@Override
    public void accept(final MeterEntity entity, final DataTable value) {
        this.entityId = entity.id();
        this.serviceId = entity.serviceId();
        this.summation.append(value);
        DataTable c = new DataTable();
        value.keys().forEach(key -> c.put(key, 1L));
        this.count.append(c);
    }
Service ID is required for sort query.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/meter/function/avg/AvgLabeledFunction.java