apache/skywalking · error · IllegalExpressionException

Series No Labeled, left or right result is empty.

Error message

Series No Labeled, left or right result is empty.

What it means

Thrown by LROp.seriesNoLabeled when two non-labeled TIME_SERIES_VALUES operands are combined: if either side's results list is completely empty there is nothing to align, so the operation aborts. Only the first MQEValues of each side is used (series are expected to be single-series).

Source

Thrown at oap-server/mqe-rt/src/main/java/org/apache/skywalking/mqe/rt/operation/LROp.java:211

                        singleResult.getResults()
                                    .get(0)
                                    .getValues()
                                    .get(0)
                                    .getDoubleValue(),
                        mqeValue.getDoubleValue(), opType
                    );
                    mqeValue.setDoubleValue(newValue);
                }
            }
        }
        return manyResult;
    }

    private static ExpressionResult seriesNoLabeled(ExpressionResult seriesLeft,
                                                    ExpressionResult seriesRight,
                                                    int opType, LROp calculate) throws IllegalExpressionException {
        if (seriesLeft.getResults().isEmpty() || seriesRight.getResults().isEmpty()) {
            throw new IllegalExpressionException("Series No Labeled, left or right result is empty.");
        }
        MQEValues mqeValuesL = seriesLeft.getResults().get(0);
        MQEValues mqeValuesR = seriesRight.getResults().get(0);
        if (mqeValuesL.getValues().size() != mqeValuesR.getValues().size()) {
            throw new IllegalExpressionException("Series No Labeled, left and right series value size not equal.");
        }
        for (int i = 0; i < mqeValuesL.getValues().size(); i++) {
            //clean metric info
            MQEValue valueL = mqeValuesL.getValues().get(i);
            MQEValue valueR = mqeValuesR.getValues().get(i);
            if (valueL.isEmptyValue() || valueR.isEmptyValue()) {
                valueL.setEmptyValue(true);
                continue;
            }
            //time should be mapped
            double newValue = calculate.apply(valueL.getDoubleValue(), valueR.getDoubleValue(), opType);
            mqeValuesL.getValues().get(i).setDoubleValue(newValue);
        }

View on GitHub (pinned to 102af09b4a)

Solutions

1. Run each series operand alone to confirm both return data in the same time range
2. Align the time range and step of both metrics — same duration and step produces comparable point counts
3. If empty series are expected, use viewAsSeq or isPresent-based logic instead of a plain binary op
4. Verify the metric names exist and data is actually being ingested (check UI or raw metric query)

Example fix

// before
query: metric_old + metric_new   // metric_old has no data in range
// after
query: viewAsSeq(metric_old, metric_new)  // or narrow the range to where both have data

ExpressionResult l = mqeService.eval(leftExpr), r = mqeService.eval(rightExpr);
boolean ok = !l.getResults().isEmpty() && !r.getResults().isEmpty();

catch (IllegalExpressionException e) { /* check data presence in range first */ }

When it happens

Trigger: MQE expression 'seriesA + seriesB' where seriesA or seriesB returned zero results (no data points / no series at all) in the queried time range. Reached from seriesBinaryOp when neither side isLabeledResult().

Common situations: One of the metrics has no data in the selected time window (e.g. service deployed recently, metrics dropped after OAP restart with empty storage); typo'd metric name that resolves to a type but returns nothing; querying a time range before the metric existed; storage (BanyanDB/ES) retention having evicted the data.

Related errors

• Single to Single, left result is empty or has more than one
• Single to Single, right result is empty or has more than one
• Single Labeled to Single Labeled, left labeled result is emp
• Single Labeled to Single Labeled, right labeled result has m
• Many to One, single result is empty or has more than one val

AI-assisted analysis of apache/skywalking@102af09b4a (2026-08-14). Data as JSON: /api/errors/557dd9c7d5f3b254. Report an issue: GitHub.