Review

class IndexReader {
  /** Expert: returns an IndexReader reading the index in the given
   *  {@link IndexCommit}.  You should pass readOnly=true, since it
   *  gives much better concurrent performance, unless you
   *  intend to do write operations (delete documents or
   *  change norms) with the reader.
   * @param commit the commit point to open
   * @param readOnly true if no changes (deletions, norms) will be made with this IndexReader
   * @throws CorruptIndexException if the index is corrupt
   * @throws IOException if there is a low-level IO error
   */
  public static IndexReader open(final IndexCommit commit, boolean readOnly) throws CorruptIndexException, IOException {
    return open(commit.getDirectory(), null, commit, readOnly, DEFAULT_TERMS_INDEX_DIVISOR);
  }

}