public static int getColumnNumber(Configuration conf) {
    return HiveConf.getIntVar(conf, HiveConf.ConfVars.HIVE_RCFILE_COLUMN_NUMBER_CONF);
  }
Returns the number of columns set in the conf for writers.

@param conf
@return number of columns for RCFile's writer
ql/src/java/org/apache/hadoop/hive/ql/io/RCFileOutputFormat.java