private void failIfColAliasExists(Set<String> nameSet, String name)
      throws SemanticException {
    if (nameSet.contains(name)) {
      throw new SemanticException(ErrorMsg.COLUMN_ALIAS_ALREADY_EXISTS
          .getMsg(name));
    }
    nameSet.add(name);
  }
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