Index: lucene/core/src/test/org/apache/lucene/index/TestMergedSegmentFilter.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/index/TestMergedSegmentFilter.java	(revision 0)
+++ lucene/core/src/test/org/apache/lucene/index/TestMergedSegmentFilter.java	(working copy)
@@ -0,0 +1,192 @@
+package org.apache.lucene.index;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import org.junit.Assert;
+
+import java.util.List;
+import java.util.ArrayList;
+import java.io.IOException;
+import java.util.Iterator;
+
+import org.apache.lucene.analysis.*;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.util.Version;
+import org.apache.lucene.document.Field;
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.FieldType;
+import org.apache.lucene.util.LuceneTestCase;
+import org.apache.lucene.util.Bits;
+
+
+public class TestMergedSegmentFilter extends LuceneTestCase {
+
+
+  public void addDocument(IndexWriter writer) throws IOException {
+    final FieldType type = new FieldType();
+    type.setIndexed(true);
+    type.setStored(true);
+    type.setTokenized(true);
+    type.setIndexOptions(FieldInfo.IndexOptions.DOCS_AND_FREQS_AND_POSITIONS);
+
+    final Document doc = new Document();
+    doc.add( new Field("a", "A Value", type) );
+    doc.add( new Field("b", "B Value", type) );
+    doc.add( new Field("c", "C Value", type) );
+    writer.addDocument(doc);
+  }
+
+
+  /**
+   * Test removing a field during segment merging.
+   */
+  public void testRemoveField() throws IOException {
+    final IndexWriterConfig config = new IndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random()));
+    final Directory dir = newDirectory();
+    try {
+      final IndexWriter writer = new IndexWriter(dir, config);
+      addDocument(writer);
+      writer.commit();
+      addDocument(writer);
+      writer.commit();
+      DirectoryReader reader = DirectoryReader.open(writer, true);
+      // get a NRT reader:
+      Assert.assertEquals("segments needed", 2, reader.leaves().size());
+      // do this after getting the NRT reader:
+      writer.deleteAll();
+      // readd all segments and transform them:
+      for (AtomicReaderContext ctx : reader.leaves()) {
+        writer.addIndexes(new RemoveFieldReader(ctx.reader()));
+      }
+      reader.close();
+      writer.close();
+
+      reader = DirectoryReader.open(dir);
+      try {
+        Assert.assertEquals("segments needed", 2, reader.leaves().size());
+
+        for (AtomicReaderContext segment : reader.leaves()) {
+          Assert.assertNotNull(segment.reader().terms("a"));
+          Assert.assertNull(segment.reader().terms("b"));
+          Assert.assertNotNull(segment.reader().terms("c"));
+        }
+      } finally {
+        reader.close();
+      }
+    } finally {
+      dir.close();
+    }
+  }
+
+  private static final class RemoveFieldReader extends AtomicReader {
+    private final AtomicReader reader;
+
+    public RemoveFieldReader(AtomicReader reader) {
+      this.reader = reader;
+    }
+
+    @Override
+    public Fields fields() throws IOException {
+      return new RemoveFieldFields(reader.fields());
+    }
+
+    @Override
+    public DocValues docValues(String field) throws IOException {
+      return reader.docValues(field);
+    }
+  
+    @Override
+    public DocValues normValues(String field) throws IOException {
+      return reader.normValues(field);
+    }
+
+    @Override
+    public FieldInfos getFieldInfos() {
+      return reader.getFieldInfos();
+    }
+  
+    @Override
+    public Bits getLiveDocs() {
+      return reader.getLiveDocs();
+    }
+
+    @Override
+    public void document(int doc, StoredFieldVisitor visitor) throws IOException {
+      reader.document(doc, visitor);
+    }
+    
+    @Override
+    public Fields getTermVectors(int doc) throws IOException {
+      return reader.getTermVectors(doc);
+    }
+
+    @Override
+    public int numDocs() {
+      return reader.numDocs();
+    }
+
+    @Override
+    public int maxDoc() {
+      return reader.maxDoc();
+    }
+
+    @Override
+    public boolean hasDeletions() {
+      return reader.hasDeletions();
+    }
+
+    @Override
+    public void doClose() throws IOException {
+      reader.doClose();
+    }
+
+  }
+
+  private static final class RemoveFieldFields extends Fields {
+    public final Fields fields;
+    private final List<String> fieldNames = new ArrayList<String>();
+
+    public RemoveFieldFields(Fields fields) {
+      this.fields = fields;
+      for (String name : fields) {
+        if (!"b".equals(name)) {
+          fieldNames.add(name);
+        }
+      }
+    }
+
+    @Override
+    public Iterator<String> iterator() {
+      return fieldNames.iterator();
+    }
+
+    @Override
+    public Terms terms(String field) throws IOException {
+      if ("b".equals(field)) {
+        return null;
+      } else {
+        return fields.terms(field);
+      }
+    }
+
+    @Override
+    public int size() {
+      return fieldNames.size();
+    }
+  }
+}
Index: lucene/core/src/test/org/apache/lucene/index/TestMergedSegmentFilter.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/index/TestMergedSegmentFilter.java	(revision 0)
+++ lucene/core/src/test/org/apache/lucene/index/TestMergedSegmentFilter.java	(working copy)

Property changes on: lucene/core/src/test/org/apache/lucene/index/TestMergedSegmentFilter.java
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