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();
}
}
}
private void MergeBlocks(int blockCount, int field, StreamWriter output, long bufferSizeInBytes)
{
long blockSize = bufferSizeInBytes / (blockCount + 1);
List <Stream> blockStreams = new List <Stream>();
try
{
List <IEnumerator <Record> > blockRecordsEnumerators = new List <IEnumerator <Record> >();
for (int i = 0; i < blockCount; i++)
{
Stream blockStream = _tempStreams.OpenBlockStream(i);
blockStreams.Add(blockStream);
StreamReader blockStreamReader = new StreamReader(blockStream);
RecordsReader blockReader = new RecordsReader(blockStreamReader, blockSize);
blockRecordsEnumerators.Add(blockReader.ReadRecords().GetEnumerator());
}
using (BufferedRecordsWriter recordsWriter = new BufferedRecordsWriter(output, blockSize))
{
MergeBlocks(blockRecordsEnumerators, recordsWriter, field);
}
}
finally
{
foreach (Stream s in blockStreams)
{
s.Dispose();
}
}
}
