@Override
    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (!(o instanceof HistogramFunction))
            return false;
        HistogramFunction function = (HistogramFunction) o;
        return Objects.equals(entityId, function.entityId) &&
            getTimeBucket() == function.getTimeBucket();
    }
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