@Override
    public final boolean combine(Metrics metrics) {
        final MaxLabeledFunction maxLabeledFunction = (MaxLabeledFunction) metrics;
        this.value.setMaxValue(maxLabeledFunction.getValue());
        return true;
    }
Service ID is required for sort query.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/meter/function/max/MaxLabeledFunction.java