@Explain(displayName = "skewedColumnNames", explainLevels = { Level.USER, Level.DEFAULT, Level.EXTENDED })
  public List<String> getSkewedColumnNames() {
    return skewedColumnNames;
  }
DDL task description for ALTER TABLE ... [SKEWED BY ... ON ...] [[NOT] STORED AS DIRECTORIES] commands.
ql/src/java/org/apache/hadoop/hive/ql/ddl/table/storage/skewed/AlterTableSkewedByDesc.java