apache/beam · error · UnsupportedOperationException

the function is not supported for now: ${cepKind}

Error message

the function is not supported for now: ${cepKind}

What it means

NFA.evalLeftSideCondition evaluates the left operand of a comparison by recursively reducing CEPOperator calls (e.g. CLASS, PREV, PLUS). Only a fixed set of CepKinds is handled; any other operator kind (PLUS intervals, EXTRACT, etc. not implemented) throws UnsupportedOperationException naming the CepKind.

Source

Thrown at sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/nfa/NFA.java:522

    private CEPLiteral evalLeftSideCondition(CEPOperation inputOperation, Event inputEvent) {
      if (inputOperation instanceof CEPLiteral) {
        return (CEPLiteral) inputOperation;
      } else if (inputOperation.getClass() == CEPFieldRef.class) {
        return inputEvent.toCEPLiteral((CEPFieldRef) inputOperation);
      } else if (inputOperation.getClass() == CEPCall.class) {
        CEPCall call = (CEPCall) inputOperation;
        CEPOperator operator = call.getOperator();
        List<CEPOperation> operands = call.getOperands();
        switch (operator.getCepKind()) {
          case LAST:
            return last(
                operands.get(0), evalLeftSideCondition(operands.get(1), inputEvent), inputEvent);
          case PLUS:
            return plus(
                evalLeftSideCondition(operands.get(0), inputEvent),
                evalLeftSideCondition(operands.get(1), inputEvent));
          default:
            throw new UnsupportedOperationException(
                "the function is not supported for now: " + operator.getCepKind().toString());
        }
      } else {
        throw new IllegalStateException(
            "the left side CEP operation is not legal: " + inputOperation.getClass().toString());
      }
    }

    // evaluates the condition value (right) given an input event
    private CEPLiteral evalRightSideCondition(CEPOperation inputOperation, Event inputEvent) {
      if (inputOperation instanceof CEPLiteral) {
        return (CEPLiteral) inputOperation;
      } else if (inputOperation.getClass() == CEPCall.class) {
        CEPCall call = (CEPCall) inputOperation;
        CEPOperator operator = call.getOperator();
        List<CEPOperation> operands = call.getOperands();
        switch (operator.getCepKind()) {
          case PLUS:

View on GitHub (pinned to 12126d8942)

Solutions

1. Rewrite the condition so the left side only uses supported functions (field access, PREV, supported arithmetic).
2. Precompute the expression as a new schema field upstream and compare that field in DEFINE.
3. Extend evalLeftSideCondition with a case for the missing CepKind (mirroring the plus() helper).
4. Symmetrically check evalRightSideCondition — the same operator must be supported on the side where it appears.

Example fix

// before
DEFINE A AS A.price - A.cost > 0
// after (upstream field)
.addField("margin", FieldType.DOUBLE) // price - cost
// DEFINE A AS A.margin > 0

// Check the left-side CepKind before building the query
if (!SUPPORTED_LEFT_KINDS.contains(cepKind)) {
  throw new IllegalArgumentException("Left-side operator not supported by CEP: " + cepKind);
}

boolean isSupportedLeftOp(CEPOperation op) { return op instanceof CEPOperator && SUPPORTED_LEFT_KINDS.contains(((CEPOperator) op).getCepKind()); }

try { return evalLeftSideCondition(op, event); } catch (UnsupportedOperationException e) { throw new QueryValidationException("Unsupported operator in DEFINE left side", e); }

When it happens

Trigger: A DEFINE left-side expression using an arithmetic/logical operator whose CepKind is absent from the switch (e.g. MINUS, DIVIDE, TIMES, EXTRACT) in a MATCH_RECOGNIZE query.

Common situations: Writing conditions like A.price - A.cost > 0 or division/comparison of computed expressions that the CEP layer does not yet support.

Related errors

• RexNode not supported: ${className}
• the function in Measures is not recognized.
• The type is not supported: ${typeName}
• the comparator is not supported: ${comparator}
• the left side CEP operation is not legal: ${class}

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/411e5575b8c96778. Report an issue: GitHub.