[QUESTION][C#] Append values to PrimitiveArray

[Aleksei Smirnov <ax...@mail.ru.INVALID>]

Hello All,
 
I am experiencing  issues with finding documentation on .Net API of apache arrow. Are there any examples or sample projects, that can be used for learning?
 
Currently I am  trying to implement ability to append extra values to existing primitives arrays, but I was not able to figure out a correct API for that.
 
The best way that I found was to create new PrimitiveArray, based on the values in existing array (by coping values buffers).
 
To achieve this I created 2 new buffer builders (value and bitmap). Coping existing values from the source array to new  value buffer was quite straightforward:
 
var  valueBufferBuilder =  new  ArrowBuffer.Builder<T>();
 
var  valueBufferSpan =  sourceArray .ValueBuffer.Span.CastTo<T>();
 
if  (!valueBufferSpan.IsEmpty)
valueBufferBuilder.Append(valueBufferSpan.Slice(0, Length));
 
after coping values from the source array, I was able to finally append a new value
 
valueBufferBuilder.Append(value ??  default );
 
Unfortunately, I didn’t manage to find a similar way to achieve the same for the bitmap buffer. However, I found a code that performs this task in ArrayDataConcatenator class (not the most efficient one as it sets bit by bit in a cycle and this can lead to high CPU usage especially on large arrays, so I am not sure, that I should use it):
 
var  validityBufferSpan =  sourceArray .NullBitmapBuffer.Span;
 
for  ( int  i = 0; i <  sourceArray .Length; i++)
{
validityBufferBuilder.Append(validityBufferSpan.IsEmpty || BitUtility.GetBit(validityBufferSpan, i));
}
 
validityBufferBuilder.Append(value.HasValue);
 
After both buffers were filled, I was able to construct primitive array by writing:
 
var  data =  new  ArrayData( sourceArray .Data.DataType,  sourceArray.L ength  + 1 , -1, 0,  new  ArrowBuffer[] { validityBufferBuilder.Build(), valueBufferBuilder.Build() });
 
var  targetA rray = ArrowArrayFactory.BuildArray(data);
 
Could you please tell if it’s a correct approach or there is a better way to do it?
 
What do you think about extending .Net Apache Arrow API by adding extra constructor to BitMapBuilder? This constructor will copy validity buffer and avoid using GetBit/Append pair for each bit inside it, like:
 
public BitmapBuilder(Span<byte> initialValues, int validBits)
 
Best regards,
Alexey
 
--
Alexey Smirnov