@Explain(displayName = "if not exists", displayOnlyOnTrue = true,
      explainLevels = { Level.USER, Level.DEFAULT, Level.EXTENDED })
  public boolean isIfNotExists() {
    return ifNotExists;
  }
@return location of partition in relation to table
ql/src/java/org/apache/hadoop/hive/ql/ddl/table/partition/add/AlterTableAddPartitionDesc.java