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 static List <T> Merge <T>(List <T> list, int chunkCount, int chunkSize, IComparer <T> comparer)
{
int[] chunkIndexes = new int[chunkCount];
int[] chunkEnds = new int[chunkCount];
for (int i = 0; i < chunkCount; i++)
{
chunkIndexes[i] = i * chunkSize;
chunkEnds[i] = i * chunkSize + chunkSize;
}
chunkEnds[chunkEnds.Length - 1] = list.Count;
MinHeap <int> heap = new MinHeap <int>(chunkCount,
new SelectComparer <int, T>(i => list[chunkIndexes[i]], comparer));
for (int i = 0; i < chunkCount; i++)
{
heap.Add(i);
}
List <T> result = new List <T>(list.Count);
for (int i = 0; i < list.Count; i++)
{
result.Add(list[chunkIndexes[heap.Root]]);
chunkIndexes[heap.Root]++;
if (chunkIndexes[heap.Root] == chunkEnds[heap.Root])
{
heap.Extract();
}
else
{
heap.DownHeap();
}
}
return(result);
}