Index: CHANGES.txt
===================================================================
--- CHANGES.txt	(revision 888398)
+++ CHANGES.txt	(working copy)
@@ -8,6 +8,10 @@
   class is no longer used by Lucene.  (Gunnar Wagenknecht via Mike
   McCandless)
 
+* LUCENE-2135: Added FieldCache.purge(IndexReader) method to the
+  interface.  Anyone implementing FieldCache externally will need to
+  fix their code to implement this, on upgrading.  (Mike McCandless)
+
 Changes in runtime behavior
 
 API Changes
@@ -75,6 +79,10 @@
   This avoid the overhead of using a PQ unecessarily.  (Mike
   McCandless)
 
+* LUCENE-2135: On IndexReader.close, forcefully evict any entries from
+  the FieldCache rather than waiting for the WeakHashMap to release
+  the reference (Mike McCandless)
+
 Build
 
 Test Cases
Index: src/test/org/apache/lucene/index/TestIndexReader.java
===================================================================
--- src/test/org/apache/lucene/index/TestIndexReader.java	(revision 888398)
+++ src/test/org/apache/lucene/index/TestIndexReader.java	(working copy)
@@ -1620,9 +1620,9 @@
 
     // Clone reader
     IndexReader r2 = (IndexReader) r.clone();
+    final int[] ints2 = FieldCache.DEFAULT.getInts(r2, "number");
     r.close();
     assertTrue(r2 != r);
-    final int[] ints2 = FieldCache.DEFAULT.getInts(r2, "number");
     r2.close();
 
     assertEquals(1, ints2.length);
@@ -1656,9 +1656,9 @@
 
     // Reopen reader1 --> reader2
     IndexReader r2 = r.reopen();
-    r.close();
     IndexReader sub0 = r2.getSequentialSubReaders()[0];
     final int[] ints2 = FieldCache.DEFAULT.getInts(sub0, "number");
+    r.close();
     r2.close();
     assertTrue(ints == ints2);
 
@@ -1694,10 +1694,10 @@
 
     // Reopen reader1 --> reader2
     IndexReader r2 = r.reopen(true);
-    r.close();
     assertTrue(r2 instanceof ReadOnlyDirectoryReader);
     IndexReader[] subs = r2.getSequentialSubReaders();
     final int[] ints2 = FieldCache.DEFAULT.getInts(subs[0], "number");
+    r.close();
     r2.close();
 
     assertTrue(subs[0] instanceof ReadOnlySegmentReader);
Index: src/java/org/apache/lucene/search/FieldCache.java
===================================================================
--- src/java/org/apache/lucene/search/FieldCache.java	(revision 888398)
+++ src/java/org/apache/lucene/search/FieldCache.java	(working copy)
@@ -594,6 +594,15 @@
   public abstract void purgeAllCaches();
 
   /**
+   * Expert: drops all cache entries associated with this
+   * reader.  NOTE: this reader must precisely match the
+   * reader that the cache entry is keyed on. If you pass a
+   * top-level reader, it usually will have no effect as
+   * Lucene now caches at the segment reader level.
+   */
+  public abstract void purge(IndexReader r);
+
+  /**
    * If non-null, FieldCacheImpl will warn whenever
    * entries are created that are not sane according to
    * {@link org.apache.lucene.util.FieldCacheSanityChecker}.
Index: src/java/org/apache/lucene/search/FieldCacheImpl.java
===================================================================
--- src/java/org/apache/lucene/search/FieldCacheImpl.java	(revision 888398)
+++ src/java/org/apache/lucene/search/FieldCacheImpl.java	(working copy)
@@ -61,6 +61,12 @@
   public void purgeAllCaches() {
     init();
   }
+
+  public void purge(IndexReader r) {
+    for(Cache c : caches.values()) {
+      c.purge(r);
+    }
+  }
   
   public CacheEntry[] getCacheEntries() {
     List<CacheEntry> result = new ArrayList<CacheEntry>(17);
@@ -144,6 +150,14 @@
     protected abstract Object createValue(IndexReader reader, Entry key)
         throws IOException;
 
+    /** Remove this reader from the cache, if present. */
+    public void purge(IndexReader r) {
+      Object readerKey = r.getFieldCacheKey();
+      synchronized(readerCache) {
+        readerCache.remove(readerKey);
+      }
+    }
+
     public Object get(IndexReader reader, Entry key) throws IOException {
       Map<Entry,Object> innerCache;
       Object value;
Index: src/java/org/apache/lucene/index/SegmentReader.java
===================================================================
--- src/java/org/apache/lucene/index/SegmentReader.java	(revision 888398)
+++ src/java/org/apache/lucene/index/SegmentReader.java	(working copy)
@@ -38,6 +38,8 @@
 import org.apache.lucene.util.BitVector;
 import org.apache.lucene.util.CloseableThreadLocal;
 
+import org.apache.lucene.search.FieldCache; // not great (circular); used only to purge FieldCache entry on close
+
 /** @version $Id */
 /**
  * <p><b>NOTE:</b> This API is new and still experimental
@@ -92,16 +94,19 @@
     final int readBufferSize;
     final int termsIndexDivisor;
 
+    private final SegmentReader origInstance;
+
     TermInfosReader tis;
     FieldsReader fieldsReaderOrig;
     TermVectorsReader termVectorsReaderOrig;
     CompoundFileReader cfsReader;
     CompoundFileReader storeCFSReader;
 
-    CoreReaders(Directory dir, SegmentInfo si, int readBufferSize, int termsIndexDivisor) throws IOException {
+    CoreReaders(SegmentReader origInstance, Directory dir, SegmentInfo si, int readBufferSize, int termsIndexDivisor) throws IOException {
       segment = si.name;
       this.readBufferSize = readBufferSize;
       this.dir = dir;
+      this.origInstance = origInstance;
 
       boolean success = false;
 
@@ -232,6 +237,11 @@
         if (storeCFSReader != null) {
           storeCFSReader.close();
         }
+
+        // Force FieldCache to evict our entries at this point
+        if (freqStream != null) {
+          FieldCache.DEFAULT.purge(origInstance);
+        }
       }
     }
 
@@ -573,7 +583,7 @@
     boolean success = false;
 
     try {
-      instance.core = new CoreReaders(dir, si, readBufferSize, termInfosIndexDivisor);
+      instance.core = new CoreReaders(instance, dir, si, readBufferSize, termInfosIndexDivisor);
       if (doOpenStores) {
         instance.core.openDocStores(si);
       }