presto-main/src/main/java/io/prestosql/operator/aggregation/histogram/HistogramStateFactory.java/HistogramStateFactory/HistogramStateFactory
class HistogramStateFactory:    public HistogramStateFactory(
            Type keyType, int
            expectedEntriesCount,
            HistogramGroupImplementation mode)
    {
        this.keyType = keyType;
        this.expectedEntriesCount = expectedEntriesCount;
        this.mode = mode;
    }