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 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);
}
}
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;
}
}
}
