@Override
  public String toString() {
    StringBuilder buffer = new StringBuilder();
    buildString(false, buffer);
    return buffer.toString();
  }
The inner representation of the SearchArgument. Most users should not
need this interface, it is only for file formats that need to translate
the SearchArgument into an internal form.
storage-api/src/java/org/apache/hadoop/hive/ql/io/sarg/ExpressionTree.java