public void test() throws Exception {
    IndexWriterConfig defaultConfig = new IndexWriterConfig(null);
    Codec defaultCodec = defaultConfig.getCodec();
    if ((new IndexWriterConfig(null)).getCodec() instanceof CompressingCodec) {
      Pattern regex = Pattern.compile("maxDocsPerChunk=(\\d+), blockSize=(\\d+)");
      Matcher matcher = regex.matcher(defaultCodec.toString());
      assertTrue(
          "Unexpected CompressingCodec toString() output: " + defaultCodec.toString(),
          matcher.find());
      int maxDocsPerChunk = Integer.parseInt(matcher.group(1));
      int blockSize = Integer.parseInt(matcher.group(2));
      int product = maxDocsPerChunk * blockSize;
      assumeTrue(
          defaultCodec.getName()
              + " maxDocsPerChunk ("
              + maxDocsPerChunk
              + ") * blockSize ("
              + blockSize
              + ") < 16 - this can trigger OOM with -Dtests.heapsize=30g",
          product >= 16);
    }

    BaseDirectoryWrapper dir = newFSDirectory(createTempDir("2BPostingsBytes1"));
    if (dir instanceof MockDirectoryWrapper) {
      ((MockDirectoryWrapper) dir).setThrottling(MockDirectoryWrapper.Throttling.NEVER);
    }

    IndexWriter w =
        new IndexWriter(
            dir,
            new IndexWriterConfig(new MockAnalyzer(random()))
                .setMaxBufferedDocs(IndexWriterConfig.DISABLE_AUTO_FLUSH)
                .setRAMBufferSizeMB(256.0)
                .setMergeScheduler(new ConcurrentMergeScheduler())
                .setMergePolicy(newLogMergePolicy(false, 10))
                .setOpenMode(IndexWriterConfig.OpenMode.CREATE)
                .setCodec(TestUtil.getDefaultCodec()));

    MergePolicy mp = w.getConfig().getMergePolicy();
    if (mp instanceof LogByteSizeMergePolicy) {
      // 1 petabyte:
      ((LogByteSizeMergePolicy) mp).setMaxMergeMB(1024 * 1024 * 1024);
    }

    Document doc = new Document();
    FieldType ft = new FieldType(TextField.TYPE_NOT_STORED);
    ft.setIndexOptions(IndexOptions.DOCS_AND_FREQS);
    ft.setOmitNorms(true);
    MyTokenStream tokenStream = new MyTokenStream();
    Field field = new Field("field", tokenStream, ft);
    doc.add(field);

    final int numDocs = 1000;
    for (int i = 0; i < numDocs; i++) {
      if (i % 2 == 1) { // trick blockPF's little optimization
        tokenStream.n = 65536;
      } else {
        tokenStream.n = 65537;
      }
      w.addDocument(doc);
    }
    w.forceMerge(1);
    w.close();

    DirectoryReader oneThousand = DirectoryReader.open(dir);
    DirectoryReader subReaders[] = new DirectoryReader[1000];
    Arrays.fill(subReaders, oneThousand);
    BaseDirectoryWrapper dir2 = newFSDirectory(createTempDir("2BPostingsBytes2"));
    if (dir2 instanceof MockDirectoryWrapper) {
      ((MockDirectoryWrapper) dir2).setThrottling(MockDirectoryWrapper.Throttling.NEVER);
    }
    IndexWriter w2 = new IndexWriter(dir2, new IndexWriterConfig(null));
    TestUtil.addIndexesSlowly(w2, subReaders);
    w2.forceMerge(1);
    w2.close();
    oneThousand.close();

    DirectoryReader oneMillion = DirectoryReader.open(dir2);
    subReaders = new DirectoryReader[2000];
    Arrays.fill(subReaders, oneMillion);
    BaseDirectoryWrapper dir3 = newFSDirectory(createTempDir("2BPostingsBytes3"));
    if (dir3 instanceof MockDirectoryWrapper) {
      ((MockDirectoryWrapper) dir3).setThrottling(MockDirectoryWrapper.Throttling.NEVER);
    }
    IndexWriter w3 = new IndexWriter(dir3, new IndexWriterConfig(null));
    TestUtil.addIndexesSlowly(w3, subReaders);
    w3.forceMerge(1);
    w3.close();
    oneMillion.close();

    dir.close();
    dir2.close();
    dir3.close();
  }
  // @Absurd @Ignore takes ~20GB-30GB of space and 10 minutes.
  // with some codecs needs more heap space as well.
  @Ignore("Very slow. Enable manually by removing @Ignore.")
  public void test() throws Exception {
    BaseDirectoryWrapper dir = newFSDirectory(_TestUtil.getTempDir("2BPostingsBytes1"));
    if (dir instanceof MockDirectoryWrapper) {
      ((MockDirectoryWrapper) dir).setThrottling(MockDirectoryWrapper.Throttling.NEVER);
    }

    IndexWriter w =
        new IndexWriter(
            dir,
            new IndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random()))
                .setMaxBufferedDocs(IndexWriterConfig.DISABLE_AUTO_FLUSH)
                .setRAMBufferSizeMB(256.0)
                .setMergeScheduler(new ConcurrentMergeScheduler())
                .setMergePolicy(newLogMergePolicy(false, 10))
                .setOpenMode(IndexWriterConfig.OpenMode.CREATE));

    MergePolicy mp = w.getConfig().getMergePolicy();
    if (mp instanceof LogByteSizeMergePolicy) {
      // 1 petabyte:
      ((LogByteSizeMergePolicy) mp).setMaxMergeMB(1024 * 1024 * 1024);
    }

    Document doc = new Document();
    FieldType ft = new FieldType(TextField.TYPE_NOT_STORED);
    ft.setIndexOptions(IndexOptions.DOCS_AND_FREQS);
    ft.setOmitNorms(true);
    MyTokenStream tokenStream = new MyTokenStream();
    Field field = new Field("field", tokenStream, ft);
    doc.add(field);

    final int numDocs = 1000;
    for (int i = 0; i < numDocs; i++) {
      if (i % 2 == 1) { // trick blockPF's little optimization
        tokenStream.n = 65536;
      } else {
        tokenStream.n = 65537;
      }
      w.addDocument(doc);
    }
    w.forceMerge(1);
    w.close();

    DirectoryReader oneThousand = DirectoryReader.open(dir);
    IndexReader subReaders[] = new IndexReader[1000];
    Arrays.fill(subReaders, oneThousand);
    MultiReader mr = new MultiReader(subReaders);
    BaseDirectoryWrapper dir2 = newFSDirectory(_TestUtil.getTempDir("2BPostingsBytes2"));
    if (dir2 instanceof MockDirectoryWrapper) {
      ((MockDirectoryWrapper) dir2).setThrottling(MockDirectoryWrapper.Throttling.NEVER);
    }
    IndexWriter w2 = new IndexWriter(dir2, new IndexWriterConfig(TEST_VERSION_CURRENT, null));
    w2.addIndexes(mr);
    w2.forceMerge(1);
    w2.close();
    oneThousand.close();

    DirectoryReader oneMillion = DirectoryReader.open(dir2);
    subReaders = new IndexReader[2000];
    Arrays.fill(subReaders, oneMillion);
    mr = new MultiReader(subReaders);
    BaseDirectoryWrapper dir3 = newFSDirectory(_TestUtil.getTempDir("2BPostingsBytes3"));
    if (dir3 instanceof MockDirectoryWrapper) {
      ((MockDirectoryWrapper) dir3).setThrottling(MockDirectoryWrapper.Throttling.NEVER);
    }
    IndexWriter w3 = new IndexWriter(dir3, new IndexWriterConfig(TEST_VERSION_CURRENT, null));
    w3.addIndexes(mr);
    w3.forceMerge(1);
    w3.close();
    oneMillion.close();

    dir.close();
    dir2.close();
    dir3.close();
  }