FieldCache.DEFAULT.getFloats(reader, field, (FieldCache.FloatParser) parser);
+        final float[] values = FieldCache.DEFAULT.getFloats(info.reader, field, (FieldCache.FloatParser) parser);
         // ignore deleted docs if range doesn't contain 0
-        return new FieldCacheDocIdSet(reader, !(inclusiveLowerPoint <= 0.0f && inclusiveUpperPoint >= 0.0f)) {
+        return new FieldCacheDocIdSet(info.reader, !(inclusiveLowerPoint <= 0.0f && inclusiveUpperPoint >= 0.0f)) {
           @Override
           boolean matchDoc(int doc) {
             return values[doc] >= inclusiveLowerPoint && values[doc] <= inclusiveUpperPoint;
@@ -411,7 +412,7 @@
   public static FieldCacheRangeFilter<Double> newDoubleRange(String field, FieldCache.DoubleParser parser, Double lowerVal, Double upperVal, boolean includeLower, boolean includeUpper) {
     return new FieldCacheRangeFilter<Double>(field, parser, lowerVal, upperVal, includeLower, includeUpper) {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
         // we transform the floating point numbers to sortable integers
         // using NumericUtils to easier find the next bigger/lower value
         final double inclusiveLowerPoint, inclusiveUpperPoint;
@@ -437,9 +438,9 @@
         if (inclusiveLowerPoint > inclusiveUpperPoint)
           return DocIdSet.EMPTY_DOCIDSET;
         
-        final double[] values = FieldCache.DEFAULT.getDoubles(reader, field, (FieldCache.DoubleParser) parser);
+        final double[] values = FieldCache.DEFAULT.getDoubles(info.reader, field, (FieldCache.DoubleParser) parser);
         // ignore deleted docs if range doesn't contain 0
-        return new FieldCacheDocIdSet(reader, !(inclusiveLowerPoint <= 0.0 && inclusiveUpperPoint >= 0.0)) {
+        return new FieldCacheDocIdSet(info.reader, !(inclusiveLowerPoint <= 0.0 && inclusiveUpperPoint >= 0.0)) {
           @Override
           boolean matchDoc(int doc) {
             return values[doc] >= inclusiveLowerPoint && values[doc] <= inclusiveUpperPoint;
Index: lucene/src/java/org/apache/lucene/search/FieldCacheTermsFilter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/FieldCacheTermsFilter.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/FieldCacheTermsFilter.java	(working copy)
@@ -21,6 +21,7 @@
 
 import org.apache.lucene.index.DocsEnum; // javadoc @link
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.util.OpenBitSet;
 import org.apache.lucene.util.BytesRef;
 
@@ -115,8 +116,8 @@
   }
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-    return new FieldCacheTermsFilterDocIdSet(getFieldCache().getTermsIndex(reader, field));
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+    return new FieldCacheTermsFilterDocIdSet(getFieldCache().getTermsIndex(info.reader, field));
   }
 
   protected class FieldCacheTermsFilterDocIdSet extends DocIdSet {
Index: lucene/src/java/org/apache/lucene/search/Filter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/Filter.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/Filter.java	(working copy)
@@ -19,7 +19,7 @@
 
 import java.io.IOException;
 
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.util.DocIdBitSet;
 
 /** 
@@ -38,8 +38,8 @@
    * must refer to document IDs for that segment, not for
    * the top-level reader.
    * 
-   * @param reader a {@link IndexReader} instance opened on the index currently
-   *         searched on. Note, it is likely that the provided reader does not
+   * @param info a {@link ReaderContext} instance opened on the index currently
+   *         searched on. Note, it is likely that the provided reader info does not
    *         represent the whole underlying index i.e. if the index has more than
    *         one segment the given reader only represents a single segment.
    *          
@@ -49,5 +49,5 @@
    * 
    * @see DocIdBitSet
    */
-  public abstract DocIdSet getDocIdSet(IndexReader reader) throws IOException;
+  public abstract DocIdSet getDocIdSet(ReaderContext info) throws IOException;
 }
Index: lucene/src/java/org/apache/lucene/search/FilteredQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/FilteredQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/FilteredQuery.java	(working copy)
@@ -18,6 +18,7 @@
  */
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.util.ToStringUtils;
 
@@ -81,7 +82,7 @@
       }
 
       @Override
-      public Explanation explain (IndexReader ir, int i) throws IOException {
+      public Explanation explain (ReaderContext ir, int i) throws IOException {
         Explanation inner = weight.explain (ir, i);
         if (getBoost()!=1) {
           Explanation preBoost = inner;
@@ -111,7 +112,7 @@
 
       // return a filtering scorer
       @Override
-      public Scorer scorer(IndexReader indexReader, boolean scoreDocsInOrder, boolean topScorer)
+      public Scorer scorer(ReaderContext indexReader, boolean scoreDocsInOrder, boolean topScorer)
           throws IOException {
         final Scorer scorer = weight.scorer(indexReader, true, false);
         if (scorer == null) {
Index: lucene/src/java/org/apache/lucene/search/IndexSearcher.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/IndexSearcher.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/IndexSearcher.java	(working copy)
@@ -18,13 +18,14 @@
  */
 
 import java.io.IOException;
-import java.util.ArrayList;
-import java.util.List;
 
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.FieldSelector;
 import org.apache.lucene.index.CorruptIndexException;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
+import org.apache.lucene.index.IndexReader.CompositeContext;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.ReaderUtil;
@@ -50,8 +51,8 @@
   
   // NOTE: these members might change in incompatible ways
   // in the next release
-  protected IndexReader[] subReaders;
-  protected int[] docStarts;
+  private final ReaderContext readerContext;
+  private final AtomicContext[] leafContexts;
 
   /** Creates a searcher searching the index in the named
    *  directory, with readOnly=true
@@ -89,29 +90,25 @@
    * @lucene.experimental */
   public IndexSearcher(IndexReader reader, IndexReader[] subReaders, int[] docStarts) {
     this.reader = reader;
-    this.subReaders = subReaders;
-    this.docStarts = docStarts;
+    AtomicContext[] leafReaders = new AtomicContext[subReaders.length];
+    CompositeContext topLevel = new CompositeContext(reader, leafReaders, leafReaders);
+    for (int i = 0; i < subReaders.length; i++) {
+      leafReaders[i] = new AtomicContext(topLevel, subReaders[i], i, docStarts[i], i, docStarts[i]);      
+    }
+    leafContexts = topLevel.leafs;
+    readerContext = topLevel;
+    assert leafContexts.length > 0;
     closeReader = false;
   }
   
+  
   private IndexSearcher(IndexReader r, boolean closeReader) {
     reader = r;
     this.closeReader = closeReader;
-
-    List<IndexReader> subReadersList = new ArrayList<IndexReader>();
-    gatherSubReaders(subReadersList, reader);
-    subReaders = subReadersList.toArray(new IndexReader[subReadersList.size()]);
-    docStarts = new int[subReaders.length];
-    int maxDoc = 0;
-    for (int i = 0; i < subReaders.length; i++) {
-      docStarts[i] = maxDoc;
-      maxDoc += subReaders[i].maxDoc();
-    }
+    readerContext = reader.topLevelReaderContext();
+    leafContexts = readerContext.forceLeafs();
   }
 
-  protected void gatherSubReaders(List<IndexReader> allSubReaders, IndexReader r) {
-    ReaderUtil.gatherSubReaders(allSubReaders, r);
-  }
 
   /** Return the {@link IndexReader} this searches. */
   public IndexReader getIndexReader() {
@@ -207,27 +204,27 @@
       throws IOException {
     
     if (filter == null) {
-      for (int i = 0; i < subReaders.length; i++) { // search each subreader
-        collector.setNextReader(subReaders[i], docStarts[i]);
-        Scorer scorer = weight.scorer(subReaders[i], !collector.acceptsDocsOutOfOrder(), true);
+      for (int i = 0; i < leafContexts.length; i++) { // search each subreader
+        collector.setNextReader(leafContexts[i].reader, leafContexts[i].docBase);
+        Scorer scorer = weight.scorer(leafContexts[i], !collector.acceptsDocsOutOfOrder(), true);
         if (scorer != null) {
           scorer.score(collector);
         }
       }
     } else {
-      for (int i = 0; i < subReaders.length; i++) { // search each subreader
-        collector.setNextReader(subReaders[i], docStarts[i]);
-        searchWithFilter(subReaders[i], weight, filter, collector);
+      for (int i = 0; i < leafContexts.length; i++) { // search each subreader
+        collector.setNextReader(leafContexts[i].reader, leafContexts[i].docBase);
+        searchWithFilter(leafContexts[i], weight, filter, collector);
       }
     }
   }
 
-  private void searchWithFilter(IndexReader reader, Weight weight,
+  private void searchWithFilter(ReaderContext info, Weight weight,
       final Filter filter, final Collector collector) throws IOException {
 
     assert filter != null;
     
-    Scorer scorer = weight.scorer(reader, true, false);
+    Scorer scorer = weight.scorer(info, true, false);
     if (scorer == null) {
       return;
     }
@@ -236,7 +233,7 @@
     assert docID == -1 || docID == DocIdSetIterator.NO_MORE_DOCS;
 
     // CHECKME: use ConjunctionScorer here?
-    DocIdSet filterDocIdSet = filter.getDocIdSet(reader);
+    DocIdSet filterDocIdSet = filter.getDocIdSet(info);
     if (filterDocIdSet == null) {
       // this means the filter does not accept any documents.
       return;
@@ -280,10 +277,10 @@
 
   @Override
   public Explanation explain(Weight weight, int doc) throws IOException {
-    int n = ReaderUtil.subIndex(doc, docStarts);
-    int deBasedDoc = doc - docStarts[n];
+    int n = ReaderUtil.subIndex(doc, leafContexts);
+    int deBasedDoc = doc - leafContexts[n].docBase;
     
-    return weight.explain(subReaders[n], deBasedDoc);
+    return weight.explain(leafContexts[n], deBasedDoc);
   }
 
   private boolean fieldSortDoTrackScores;
@@ -305,4 +302,9 @@
     fieldSortDoTrackScores = doTrackScores;
     fieldSortDoMaxScore = doMaxScore;
   }
+  
+  @Override
+  public ReaderContext topLevelReaderContext() {
+    return readerContext;
+  }
 }
Index: lucene/src/java/org/apache/lucene/search/MatchAllDocsQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/MatchAllDocsQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/MatchAllDocsQuery.java	(working copy)
@@ -18,6 +18,7 @@
  */
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.MultiFields;
 import org.apache.lucene.util.ToStringUtils;
@@ -127,13 +128,13 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
-      return new MatchAllScorer(reader, similarity, this,
-          normsField != null ? reader.norms(normsField) : null);
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+      return new MatchAllScorer(context.reader, similarity, this,
+          normsField != null ? context.reader.norms(normsField) : null);
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc) {
+    public Explanation explain(ReaderContext context, int doc) {
       // explain query weight
       Explanation queryExpl = new ComplexExplanation
         (true, getValue(), "MatchAllDocsQuery, product of:");
Index: lucene/src/java/org/apache/lucene/search/MultiPhraseQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/MultiPhraseQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/MultiPhraseQuery.java	(working copy)
@@ -21,6 +21,7 @@
 import java.util.*;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.DocsEnum;
 import org.apache.lucene.index.DocsAndPositionsEnum;
@@ -167,10 +168,10 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
       if (termArrays.size() == 0)                  // optimize zero-term case
         return null;
-
+      final IndexReader reader = context.reader;
       final Bits delDocs = reader.getDeletedDocs();
       
       PhraseQuery.PostingsAndFreq[] postingsFreqs = new PhraseQuery.PostingsAndFreq[termArrays.size()];
@@ -219,7 +220,7 @@
 
       if (slop == 0) {
         ExactPhraseScorer s = new ExactPhraseScorer(this, postingsFreqs, similarity,
-                                                    reader.norms(field));
+            reader.norms(field));
         if (s.noDocs) {
           return null;
         } else {
@@ -232,7 +233,7 @@
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc)
+    public Explanation explain(ReaderContext context, int doc)
       throws IOException {
       ComplexExplanation result = new ComplexExplanation();
       result.setDescription("weight("+getQuery()+" in "+doc+"), product of:");
@@ -263,7 +264,7 @@
       fieldExpl.setDescription("fieldWeight("+getQuery()+" in "+doc+
                                "), product of:");
 
-      Scorer scorer = scorer(reader, true, false);
+      Scorer scorer = scorer(context, true, false);
       if (scorer == null) {
         return new Explanation(0.0f, "no matching docs");
       }
@@ -283,7 +284,7 @@
       fieldExpl.addDetail(idfExpl);
 
       Explanation fieldNormExpl = new Explanation();
-      byte[] fieldNorms = reader.norms(field);
+      byte[] fieldNorms = context.reader.norms(field);
       float fieldNorm =
         fieldNorms!=null ? similarity.decodeNormValue(fieldNorms[doc]) : 1.0f;
       fieldNormExpl.setValue(fieldNorm);
Index: lucene/src/java/org/apache/lucene/search/MultiSearcher.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/MultiSearcher.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/MultiSearcher.java	(working copy)
@@ -126,19 +126,20 @@
     }
   }
 
-  private Searchable[] searchables;
-  private int[] starts;
-  private int maxDoc = 0;
+  private final Searchable[] searchables;
+  private final int[] starts;
+  private final int maxDoc;
 
   /** Creates a searcher which searches <i>searchers</i>. */
   public MultiSearcher(Searchable... searchables) throws IOException {
     this.searchables = searchables;
-
+    int docCount = 0;
     starts = new int[searchables.length + 1];	  // build starts array
     for (int i = 0; i < searchables.length; i++) {
-      starts[i] = maxDoc;
-      maxDoc += searchables[i].maxDoc();          // compute maxDocs
+      starts[i] = docCount;
+      docCount += searchables[i].maxDoc();          // compute maxDocs
     }
+    maxDoc = docCount;
     starts[searchables.length] = maxDoc;
   }
   
Index: lucene/src/java/org/apache/lucene/search/MultiTermQueryWrapperFilter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/MultiTermQueryWrapperFilter.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/MultiTermQueryWrapperFilter.java	(working copy)
@@ -19,8 +19,8 @@
 
 import java.io.IOException;
 
-import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.Fields;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Terms;
 import org.apache.lucene.index.TermsEnum;
 import org.apache.lucene.index.DocsEnum;
@@ -105,8 +105,8 @@
    * results.
    */
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-    final Fields fields = MultiFields.getFields(reader);
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+    final Fields fields = MultiFields.getFields(info.reader);
     if (fields == null) {
       // reader has no fields
       return DocIdSet.EMPTY_DOCIDSET;
@@ -122,9 +122,9 @@
     assert termsEnum != null;
     if (termsEnum.next() != null) {
       // fill into a OpenBitSet
-      final OpenBitSet bitSet = new OpenBitSet(reader.maxDoc());
+      final OpenBitSet bitSet = new OpenBitSet(info.reader.maxDoc());
       int termCount = 0;
-      final Bits delDocs = MultiFields.getDeletedDocs(reader);
+      final Bits delDocs = MultiFields.getDeletedDocs(info.reader);
       DocsEnum docsEnum = null;
       do {
         termCount++;
Index: lucene/src/java/org/apache/lucene/search/PhraseQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/PhraseQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/PhraseQuery.java	(working copy)
@@ -21,6 +21,7 @@
 import java.util.Set;
 import java.util.ArrayList;
 
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.DocsAndPositionsEnum;
 import org.apache.lucene.index.IndexReader;
@@ -174,10 +175,10 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
       if (terms.size() == 0)			  // optimize zero-term case
         return null;
-
+      final IndexReader reader = context.reader;
       PostingsAndFreq[] postingsFreqs = new PostingsAndFreq[terms.size()];
       final Bits delDocs = reader.getDeletedDocs();
       for (int i = 0; i < terms.size(); i++) {
@@ -206,7 +207,7 @@
 
       if (slop == 0) {				  // optimize exact case
         ExactPhraseScorer s = new ExactPhraseScorer(this, postingsFreqs, similarity,
-                                                    reader.norms(field));
+            reader.norms(field));
         if (s.noDocs) {
           return null;
         } else {
@@ -215,12 +216,12 @@
       } else {
         return
           new SloppyPhraseScorer(this, postingsFreqs, similarity, slop,
-                                 reader.norms(field));
+              reader.norms(field));
       }
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc)
+    public Explanation explain(ReaderContext context, int doc)
       throws IOException {
 
       Explanation result = new Explanation();
@@ -267,7 +268,7 @@
       fieldExpl.setDescription("fieldWeight("+field+":"+query+" in "+doc+
                                "), product of:");
 
-      Scorer scorer = scorer(reader, true, false);
+      Scorer scorer = scorer(context, true, false);
       if (scorer == null) {
         return new Explanation(0.0f, "no matching docs");
       }
@@ -287,7 +288,7 @@
       fieldExpl.addDetail(idfExpl);
 
       Explanation fieldNormExpl = new Explanation();
-      byte[] fieldNorms = reader.norms(field);
+      byte[] fieldNorms = context.reader.norms(field);
       float fieldNorm =
         fieldNorms!=null ? similarity.decodeNormValue(fieldNorms[doc]) : 1.0f;
       fieldNormExpl.setValue(fieldNorm);
Index: lucene/src/java/org/apache/lucene/search/QueryWrapperFilter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/QueryWrapperFilter.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/QueryWrapperFilter.java	(working copy)
@@ -18,9 +18,11 @@
  */
 
 import java.io.IOException;
-
-
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.FieldSelector;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
+import org.apache.lucene.index.Term;
 
 /** 
  * Constrains search results to only match those which also match a provided
@@ -48,12 +50,13 @@
   }
 
   @Override
-  public DocIdSet getDocIdSet(final IndexReader reader) throws IOException {
-    final Weight weight = query.weight(new IndexSearcher(reader));
+  public DocIdSet getDocIdSet(final ReaderContext info) throws IOException {
+    // nocommit - we should somehow know which
+    final Weight weight = query.weight(new WeightOnlyearcher(info));
     return new DocIdSet() {
       @Override
       public DocIdSetIterator iterator() throws IOException {
-        return weight.scorer(reader, true, false);
+        return weight.scorer(info, true, false);
       }
       @Override
       public boolean isCacheable() { return false; }
@@ -76,4 +79,94 @@
   public int hashCode() {
     return query.hashCode() ^ 0x923F64B9;
   }
+
+  /*
+   * nocommit - This searcher acts like a Searcher build from a sub reader
+   * in the given ReaderInfos but returns the ReaderInfo array as it would be
+   * build from the subs parent. This is needed to allow the created Weight to
+   * hold the ReaderInfo array of the top level IR for caching and assertion
+   * purposes. 
+   * 
+   * this should work somehow differently - will leave it like that for now
+   */
+  private static final class WeightOnlyearcher extends Searcher {
+    private final ReaderContext context;
+    private final IndexReader reader;
+    
+    public WeightOnlyearcher(ReaderContext context) {
+      this.context = context;
+      this.reader = context.reader;
+    }
+
+    @Override
+    public int docFreq(Term term) throws IOException {
+      return reader.docFreq(term);
+    }
+
+    @Override
+    public int[] docFreqs(Term[] terms) throws IOException {
+      final int[] result = new int[terms.length];
+      for (int i = 0; i < terms.length; i++) {
+        result[i] = docFreq(terms[i]);
+      }
+      return result;
+    }
+
+    @Override
+    public int maxDoc() {
+      return reader.maxDoc();
+    }
+
+    @Override
+    public Query rewrite(Query original) throws IOException {
+      Query query = original;
+      
+      for (Query rewrittenQuery = query.rewrite(reader); rewrittenQuery != query;
+           rewrittenQuery = query.rewrite(reader)) {
+        query = rewrittenQuery;
+      }
+      return query;
+    }
+
+
+    @Override
+    public void close() {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Document doc(int i) {
+      throw new UnsupportedOperationException();
+    }
+    
+    @Override
+    public Document doc(int i, FieldSelector fieldSelector) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Explanation explain(Weight weight,int doc) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public void search(Weight weight, Filter filter, Collector results) {
+      throw new UnsupportedOperationException();
+    }
+    
+    @Override
+    public TopDocs search(Weight weight,Filter filter,int n) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public TopFieldDocs search(Weight weight,Filter filter,int n,Sort sort) {
+      throw new UnsupportedOperationException();
+    }
+    
+    @Override
+    public ReaderContext topLevelReaderContext() {
+      return context;
+    }
+  }
 }
Index: lucene/src/java/org/apache/lucene/search/Searcher.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/Searcher.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/Searcher.java	(working copy)
@@ -21,6 +21,7 @@
 
 import org.apache.lucene.document.Document;
 import org.apache.lucene.index.CorruptIndexException;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.document.FieldSelector;
 
@@ -168,6 +169,14 @@
     }
     return result;
   }
+  
+  /**
+   * TODO
+   * @return
+   */
+  public ReaderContext topLevelReaderContext() {
+    return null;
+  }
 
   abstract public void search(Weight weight, Filter filter, Collector results) throws IOException;
   abstract public void close() throws IOException;
Index: lucene/src/java/org/apache/lucene/search/SpanQueryFilter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/SpanQueryFilter.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/SpanQueryFilter.java	(working copy)
@@ -17,6 +17,7 @@
 
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.spans.SpanQuery;
 import org.apache.lucene.search.spans.Spans;
 import org.apache.lucene.util.OpenBitSet;
@@ -52,8 +53,8 @@
   }
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-    SpanFilterResult result = bitSpans(reader);
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+    SpanFilterResult result = bitSpans(info.reader);
     return result.getDocIdSet();
   }
 
Index: lucene/src/java/org/apache/lucene/search/TermQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/TermQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/TermQuery.java	(working copy)
@@ -21,8 +21,10 @@
 import java.util.Set;
 
 import org.apache.lucene.index.DocsEnum;
-import org.apache.lucene.index.Term;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
+import org.apache.lucene.index.IndexReader.ReaderContext;
+import org.apache.lucene.index.Term;
 import org.apache.lucene.search.Explanation.IDFExplanation;
 import org.apache.lucene.util.ToStringUtils;
 
@@ -40,10 +42,12 @@
     private float queryNorm;
     private float queryWeight;
     private IDFExplanation idfExp;
+    private transient final ReaderContext searcherContext;
 
     public TermWeight(Searcher searcher)
       throws IOException {
       this.similarity = getSimilarity(searcher);
+      searcherContext = searcher.topLevelReaderContext();
       if (docFreq != -1) {
         idfExp = similarity.idfExplain(term, searcher, docFreq);
       } else {
@@ -75,7 +79,10 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+      assert searcherContext == null || context.isAtomic;
+      assert searcherContext == null || searcherContext.leafs() == null || searcherContext.leafs()[((AtomicContext)context).ord] == context;
+      final IndexReader reader = context.reader;
       DocsEnum docs = reader.termDocsEnum(reader.getDeletedDocs(),
                                           term.field(),
                                           term.bytes());
@@ -88,8 +95,9 @@
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc)
+    public Explanation explain(ReaderContext context, int doc)
       throws IOException {
+      final IndexReader reader = context.reader;
 
       ComplexExplanation result = new ComplexExplanation();
       result.setDescription("weight("+getQuery()+" in "+doc+"), product of:");
Index: lucene/src/java/org/apache/lucene/search/Weight.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/Weight.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/Weight.java	(working copy)
@@ -21,6 +21,7 @@
 import java.io.Serializable;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 /**
  * Expert: Calculate query weights and build query scorers.
@@ -41,7 +42,7 @@
  * query.
  * <li>The query normalization factor is passed to {@link #normalize(float)}. At
  * this point the weighting is complete.
- * <li>A <code>Scorer</code> is constructed by {@link #scorer(IndexReader,boolean,boolean)}.
+ * <li>A <code>Scorer</code> is constructed by {@link #scorer(ReaderContext,boolean,boolean)}.
  * </ol>
  * 
  * @since 2.9
@@ -51,12 +52,12 @@
   /**
    * An explanation of the score computation for the named document.
    * 
-   * @param reader sub-reader containing the give doc
-   * @param doc
+   * @param context the readers context to create the {@link Explanation} for.
+   * @param doc the document's id relative to the given context's reader
    * @return an Explanation for the score
    * @throws IOException
    */
-  public abstract Explanation explain(IndexReader reader, int doc) throws IOException;
+  public abstract Explanation explain(ReaderContext context, int doc) throws IOException;
 
   /** The query that this concerns. */
   public abstract Query getQuery();
@@ -79,8 +80,8 @@
    * <b>NOTE:</b> null can be returned if no documents will be scored by this
    * query.
    * 
-   * @param reader
-   *          the {@link IndexReader} for which to return the {@link Scorer}.
+   * @param context
+   *          the {@link ReaderContext} for which to return the {@link Scorer}.
    * @param scoreDocsInOrder
    *          specifies whether in-order scoring of documents is required. Note
    *          that if set to false (i.e., out-of-order scoring is required),
@@ -96,7 +97,7 @@
    * @return a {@link Scorer} which scores documents in/out-of order.
    * @throws IOException
    */
-  public abstract Scorer scorer(IndexReader reader, boolean scoreDocsInOrder,
+  public abstract Scorer scorer(ReaderContext context, boolean scoreDocsInOrder,
       boolean topScorer) throws IOException;
   
   /** The sum of squared weights of contained query clauses. */
@@ -106,7 +107,7 @@
    * Returns true iff this implementation scores docs only out of order. This
    * method is used in conjunction with {@link Collector}'s
    * {@link Collector#acceptsDocsOutOfOrder() acceptsDocsOutOfOrder} and
-   * {@link #scorer(org.apache.lucene.index.IndexReader, boolean, boolean)} to
+   * {@link #scorer(ReaderContext, boolean, boolean)} to
    * create a matching {@link Scorer} instance for a given {@link Collector}, or
    * vice versa.
    * <p>
Index: lucene/src/java/org/apache/lucene/search/function/CustomScoreQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/function/CustomScoreQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/function/CustomScoreQuery.java	(working copy)
@@ -22,6 +22,7 @@
 import java.util.Arrays;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.ComplexExplanation;
 import org.apache.lucene.search.Explanation;
@@ -239,40 +240,40 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
       // Pass true for "scoresDocsInOrder", because we
       // require in-order scoring, even if caller does not,
       // since we call advance on the valSrcScorers.  Pass
       // false for "topScorer" because we will not invoke
       // score(Collector) on these scorers:
-      Scorer subQueryScorer = subQueryWeight.scorer(reader, true, false);
+      Scorer subQueryScorer = subQueryWeight.scorer(context, true, false);
       if (subQueryScorer == null) {
         return null;
       }
       Scorer[] valSrcScorers = new Scorer[valSrcWeights.length];
       for(int i = 0; i < valSrcScorers.length; i++) {
-         valSrcScorers[i] = valSrcWeights[i].scorer(reader, true, topScorer);
+         valSrcScorers[i] = valSrcWeights[i].scorer(context, true, topScorer);
       }
-      return new CustomScorer(similarity, reader, this, subQueryScorer, valSrcScorers);
+      return new CustomScorer(similarity, context.reader, this, subQueryScorer, valSrcScorers);
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
-      Explanation explain = doExplain(reader, doc);
+    public Explanation explain(ReaderContext context, int doc) throws IOException {
+      Explanation explain = doExplain(context, doc);
       return explain == null ? new Explanation(0.0f, "no matching docs") : explain;
     }
     
-    private Explanation doExplain(IndexReader reader, int doc) throws IOException {
-      Explanation subQueryExpl = subQueryWeight.explain(reader, doc);
+    private Explanation doExplain(ReaderContext info, int doc) throws IOException {
+      Explanation subQueryExpl = subQueryWeight.explain(info, doc);
       if (!subQueryExpl.isMatch()) {
         return subQueryExpl;
       }
       // match
       Explanation[] valSrcExpls = new Explanation[valSrcWeights.length];
       for(int i = 0; i < valSrcWeights.length; i++) {
-        valSrcExpls[i] = valSrcWeights[i].explain(reader, doc);
+        valSrcExpls[i] = valSrcWeights[i].explain(info, doc);
       }
-      Explanation customExp = CustomScoreQuery.this.getCustomScoreProvider(reader).customExplain(doc,subQueryExpl,valSrcExpls);
+      Explanation customExp = CustomScoreQuery.this.getCustomScoreProvider(info.reader).customExplain(doc,subQueryExpl,valSrcExpls);
       float sc = getValue() * customExp.getValue();
       Explanation res = new ComplexExplanation(
         true, sc, CustomScoreQuery.this.toString() + ", product of:");
Index: lucene/src/java/org/apache/lucene/search/function/ValueSourceQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/function/ValueSourceQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/function/ValueSourceQuery.java	(working copy)
@@ -19,6 +19,7 @@
 
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.search.*;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.MultiFields;
 import org.apache.lucene.util.ToStringUtils;
@@ -99,14 +100,14 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
-      return new ValueSourceScorer(similarity, reader, this);
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+      return new ValueSourceScorer(similarity, context.reader, this);
     }
 
     /*(non-Javadoc) @see org.apache.lucene.search.Weight#explain(org.apache.lucene.index.IndexReader, int) */
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
-      DocValues vals = valSrc.getValues(reader);
+    public Explanation explain(ReaderContext context, int doc) throws IOException {
+      DocValues vals = valSrc.getValues(context.reader);
       float sc = queryWeight * vals.floatVal(doc);
 
       Explanation result = new ComplexExplanation(
Index: lucene/src/java/org/apache/lucene/search/payloads/PayloadNearQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/payloads/PayloadNearQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/payloads/PayloadNearQuery.java	(working copy)
@@ -17,7 +17,7 @@
  * limitations under the License.
  */
 
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.Explanation;
 import org.apache.lucene.search.Scorer;
 import org.apache.lucene.search.Searcher;
@@ -143,10 +143,10 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder,
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder,
         boolean topScorer) throws IOException {
-      return new PayloadNearSpanScorer(query.getSpans(reader), this,
-          similarity, reader.norms(query.getField()));
+      return new PayloadNearSpanScorer(query.getSpans(context.reader), this,
+          similarity, context.reader.norms(query.getField()));
     }
   }
 
Index: lucene/src/java/org/apache/lucene/search/payloads/PayloadTermQuery.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/payloads/PayloadTermQuery.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/payloads/PayloadTermQuery.java	(working copy)
@@ -17,9 +17,9 @@
  * limitations under the License.
  */
 
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.DocsAndPositionsEnum;
-import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.search.Searcher;
 import org.apache.lucene.search.Scorer;
 import org.apache.lucene.search.Weight;
@@ -74,10 +74,10 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder,
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder,
         boolean topScorer) throws IOException {
-      return new PayloadTermSpanScorer((TermSpans) query.getSpans(reader),
-          this, similarity, reader.norms(query.getField()));
+      return new PayloadTermSpanScorer((TermSpans) query.getSpans(context.reader),
+          this, similarity, context.reader.norms(query.getField()));
     }
 
     protected class PayloadTermSpanScorer extends SpanScorer {
Index: lucene/src/java/org/apache/lucene/search/spans/SpanWeight.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/spans/SpanWeight.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/search/spans/SpanWeight.java	(working copy)
@@ -17,7 +17,7 @@
  * limitations under the License.
  */
 
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.*;
 import org.apache.lucene.search.Explanation.IDFExplanation;
@@ -72,13 +72,13 @@
   }
 
   @Override
-  public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
-    return new SpanScorer(query.getSpans(reader), this, similarity, reader
+  public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+    return new SpanScorer(query.getSpans(context.reader), this, similarity, context.reader
         .norms(query.getField()));
   }
 
   @Override
-  public Explanation explain(IndexReader reader, int doc)
+  public Explanation explain(ReaderContext context, int doc)
     throws IOException {
 
     ComplexExplanation result = new ComplexExplanation();
@@ -111,12 +111,12 @@
     fieldExpl.setDescription("fieldWeight("+field+":"+query.toString(field)+
                              " in "+doc+"), product of:");
 
-    Explanation tfExpl = ((SpanScorer)scorer(reader, true, false)).explain(doc);
+    Explanation tfExpl = ((SpanScorer)scorer(context, true, false)).explain(doc);
     fieldExpl.addDetail(tfExpl);
     fieldExpl.addDetail(idfExpl);
 
     Explanation fieldNormExpl = new Explanation();
-    byte[] fieldNorms = reader.norms(field);
+    byte[] fieldNorms = context.reader.norms(field);
     float fieldNorm =
       fieldNorms!=null ? similarity.decodeNormValue(fieldNorms[doc]) : 1.0f;
     fieldNormExpl.setValue(fieldNorm);
Index: lucene/src/java/org/apache/lucene/util/ReaderUtil.java
===================================================================
--- lucene/src/java/org/apache/lucene/util/ReaderUtil.java	(revision 1054582)
+++ lucene/src/java/org/apache/lucene/util/ReaderUtil.java	(working copy)
@@ -19,9 +19,13 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.io.IOException;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
+import org.apache.lucene.index.IndexReader.CompositeContext;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 /**
  * Common util methods for dealing with {@link IndexReader}s.
@@ -148,6 +152,67 @@
         .toArray(new IndexReader[subReadersList.size()]);
     return subReaders[subIndex];
   }
+  
+  public static ReaderContext buildReaderContext(IndexReader reader) {
+    return new ReaderContextBuilder(reader).build();
+  }
+  
+  public static class ReaderContextBuilder {
+    private final IndexReader reader;
+    private final AtomicContext[] leafs;
+    private int leafOrd = 0;
+    private int leafDocBase = 0;
+    public ReaderContextBuilder(IndexReader reader) {
+      this.reader = reader;
+      leafs = new AtomicContext[numLeafes(reader)];
+    }
+    
+    public ReaderContext build() {
+      return build(null, reader, 0, 0);
+    }
+    
+    private ReaderContext build(CompositeContext parent, IndexReader reader, int ord, int docBase) {
+      IndexReader[] sequentialSubReaders = reader.getSequentialSubReaders();
+      if (sequentialSubReaders == null) {
+        AtomicContext atomic = new AtomicContext(parent, reader, ord, docBase, leafOrd, leafDocBase);
+        leafs[leafOrd++] = atomic;
+        leafDocBase += reader.maxDoc();
+        return atomic;
+      } else {
+        ReaderContext[] children = new ReaderContext[sequentialSubReaders.length];
+        final CompositeContext newParent;
+        if (parent == null) {
+          newParent = new CompositeContext(reader, children, leafs);
+        } else {
+          newParent = new CompositeContext(parent, reader, ord, docBase, children);
+        }
+        
+        int newDocBase = 0;
+        for (int i = 0; i < sequentialSubReaders.length; i++) {
+          build(newParent, sequentialSubReaders[i], i, newDocBase);
+          newDocBase += sequentialSubReaders[i].maxDoc();
+        }
+        return newParent;
+      }
+    }
+    
+    private int numLeafes(IndexReader reader) {
+      final AtomicInteger numLeafes = new AtomicInteger();
+      try {
+        new Gather(reader) {
+          @Override
+          protected void add(int base, IndexReader r) {
+            numLeafes.incrementAndGet();
+          }
+        }.run();
+      } catch (IOException ioe) {
+        // won't happen
+        throw new RuntimeException(ioe);
+      }
+      return numLeafes.get();
+    }
+    
+  }
 
 
   /**
@@ -175,4 +240,30 @@
     }
     return hi;
   }
+  
+  /**
+   * Returns index of the searcher/reader for document <code>n</code> in the
+   * array used to construct this searcher/reader.
+   */
+  public static int subIndex(int n, AtomicContext[] leafs) { // find
+    // searcher/reader for doc n:
+    int size = leafs.length;
+    int lo = 0; // search starts array
+    int hi = size - 1; // for first element less than n, return its index
+    while (hi >= lo) {
+      int mid = (lo + hi) >>> 1;
+      int midValue = leafs[mid].docBase;
+      if (n < midValue)
+        hi = mid - 1;
+      else if (n > midValue)
+        lo = mid + 1;
+      else { // found a match
+        while (mid + 1 < size && leafs[mid + 1].docBase == midValue) {
+          mid++; // scan to last match
+        }
+        return mid;
+      }
+    }
+    return hi;
+  }
 }
Index: lucene/src/test/org/apache/lucene/search/CachingWrapperFilterHelper.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/CachingWrapperFilterHelper.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/CachingWrapperFilterHelper.java	(working copy)
@@ -20,7 +20,8 @@
 import java.io.IOException;
 
 import junit.framework.Assert;
-import org.apache.lucene.index.IndexReader;
+
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 /**
  * A unit test helper class to test when the filter is getting cached and when it is not.
@@ -41,10 +42,10 @@
   }
   
   @Override
-  public synchronized DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+  public synchronized DocIdSet getDocIdSet(ReaderContext info) throws IOException {
 
     final int saveMissCount = missCount;
-    DocIdSet docIdSet = super.getDocIdSet(reader);
+    DocIdSet docIdSet = super.getDocIdSet(info);
 
     if (shouldHaveCache) {
       Assert.assertEquals("Cache should have data ", saveMissCount, missCount);
Index: lucene/src/test/org/apache/lucene/search/JustCompileSearch.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/JustCompileSearch.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/JustCompileSearch.java	(working copy)
@@ -23,6 +23,7 @@
 import org.apache.lucene.document.FieldSelector;
 import org.apache.lucene.index.CorruptIndexException;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.PriorityQueue;
@@ -266,7 +267,7 @@
     // still added here in case someone will add abstract methods in the future.
     
     @Override
-    public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+    public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
       return null;
     }
   }
@@ -395,7 +396,7 @@
     }
     
     @Override
-    public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+    public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
       return null;
     }    
   }
@@ -447,7 +448,7 @@
   static final class JustCompileWeight extends Weight {
 
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
+    public Explanation explain(ReaderContext context, int doc) throws IOException {
       throw new UnsupportedOperationException(UNSUPPORTED_MSG);
     }
 
@@ -472,7 +473,7 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer)
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer)
         throws IOException {
       throw new UnsupportedOperationException(UNSUPPORTED_MSG);
     }
Index: lucene/src/test/org/apache/lucene/search/MockFilter.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/MockFilter.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/MockFilter.java	(working copy)
@@ -17,7 +17,7 @@
  * limitations under the License.
  */
 
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.util.DocIdBitSet;
 import java.util.BitSet;
 
@@ -25,7 +25,7 @@
   private boolean wasCalled;
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) {
+  public DocIdSet getDocIdSet(ReaderContext info) {
     wasCalled = true;
     return new DocIdBitSet(new BitSet());
   }
Index: lucene/src/test/org/apache/lucene/search/QueryUtils.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/QueryUtils.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/QueryUtils.java	(working copy)
@@ -12,6 +12,8 @@
 import org.apache.lucene.analysis.MockAnalyzer;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.MultiReader;
@@ -258,7 +260,7 @@
    */
   public static void checkSkipTo(final Query q, final IndexSearcher s) throws IOException {
     //System.out.println("Checking "+q);
-    
+    final AtomicContext[] context = s.topLevelReaderContext().forceLeafs();
     if (q.weight(s).scoresDocsOutOfOrder()) return;  // in this case order of skipTo() might differ from that of next().
 
     final int skip_op = 0;
@@ -288,8 +290,8 @@
 
         s.search(q, new Collector() {
           private Scorer sc;
-          private IndexReader reader;
           private Scorer scorer;
+          private int leafPtr;
 
           @Override
           public void setScorer(Scorer scorer) throws IOException {
@@ -303,7 +305,7 @@
             try {
               if (scorer == null) {
                 Weight w = q.weight(s);
-                scorer = w.scorer(reader, true, false);
+                scorer = w.scorer(context[leafPtr], true, false);
               }
               
               int op = order[(opidx[0]++) % order.length];
@@ -346,14 +348,17 @@
             // previous reader, hits NO_MORE_DOCS
             if (lastReader[0] != null) {
               final IndexReader previousReader = lastReader[0];
-              Weight w = q.weight(new IndexSearcher(previousReader));
-              Scorer scorer = w.scorer(previousReader, true, false);
+              IndexSearcher indexSearcher = new IndexSearcher(previousReader);
+              Weight w = q.weight(indexSearcher);
+              Scorer scorer = w.scorer(indexSearcher.topLevelReaderContext(), true, false);
               if (scorer != null) {
                 boolean more = scorer.advance(lastDoc[0] + 1) != DocIdSetIterator.NO_MORE_DOCS;
                 Assert.assertFalse("query's last doc was "+ lastDoc[0] +" but skipTo("+(lastDoc[0]+1)+") got to "+scorer.docID(),more);
               }
+              leafPtr++;
             }
-            this.reader = lastReader[0] = reader;
+            lastReader[0] = reader;
+            assert context[leafPtr].reader == reader;
             this.scorer = null;
             lastDoc[0] = -1;
           }
@@ -368,8 +373,9 @@
           // confirm that skipping beyond the last doc, on the
           // previous reader, hits NO_MORE_DOCS
           final IndexReader previousReader = lastReader[0];
-          Weight w = q.weight(new IndexSearcher(previousReader));
-          Scorer scorer = w.scorer(previousReader, true, false);
+          IndexSearcher indexSearcher = new IndexSearcher(previousReader);
+          Weight w = q.weight(indexSearcher);
+          Scorer scorer = w.scorer(previousReader.topLevelReaderContext() , true, false);
           if (scorer != null) {
             boolean more = scorer.advance(lastDoc[0] + 1) != DocIdSetIterator.NO_MORE_DOCS;
             Assert.assertFalse("query's last doc was "+ lastDoc[0] +" but skipTo("+(lastDoc[0]+1)+") got to "+scorer.docID(),more);
@@ -384,10 +390,10 @@
     final float maxDiff = 1e-3f;
     final int lastDoc[] = {-1};
     final IndexReader lastReader[] = {null};
-
+    final ReaderContext[] context = s.topLevelReaderContext().forceLeafs();
     s.search(q,new Collector() {
       private Scorer scorer;
-      private IndexReader reader;
+      private int leafPtr;
       @Override
       public void setScorer(Scorer scorer) throws IOException {
         this.scorer = scorer;
@@ -399,7 +405,7 @@
           long startMS = System.currentTimeMillis();
           for (int i=lastDoc[0]+1; i<=doc; i++) {
             Weight w = q.weight(s);
-            Scorer scorer = w.scorer(reader, true, false);
+            Scorer scorer = w.scorer(context[leafPtr], true, false);
             Assert.assertTrue("query collected "+doc+" but skipTo("+i+") says no more docs!",scorer.advance(i) != DocIdSetIterator.NO_MORE_DOCS);
             Assert.assertEquals("query collected "+doc+" but skipTo("+i+") got to "+scorer.docID(),doc,scorer.docID());
             float skipToScore = scorer.score();
@@ -424,15 +430,17 @@
         // previous reader, hits NO_MORE_DOCS
         if (lastReader[0] != null) {
           final IndexReader previousReader = lastReader[0];
-          Weight w = q.weight(new IndexSearcher(previousReader));
-          Scorer scorer = w.scorer(previousReader, true, false);
+          IndexSearcher indexSearcher = new IndexSearcher(previousReader);
+          Weight w = q.weight(indexSearcher);
+          Scorer scorer = w.scorer(indexSearcher.topLevelReaderContext(), true, false);
           if (scorer != null) {
             boolean more = scorer.advance(lastDoc[0] + 1) != DocIdSetIterator.NO_MORE_DOCS;
             Assert.assertFalse("query's last doc was "+ lastDoc[0] +" but skipTo("+(lastDoc[0]+1)+") got to "+scorer.docID(),more);
           }
+          leafPtr++;
         }
 
-        this.reader = lastReader[0] = reader;
+        lastReader[0] = reader;
         lastDoc[0] = -1;
       }
       @Override
@@ -445,8 +453,9 @@
       // confirm that skipping beyond the last doc, on the
       // previous reader, hits NO_MORE_DOCS
       final IndexReader previousReader = lastReader[0];
-      Weight w = q.weight(new IndexSearcher(previousReader));
-      Scorer scorer = w.scorer(previousReader, true, false);
+      IndexSearcher indexSearcher = new IndexSearcher(previousReader);
+      Weight w = q.weight(indexSearcher);
+      Scorer scorer = w.scorer(indexSearcher.topLevelReaderContext(), true, false);
       if (scorer != null) {
         boolean more = scorer.advance(lastDoc[0] + 1) != DocIdSetIterator.NO_MORE_DOCS;
         Assert.assertFalse("query's last doc was "+ lastDoc[0] +" but skipTo("+(lastDoc[0]+1)+") got to "+scorer.docID(),more);
Index: lucene/src/test/org/apache/lucene/search/SingleDocTestFilter.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/SingleDocTestFilter.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/SingleDocTestFilter.java	(working copy)
@@ -17,7 +17,7 @@
  * limitations under the License.
  */
 
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.util.DocIdBitSet;
 
 import java.util.BitSet;
@@ -31,8 +31,8 @@
   }
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-    BitSet bits = new BitSet(reader.maxDoc());
+  public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+    BitSet bits = new BitSet(info.reader.maxDoc());
     bits.set(doc);
     return new DocIdBitSet(bits);
   }
Index: lucene/src/test/org/apache/lucene/search/TestBooleanPrefixQuery.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestBooleanPrefixQuery.java	(revision 1052196)
+++ lucene/src/test/org/apache/lucene/search/TestBooleanPrefixQuery.java	(working copy)
@@ -21,6 +21,7 @@
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.search.PrefixQuery;
@@ -38,7 +39,7 @@
     if (q instanceof BooleanQuery) {
       return ((BooleanQuery) q).getClauses().length;
     } else if (q instanceof ConstantScoreQuery) {
-      DocIdSetIterator iter = ((ConstantScoreQuery) q).getFilter().getDocIdSet(r).iterator();
+      DocIdSetIterator iter = ((ConstantScoreQuery) q).getFilter().getDocIdSet(r.topLevelReaderContext()).iterator();
       int count = 0;
       while(iter.nextDoc() != DocIdSetIterator.NO_MORE_DOCS) {
         count++;
Index: lucene/src/test/org/apache/lucene/search/TestCachingWrapperFilter.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestCachingWrapperFilter.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestCachingWrapperFilter.java	(working copy)
@@ -23,6 +23,8 @@
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.index.SerialMergeScheduler;
 import org.apache.lucene.index.SlowMultiReaderWrapper;
@@ -40,20 +42,20 @@
     writer.close();
 
     IndexReader reader = IndexReader.open(dir, true);
-
+    ReaderContext context = reader.topLevelReaderContext();
     MockFilter filter = new MockFilter();
     CachingWrapperFilter cacher = new CachingWrapperFilter(filter);
 
     // first time, nested filter is called
-    cacher.getDocIdSet(reader);
+    cacher.getDocIdSet(context);
     assertTrue("first time", filter.wasCalled());
 
     // make sure no exception if cache is holding the wrong docIdSet
-    cacher.getDocIdSet(reader);
+    cacher.getDocIdSet(context);
 
     // second time, nested filter should not be called
     filter.clear();
-    cacher.getDocIdSet(reader);
+    cacher.getDocIdSet(context);
     assertFalse("second time", filter.wasCalled());
 
     reader.close();
@@ -66,17 +68,18 @@
     writer.close();
 
     IndexReader reader = IndexReader.open(dir, true);
+    ReaderContext context = reader.topLevelReaderContext();
 
     final Filter filter = new Filter() {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) {
+      public DocIdSet getDocIdSet(ReaderContext info) {
         return null;
       }
     };
     CachingWrapperFilter cacher = new CachingWrapperFilter(filter);
 
     // the caching filter should return the empty set constant
-    assertSame(DocIdSet.EMPTY_DOCIDSET, cacher.getDocIdSet(reader));
+    assertSame(DocIdSet.EMPTY_DOCIDSET, cacher.getDocIdSet(context));
     
     reader.close();
     dir.close();
@@ -88,10 +91,11 @@
     writer.close();
 
     IndexReader reader = IndexReader.open(dir, true);
+    ReaderContext context = reader.topLevelReaderContext();
 
     final Filter filter = new Filter() {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) {
+      public DocIdSet getDocIdSet(ReaderContext info) {
         return new DocIdSet() {
           @Override
           public DocIdSetIterator iterator() {
@@ -103,16 +107,17 @@
     CachingWrapperFilter cacher = new CachingWrapperFilter(filter);
 
     // the caching filter should return the empty set constant
-    assertSame(DocIdSet.EMPTY_DOCIDSET, cacher.getDocIdSet(reader));
+    assertSame(DocIdSet.EMPTY_DOCIDSET, cacher.getDocIdSet(context));
     
     reader.close();
     dir.close();
   }
   
   private static void assertDocIdSetCacheable(IndexReader reader, Filter filter, boolean shouldCacheable) throws IOException {
+    ReaderContext context = reader.topLevelReaderContext();
     final CachingWrapperFilter cacher = new CachingWrapperFilter(filter);
-    final DocIdSet originalSet = filter.getDocIdSet(reader);
-    final DocIdSet cachedSet = cacher.getDocIdSet(reader);
+    final DocIdSet originalSet = filter.getDocIdSet(context);
+    final DocIdSet cachedSet = cacher.getDocIdSet(context);
     assertTrue(cachedSet.isCacheable());
     assertEquals(shouldCacheable, originalSet.isCacheable());
     //System.out.println("Original: "+originalSet.getClass().getName()+" -- cached: "+cachedSet.getClass().getName());
@@ -140,7 +145,7 @@
     // a openbitset filter is always cacheable
     assertDocIdSetCacheable(reader, new Filter() {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) {
+      public DocIdSet getDocIdSet(ReaderContext info) {
         return new OpenBitSet();
       }
     }, true);
Index: lucene/src/test/org/apache/lucene/search/TestDisjunctionMaxQuery.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestDisjunctionMaxQuery.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestDisjunctionMaxQuery.java	(working copy)
@@ -25,6 +25,7 @@
 import org.apache.lucene.index.SlowMultiReaderWrapper;
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.index.Term;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.store.Directory;
 
 import java.text.DecimalFormat;
@@ -163,9 +164,9 @@
     dq.add(tq("dek", "DOES_NOT_EXIST"));
     
     QueryUtils.check(random, dq, s);
-    
+    assertTrue(s.topLevelReaderContext().isAtomic);
     final Weight dw = dq.weight(s);
-    final Scorer ds = dw.scorer(s.getIndexReader(), true, false);
+    final Scorer ds = dw.scorer(s.topLevelReaderContext(), true, false);
     final boolean skipOk = ds.advance(3) != DocIdSetIterator.NO_MORE_DOCS;
     if (skipOk) {
       fail("firsttime skipTo found a match? ... "
@@ -177,11 +178,10 @@
     final DisjunctionMaxQuery dq = new DisjunctionMaxQuery(0.0f);
     dq.add(tq("dek", "albino"));
     dq.add(tq("dek", "DOES_NOT_EXIST"));
-    
+    assertTrue(s.topLevelReaderContext().isAtomic);
     QueryUtils.check(random, dq, s);
-    
     final Weight dw = dq.weight(s);
-    final Scorer ds = dw.scorer(s.getIndexReader(), true, false);
+    final Scorer ds = dw.scorer(s.topLevelReaderContext(), true, false);
     assertTrue("firsttime skipTo found no match",
         ds.advance(3) != DocIdSetIterator.NO_MORE_DOCS);
     assertEquals("found wrong docid", "d4", r.document(ds.docID()).get("id"));
Index: lucene/src/test/org/apache/lucene/search/TestDocIdSet.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestDocIdSet.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestDocIdSet.java	(working copy)
@@ -28,6 +28,7 @@
 import org.apache.lucene.document.Field.Index;
 import org.apache.lucene.document.Field.Store;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.LuceneTestCase;
@@ -114,7 +115,7 @@
     // Now search w/ a Filter which returns a null DocIdSet
     Filter f = new Filter() {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
         return null;
       }
     };
Index: lucene/src/test/org/apache/lucene/search/TestFilteredQuery.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestFilteredQuery.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestFilteredQuery.java	(working copy)
@@ -20,6 +20,7 @@
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.BooleanClause.Occur;
@@ -87,7 +88,7 @@
   private static Filter newStaticFilterB() {
     return new Filter() {
       @Override
-      public DocIdSet getDocIdSet (IndexReader reader) {
+      public DocIdSet getDocIdSet (ReaderContext info) {
         BitSet bitset = new BitSet(5);
         bitset.set (1);
         bitset.set (3);
@@ -158,7 +159,7 @@
   private static Filter newStaticFilterA() {
     return new Filter() {
       @Override
-      public DocIdSet getDocIdSet (IndexReader reader) {
+      public DocIdSet getDocIdSet (ReaderContext info) {
         BitSet bitset = new BitSet(5);
         bitset.set(0, 5);
         return new DocIdBitSet(bitset);
@@ -216,7 +217,7 @@
     bq.add(new TermQuery(new Term("field", "two")), BooleanClause.Occur.SHOULD);
     ScoreDoc[] hits = searcher.search(query, 1000).scoreDocs;
     assertEquals(1, hits.length);
-    QueryUtils.check(random, query,searcher);    
+    QueryUtils.check(random, query, searcher);    
   }
 }
 
Index: lucene/src/test/org/apache/lucene/search/TestFilteredSearch.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestFilteredSearch.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestFilteredSearch.java	(working copy)
@@ -25,6 +25,8 @@
 import org.apache.lucene.document.Field;
 import org.apache.lucene.index.CorruptIndexException;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
+import org.apache.lucene.index.IndexReader.AtomicContext;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.IndexWriterConfig.OpenMode;
@@ -33,6 +35,7 @@
 import org.apache.lucene.util.OpenBitSet;
 
 
+
 /**
  *
  */
@@ -59,7 +62,7 @@
     directory.close();
   }
 
-  public void searchFiltered(IndexWriter writer, Directory directory, SimpleDocIdSetFilter filter, boolean optimize) {
+  public void searchFiltered(IndexWriter writer, Directory directory, Filter filter, boolean optimize) {
     try {
       for (int i = 0; i < 60; i++) {//Simple docs
         Document doc = new Document();
@@ -75,7 +78,6 @@
      
      
       IndexSearcher indexSearcher = new IndexSearcher(directory, true);
-      filter.setTopReader(indexSearcher.getIndexReader());
       ScoreDoc[] hits = indexSearcher.search(booleanQuery, filter, 1000).scoreDocs;
       assertEquals("Number of matched documents", 1, hits.length);
       indexSearcher.close();
@@ -89,20 +91,17 @@
   public static final class SimpleDocIdSetFilter extends Filter {
     private final int[] docs;
     private int index;
-    private IndexReader topReader;
+    
     public SimpleDocIdSetFilter(int[] docs) {
       this.docs = docs;
     }
 
-    public void setTopReader(IndexReader r) {
-      topReader = r;
-    }
-
     @Override
-    public DocIdSet getDocIdSet(IndexReader reader) {
+    public DocIdSet getDocIdSet(ReaderContext info) {
+      assert info.isAtomic;
       final OpenBitSet set = new OpenBitSet();
-      int docBase = topReader.getSubReaderDocBase(reader);
-      final int limit = docBase+reader.maxDoc();
+      int docBase = ((AtomicContext)info).docBase;
+      final int limit = docBase+info.reader.maxDoc();
       for (;index < docs.length; index++) {
         final int docId = docs[index];
         if(docId > limit)
Index: lucene/src/test/org/apache/lucene/search/TestNumericRangeQuery32.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestNumericRangeQuery32.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestNumericRangeQuery32.java	(working copy)
@@ -177,13 +177,13 @@
   @Test
   public void testInverseRange() throws Exception {
     NumericRangeFilter<Integer> f = NumericRangeFilter.newIntRange("field8", 8, 1000, -1000, true, true);
-    assertSame("A inverse range should return the EMPTY_DOCIDSET instance", DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.getIndexReader()));
+    assertSame("A inverse range should return the EMPTY_DOCIDSET instance", DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.topLevelReaderContext()));
     f = NumericRangeFilter.newIntRange("field8", 8, Integer.MAX_VALUE, null, false, false);
     assertSame("A exclusive range starting with Integer.MAX_VALUE should return the EMPTY_DOCIDSET instance",
-      DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.getIndexReader()));
+      DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.topLevelReaderContext()));
     f = NumericRangeFilter.newIntRange("field8", 8, null, Integer.MIN_VALUE, false, false);
     assertSame("A exclusive range ending with Integer.MIN_VALUE should return the EMPTY_DOCIDSET instance",
-      DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.getIndexReader()));
+      DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.topLevelReaderContext()));
   }
   
   @Test
Index: lucene/src/test/org/apache/lucene/search/TestNumericRangeQuery64.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestNumericRangeQuery64.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestNumericRangeQuery64.java	(working copy)
@@ -24,6 +24,7 @@
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.RandomIndexWriter;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.LuceneTestCase;
@@ -182,13 +183,13 @@
   @Test
   public void testInverseRange() throws Exception {
     NumericRangeFilter<Long> f = NumericRangeFilter.newLongRange("field8", 8, 1000L, -1000L, true, true);
-    assertSame("A inverse range should return the EMPTY_DOCIDSET instance", DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.getIndexReader()));
+    assertSame("A inverse range should return the EMPTY_DOCIDSET instance", DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.topLevelReaderContext()));
     f = NumericRangeFilter.newLongRange("field8", 8, Long.MAX_VALUE, null, false, false);
     assertSame("A exclusive range starting with Long.MAX_VALUE should return the EMPTY_DOCIDSET instance",
-      DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.getIndexReader()));
+      DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.topLevelReaderContext()));
     f = NumericRangeFilter.newLongRange("field8", 8, null, Long.MIN_VALUE, false, false);
     assertSame("A exclusive range ending with Long.MIN_VALUE should return the EMPTY_DOCIDSET instance",
-      DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.getIndexReader()));
+      DocIdSet.EMPTY_DOCIDSET, f.getDocIdSet(searcher.topLevelReaderContext()));
   }
   
   @Test
Index: lucene/src/test/org/apache/lucene/search/TestScorerPerf.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestScorerPerf.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestScorerPerf.java	(working copy)
@@ -7,6 +7,7 @@
 import java.io.IOException;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.IndexWriterConfig.OpenMode;
@@ -141,7 +142,7 @@
     final BitSet rnd = sets[random.nextInt(sets.length)];
     Query q = new ConstantScoreQuery(new Filter() {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) {
+      public DocIdSet getDocIdSet(ReaderContext info) {
         return new DocIdBitSet(rnd);
       }
     });
Index: lucene/src/test/org/apache/lucene/search/TestSort.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestSort.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestSort.java	(working copy)
@@ -34,6 +34,7 @@
 import org.apache.lucene.document.Field;
 import org.apache.lucene.index.CorruptIndexException;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.RandomIndexWriter;
@@ -797,9 +798,9 @@
     // a filter that only allows through the first hit
     Filter filt = new Filter() {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-        BitSet bs = new BitSet(reader.maxDoc());
-        bs.set(0, reader.maxDoc());
+      public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+        BitSet bs = new BitSet(info.reader.maxDoc());
+        bs.set(0, info.reader.maxDoc());
         bs.set(docs1.scoreDocs[0].doc);
         return new DocIdBitSet(bs);
       }
Index: lucene/src/test/org/apache/lucene/search/TestTermScorer.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/TestTermScorer.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/TestTermScorer.java	(working copy)
@@ -28,6 +28,7 @@
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.SlowMultiReaderWrapper;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.store.Directory;
 
 public class TestTermScorer extends LuceneTestCase {
@@ -71,7 +72,7 @@
     
     Weight weight = termQuery.weight(indexSearcher);
     
-    Scorer ts = weight.scorer(indexSearcher.getIndexReader(), true, true);
+    Scorer ts = weight.scorer(indexSearcher.topLevelReaderContext(), true, true);
     // we have 2 documents with the term all in them, one document for all the
     // other values
     final List<TestHit> docs = new ArrayList<TestHit>();
@@ -132,7 +133,7 @@
     
     Weight weight = termQuery.weight(indexSearcher);
     
-    Scorer ts = weight.scorer(indexSearcher.getIndexReader(), true, true);
+    Scorer ts = weight.scorer(indexSearcher.topLevelReaderContext(), true, true);
     assertTrue("next did not return a doc",
         ts.nextDoc() != DocIdSetIterator.NO_MORE_DOCS);
     assertTrue("score is not correct", ts.score() == 1.6931472f);
@@ -150,7 +151,7 @@
     
     Weight weight = termQuery.weight(indexSearcher);
     
-    Scorer ts = weight.scorer(indexSearcher.getIndexReader(), true, true);
+    Scorer ts = weight.scorer(indexSearcher.topLevelReaderContext(), true, true);
     assertTrue("Didn't skip", ts.advance(3) != DocIdSetIterator.NO_MORE_DOCS);
     // The next doc should be doc 5
     assertTrue("doc should be number 5", ts.docID() == 5);
Index: lucene/src/test/org/apache/lucene/search/spans/TestNearSpansOrdered.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/spans/TestNearSpansOrdered.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/spans/TestNearSpansOrdered.java	(working copy)
@@ -168,7 +168,7 @@
   public void testSpanNearScorerSkipTo1() throws Exception {
     SpanNearQuery q = makeQuery();
     Weight w = q.weight(searcher);
-    Scorer s = w.scorer(searcher.getIndexReader(), true, false);
+    Scorer s = w.scorer(searcher.topLevelReaderContext(), true, false);
     assertEquals(1, s.advance(1));
   }
   /**
@@ -177,7 +177,7 @@
    */
   public void testSpanNearScorerExplain() throws Exception {
     SpanNearQuery q = makeQuery();
-    Explanation e = q.weight(searcher).explain(searcher.getIndexReader(), 1);
+    Explanation e = q.weight(searcher).explain(searcher.topLevelReaderContext(), 1);
     assertTrue("Scorer explanation value for doc#1 isn't positive: "
                + e.toString(),
                0.0f < e.getValue());
Index: lucene/src/test/org/apache/lucene/search/spans/TestSpans.java
===================================================================
--- lucene/src/test/org/apache/lucene/search/spans/TestSpans.java	(revision 1054582)
+++ lucene/src/test/org/apache/lucene/search/spans/TestSpans.java	(working copy)
@@ -30,6 +30,7 @@
 import org.apache.lucene.analysis.MockAnalyzer;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
 import org.apache.lucene.index.SlowMultiReaderWrapper;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.RandomIndexWriter;
@@ -421,7 +422,7 @@
       }
     };
 
-    Scorer spanScorer = snq.weight(searcher).scorer(new SlowMultiReaderWrapper(searcher.getIndexReader()), true, false);
+    Scorer spanScorer = snq.weight(searcher).scorer(new AtomicContext(new SlowMultiReaderWrapper(searcher.getIndexReader())), true, false);
 
     assertTrue("first doc", spanScorer.nextDoc() != DocIdSetIterator.NO_MORE_DOCS);
     assertEquals("first doc number", spanScorer.docID(), 11);
Index: solr/src/java/org/apache/solr/request/PerSegmentSingleValuedFaceting.java
===================================================================
--- solr/src/java/org/apache/solr/request/PerSegmentSingleValuedFaceting.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/request/PerSegmentSingleValuedFaceting.java	(working copy)
@@ -1,5 +1,8 @@
 package org.apache.solr.request;
 
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.AtomicContext;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.TermsEnum;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.DocIdSetIterator;
@@ -67,10 +70,7 @@
     // reuse the translation logic to go from top level set to per-segment set
     baseSet = docs.getTopFilter();
 
-    SolrIndexReader topReader = searcher.getReader();
-    final SolrIndexReader[] leafReaders = topReader.getLeafReaders();
-    int[] offsets = topReader.getLeafOffsets();
-
+    final AtomicContext[] leafs = searcher.topLevelReaderContext().leafs();
     // The list of pending tasks that aren't immediately submitted
     // TODO: Is there a completion service, or a delegating executor that can
     // limit the number of concurrent tasks submitted to a bigger executor?
@@ -78,8 +78,8 @@
 
     int threads = nThreads <= 0 ? Integer.MAX_VALUE : nThreads;
 
-    for (int i=0; i<leafReaders.length; i++) {
-      final SegFacet segFacet = new SegFacet(leafReaders[i], offsets[i]);
+    for (int i=0; i<leafs.length; i++) {
+      final SegFacet segFacet = new SegFacet(leafs[i]);
 
       Callable<SegFacet> task = new Callable<SegFacet>() {
         public SegFacet call() throws Exception {
@@ -101,7 +101,7 @@
     // now merge the per-segment results
     PriorityQueue<SegFacet> queue = new PriorityQueue<SegFacet>() {
       {
-        initialize(leafReaders.length);
+        initialize(leafs.length);
       }
       @Override
       protected boolean lessThan(SegFacet a, SegFacet b) {
@@ -112,7 +112,7 @@
 
     boolean hasMissingCount=false;
     int missingCount=0;
-    for (int i=0; i<leafReaders.length; i++) {
+    for (int i=0; i<leafs.length; i++) {
       SegFacet seg = null;
 
       try {
@@ -209,12 +209,9 @@
   }
 
   class SegFacet {
-    SolrIndexReader reader;
-    int readerOffset;
-
-    SegFacet(SolrIndexReader reader, int readerOffset) {
-      this.reader = reader;
-      this.readerOffset = readerOffset;
+    ReaderContext info;
+    SegFacet(ReaderContext info) {
+      this.info = info;
     }
     
     FieldCache.DocTermsIndex si;
@@ -228,7 +225,7 @@
     BytesRef tempBR = new BytesRef();
 
     void countTerms() throws IOException {
-      si = FieldCache.DEFAULT.getTermsIndex(reader, fieldName);
+      si = FieldCache.DEFAULT.getTermsIndex(info.reader, fieldName);
       // SolrCore.log.info("reader= " + reader + "  FC=" + System.identityHashCode(si));
 
       if (prefix!=null) {
@@ -250,7 +247,7 @@
         // count collection array only needs to be as big as the number of terms we are
         // going to collect counts for.
         final int[] counts = this.counts = new int[nTerms];
-        DocIdSet idSet = baseSet.getDocIdSet(reader);
+        DocIdSet idSet = baseSet.getDocIdSet(info);
         DocIdSetIterator iter = idSet.iterator();
 
 
Index: solr/src/java/org/apache/solr/schema/LatLonType.java
===================================================================
--- solr/src/java/org/apache/solr/schema/LatLonType.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/schema/LatLonType.java	(working copy)
@@ -19,6 +19,7 @@
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.Fieldable;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.MultiFields;
 import org.apache.lucene.search.*;
 import org.apache.lucene.spatial.DistanceUtils;
@@ -27,7 +28,6 @@
 import org.apache.solr.common.SolrException;
 import org.apache.solr.response.TextResponseWriter;
 import org.apache.solr.search.QParser;
-import org.apache.solr.search.SolrIndexReader;
 import org.apache.solr.search.SpatialOptions;
 import org.apache.solr.search.function.DocValues;
 import org.apache.solr.search.function.ValueSource;
@@ -371,18 +371,13 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
-      return new SpatialScorer(getSimilarity(searcher), reader, this);
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+      return new SpatialScorer(getSimilarity(searcher), context.reader, this);
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
-      SolrIndexReader topReader = (SolrIndexReader)reader;
-      SolrIndexReader[] subReaders = topReader.getLeafReaders();
-      int[] offsets = topReader.getLeafOffsets();
-      int readerPos = SolrIndexReader.readerIndex(doc, offsets);
-      int readerBase = offsets[readerPos];
-      return ((SpatialScorer)scorer(subReaders[readerPos], true, true)).explain(doc-readerBase);
+    public Explanation explain(ReaderContext context, int doc) throws IOException {
+      return ((SpatialScorer)scorer(context, true, true)).explain(doc);
     }
   }
 
Index: solr/src/java/org/apache/solr/search/DocSet.java
===================================================================
--- solr/src/java/org/apache/solr/search/DocSet.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/DocSet.java	(working copy)
@@ -23,6 +23,7 @@
 import org.apache.lucene.search.Filter;
 import org.apache.lucene.search.DocIdSetIterator;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 import java.io.IOException;
 
@@ -246,8 +247,9 @@
 
     return new Filter() {
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext ctx) throws IOException {
         int offset = 0;
+        IndexReader reader = ctx.reader;
         SolrIndexReader r = (SolrIndexReader)reader;
         while (r.getParent() != null) {
           offset += r.getBase();
Index: solr/src/java/org/apache/solr/search/SolrConstantScoreQuery.java
===================================================================
--- solr/src/java/org/apache/solr/search/SolrConstantScoreQuery.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/SolrConstantScoreQuery.java	(working copy)
@@ -2,6 +2,7 @@
 
 import org.apache.lucene.search.*;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.solr.search.function.ValueSource;
 import org.apache.solr.common.SolrException;
 
@@ -89,14 +90,14 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
-      return new ConstantScorer(similarity, reader, this);
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+      return new ConstantScorer(similarity, context, this);
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
+    public Explanation explain(ReaderContext context, int doc) throws IOException {
 
-      ConstantScorer cs = new ConstantScorer(similarity, reader, this);
+      ConstantScorer cs = new ConstantScorer(similarity, context, this);
       boolean exists = cs.docIdSetIterator.advance(doc) == doc;
 
       ComplexExplanation result = new ComplexExplanation();
@@ -123,10 +124,10 @@
     final float theScore;
     int doc = -1;
 
-    public ConstantScorer(Similarity similarity, IndexReader reader, ConstantWeight w) throws IOException {
+    public ConstantScorer(Similarity similarity, ReaderContext info, ConstantWeight w) throws IOException {
       super(similarity);
       theScore = w.getValue();
-      DocIdSet docIdSet = filter instanceof SolrFilter ? ((SolrFilter)filter).getDocIdSet(w.context, reader) : filter.getDocIdSet(reader);
+      DocIdSet docIdSet = filter instanceof SolrFilter ? ((SolrFilter)filter).getDocIdSet(w.context, info) : filter.getDocIdSet(info);
       if (docIdSet == null) {
         docIdSetIterator = DocIdSet.EMPTY_DOCIDSET.iterator();
       } else {
Index: solr/src/java/org/apache/solr/search/SolrFilter.java
===================================================================
--- solr/src/java/org/apache/solr/search/SolrFilter.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/SolrFilter.java	(working copy)
@@ -21,6 +21,7 @@
 import org.apache.lucene.search.Searcher;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 import java.util.Map;
 import java.io.IOException;
@@ -37,10 +38,10 @@
    * The context object will be passed to getDocIdSet() where this info can be retrieved. */
   public abstract void createWeight(Map context, Searcher searcher) throws IOException;
   
-  public abstract DocIdSet getDocIdSet(Map context, IndexReader reader) throws IOException;
+  public abstract DocIdSet getDocIdSet(Map context, ReaderContext readerContext) throws IOException;
 
   @Override
-  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-    return getDocIdSet(null, reader);
+  public DocIdSet getDocIdSet(ReaderContext context) throws IOException {
+    return getDocIdSet(null, context);
   }
 }
Index: solr/src/java/org/apache/solr/search/SolrIndexReader.java
===================================================================
--- solr/src/java/org/apache/solr/search/SolrIndexReader.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/SolrIndexReader.java	(working copy)
@@ -19,12 +19,14 @@
 
 
 import org.apache.lucene.index.*;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.LockObtainFailedException;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.FieldSelector;
 import org.apache.lucene.util.Bits;
 import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.ReaderUtil;
 
 import java.io.IOException;
 import java.util.Collection;
@@ -40,6 +42,7 @@
   private int[] leafOffsets;
   private final SolrIndexReader parent;
   private final int base; // docid offset of this reader within parent
+  private final ReaderContext topLevelContext;
 
   private static int[] zeroIntArray = new int[]{0};
 
@@ -79,7 +82,7 @@
       leafReaders = new SolrIndexReader[]{this};
       leafOffsets = zeroIntArray;
     }
-
+    topLevelContext = ReaderUtil.buildReaderContext(this);
   }
 
   private SolrIndexReader[] getLeaves(int numLeaves) {
@@ -364,11 +367,6 @@
   }
 
   @Override
-  public int getSubReaderDocBase(IndexReader subReader) {
-    return in.getSubReaderDocBase(subReader);
-  }
-
-  @Override
   public int hashCode() {
     return in.hashCode();
   }
@@ -493,6 +491,11 @@
   public int getTermInfosIndexDivisor() {
     return in.getTermInfosIndexDivisor();
   }
+  
+  @Override
+  public ReaderContext topLevelReaderContext() {
+    return topLevelContext;
+  }
 }
 
 
Index: solr/src/java/org/apache/solr/search/SolrIndexSearcher.java
===================================================================
--- solr/src/java/org/apache/solr/search/SolrIndexSearcher.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/SolrIndexSearcher.java	(working copy)
@@ -904,7 +904,7 @@
   * This method is not cache-aware and no caches are checked.
   */
   public DocSet convertFilter(Filter lfilter) throws IOException {
-    DocIdSet docSet = lfilter.getDocIdSet(this.reader);
+    DocIdSet docSet = lfilter.getDocIdSet(this.reader.topLevelReaderContext());
     OpenBitSet obs = new OpenBitSet();
     DocIdSetIterator it = docSet.iterator();
     int doc;
Index: solr/src/java/org/apache/solr/search/SortedIntDocSet.java
===================================================================
--- solr/src/java/org/apache/solr/search/SortedIntDocSet.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/SortedIntDocSet.java	(working copy)
@@ -22,6 +22,7 @@
 import org.apache.lucene.search.DocIdSetIterator;
 import org.apache.lucene.search.Filter;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 
 import java.io.IOException;
 
@@ -551,8 +552,9 @@
       int lastEndIdx = 0;
 
       @Override
-      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(ReaderContext context) throws IOException {
         int offset = 0;
+        IndexReader reader = context.reader;
         SolrIndexReader r = (SolrIndexReader)reader;
         while (r.getParent() != null) {
           offset += r.getBase();
Index: solr/src/java/org/apache/solr/search/function/BoostedQuery.java
===================================================================
--- solr/src/java/org/apache/solr/search/function/BoostedQuery.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/function/BoostedQuery.java	(working copy)
@@ -19,6 +19,7 @@
 
 import org.apache.lucene.search.*;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.util.ToStringUtils;
 import org.apache.solr.search.SolrIndexReader;
 
@@ -91,33 +92,26 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
-      Scorer subQueryScorer = qWeight.scorer(reader, true, false);
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+      Scorer subQueryScorer = qWeight.scorer(context, true, false);
       if(subQueryScorer == null) {
         return null;
       }
-      return new BoostedQuery.CustomScorer(getSimilarity(searcher), searcher, reader, this, subQueryScorer, boostVal);
+      return new BoostedQuery.CustomScorer(getSimilarity(searcher), searcher, context.reader, this, subQueryScorer, boostVal);
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
-      SolrIndexReader topReader = (SolrIndexReader)reader;
-      SolrIndexReader[] subReaders = topReader.getLeafReaders();
-      int[] offsets = topReader.getLeafOffsets();
-      int readerPos = SolrIndexReader.readerIndex(doc, offsets);
-      int readerBase = offsets[readerPos];
-
-      Explanation subQueryExpl = qWeight.explain(reader,doc);
+    public Explanation explain(ReaderContext readerContext, int doc) throws IOException {
+      Explanation subQueryExpl = qWeight.explain(readerContext,doc);
       if (!subQueryExpl.isMatch()) {
         return subQueryExpl;
       }
-
-      DocValues vals = boostVal.getValues(context, subReaders[readerPos]);
-      float sc = subQueryExpl.getValue() * vals.floatVal(doc-readerBase);
+      DocValues vals = boostVal.getValues(context, readerContext.reader);
+      float sc = subQueryExpl.getValue() * vals.floatVal(doc);
       Explanation res = new ComplexExplanation(
         true, sc, BoostedQuery.this.toString() + ", product of:");
       res.addDetail(subQueryExpl);
-      res.addDetail(vals.explain(doc-readerBase));
+      res.addDetail(vals.explain(doc));
       return res;
     }
   }
@@ -168,7 +162,7 @@
     }
 
     public Explanation explain(int doc) throws IOException {
-      Explanation subQueryExpl = weight.qWeight.explain(reader,doc);
+      Explanation subQueryExpl = weight.qWeight.explain(reader.topLevelReaderContext() ,doc);
       if (!subQueryExpl.isMatch()) {
         return subQueryExpl;
       }
Index: solr/src/java/org/apache/solr/search/function/FunctionQuery.java
===================================================================
--- solr/src/java/org/apache/solr/search/function/FunctionQuery.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/function/FunctionQuery.java	(working copy)
@@ -18,10 +18,10 @@
 package org.apache.solr.search.function;
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.search.*;
 import org.apache.lucene.index.MultiFields;
 import org.apache.lucene.util.Bits;
-import org.apache.solr.search.SolrIndexReader;
 
 import java.io.IOException;
 import java.util.Set;
@@ -94,18 +94,13 @@
     }
 
     @Override
-    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
-      return new AllScorer(getSimilarity(searcher), reader, this);
+    public Scorer scorer(ReaderContext context, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
+      return new AllScorer(getSimilarity(searcher), context.reader, this);
     }
 
     @Override
-    public Explanation explain(IndexReader reader, int doc) throws IOException {
-      SolrIndexReader topReader = (SolrIndexReader)reader;
-      SolrIndexReader[] subReaders = topReader.getLeafReaders();
-      int[] offsets = topReader.getLeafOffsets();
-      int readerPos = SolrIndexReader.readerIndex(doc, offsets);
-      int readerBase = offsets[readerPos];
-      return ((AllScorer)scorer(subReaders[readerPos], true, true)).explain(doc-readerBase);
+    public Explanation explain(ReaderContext context, int doc) throws IOException {
+      return ((AllScorer)scorer(context, true, true)).explain(doc);
     }
   }
 
Index: solr/src/java/org/apache/solr/search/function/QueryValueSource.java
===================================================================
--- solr/src/java/org/apache/solr/search/function/QueryValueSource.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/function/QueryValueSource.java	(working copy)
@@ -90,7 +90,7 @@
     try {
       if (doc < lastDocRequested) {
         // out-of-order access.... reset scorer.
-        scorer = weight.scorer(reader, true, false);
+        scorer = weight.scorer(reader.topLevelReaderContext(), true, false);
         if (scorer==null) return defVal;
         scorerDoc = -1;
       }
Index: solr/src/java/org/apache/solr/search/function/ValueSourceRangeFilter.java
===================================================================
--- solr/src/java/org/apache/solr/search/function/ValueSourceRangeFilter.java	(revision 1054582)
+++ solr/src/java/org/apache/solr/search/function/ValueSourceRangeFilter.java	(working copy)
@@ -20,7 +20,7 @@
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.DocIdSetIterator;
 import org.apache.lucene.search.Searcher;
-import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.solr.search.SolrFilter;
 
 import java.io.IOException;
@@ -49,10 +49,10 @@
     this.includeUpper = upperVal != null && includeUpper;
   }
 
-  public DocIdSet getDocIdSet(final Map context, final IndexReader reader) throws IOException {
+  public DocIdSet getDocIdSet(final Map context, final ReaderContext readerContext) throws IOException {
      return new DocIdSet() {
        public DocIdSetIterator iterator() throws IOException {
-         return valueSource.getValues(context, reader).getRangeScorer(reader, lowerVal, upperVal, includeLower, includeUpper);
+         return valueSource.getValues(context, readerContext.reader).getRangeScorer(readerContext.reader, lowerVal, upperVal, includeLower, includeUpper);
        }
      };
   }
Index: solr/src/test/org/apache/solr/common/util/ContentStreamTest.java
===================================================================
--- solr/src/test/org/apache/solr/common/util/ContentStreamTest.java	(revision 1054582)
+++ solr/src/test/org/apache/solr/common/util/ContentStreamTest.java	(working copy)
@@ -25,6 +25,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.StringReader;
+import java.net.ConnectException;
 import java.net.URL;
 
 import org.apache.commons.io.IOUtils;
@@ -65,12 +66,16 @@
   {
     String content = null;
     URL url = new URL( "http://svn.apache.org/repos/asf/lucene/dev/trunk/" );
-    InputStream in = url.openStream();
+    InputStream in = null;
     try {
+      in = url.openStream();
       content = IOUtils.toString( in );
-    } 
-    finally {
-      IOUtils.closeQuietly(in);
+    } catch (ConnectException ex) {
+      assumeNoException("Unable to connect to " + url + " to run the test.", ex);
+    }finally {
+      if (in != null) {
+        IOUtils.closeQuietly(in);
+      }
     }
     
     assertTrue( content.length() > 10 ); // found something...
Index: solr/src/test/org/apache/solr/search/TestDocSet.java
===================================================================
--- solr/src/test/org/apache/solr/search/TestDocSet.java	(revision 1054582)
+++ solr/src/test/org/apache/solr/search/TestDocSet.java	(working copy)
@@ -26,6 +26,7 @@
 import org.apache.lucene.util.OpenBitSetIterator;
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.FilterIndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.MultiReader;
 import org.apache.lucene.search.Filter;
 import org.apache.lucene.search.DocIdSet;
@@ -404,6 +405,7 @@
   }
 
   public void doFilterTest(SolrIndexReader reader) throws IOException {
+    ReaderContext topLevelContext = reader.topLevelReaderContext();
     OpenBitSet bs = getRandomSet(reader.maxDoc(), rand.nextInt(reader.maxDoc()+1));
     DocSet a = new BitDocSet(bs);
     DocSet b = getIntDocSet(bs);
@@ -412,23 +414,23 @@
     Filter fb = b.getTopFilter();
 
     // test top-level
-    DocIdSet da = fa.getDocIdSet(reader);
-    DocIdSet db = fb.getDocIdSet(reader);
+    DocIdSet da = fa.getDocIdSet(topLevelContext);
+    DocIdSet db = fb.getDocIdSet(topLevelContext);
     doTestIteratorEqual(da, db);
 
     // first test in-sequence sub readers
-    for (SolrIndexReader sir : reader.getLeafReaders()) {
-      da = fa.getDocIdSet(sir);
-      db = fb.getDocIdSet(sir);
+    for (ReaderContext readerInfo : topLevelContext.leafs()) {
+      da = fa.getDocIdSet(readerInfo);
+      db = fb.getDocIdSet(readerInfo);
       doTestIteratorEqual(da, db);
     }  
 
-    int nReaders = reader.getLeafReaders().length;
+    int nReaders = topLevelContext.leafs().length;
     // now test out-of-sequence sub readers
     for (int i=0; i<nReaders; i++) {
-      SolrIndexReader sir = reader.getLeafReaders()[rand.nextInt(nReaders)];
-      da = fa.getDocIdSet(sir);
-      db = fb.getDocIdSet(sir);
+      ReaderContext readerInfo = topLevelContext.leafs()[rand.nextInt(nReaders)];
+      da = fa.getDocIdSet(readerInfo);
+      db = fb.getDocIdSet(readerInfo);
       doTestIteratorEqual(da, db);
     }
   }
Index: solr/src/test/org/apache/solr/search/TestSort.java
===================================================================
--- solr/src/test/org/apache/solr/search/TestSort.java	(revision 1054582)
+++ solr/src/test/org/apache/solr/search/TestSort.java	(working copy)
@@ -21,6 +21,7 @@
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexReader.ReaderContext;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.search.*;
@@ -106,8 +107,8 @@
       for (int i=0; i<qiter; i++) {
         Filter filt = new Filter() {
           @Override
-          public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
-            return randSet(reader.maxDoc());
+          public DocIdSet getDocIdSet(ReaderContext info) throws IOException {
+            return randSet(info.reader.maxDoc());
           }
         };
 
Index: solr/src/test/org/apache/solr/update/DirectUpdateHandlerTest.java
===================================================================
--- solr/src/test/org/apache/solr/update/DirectUpdateHandlerTest.java	(revision 1054582)
+++ solr/src/test/org/apache/solr/update/DirectUpdateHandlerTest.java	(working copy)
@@ -245,7 +245,7 @@
     SolrQueryRequest sr = req("q","foo");
     SolrIndexReader r = sr.getSearcher().getReader();
     assertTrue(r.maxDoc() > r.numDocs());   // should have deletions
-    assertTrue(r.getLeafReaders().length > 1);  // more than 1 segment
+    assertFalse(r.topLevelReaderContext().isAtomic);  // more than 1 segment
     sr.close();
 
     assertU(commit("expungeDeletes","true"));
@@ -254,7 +254,7 @@
     r = sr.getSearcher().getReader();
     assertEquals(r.maxDoc(), r.numDocs());  // no deletions
     assertEquals(4,r.maxDoc());             // no dups
-    assertTrue(r.getLeafReaders().length > 1);  // still more than 1 segment
+    assertFalse(r.topLevelReaderContext().isAtomic);  //still more than 1 segment
     sr.close();
   }
   
