@Explain(displayName = "constraint name", explainLevels = { Level.USER, Level.DEFAULT, Level.EXTENDED })
  public String getConstraintName() {
    return constraintName;
  }
DDL task description for ALTER TABLE ... DROP CONSTRAINT ... commands.
ql/src/java/org/apache/hadoop/hive/ql/ddl/table/constraint/drop/AlterTableDropConstraintDesc.java