private Class<? extends RecordReader> getRecordReader(ASTNode node)
      throws SemanticException {
    String name;

    if (node.getChildCount() == 0) {
      name = conf.getVar(HiveConf.ConfVars.HIVE_SCRIPT_RECORD_READER);
    } else {
      name = unescapeSQLString(node.getChild(0).getText());
    }

    try {
      return (Class<? extends RecordReader>) Class.forName(name, true,
          Utilities.getSessionSpecifiedClassLoader());
    } catch (ClassNotFoundException e) {
      throw new SemanticException(e);
    }
  }
create a filter plan. The condition and the inputs are specified.

@param qb
         current query block
@param condn
         The condition to be resolved
@param input
         the input operator
ql/src/java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java