eerhardt commented on a change in pull request #7654: URL: https://github.com/apache/arrow/pull/7654#discussion_r469456287
########## File path: csharp/src/Apache.Arrow/Arrays/Date64Array.cs ########## @@ -15,56 +15,103 @@ using Apache.Arrow.Types; using System; -using System.Collections.Generic; -using Apache.Arrow.Memory; namespace Apache.Arrow { + /// <summary> + /// The <see cref="Date64Array"/> class holds an array of dates in the <c>Date64</c> format, where each date is + /// stored as the number of milliseconds since the dawn of (UNIX) time, excluding leap seconds, in multiples of + /// 86400000. + /// </summary> public class Date64Array: PrimitiveArray<long> { + private const long MillisecondsPerDay = 86400000; + public Date64Array( ArrowBuffer valueBuffer, ArrowBuffer nullBitmapBuffer, int length, int nullCount, int offset) : this(new ArrayData(Date64Type.Default, length, nullCount, offset, new[] { nullBitmapBuffer, valueBuffer })) { } - public class Builder : PrimitiveArrayBuilder<DateTimeOffset, long, Date64Array, Builder> + /// <summary> + /// The <see cref="Builder"/> class can be used to fluently build <see cref="Date64Array"/> objects. + /// </summary> + public class Builder : DateArrayBuilder<long, Date64Array, Builder> { - internal class DateBuilder: PrimitiveArrayBuilder<long, Date64Array, DateBuilder> + private class DateBuilder: PrimitiveArrayBuilder<long, Date64Array, DateBuilder> { protected override Date64Array Build( ArrowBuffer valueBuffer, ArrowBuffer nullBitmapBuffer, int length, int nullCount, int offset) => new Date64Array(valueBuffer, nullBitmapBuffer, length, nullCount, offset); - } + } + /// <summary> + /// Construct a new instance of the <see cref="Builder"/> class. + /// </summary> public Builder() : base(new DateBuilder()) { } - protected override long ConvertTo(DateTimeOffset value) + protected override long Convert(DateTime dateTime) + { + var dateTimeOffset = new DateTimeOffset( + DateTime.SpecifyKind(dateTime.Date, DateTimeKind.Unspecified), + TimeSpan.Zero); + return dateTimeOffset.ToUnixTimeMilliseconds(); + } + + protected override long Convert(DateTimeOffset dateTimeOffset) { - return value.ToUnixTimeMilliseconds(); + // The internal value stored for a DateTimeOffset can be thought of as the number of milliseconds, + // in multiples of 86400000, that have passed since the UNIX epoch. It is not the same as what would + // result from encoding the date from the DateTimeOffset.Date property. + long millis = dateTimeOffset.ToUnixTimeMilliseconds(); + long days = millis / MillisecondsPerDay; + return (millis < 0 ? days - 1 : days) * MillisecondsPerDay; Review comment: > From what I can tell, the Date64 builder (neither in this PR nor in master) has never had an Append(long) method. You're right - sorry I got confused between the different languages' implementations. I started a conversation on the dev list about this topic, and @wesm had a good idea that we could consider here: > I think we should validate optionally in ValidateFull in C++. I think to validate unconditionally would be too computationally expensive https://issues.apache.org/jira/browse/ARROW-9705 I think you've convinced me that the default/right/safe behavior is to ensure the spec is enforced, so ensuring appending a `DateTimeOffset` to a `Date64Array` makes the underlying `long` value divisible by `86400000` is the right thing to do. If necessary, in the future we could add a `long` overload which doesn't do validation in the off chance that someone really did want non-zero time in their `Date64Array`. Thanks for working through this with me. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org