@Override
    public boolean combine(final Metrics metrics) {
        HistogramFunction histogram = (HistogramFunction) metrics;

        if (!dataset.keysEqual(histogram.getDataset())) {
            log.warn("Incompatible input [{}}] for current HistogramFunction[{}], entity {}",
                     histogram, this, entityId
            );
            return true;
        }
        this.dataset.append(histogram.dataset);
        return true;
    }
Histogram includes data range buckets and the amount matched/grouped in the buckets. This is for original histogram
graph visualization
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/meter/function/HistogramFunction.java