@Explain(displayName = "spec", explainLevels = { Level.USER, Level.DEFAULT, Level.EXTENDED })
  public String getExplainOutput() {
    return executeSpec.toString();
  }
DDL task task description for ALTER TABLE ... EXECUTE commands.
ql/src/java/org/apache/hadoop/hive/ql/ddl/table/execute/AlterTableExecuteDesc.java