eerhardt commented on a change in pull request #7671:
URL: https://github.com/apache/arrow/pull/7671#discussion_r453042194
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File path: csharp/src/Apache.Arrow/Arrays/BinaryArray.cs
##########
@@ -237,7 +329,9 @@ public ReadOnlySpan<byte> GetBytes(int index)
if (IsNull(index))
{
- return null;
+ // Note that `return null;` is valid syntax, but would be
misleading as `null` in the context of a span
+ // is actually returned as an empty span.
+ return ReadOnlySpan<byte>.Empty;
Review comment:
I've been confused and bit by this a few times in different projects.
All the following ways produce an "equivalent" span:
* `return null` (this uses the implicit operator from an array)
* `return default`
* `return ReadOnlySpan<T>.Empty` (this just says `return default`
underneath the covers)
I agree that `ReadOnlySpan<T>.Empty` is the most clear thing to return here.
Next would be `return default`. `return null` is the worst of the three options
IMO.
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File path: csharp/src/Apache.Arrow/Arrays/BinaryArray.cs
##########
@@ -66,87 +66,158 @@ protected BuilderBase(IArrowType dataType)
ValueOffsets = new ArrowBuffer.Builder<int>();
ValueBuffer = new ArrowBuffer.Builder<byte>();
ValidityBuffer = new ArrowBuffer.BitmapBuilder();
+
+ // From the docs:
+ //
+ // The offsets buffer contains length + 1 signed integers
(either 32-bit or 64-bit, depending on the
+ // logical type), which encode the start position of each slot
in the data buffer. The length of the
+ // value in each slot is computed using the difference between
the offset at that slot’s index and the
+ // subsequent offset.
+ //
+ // In this builder, we choose to append the first offset
(zero) upon construction, and each trailing
+ // offset is then added after each individual item has been
appended.
+ ValueOffsets.Append(this.Offset);
}
protected abstract TArray Build(ArrayData data);
- public int Length => ValueOffsets.Length;
+ /// <summary>
+ /// Gets the length of the array built so far.
+ /// </summary>
+ public int Length => ValueOffsets.Length - 1;
+ /// <summary>
+ /// Build an Arrow array from the appended contents so far.
+ /// </summary>
+ /// <param name="allocator">Optional memory allocator.</param>
+ /// <returns>Returns an array of type <typeparamref
name="TArray"/>.</returns>
public TArray Build(MemoryAllocator allocator = default)
{
- ValueOffsets.Append(Offset);
-
- ArrowBuffer validityBuffer = NullCount > 0
- ? ValidityBuffer.Build(allocator)
- : ArrowBuffer.Empty;
-
- var data = new ArrayData(DataType, ValueOffsets.Length - 1,
NullCount, 0,
- new[] { validityBuffer, ValueOffsets.Build(allocator),
ValueBuffer.Build(allocator) });
+ var bufs = new[]
+ {
+ NullCount > 0 ? ValidityBuffer.Build(allocator) :
ArrowBuffer.Empty,
+ ValueOffsets.Build(allocator),
+ ValueBuffer.Build(allocator),
+ };
+ var data = new ArrayData(
+ DataType,
+ length: ValueOffsets.Length - 1,
Review comment:
Can this line just be `Length` ?
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