mr-smidge commented on a change in pull request #7654:
URL: https://github.com/apache/arrow/pull/7654#discussion_r458452083
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File path: csharp/src/Apache.Arrow/Arrays/Date64Array.cs
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@@ -15,56 +15,94 @@
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.
+ /// </summary>
public class Date64Array: PrimitiveArray<long>
{
+ private static readonly DateTime _epoch = new DateTime(1970, 1, 1, 0,
0, 0, DateTimeKind.Unspecified);
+
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)
+ {
+ return (long)(dateTime - _epoch).TotalMilliseconds;
+ }
+
+ protected override long Convert(DateTimeOffset dateTimeOffset)
{
- return value.ToUnixTimeMilliseconds();
+ return (long)(dateTimeOffset.Date - _epoch).TotalMilliseconds;
Review comment:
> ... at this very moment in time, the exact same number of days have
passed since the Unix Epoch for me and for you, even though we are in different
time zones and our local calendars may be on different days
Ok, I agree with this, because the UNIX Epoch is a point in time rather than
a date, and a "day" in this context must therefore be a block of 24 hours
rather than a box on a calendar.
Alternatively, if someone said "number of days passed since 1st Jan 1970",
then a "day" must be a box on a calendar, because no time element has been
mentioned: only dates. This day count could indeed be different for us in
different time zones at the very same moment in time.
I'm happy with the idea that the `DateXX` array builders can accept a
`DateTimeOffset` and interpret it as the number of 24-hour blocks since the
UNIX Epoch. I'll ensure this is fully documented, as I don't find this the
intuitive interpretation and I'm sure I'm not alone here.
Thank you for clarifying :smile:.
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