[Mondrian] Problem moving UDF returning a list from 2.4 to 3.1.1

Eric McDermid mcdermid at stonecreek.com
Fri Jul 31 13:35:41 EDT 2009

I'm having some trouble with a UDF returning a List that worked under  
2.4, but fails with a parse error under 3.1.1.  I'm not sure whether  
the problem is a flaw in the UDF or in how the newer version of  
Mondrian is attempting to use it.

Here's the function, which simply reverses the order of a set:

   public class ReverseFunction implements UserDefinedFunction {
	public Object execute(Evaluator eval, Argument[] args) {
		List memberList = (List) args[0].evaluate(eval);
		return memberList;
	public String getDescription() {
		return "Reverses the order of a set";
	public String getName() {
		return "Reverse";
	public Type[] getParameterTypes() {
		return new Type[] {new SetType(MemberType.Unknown)};
	public String[] getReservedWords() {
		return null;
	public Type getReturnType(Type[] arg0) {
		return arg0[0];
	public Syntax getSyntax() {
		return Syntax.Function;

The stack trace for the underlying cause of the error is here:

Caused by: mondrian.olap.MondrianException: Mondrian Error:Internal  
error: Cannot convert calc to list: mondrian.olap.fun.UdfResolver 
$CalcImpl at 315d04
	at mondrian.resource.MondrianResource$_Def0.ex(MondrianResource.java: 
	at mondrian.olap.Util.newInternal(Util.java:1465)
	at mondrian.olap.fun.SetFunDef 
	at mondrian.olap.fun.SetFunDef 
	at mondrian.olap.fun.SetFunDef 
	at mondrian.olap.fun.SetFunDef.compileCall(SetFunDef.java:89)
	at mondrian.mdx.ResolvedFunCall.accept(ResolvedFunCall.java:152)
	at mondrian.olap.QueryAxis.compile(QueryAxis.java:122)
	at mondrian.olap.Query.compile(Query.java:519)
	at mondrian.olap.Query.resolve(Query.java:456)
	at mondrian.olap.Query.<init>(Query.java:231)
	at mondrian.olap.Query.<init>(Query.java:187)
	at mondrian.olap.Parser.makeQuery(Parser.java:870)
	at mondrian.olap.CUP$Parser$actions.CUP$Parser$do_action(Parser.java: 
	at mondrian.olap.Parser.do_action(Parser.java:699)
	at java_cup.runtime.lr_parser.parse(lr_parser.java:569)
	at mondrian.olap.Parser.parseInternal(Parser.java:772)

The immediate problem is in AbstractExpCompiler.compileList().  It  
compiles the expression "Reverse([Requested Dates])", gets a  
mondrian.olap.fun.UdfResolver$CalcImpl instance as a result, then  
complains because said calc is neither null, a ListCalc, or an IterCalc.

UDF documentation seems a little thin, and I've been unable to find an  
example of a UDF returning a list in either mondrian/udf or in UdfTest  
to use as a reference point.  Searching the archive, I do see that  
Pappyn Bart asked a somewhat similar question back in 2007, but I  
didn't see a clear resolution.

Can anyone help me sort this problem out, or failing that at least  
point me to an example of a UDF that does successfully return a list  
that I can compare against?

  -- Eric

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