private void MergeBlocks(List <IEnumerator <Record> > blockRecordsEnumerators,
BufferedRecordsWriter recordsWriter, int field)
{
IRecordFieldComparer comparer = _recordComparer.CreateRecordFieldComparer(field);
var currentRecordComparer = new SelectComparer <int, Record>(
i => blockRecordsEnumerators[i].Current,
comparer);
var heap = new MinHeap <int>(blockRecordsEnumerators.Count, currentRecordComparer);
for (int i = 0; i < blockRecordsEnumerators.Count; i++)
{
blockRecordsEnumerators[i].MoveNext();
heap.Add(i);
}
while (heap.Size > 0)
{
recordsWriter.WriteRecord(blockRecordsEnumerators[heap.Root].Current);
bool empty = !blockRecordsEnumerators[heap.Root].MoveNext();
if (empty)
{
heap.Extract();
}
else
{
heap.DownHeap();
}
}
}
/// <summary>
/// Reads records by blocks of specific size returning one after another.
/// </summary>
public IEnumerable <RecordsBuffer> ReadBlocks()
{
IsLastBlock = false;
RecordsBuffer recordsBuffer = new RecordsBuffer(_bufferSizeInBytes);
Record? recordToCompare = null;
IRecordFieldComparer comparer = _readWhileSameFieldValue != -1
? _recordComparer.CreateRecordFieldComparer(_readWhileSameFieldValue)
: null;
if (_hasRecordAhead)
{
recordToCompare = _recordAhead;
recordsBuffer.AddRecord(_recordAhead);
_hasRecordAhead = false;
}
string line = null;
while ((line = _streamReader.ReadLine()) != null)
{
Record record = _recordParser.Parse(line);
if (_readWhileSameFieldValue >= 0)
{
if (recordToCompare == null)
{
recordToCompare = record;
}
else if (comparer.Compare(record, recordToCompare.Value) != 0)
{
_recordAhead = record;
_hasRecordAhead = true;
break;
}
}
bool added = recordsBuffer.AddRecord(record);
if (!added)
{
if (recordsBuffer.Records.Count == 0)
{
throw new InvalidOperationException("Buffer is too small. Can't add even one record.");
}
yield return(recordsBuffer);
recordsBuffer = new RecordsBuffer(_bufferSizeInBytes);
recordsBuffer.AddRecord(record);
}
}
if (recordsBuffer.Records.Count > 0)
{
IsLastBlock = true;
yield return(recordsBuffer);
}
}
/// <summary>
/// Sorts records by specified field.
/// </summary>
/// <param name="field">Field index by which sorting will happen.</param>
public void Sort(int field)
{
IRecordFieldComparer comparer = _recordComparer.CreateRecordFieldComparer(field);
Records = Records.ParallelSort(comparer);
}