public void addRHSSemijoinColumns(String alias, ASTNode column) {
    List<ASTNode> cols = rhsSemijoin.get(alias);
    if (cols == null) {
      cols = new ArrayList<ASTNode>();
      cols.add(column);
      rhsSemijoin.put(alias, cols);
    } else {
      cols.add(column);
    }
  }
Remeber the mapping of table alias to set of columns.

@param alias
@param column
ql/src/java/org/apache/hadoop/hive/ql/parse/QBJoinTree.java