@Override
  public void generateCanonicalizedExpression(StringBuilder clauseBuffer, ExecutionContext context)
      throws AmbiguousNameException, TypeMismatchException {
    if (_obj == null) {
      clauseBuffer.insert(0, "null");
    } else if (_obj instanceof String) {
      clauseBuffer.insert(0, '\'').insert(0, _obj).insert(0, '\'');
    } else {
      clauseBuffer.insert(0, _obj);
    }
  }
creates new PdxString from String and caches it
geode-core/src/main/java/org/apache/geode/cache/query/internal/CompiledLiteral.java