presto-main/src/main/java/io/prestosql/operator/aggregation/histogram/LegacyHistogramGroupState.java/LegacyHistogramGroupState/get
class LegacyHistogramGroupState:    @Override
    public TypedHistogram get()
    {
        TypedHistogram typedHistogram = typedHistograms.get(getGroupId());

        if (typedHistogram == null) {
            SingleTypedHistogram newTypedHistogram = new SingleTypedHistogram(keyType, expectedEntriesCount);

            typedHistograms.set(getGroupId(), newTypedHistogram);
            typedHistogram = newTypedHistogram;
            size += typedHistogram.getEstimatedSize();
        }

        return typedHistogram;
    }