rcfile/src/main/java/com/twitter/elephantbird/mapreduce/output/RCFileThriftOutputFormat.java
public static void setClassConf(Class<? extends TBase<?, ?> > thriftClass, Configuration conf) {
    ThriftUtils.setClassConf(conf, RCFileThriftOutputFormat.class, thriftClass);
  }
public static void setClassConf(Class<? extends TBase<?, ?> > thriftClass, Configuration conf) {
    ThriftUtils.setClassConf(conf, RCFileThriftOutputFormat.class, thriftClass);
  }
Stores supplied class name in configuration. This configuration is
read on the remote tasks to initialize the output format correctly.