apache/skywalking · error · IllegalExpressionException

Unsupported sort order.

Error message

Unsupported sort order.

What it means

SortLabelValuesOp.doSortLabelValuesOp sorts labeled results by label values; the order token must be exactly MQEParser.ASC or MQEParser.DES. Any other integer reaching the else branch throws 'Unsupported sort order.'. This op backs the sortLabelsForLabeledValues(...) MQE construct; a well-formed parse yields ASC or DES, so other values indicate grammar/runtime mismatch or direct API misuse.

Source

Thrown at oap-server/mqe-rt/src/main/java/org/apache/skywalking/mqe/rt/operation/SortLabelValuesOp.java:50

import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.toList;

@Slf4j
public class SortLabelValuesOp {
    public static ExpressionResult doSortLabelValuesOp(ExpressionResult expResult,
                                                      int order,
                                                      List<String> labelNames) throws IllegalExpressionException {
        if (CollectionUtils.isNotEmpty(labelNames)) {
            labelNames = labelNames.stream().distinct().collect(toList());
            if (MQEParser.ASC == order) {
                expResult.setResults(
                    sort(expResult.getResults(), labelNames, labelNames.get(0), Comparator.naturalOrder()));
            } else if (MQEParser.DES == order) {
                expResult.setResults(
                    sort(expResult.getResults(), labelNames, labelNames.get(0), Comparator.reverseOrder()));
            } else {
                throw new IllegalExpressionException("Unsupported sort order.");
            }
        }
        return expResult;
    }

    private static List<MQEValues> sort(List<MQEValues> results,
                                        List<String> sortLabels,
                                        String currentSortLabel,
                                        Comparator<String> comparator) {
        if (!sortLabels.contains(currentSortLabel)) {
            log.error("Current sort label {} not found in the sort labels {} ", currentSortLabel, sortLabels);
            return results;
        }
        if (sortLabels.indexOf(
            currentSortLabel) == sortLabels.size() - 1) { //only one label or the latest label no need to group
            results.sort(Comparator.comparing(mqeValues -> mqeValues.getMetric()
                                                                    .getLabels()
                                                                    .stream()

View on GitHub (pinned to 102af09b4a)

Solutions

1. Use the documented MQE syntax: sortLabelsForLabeledValues(metric, ASC, labelNames) or DES
2. If calling programmatically, pass MQEParser.ASC or MQEParser.DES exactly, sourced from the same generated parser version as mqe-rt
3. For new sort-order tokens in a fork, add an else-if branch in doSortLabelValuesOp
4. Ensure mqe-grammar and mqe-rt jars match versions

Example fix

// before
SortLabelValuesOp.doSortLabelValuesOp(result, 0, labels);  // 0 is neither ASC nor DES
// after
SortLabelValuesOp.doSortLabelValuesOp(result, MQEParser.ASC, labels);

if (order != MQEParser.ASC && order != MQEParser.DES) {
    throw new IllegalArgumentException("order must be MQEParser.ASC or MQEParser.DES");
}

boolean isValidSortOrder(int order) { return order == MQEParser.ASC || order == MQEParser.DES; }

catch (IllegalExpressionException e) { /* bad sort order constant passed to sortLabelsForLabeledValues */ }

When it happens

Trigger: Calling sortLabelsForLabeledValues with an order argument that is neither the ASC nor DES token constant — e.g. passing a SQL-style 'asc'/'desc' string mapping, 0/1 ints, or a custom grammar token after a fork; or a visitor bug passing the wrong token type.

Common situations: Custom grammar forks adding a new sort direction; calling the mqe-rt operation classes directly from plugin code with hand-built opType constants; version skew between the generated parser and the runtime operations jar.

Related errors

• Unsupported function.
• Unsupported function.
• Unsupported function.
• Unsupported aggregateLabels function.
• Unsupported aggregation operation.

AI-assisted analysis of apache/skywalking@102af09b4a (2026-08-14). Data as JSON: /api/errors/6af5705c6597142c. Report an issue: GitHub.