private void CompensatePages(BTreePage left, BTreePage right, BTreePage parent, int childrenIndex)
{
int parentRecordIndex = 0, recordsToTransfer;
if (left.GetPresentRecords() < right.GetPresentRecords())
{
for (var i = 0; i < parent.Childrens.Count; i++)
{
if (parent.Childrens[i] == left.SelfIndex)
{
parentRecordIndex = i;
}
}
//parentRecordIndex = childrenIndex - 1;
recordsToTransfer = (right.GetPresentRecords() - left.GetPresentRecords()) / 2;
left.InsertRecord(parent.Records[parentRecordIndex]);
for (var i = 0; i < recordsToTransfer - 1; i++)
{
left.InsertRecord(right.PopRecordAt(0, false));
}
if (!right.IsLeaf)
{
for (var i = 0; i < recordsToTransfer; i++)
{
left.Childrens.Add(right.PopChildrenAt(0));
}
}
parent.Records[parentRecordIndex] = right.PopRecordAt(0, false);
}
else
{
for (var i = 0; i < parent.Childrens.Count; i++)
{
if (parent.Childrens[i] == left.SelfIndex)
{
parentRecordIndex = i;
}
}
//parentRecordIndex = childrenIndex;
recordsToTransfer = (left.GetPresentRecords() - right.GetPresentRecords()) / 2;
right.InsertRecord(parent.Records[parentRecordIndex]);
for (var i = 0; i < recordsToTransfer - 1; i++)
{
right.InsertRecord(left.PopRecordAt(left.Records.Count - 1, false));
}
if (!left.IsLeaf)
{
for (var i = 0; i < recordsToTransfer; i++)
{
right.Childrens.Insert(0, left.PopChildrenAt(left.Childrens.Count - 1));
}
}
parent.Records[parentRecordIndex] = left.PopRecordAt(left.Records.Count - 1, false);
}
}
public BTree(Stream bTreeStream, Stream dataStream, Stream bTreeMap, Stream dataMap, bool create)
{
BtreeIO = new BufferedIO(bTreeStream, (int)Static.PageSize);
DataIO = new BufferedIO(dataStream, Record.ByteSize);
if (create)
{
bTreeStream.SetLength(0);
dataStream.SetLength(0);
bTreeMap.SetLength(0);
dataMap.SetLength(0);
BTreeHeader = new BTreeHeaderPage(Static.FirstRootIndex);
RootPage = new BTreePage(0, Static.FirstRootIndex);
BTreeFreeSpaceMap = new FreeSpaceMap(bTreeMap, 2);
DataFreeSpaceMap = new FreeSpaceMap(dataMap, 0);
}
else
{
BTreeHeader = new BTreeHeaderPage(BtreeIO.ReadPage(0));
RootPage = new BTreePage(BtreeIO.ReadPage(BTreeHeaderPage.RootIndex));
BTreeFreeSpaceMap = new FreeSpaceMap(bTreeMap, bTreeStream.Length / Static.PageSize);
DataFreeSpaceMap = new FreeSpaceMap(dataMap, dataStream.Length / Record.ByteSize);
}
}
private void Split()
{
if (_currentPage.SelfIndex == BTreeHeaderPage.RootIndex) //root split
{
SplitRoot();
return;
}
var pathPart = _path.Pop();
var parentPage = pathPart.ParentPage;
var childrenIndex = pathPart.ChildrenIndex;
var newPage = new BTreePage(parentPage.SelfIndex, BTreeFreeSpaceMap.AllocatePage());
if (!_currentPage.IsLeaf)
{
newPage.IsLeaf = false;
}
parentPage.Childrens.Insert(childrenIndex, newPage.SelfIndex);
var recordsPerPage = _currentPage.GetPresentRecords() / 2;
for (var i = 0; i < recordsPerPage; i++)
{
newPage.InsertRecord(_currentPage.PopRecordAt(0, false));
}
if (!_currentPage.IsLeaf)
{
for (var i = 0; i < recordsPerPage + 1; i++)
{
newPage.Childrens.Add(_currentPage.PopChildrenAt(0));
}
}
var forParent = _currentPage.PopRecordAt(0, false);
BtreeIO.WritePage(_currentPage.GetBTreePage(), _currentPage.SelfIndex);
BtreeIO.WritePage(newPage.GetBTreePage(), newPage.SelfIndex);
try {
parentPage.InsertRecord(forParent);
BtreeIO.WritePage(parentPage.GetBTreePage(), parentPage.SelfIndex);
} catch (PageOverflowException) {
_currentPage = parentPage;
if (Compensate())
{
return;
}
Split();
}
}
private BTreePage GetPageFromSubTreeWithHighestKey(BTreePage subTreeRootPage)
{
var currentPage = subTreeRootPage;
while (currentPage.IsLeaf == false)
{
currentPage = new BTreePage(BtreeIO.ReadPage(currentPage.Childrens[currentPage.Childrens.Count - 1]));
}
return(currentPage);
}
private bool Compensate()
{
if (_currentPage.SelfIndex == BTreeHeaderPage.RootIndex)
{
return(false);
}
var partPath = _path.Peek();
var parentPage = partPath.ParentPage;
var childrenIndex = partPath.ChildrenIndex;
BTreePage leftBrother, rightBrother;
if (childrenIndex == 0)
{
leftBrother = null;
rightBrother = new BTreePage(BtreeIO.ReadPage(parentPage.Childrens[childrenIndex + 1]));
}
else if (childrenIndex == parentPage.GetPresentRecords())
{
leftBrother = new BTreePage(BtreeIO.ReadPage(parentPage.Childrens[childrenIndex - 1]));
rightBrother = null;
}
else
{
leftBrother = new BTreePage(BtreeIO.ReadPage(parentPage.Childrens[childrenIndex - 1]));
rightBrother = new BTreePage(BtreeIO.ReadPage(parentPage.Childrens[childrenIndex + 1]));
}
var sumWithLeft = leftBrother?.GetPresentRecords() + _currentPage.GetPresentRecords();
var sumWithRight = rightBrother?.GetPresentRecords() + _currentPage.GetPresentRecords();
if (sumWithLeft >= 2 * Static.MemMin && sumWithLeft <= 2 * Static.MemMax)
{
CompensatePages(leftBrother, _currentPage, parentPage, childrenIndex);
BtreeIO.WritePage(leftBrother.GetBTreePage(), leftBrother.SelfIndex);
}
else if (sumWithRight >= 2 * Static.MemMin && sumWithRight <= 2 * Static.MemMax)
{
CompensatePages(_currentPage, rightBrother, parentPage, childrenIndex);
BtreeIO.WritePage(rightBrother.GetBTreePage(), rightBrother.SelfIndex);
}
else
{
return(false);
}
BtreeIO.WritePage(_currentPage.GetBTreePage(), _currentPage.SelfIndex);
BtreeIO.WritePage(parentPage.GetBTreePage(), parentPage.SelfIndex);
return(true);
}
private NodeRecord FindByKey(long key)
{
_currentPage = RootPage;
_path = new Stack <PathPart>();
while (true)
{
var record = _currentPage.FindRecord(key);
if (record != null)
{
return(record);
}
if (_currentPage.IsLeaf)
{
return(null);
}
_parentPage = _currentPage;
if (key < _currentPage.Records[0].Key)
{
_childrenIndex = 0;
_currentPage = new BTreePage(BtreeIO.ReadPage(_currentPage.Childrens[_childrenIndex]));
}
else if (key > _currentPage.Records[_currentPage.Records.Count - 1].Key)
{
_childrenIndex = _currentPage.Records.Count;
_currentPage = new BTreePage(BtreeIO.ReadPage(_currentPage.Childrens[_childrenIndex]));
}
else
{
for (var i = 0; i < _currentPage.Records.Count - 1; i++)
{
if (key > _currentPage.Records[i].Key && key < _currentPage.Records[i + 1].Key)
{
_childrenIndex = i + 1;
_currentPage = new BTreePage(BtreeIO.ReadPage(_currentPage.Childrens[_childrenIndex]));
break;
}
}
}
_path.Push(new PathPart {
ParentPage = _parentPage,
ChildrenIndex = _childrenIndex
});
}
}
private void SplitRoot()
{
var rootPage = new BTreePage(0, BTreeFreeSpaceMap.AllocatePage());
rootPage.IsLeaf = false;
_currentPage.ParentIndex = rootPage.SelfIndex;
var newPage = new BTreePage(rootPage.SelfIndex, BTreeFreeSpaceMap.AllocatePage());
if (!_currentPage.IsLeaf)
{
newPage.IsLeaf = false;
}
rootPage.Childrens.Add(newPage.SelfIndex);
rootPage.Childrens.Add(_currentPage.SelfIndex);
var recordsPerPage = _currentPage.GetPresentRecords() / 2;
for (var i = 0; i < recordsPerPage; i++)
{
newPage.InsertRecord(_currentPage.PopRecordAt(0, false));
}
if (!_currentPage.IsLeaf)
{
for (var i = 0; i < recordsPerPage + 1; i++)
{
newPage.Childrens.Add(_currentPage.PopChildrenAt(0));
}
}
rootPage.InsertRecord(_currentPage.PopRecordAt(0, false));
BtreeIO.WritePage(_currentPage.GetBTreePage(), _currentPage.SelfIndex);
BtreeIO.WritePage(newPage.GetBTreePage(), newPage.SelfIndex);
BtreeIO.WritePage(rootPage.GetBTreePage(), rootPage.SelfIndex);
RootPage = rootPage;
BTreeHeaderPage.RootIndex = RootPage.SelfIndex;
}
public void DisplayTree(BTreePage page, int tabs = 0) //root
{
for (var i = 0; i < page.Records.Count; i++)
{
if (!page.IsLeaf)
{
DisplayTree(new BTreePage(BtreeIO.ReadPage(page.Childrens[i])), tabs + 1);
}
var record = DataIO.ReadRecord(page.Records[i].RecordIndex);
var outString = new string(' ', 112);
outString = outString.Insert(tabs * 4, page.Records[i].Key.ToString());
outString = outString.Insert(80, record.Radius.ToString());
outString = outString.Insert(100, record.Angle.ToString());
outString = outString.Insert(110, tabs.ToString());
Console.WriteLine(outString);
}
if (!page.IsLeaf)
{
DisplayTree(new BTreePage(BtreeIO.ReadPage(page.Childrens[page.Childrens.Count - 1])), tabs + 1);
}
}
private void Merge()
{
var partPath = _path.Pop();
var parentPage = partPath.ParentPage;
var childrenIndex = partPath.ChildrenIndex;
BTreePage leftBrother = null, rightBrother = null;
if (childrenIndex == 0) //zrobic zapisy
{
rightBrother = new BTreePage(BtreeIO.ReadPage(parentPage.Childrens[childrenIndex + 1]));
var recordsToTransfer = rightBrother.GetPresentRecords();
for (var i = 0; i < recordsToTransfer; i++)
{
_currentPage.InsertRecord(rightBrother.PopRecordAt(0, true));
}
if (!_currentPage.IsLeaf)
{
for (var i = 0; i < recordsToTransfer + 1; i++)
{
_currentPage.Childrens.Add(rightBrother.PopChildrenAt(0));
}
}
parentPage.PopChildrenAt(childrenIndex + 1);
_currentPage.InsertRecord(parentPage.Records[childrenIndex]);
BTreeFreeSpaceMap.FreePage(rightBrother.SelfIndex);
BtreeIO.WritePage(_currentPage.GetBTreePage(), _currentPage.SelfIndex);
}
else
{
leftBrother = new BTreePage(BtreeIO.ReadPage(parentPage.Childrens[childrenIndex - 1]));
var recordsToTransfer = _currentPage.GetPresentRecords();
for (var i = 0; i < recordsToTransfer; i++)
{
leftBrother.InsertRecord(_currentPage.PopRecordAt(0, true));
}
if (!_currentPage.IsLeaf)
{
for (var i = 0; i < recordsToTransfer + 1; i++)
{
leftBrother.Childrens.Add(_currentPage.PopChildrenAt(0));
}
}
parentPage.PopChildrenAt(childrenIndex);
leftBrother.InsertRecord(parentPage.Records[childrenIndex - 1]);
BTreeFreeSpaceMap.FreePage(_currentPage.SelfIndex);
BtreeIO.WritePage(leftBrother.GetBTreePage(), leftBrother.SelfIndex);
}
try {
if (childrenIndex == 0)
{
parentPage.PopRecordAt(childrenIndex, false);
}
else
{
parentPage.PopRecordAt(childrenIndex - 1, false);
}
BtreeIO.WritePage(parentPage.GetBTreePage(), parentPage.SelfIndex);
} catch (PageDeficitException ex) {
_currentPage = parentPage;
if (!Compensate())
{
Merge();
}
} catch (RootPageDeficitException ex) {
BTreeFreeSpaceMap.FreePage(RootPage.SelfIndex);
if (childrenIndex == 0)
{
RootPage = _currentPage;
BTreeHeaderPage.RootIndex = _currentPage.SelfIndex;
}
else
{
RootPage = leftBrother;
BTreeHeaderPage.RootIndex = leftBrother.SelfIndex;
}
}
}
public void RemoveRecordByKey(long key)
{
var record = FindByKey(key);
if (record == null)
{
throw new KeyDoesNotExistException();
}
var recordIndex = 0;
BTreePage leafPage;
try {
if (_currentPage.IsLeaf)
{
_currentPage.RemoveRecord(key);
BtreeIO.WritePage(_currentPage.GetBTreePage(), _currentPage.SelfIndex);
return;
}
} catch (PageDeficitException) {
if (!Compensate())
{
Merge();
}
return;
} finally {
DataFreeSpaceMap.FreePage(record.RecordIndex);
}
for (var i = 0; i < _currentPage.GetPresentRecords(); i++)
{
if (_currentPage.Records[i].Key == record.Key)
{
recordIndex = i;
}
}
if (recordIndex == 0)
{
leafPage = GetPageFromSubTreeWithLowestKey(
new BTreePage(BtreeIO.ReadPage(_currentPage.Childrens[recordIndex + 1]))
);
var input = leafPage.Records[0];
_currentPage.SwapRecord(input, record);
leafPage.SwapRecord(record, input);
}
else
{
leafPage = GetPageFromSubTreeWithHighestKey(
new BTreePage(BtreeIO.ReadPage(_currentPage.Childrens[recordIndex]))
);
var input = leafPage.Records[leafPage.GetPresentRecords() - 1];
_currentPage.SwapRecord(input, record);
leafPage.SwapRecord(record, input);
}
BtreeIO.WritePage(_currentPage.GetBTreePage(), _currentPage.SelfIndex);
try {
FindByKey(leafPage.Records[1].Key); //dla odswiezenia sciezki _path
leafPage.RemoveRecord(key);
} catch (PageDeficitException) {
_currentPage = leafPage;
if (!Compensate())
{
Merge();
}
return;
}
BtreeIO.WritePage(leafPage.GetBTreePage(), leafPage.SelfIndex);
}
