Index: lucene/src/java/org/apache/lucene/index/ParallelReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/ParallelReader.java	(revision 944320)
+++ lucene/src/java/org/apache/lucene/index/ParallelReader.java	(revision )
@@ -561,7 +561,7 @@
       }
     }
 
-    FieldCache.DEFAULT.purge(this);
+    raiseCacheEvictionEvent(this);
   }
 
   @Override
Index: lucene/src/java/org/apache/lucene/index/MultiReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/MultiReader.java	(revision 931278)
+++ lucene/src/java/org/apache/lucene/index/MultiReader.java	(revision )
@@ -462,7 +462,7 @@
     // NOTE: only needed in case someone had asked for
     // FieldCache for top-level reader (which is generally
     // not a good idea):
-    FieldCache.DEFAULT.purge(this);
+    raiseCacheEvictionEvent(this);
   }
   
   @Override
Index: lucene/src/java/org/apache/lucene/index/IndexReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/IndexReader.java	(revision 933613)
+++ lucene/src/java/org/apache/lucene/index/IndexReader.java	(revision )
@@ -19,6 +19,7 @@
 
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.FieldSelector;
+import org.apache.lucene.search.FieldCache;
 import org.apache.lucene.search.Similarity;
 import org.apache.lucene.index.codecs.CodecProvider;
 import org.apache.lucene.store.*;
@@ -33,6 +34,7 @@
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Map;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.atomic.AtomicInteger;
 
 /** IndexReader is an abstract class, providing an interface for accessing an
@@ -80,7 +82,22 @@
 */
 public abstract class IndexReader implements Cloneable,Closeable {
 
-  /**
+    /**
+     * A custom listener that can be added to the index reader which will
+     * be called when the index reader (or its {@link org.apache.lucene.index.IndexReader#getFieldCacheKey()})
+     * can be removed from a custom cache.
+     */
+    public static interface CacheEvictionListener {
+      void purgeReaderCache(IndexReader reader);
+    }
+
+    private static class FieldCacheCacheEvictionListener implements CacheEvictionListener {
+        public void purgeReaderCache(IndexReader reader) {
+            FieldCache.DEFAULT.purge(reader);
+        }
+    }
+
+  /**
    * Constants describing field properties, for example used for
    * {@link IndexReader#getFieldNames(FieldOption)}.
    */
@@ -123,6 +140,8 @@
   
   private final AtomicInteger refCount = new AtomicInteger();
 
+  CopyOnWriteArrayList<CacheEvictionListener> cacheEvictionListeners = new CopyOnWriteArrayList<CacheEvictionListener>();
+
   static int DEFAULT_TERMS_INDEX_DIVISOR = 1;
 
   /** Expert: returns the current refCount for this reader */
@@ -199,8 +218,15 @@
   
   protected IndexReader() { 
     refCount.set(1);
+    cacheEvictionListeners.add(new FieldCacheCacheEvictionListener());
   }
-  
+
+  protected void raiseCacheEvictionEvent(IndexReader reader) {
+      for (CacheEvictionListener listener : cacheEvictionListeners) {
+          listener.purgeReaderCache(reader);
+      }
+  }
+  
   /**
    * @throws AlreadyClosedException if this IndexReader is closed
    */
@@ -1366,6 +1392,16 @@
     throw new UnsupportedOperationException();
   }
 
+  /** Expert - When caching (ususaly using #getFieldCacheKey) can be used
+   *  to eagerly release cache entries */
+  public void addCacheEvictionListener(CacheEvictionListener listener) {
+      cacheEvictionListeners.add(listener);
+  }
+
+  public void removeCacheEvictionListener(CacheEvictionListener listener) {
+      cacheEvictionListeners.remove(listener);
+  }
+
   /** Expert */
   public Object getFieldCacheKey() {
     return this;
Index: lucene/src/java/org/apache/lucene/index/FilterIndexReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/FilterIndexReader.java	(revision 944320)
+++ lucene/src/java/org/apache/lucene/index/FilterIndexReader.java	(revision )
@@ -261,7 +261,7 @@
     // NOTE: only needed in case someone had asked for
     // FieldCache for top-level reader (which is generally
     // not a good idea):
-    FieldCache.DEFAULT.purge(this);
+    raiseCacheEvictionEvent(this);
   }
 
 
Index: lucene/src/java/org/apache/lucene/index/DirectoryReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/DirectoryReader.java	(revision 944320)
+++ lucene/src/java/org/apache/lucene/index/DirectoryReader.java	(revision )
@@ -956,7 +956,7 @@
     // NOTE: only needed in case someone had asked for
     // FieldCache for top-level reader (which is generally
     // not a good idea):
-    FieldCache.DEFAULT.purge(this);
+    raiseCacheEvictionEvent(this);
 
     if (writer != null) {
       // Since we just closed, writer may now be able to
Index: lucene/src/java/org/apache/lucene/index/SegmentReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/SegmentReader.java	(revision 944320)
+++ lucene/src/java/org/apache/lucene/index/SegmentReader.java	(revision )
@@ -201,7 +201,7 @@
         // origInstance will be null, and we don't want
         // to call FieldCache.purge (it leads to NPE):
         if (origInstance != null) {
-          FieldCache.DEFAULT.purge(origInstance);
+          origInstance.raiseCacheEvictionEvent(origInstance);
         }
       }
     }
@@ -648,6 +648,7 @@
     try {
       core.incRef();
       clone.core = core;
+      clone.cacheEvictionListeners = cacheEvictionListeners;
       clone.readOnly = openReadOnly;
       clone.si = si;
       clone.readBufferSize = readBufferSize;