public R_Tree(CacheManager cache)
{
Cache = cache;
Leaf rootNode = new Leaf(Address.Empty);
root = rootNode.Address;
Cache.WritePageData(rootNode);
TreeHeight = 1;
Cache.FlushCache();
}
protected virtual PageData LookupPageData(Address address)
{
PageData data;
Page page = LookupPage(address);
Byte type = page.Data[0], childType = page.Data[1];
if (type == (Byte)PageDataType.Node || type == (Byte)PageDataType.Leaf)
if (childType == (Byte)NodeChildType.Leaf)
data = new Node(address, typeof(Leaf), page.Data);
else if (childType == (Byte)NodeChildType.Node)
data = new Node(address, typeof(Node), page.Data);
else if (childType == (Byte)NodeChildType.Record)
data = new Leaf(address, page.Data);
else
throw new Exception("Not a node");
else if (type == (Byte)PageDataType.Record)
data = new Record(address, page.Data);
else if (type == (Byte)PageDataType.IndexUnitSector)
data = new Sector(address, page.Data);
else
throw new Exception("Not valid Page Data");
CacheOverflowCheck();
return data;
}
protected override List<Node> Split(Node nodeToBeSplit)
{
//
//Determine Axis
//
//Sort each axis by upper and lower corners
List<NodeEntry> xLowerSorted = new List<NodeEntry>(nodeToBeSplit.NodeEntries),
xUpperSorted = new List<NodeEntry>(nodeToBeSplit.NodeEntries),
yLowerSorted = new List<NodeEntry>(nodeToBeSplit.NodeEntries),
yUpperSorted = new List<NodeEntry>(nodeToBeSplit.NodeEntries);
xLowerSorted.Sort(new NodeEntryLowerAxisComparerX());
xUpperSorted.Sort(new NodeEntryUpperAxisComparerX());
yLowerSorted.Sort(new NodeEntryLowerAxisComparerY());
yUpperSorted.Sort(new NodeEntryUpperAxisComparerY());
//Generate Distributions
List<Pair<Node, Node>> xLowerDistributions = new List<Pair<Node, Node>>(),
xUpperDistributions = new List<Pair<Node, Node>>(),
yLowerDistributions = new List<Pair<Node, Node>>(),
yUpperDistributions = new List<Pair<Node, Node>>();
Dictionary<List<NodeEntry>, List<Pair<Node, Node>>> axii =
new Dictionary<List<NodeEntry>, List<Pair<Node, Node>>>();
axii.Add(xLowerSorted, xLowerDistributions);
axii.Add(xUpperSorted, xUpperDistributions);
axii.Add(yLowerSorted, yLowerDistributions);
axii.Add(yUpperSorted, yUpperDistributions);
foreach (KeyValuePair<List<NodeEntry>, List<Pair<Node, Node>>> axis in axii)
for (int i = 0; i < Constants.MAXIMUM_ENTRIES_PER_NODE - 2 * Constants.MINIMUM_ENTRIES_PER_NODE + 2; i++)
{
Node group1, group2;
if (nodeToBeSplit is Leaf)
{
group1 = new Leaf(nodeToBeSplit.Parent);
group2 = new Leaf(nodeToBeSplit.Parent);
}
else
{
group1 = new Node(nodeToBeSplit.Parent, nodeToBeSplit.ChildType);
group2 = new Node(nodeToBeSplit.Parent, nodeToBeSplit.ChildType);
}
foreach (NodeEntry entry in axis.Key.GetRange(0, Constants.MINIMUM_ENTRIES_PER_NODE+ i))
group1.AddNodeEntry(entry);
foreach (NodeEntry entry in axis.Key.GetRange(Constants.MINIMUM_ENTRIES_PER_NODE + i, axis.Key.Count - (Constants.MINIMUM_ENTRIES_PER_NODE+ i)))
group2.AddNodeEntry(entry);
axis.Value.Add(new Pair<Node, Node>(group1, group2));
}
//Sum margins
Single xLowerMarginSum = 0, xUpperMarginSum = 0, yLowerMarginSum = 0, yUpperMarginSum = 0;
foreach (Pair<Node, Node> distribution in xLowerDistributions)
xLowerMarginSum += GetMargin(distribution.Value1, distribution.Value2);
foreach (Pair<Node, Node> distribution in xUpperDistributions)
xUpperMarginSum += GetMargin(distribution.Value1, distribution.Value2);
foreach (Pair<Node, Node> distribution in yLowerDistributions)
yLowerMarginSum += GetMargin(distribution.Value1, distribution.Value2);
foreach (Pair<Node, Node> distribution in yUpperDistributions)
yUpperMarginSum += GetMargin(distribution.Value1, distribution.Value2);
//Choose Axis
List<Pair<Node, Node>> chosenAxis;
if (xLowerMarginSum <= xUpperMarginSum && xLowerMarginSum <= yLowerMarginSum && xLowerMarginSum <= yUpperMarginSum)
chosenAxis = xLowerDistributions;
else if (xUpperMarginSum <= xLowerMarginSum && xUpperMarginSum <= yLowerMarginSum && xUpperMarginSum <= yUpperMarginSum)
chosenAxis = xUpperDistributions;
else if (yLowerMarginSum <= xUpperMarginSum && yLowerMarginSum <= xLowerMarginSum && yLowerMarginSum <= yUpperMarginSum)
chosenAxis = yLowerDistributions;
else
chosenAxis = yUpperDistributions;
//
//Determine Distribution
//
Pair<Node, Node> chosenDistribution = chosenAxis[0];
Single minimumOverlapArea = GetOverlap(chosenDistribution.Value1, chosenDistribution.Value2);
foreach (Pair<Node, Node> distribution in chosenAxis)
{
Single overlapArea = GetOverlap(distribution.Value1, distribution.Value2);
if ((overlapArea == minimumOverlapArea &&
GetFutureSize(distribution.Value1.CalculateMinimumBoundingBox(), distribution.Value2.CalculateMinimumBoundingBox()) <
GetFutureSize(chosenDistribution.Value1.CalculateMinimumBoundingBox(), chosenDistribution.Value2.CalculateMinimumBoundingBox())
) ||
overlapArea < minimumOverlapArea)
{
chosenDistribution = distribution;
minimumOverlapArea = overlapArea;
}
}
//
//Distribute
//
List<Node> newNodes = new List<Node>();
newNodes.Add(chosenDistribution.Value1);
newNodes.Add(chosenDistribution.Value2);
foreach (Node newNode in newNodes)
{
if (!(newNode is Leaf))
foreach (NodeEntry entry in newNode.NodeEntries)
{
Node child = Cache.LookupNode(entry.Child);
child.Parent = newNode.Address;
Cache.WritePageData(child);
}
Cache.WritePageData(newNode);
}
return newNodes;
}
protected virtual List<Node> Split(Node nodeToBeSplit)
{
List<NodeEntry> entries = new List<NodeEntry>(nodeToBeSplit.NodeEntries);
List<NodeEntry> seeds = PickSeeds(entries);
entries.Remove(seeds[0]);
entries.Remove(seeds[1]);
Node node1, node2;
if (nodeToBeSplit is Leaf)
{
node1 = new Leaf(nodeToBeSplit.Parent);
node2 = new Leaf(nodeToBeSplit.Parent);
}
else
{
node1 = new Node(nodeToBeSplit.Parent, nodeToBeSplit.ChildType);
node2 = new Node(nodeToBeSplit.Parent, nodeToBeSplit.ChildType);
}
node1.AddNodeEntry(seeds[0]);
node2.AddNodeEntry(seeds[1]);
if (!(seeds[0] is LeafEntry))
{
Node child = Cache.LookupNode(seeds[0].Child);
child.Parent = node1.Address;
Cache.WritePageData(child);
}
if (!(seeds[1] is LeafEntry))
{
Node child = Cache.LookupNode(seeds[1].Child);
child.Parent = node2.Address;
Cache.WritePageData(child);
}
while (entries.Count > 0)
{
if (node1.NodeEntries.Count + entries.Count == Constants.MINIMUM_ENTRIES_PER_NODE)
{
foreach (NodeEntry entry in entries)
{
node1.AddNodeEntry(entry);
if(!(entry is LeafEntry))
{
Node child = Cache.LookupNode(entry.Child);
child.Parent = node1.Address;
Cache.WritePageData(child);
}
}
break;
}
else if (node2.NodeEntries.Count + entries.Count == Constants.MINIMUM_ENTRIES_PER_NODE)
{
foreach (NodeEntry entry in entries)
{
node2.AddNodeEntry(entry);
if (!(entry is LeafEntry))
{
Node child = Cache.LookupNode(entry.Child);
child.Parent = node2.Address;
Cache.WritePageData(child);
}
}
break;
}
MinimumBoundingBox minimumBoundingBox1 = node1.CalculateMinimumBoundingBox(),
minimumBoundingBox2 = node2.CalculateMinimumBoundingBox();
NodeEntry nextEntry = PickNext(entries, minimumBoundingBox1, minimumBoundingBox2);
entries.Remove(nextEntry);
Node nodeToEnter;
if (GetFutureSize(nextEntry.MinimumBoundingBox, minimumBoundingBox1) ==
GetFutureSize(nextEntry.MinimumBoundingBox, minimumBoundingBox2))
{
if (minimumBoundingBox1.GetArea() == minimumBoundingBox2.GetArea())
if (node1.NodeEntries.Count <= node2.NodeEntries.Count)
nodeToEnter = node1;
else
nodeToEnter = node2;
else if (minimumBoundingBox1.GetArea() < minimumBoundingBox2.GetArea())
nodeToEnter = node1;
else
nodeToEnter = node2;
}
else if (GetFutureSize(nextEntry.MinimumBoundingBox, minimumBoundingBox1) <
GetFutureSize(nextEntry.MinimumBoundingBox, minimumBoundingBox2))
nodeToEnter = node1;
else
nodeToEnter = node2;
nodeToEnter.AddNodeEntry(nextEntry);
if (!(nextEntry is LeafEntry))
{
Node child = Cache.LookupNode(nextEntry.Child);
child.Parent = nodeToEnter.Address;
Cache.WritePageData(child);
}
}
List<Node> newNodes = new List<Node>();
newNodes.Add(node1);
newNodes.Add(node2);
return newNodes;
}
protected virtual void Insert(Record record, Leaf leaf)
{
leaf.AddNodeEntry(new LeafEntry(record.BoundingBox, record.Address));
}