public void put(String tabAlias, String colAlias, ColumnInfo colInfo) {
    if (!putInternal(tabAlias, colAlias, colInfo)) {
      return;
    }
    if (colAlias != null) {
      colInfo.setAlias(colAlias.toLowerCase());
    }
  }
Retrieves the source expression matching a given ASTNode's
string rendering exactly.
ql/src/java/org/apache/hadoop/hive/ql/parse/RowResolver.java