/// <summary>
/// Returns an <see cref="IEnumerable{RecordBatch}"/> without copying data
/// </summary>
public IEnumerable <RecordBatch> ToArrowRecordBatches()
{
Apache.Arrow.Schema.Builder schemaBuilder = new Apache.Arrow.Schema.Builder();
int columnCount = Columns.Count;
for (int i = 0; i < columnCount; i++)
{
DataFrameColumn column = Columns[i];
Field field = column.GetArrowField();
schemaBuilder.Field(field);
}
Schema schema = schemaBuilder.Build();
List <Apache.Arrow.Array> arrays = new List <Apache.Arrow.Array>();
int recordBatchLength = Int32.MaxValue;
int numberOfRowsInThisRecordBatch = (int)Math.Min(recordBatchLength, RowCount);
long numberOfRowsProcessed = 0;
// Sometimes .NET for Spark passes in DataFrames with no rows. In those cases, we just return a RecordBatch with the right Schema and no rows
do
{
for (int i = 0; i < columnCount; i++)
{
DataFrameColumn column = Columns[i];
numberOfRowsInThisRecordBatch = (int)Math.Min(numberOfRowsInThisRecordBatch, column.GetMaxRecordBatchLength(numberOfRowsProcessed));
}
for (int i = 0; i < columnCount; i++)
{
DataFrameColumn column = Columns[i];
arrays.Add(column.ToArrowArray(numberOfRowsProcessed, numberOfRowsInThisRecordBatch));
}
numberOfRowsProcessed += numberOfRowsInThisRecordBatch;
yield return(new RecordBatch(schema, arrays, numberOfRowsInThisRecordBatch));
} while (numberOfRowsProcessed < RowCount);
}
public static Table BuildTable(List <TDataLayout> data)
{
PropertyInfo[] properties = typeof(TDataLayout).GetProperties(BindingFlags.Public | BindingFlags.Instance).Where(p => p.GetCustomAttribute <ArrowPropertyAttribute>() != null).ToArray();
//int length = data.Count;
List <Field> fields = new List <Field>(properties.Length);
Apache.Arrow.Schema.Builder schemaBuilder = new Apache.Arrow.Schema.Builder();
foreach (PropertyInfo property in properties)
{
ArrowPropertyAttribute arrowPropertyAttribute = property.GetCustomAttribute <ArrowPropertyAttribute>();
Field field = new Field.Builder().Name(arrowPropertyAttribute.Name).DataType(arrowPropertyAttribute.ArrowType()).Build();
schemaBuilder.Field(field);
fields.Add(field);
}
List <List <object> > transformData = new List <List <object> >(properties.Length);
for (int i = 0; i < properties.Length; ++i)
{
transformData.Add(new List <object>(data.Count));
}
for (int i = 0; i < data.Count; ++i)
{
int j = 0;
foreach (object property in data[i])
{
transformData[j++][i] = property;
}
}
List <Column> columns = new List <Column>(properties.Length);
for (int i = 0; i < properties.Length; ++i)
{
Array array = ArrowUtilities.MakeArrayBuffer(fields[i].DataType,
transformData[i]);
Column column = new Column(fields[i],
new Array[]
{
array
});
columns.Add(column);
}
//NativeMemoryAllocator memoryAllocator = new NativeMemoryAllocator(32);
Table table = new Table(schemaBuilder.Build(),
columns);
return(table);
}