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diff --git a/java/com/google/gerrit/lucene/WrappableSearcherManager.java b/java/com/google/gerrit/lucene/WrappableSearcherManager.java
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+++ b/java/com/google/gerrit/lucene/WrappableSearcherManager.java
@@ -0,0 +1,218 @@
+package com.google.gerrit.lucene;
+
+/*
+ * 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 java.io.IOException;
+import org.apache.lucene.index.DirectoryReader;
+import org.apache.lucene.index.FilterDirectoryReader;
+import org.apache.lucene.index.FilterLeafReader;
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexWriter;
+import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.search.ReferenceManager;
+import org.apache.lucene.search.SearcherFactory;
+import org.apache.lucene.store.Directory;
+
+/**
+ * Utility class to safely share {@link IndexSearcher} instances across multiple threads, while
+ * periodically reopening. This class ensures each searcher is closed only once all threads have
+ * finished using it.
+ *
+ * <p>Use {@link #acquire} to obtain the current searcher, and {@link #release} to release it, like
+ * this:
+ *
+ * <pre class="prettyprint">
+ * IndexSearcher s = manager.acquire();
+ * try {
+ *   // Do searching, doc retrieval, etc. with s
+ * } finally {
+ *   manager.release(s);
+ * }
+ * // Do not use s after this!
+ * s = null;
+ * </pre>
+ *
+ * <p>In addition you should periodically call {@link #maybeRefresh}. While it's possible to call
+ * this just before running each query, this is discouraged since it penalizes the unlucky queries
+ * that need to refresh. It's better to use a separate background thread, that periodically calls
+ * {@link #maybeRefresh}. Finally, be sure to call {@link #close} once you are done.
+ *
+ * @see SearcherFactory
+ * @lucene.experimental
+ */
+// This file was copied from:
+// https://github.com/apache/lucene-solr/blob/lucene_solr_5_0/lucene/core/src/java/org/apache/lucene/search/SearcherManager.java
+// The only change (other than class name and import fixes)
+// is to skip the check in getSearcher that searcherFactory.newSearcher wraps
+// the provided searcher exactly.
+final class WrappableSearcherManager extends ReferenceManager<IndexSearcher> {
+
+  private final SearcherFactory searcherFactory;
+
+  /**
+   * Creates and returns a new SearcherManager from the given {@link IndexWriter}.
+   *
+   * @param writer the IndexWriter to open the IndexReader from.
+   * @param applyAllDeletes If <code>true</code>, all buffered deletes will be applied (made
+   *     visible) in the {@link IndexSearcher} / {@link DirectoryReader}. If <code>false</code>, the
+   *     deletes may or may not be applied, but remain buffered (in IndexWriter) so that they will
+   *     be applied in the future. Applying deletes can be costly, so if your app can tolerate
+   *     deleted documents being returned you might gain some performance by passing <code>false
+   *     </code>. See {@link DirectoryReader#openIfChanged(DirectoryReader, IndexWriter, boolean)}.
+   * @param searcherFactory An optional {@link SearcherFactory}. Pass <code>null</code> if you don't
+   *     require the searcher to be warmed before going live or other custom behavior.
+   * @throws IOException if there is a low-level I/O error
+   */
+  WrappableSearcherManager(
+      IndexWriter writer, boolean applyAllDeletes, SearcherFactory searcherFactory)
+      throws IOException {
+    // TODO(davido): Make it configurable
+    // If true, new deletes will be written down to index files instead of carried over from writer
+    // to reader directly in heap
+    boolean writeAllDeletes = false;
+    if (searcherFactory == null) {
+      searcherFactory = new SearcherFactory();
+    }
+    this.searcherFactory = searcherFactory;
+    current =
+        getSearcher(
+            searcherFactory, DirectoryReader.open(writer, applyAllDeletes, writeAllDeletes));
+  }
+
+  /**
+   * Creates and returns a new SearcherManager from the given {@link Directory}.
+   *
+   * @param dir the directory to open the DirectoryReader on.
+   * @param searcherFactory An optional {@link SearcherFactory}. Pass <code>null</code> if you don't
+   *     require the searcher to be warmed before going live or other custom behavior.
+   * @throws IOException if there is a low-level I/O error
+   */
+  WrappableSearcherManager(Directory dir, SearcherFactory searcherFactory) throws IOException {
+    if (searcherFactory == null) {
+      searcherFactory = new SearcherFactory();
+    }
+    this.searcherFactory = searcherFactory;
+    current = getSearcher(searcherFactory, DirectoryReader.open(dir));
+  }
+
+  /**
+   * Creates and returns a new SearcherManager from an existing {@link DirectoryReader}. Note that
+   * this steals the incoming reference.
+   *
+   * @param reader the DirectoryReader.
+   * @param searcherFactory An optional {@link SearcherFactory}. Pass <code>null</code> if you don't
+   *     require the searcher to be warmed before going live or other custom behavior.
+   * @throws IOException if there is a low-level I/O error
+   */
+  WrappableSearcherManager(DirectoryReader reader, SearcherFactory searcherFactory)
+      throws IOException {
+    if (searcherFactory == null) {
+      searcherFactory = new SearcherFactory();
+    }
+    this.searcherFactory = searcherFactory;
+    this.current = getSearcher(searcherFactory, reader);
+  }
+
+  @Override
+  protected void decRef(IndexSearcher reference) throws IOException {
+    reference.getIndexReader().decRef();
+  }
+
+  @Override
+  protected IndexSearcher refreshIfNeeded(IndexSearcher referenceToRefresh) throws IOException {
+    final IndexReader r = referenceToRefresh.getIndexReader();
+    assert r instanceof DirectoryReader
+        : "searcher's IndexReader should be a DirectoryReader, but got " + r;
+    final IndexReader newReader = DirectoryReader.openIfChanged((DirectoryReader) r);
+    if (newReader == null) {
+      return null;
+    }
+    return getSearcher(searcherFactory, newReader);
+  }
+
+  @Override
+  protected boolean tryIncRef(IndexSearcher reference) {
+    return reference.getIndexReader().tryIncRef();
+  }
+
+  @Override
+  protected int getRefCount(IndexSearcher reference) {
+    return reference.getIndexReader().getRefCount();
+  }
+
+  /**
+   * Returns <code>true</code> if no changes have occured since this searcher ie. reader was opened,
+   * otherwise <code>false</code>.
+   *
+   * @see DirectoryReader#isCurrent()
+   */
+  public boolean isSearcherCurrent() throws IOException {
+    final IndexSearcher searcher = acquire();
+    try {
+      final IndexReader r = searcher.getIndexReader();
+      assert r instanceof DirectoryReader
+          : "searcher's IndexReader should be a DirectoryReader, but got " + r;
+      return ((DirectoryReader) r).isCurrent();
+    } finally {
+      release(searcher);
+    }
+  }
+
+  /**
+   * Expert: creates a searcher from the provided {@link IndexReader} using the provided {@link
+   * SearcherFactory}. NOTE: this decRefs incoming reader on throwing an exception.
+   */
+  @SuppressWarnings("resource")
+  public static IndexSearcher getSearcher(SearcherFactory searcherFactory, IndexReader reader)
+      throws IOException {
+    boolean success = false;
+    final IndexSearcher searcher;
+    try {
+      searcher = searcherFactory.newSearcher(reader, null);
+      // Modification for Gerrit: Allow searcherFactory to transitively wrap the
+      // provided reader.
+      IndexReader unwrapped = searcher.getIndexReader();
+      while (true) {
+        if (unwrapped == reader) {
+          break;
+        } else if (unwrapped instanceof FilterDirectoryReader) {
+          unwrapped = ((FilterDirectoryReader) unwrapped).getDelegate();
+        } else if (unwrapped instanceof FilterLeafReader) {
+          unwrapped = ((FilterLeafReader) unwrapped).getDelegate();
+        } else {
+          break;
+        }
+      }
+
+      if (unwrapped != reader) {
+        throw new IllegalStateException(
+            "SearcherFactory must wrap the provided reader (got "
+                + searcher.getIndexReader()
+                + " but expected "
+                + reader
+                + ")");
+      }
+      success = true;
+    } finally {
+      if (!success) {
+        reader.decRef();
+      }
+    }
+    return searcher;
+  }
+}