rcfile/src/main/java/com/twitter/elephantbird/util/RCFileUtil.java
public static ColumnarMetadata readMetadata(Configuration conf, Path rcfile)
                                              throws IOException {

    Metadata metadata = null;

    Configuration confCopy = new Configuration(conf);
    // set up conf to read all the columns
    ColumnProjectionUtils.setFullyReadColumns(confCopy);

    RCFile.Reader reader = new RCFile.Reader(rcfile.getFileSystem(confCopy),
                                             rcfile,
                                             confCopy);

    //ugly hack to get metadata. RCFile has to provide access to metata
    try {
      Field f = RCFile.Reader.class.getDeclaredField("metadata");
      f.setAccessible(true);
      metadata = (Metadata)f.get(reader);
    } catch (Throwable t) {
      throw new IOException("Could not access metadata field in RCFile reader", t);
    }

    reader.close();

    Text metadataKey = new Text(COLUMN_METADATA_PROTOBUF_KEY);

    if (metadata == null || metadata.get(metadataKey) == null) {
      throw new IOException("could not find ColumnarMetadata in " + rcfile);
    }

    return ColumnarMetadata.parseFrom(metadata.get(metadataKey).getBytes());
  }
public static ColumnarMetadata readMetadata(Configuration conf, Path rcfile)
                                              throws IOException {

    Metadata metadata = null;

    Configuration confCopy = new Configuration(conf);
    // set up conf to read all the columns
    ColumnProjectionUtils.setFullyReadColumns(confCopy);

    RCFile.Reader reader = new RCFile.Reader(rcfile.getFileSystem(confCopy),
                                             rcfile,
                                             confCopy);

    //ugly hack to get metadata. RCFile has to provide access to metata
    try {
      Field f = RCFile.Reader.class.getDeclaredField("metadata");
      f.setAccessible(true);
      metadata = (Metadata)f.get(reader);
    } catch (Throwable t) {
      throw new IOException("Could not access metadata field in RCFile reader", t);
    }

    reader.close();

    Text metadataKey = new Text(COLUMN_METADATA_PROTOBUF_KEY);

    if (metadata == null || metadata.get(metadataKey) == null) {
      throw new IOException("could not find ColumnarMetadata in " + rcfile);
    }

    return ColumnarMetadata.parseFrom(metadata.get(metadataKey).getBytes());
  }
reads {@link ColumnarMetadata} stored in an RCFile.
@throws IOException if metadata is not stored or in case of any other error.