presto-main/src/main/java/io/prestosql/operator/BigintGroupByHash.java/BigintGroupByHash/getEstimatedSize
class BigintGroupByHash:    @Override
    public long getEstimatedSize()
    {
        return INSTANCE_SIZE +
                groupIds.sizeOf() +
                values.sizeOf() +
                valuesByGroupId.sizeOf() +
                preallocatedMemoryInBytes;
    }