private bool RedistributeBranchElements(TreeBranch branch, int childIndex, TreeBranch child)
{
// We distribute the nodes in the child branch with the branch
// immediately to the right. If that's not possible, then we distribute
// with the left.
// If branch has only a single value, return immediately
int branchSize = branch.ChildCount;
if (branchSize == 1)
{
return(false);
}
int leftI, rightI;
TreeBranch left, right;
if (childIndex < branchSize - 1)
{
// Distribute with the right
leftI = childIndex;
rightI = childIndex + 1;
left = child;
right = (TreeBranch)UnfreezeNode(FetchNode(branch.GetChild(childIndex + 1)));
branch.SetChild(right.Id, childIndex + 1);
}
else
{
// Distribute with the left
leftI = childIndex - 1;
rightI = childIndex;
left = (TreeBranch)UnfreezeNode(FetchNode(branch.GetChild(childIndex - 1)));
right = child;
branch.SetChild(left.Id, childIndex - 1);
}
// Get the mid value key reference
Key midKey = branch.GetKey(rightI);
// Perform the merge,
Key newMidKey = left.Merge(right, midKey);
// Reset the leaf element count
branch.SetChildLeafElementCount(left.LeafElementCount, leftI);
branch.SetChildLeafElementCount(right.LeafElementCount, rightI);
// If after the merge the right branch is empty, we need to remove it
if (right.IsEmpty)
{
// Delete the node
DeleteNode(right.Id);
// And remove it from the branch,
branch.RemoveChild(rightI);
return(true);
}
// Otherwise set the key reference
branch.SetKeyToLeft(newMidKey, rightI);
return(false);
}
public void DeleteLeaf(Key key)
{
// Set up the state
StackFrame frame = StackEnd(0);
NodeId thisRef = frame.NodeId;
TreeBranch branchNode = null;
int deleteNodeSize = -1;
Key leftKey = null;
// Walk back through the rest of the stack
int sz = FrameCount;
for (int i = 1; i < sz; ++i)
{
// Find the child_i for the child
// This is the child_i of the child in the current branch
int childIndex = frame.ChildIndex;
// Move the stack frame,
frame = StackEnd(i);
NodeId childId = thisRef;
thisRef = frame.NodeId;
TreeBranch childBranch = branchNode;
branchNode = (TreeBranch)UnfreezeNode(FetchNode(thisRef));
if (deleteNodeSize == -1)
{
deleteNodeSize =
(int)branchNode.GetChildLeafElementCount(childIndex);
}
// If the child branch is empty,
if (childBranch == null || childBranch.IsEmpty)
{
// Delete the reference to it,
if (childIndex == 0 && branchNode.ChildCount > 1)
{
leftKey = branchNode.GetKey(1);
}
branchNode.RemoveChild(childIndex);
// Delete the child branch,
DeleteNode(childId);
}
// Not empty,
else
{
// Replace with the new child node reference
branchNode.SetChild(childBranch.Id, childIndex);
// Set the element count
long newChildSize =
branchNode.GetChildLeafElementCount(childIndex) -
deleteNodeSize;
branchNode.SetChildLeafElementCount(newChildSize, childIndex);
// Can we set the left key reference?
if (childIndex > 0 && leftKey != null)
{
branchNode.SetKeyToLeft(leftKey, childIndex);
leftKey = null;
}
// Has the size of the child reached the lower threshold?
if (childBranch.ChildCount <= 2)
{
// If it has, we need to redistribute the children,
RedistributeBranchElements(branchNode, childIndex, childBranch);
}
}
}
// Finally, set the root node
// If the branch node is a single element, we set the root as the child,
if (branchNode.ChildCount == 1)
{
// This shrinks the height of the tree,
RootNodeId = branchNode.GetChild(0);
DeleteNode(branchNode.Id);
if (TreeHeight != -1)
{
TreeHeight = TreeHeight - 1;
}
}
else
{
// Otherwise, we set the branch node.
RootNodeId = branchNode.Id;
}
// Reset the object
Reset();
}
public void SetupForPosition(Key key, long posit)
{
// If the current leaf is set
if (currentLeaf != null)
{
StackFrame frame = StackEnd(0);
long leafStart = frame.Offset;
long leafEnd = leafStart + currentLeaf.Length;
// If the position is at the leaf end, or if the keys aren't equal, we
// need to reset the stack. This ensures that we correctly place the
// pointer.
if (!key.Equals(Key.Tail) &&
(posit == leafEnd || !key.Equals(currentLeafKey)))
{
StackClear();
currentLeaf = null;
currentLeafKey = null;
}
else
{
// Check whether the position is within the bounds of the current leaf
// If 'posit' is within this leaf
if (posit >= leafStart && posit < leafEnd)
{
// If the position is within the current leaf, set up the internal
// vars as necessary.
leafOffset = (int)(posit - leafStart);
return;
}
// If it's not, we reset the stack and start fresh,
StackClear();
currentLeaf = null;
currentLeafKey = null;
}
}
// ISSUE: It appears looking at the code above, the stack will always be
// empty and current_leaf will always be null if we get here.
// If the stack is empty, push the root node,
if (StackEmpty)
{
// Push the root node onto the top of the stack.
StackPush(-1, 0, RootNodeId);
// Set up the current_leaf_key to the default value
currentLeafKey = Key.Head;
}
// Otherwise, we need to setup by querying the BTree.
while (true)
{
if (StackEmpty)
{
throw new ApplicationException("Position out of bounds. p = " + posit);
}
// Pop the last stack frame,
StackFrame frame = StackPop();
NodeId nodePointer = frame.NodeId;
long leftSideOffset = frame.Offset;
int nodeChildIndex = frame.ChildIndex;
// Relative offset within this node
long relativeOffset = posit - leftSideOffset;
// If the node is not on the heap,
if (!IsHeapNode(nodePointer))
{
// The node is not on the heap. We optimize here.
// If we know the node is going to be a leaf node, we set up a
// temporary leaf node object with as much information as we know.
// Check if we know this is a leaf
int treeHeight = TreeHeight;
if (treeHeight != -1 &&
(stackSize / StackFrameSize) + 1 == treeHeight)
{
// Fetch the parent node,
frame = StackEnd(0);
NodeId twigNodePointer = frame.NodeId;
TreeBranch twig = (TreeBranch)FetchNode(twigNodePointer);
long leafSize =
twig.GetChildLeafElementCount(nodeChildIndex);
// This object holds off fetching the contents of the leaf node
// unless it's absolutely required.
TreeLeaf leaf =
new PlaceholderLeaf(ts, nodePointer, (int)leafSize);
currentLeaf = leaf;
StackPush(nodeChildIndex, leftSideOffset, nodePointer);
// Set up the leaf offset and return
leafOffset = (int)relativeOffset;
return;
}
}
// Fetch the node
ITreeNode node = FetchNode(nodePointer);
if (node is TreeLeaf)
{
// Node is a leaf node
TreeLeaf leaf = (TreeLeaf)node;
currentLeaf = leaf;
StackPush(nodeChildIndex, leftSideOffset, nodePointer);
// Set up the leaf offset and return
leafOffset = (int)relativeOffset;
// Update the tree_height value,
TreeHeight = stackSize / StackFrameSize;
return;
}
// Node is a branch node
TreeBranch branch = (TreeBranch)node;
int childIndex = branch.IndexOfChild(key, relativeOffset);
if (childIndex != -1)
{
// Push the current details,
StackPush(nodeChildIndex, leftSideOffset, nodePointer);
// Found child so push the details
StackPush(childIndex,
branch.GetChildOffset(childIndex) + leftSideOffset,
branch.GetChild(childIndex));
// Set up the left key
if (childIndex > 0)
{
currentLeafKey = branch.GetKey(childIndex);
}
}
} // while (true)
}
private TreeGraph CreateRootGraph(Key leftKey, long reference)
{
// The node being returned
TreeGraph graph;
// Open the area
IArea area = store.GetArea(reference);
// What type of node is this?
short nodeType = area.ReadInt2();
// The version
short ver = area.ReadInt2();
if (nodeType == LeafType) {
// Read the reference count,
long refCount = area.ReadInt4();
// The number of bytes in the leaf
int leafSize = area.ReadInt4();
// Set up the leaf node object
graph = new TreeGraph("leaf", reference);
graph.SetProperty("ver", ver);
graph.SetProperty("key", leftKey.ToString());
graph.SetProperty("reference_count", refCount);
graph.SetProperty("leaf_size", leafSize);
} else if (nodeType == BranchType) {
// The data size area containing the children information
int childDataSize = area.ReadInt4();
long[] data = new long[childDataSize];
for (int i = 0; i < childDataSize; ++i) {
data[i] = area.ReadInt8();
}
// Create the TreeBranch object to query it
TreeBranch branch = new TreeBranch(reference, data, childDataSize);
// Set up the branch node object
graph = new TreeGraph("branch", reference);
graph.SetProperty("ver", ver);
graph.SetProperty("key", leftKey.ToString());
graph.SetProperty("branch_size", branch.ChildCount);
// Recursively add each child into the tree
for (int i = 0; i < branch.ChildCount; ++i) {
long child_ref = branch.GetChild(i);
// If the ref is a special node, skip it
if ((child_ref & 0x01000000000000000L) != 0) {
// Should we record special nodes?
} else {
Key newLeftKey = (i > 0) ? branch.GetKey(i) : leftKey;
TreeGraph bn = new TreeGraph("child_meta", reference);
bn.SetProperty("extent", branch.GetChildLeafElementCount(i));
graph.AddChild(bn);
graph.AddChild(CreateRootGraph(newLeftKey, child_ref));
}
}
} else {
throw new IOException("Unknown node type: " + nodeType);
}
return graph;
}
private bool RedistributeBranchElements(TreeBranch branch, int childIndex, TreeBranch child)
{
// We distribute the nodes in the child branch with the branch
// immediately to the right. If that's not possible, then we distribute
// with the left.
// If branch has only a single value, return immediately
int branchSize = branch.ChildCount;
if (branchSize == 1) {
return false;
}
int leftI, rightI;
TreeBranch left, right;
if (childIndex < branchSize - 1) {
// Distribute with the right
leftI = childIndex;
rightI = childIndex + 1;
left = child;
right = (TreeBranch)UnfreezeNode(FetchNode(branch.GetChild(childIndex + 1)));
branch.SetChild(right.Id, childIndex + 1);
} else {
// Distribute with the left
leftI = childIndex - 1;
rightI = childIndex;
left = (TreeBranch)UnfreezeNode(FetchNode(branch.GetChild(childIndex - 1)));
right = child;
branch.SetChild(left.Id, childIndex - 1);
}
// Get the mid value key reference
Key midKey = branch.GetKey(rightI);
// Perform the merge,
Key newMidKey = left.Merge(right, midKey);
// Reset the leaf element count
branch.SetChildLeafElementCount(left.LeafElementCount, leftI);
branch.SetChildLeafElementCount(right.LeafElementCount, rightI);
// If after the merge the right branch is empty, we need to remove it
if (right.IsEmpty) {
// Delete the node
DeleteNode(right.Id);
// And remove it from the branch,
branch.RemoveChild(rightI);
return true;
}
// Otherwise set the key reference
branch.SetKeyToLeft(newMidKey, rightI);
return false;
}
private TreeReportNode CreateDiagnosticRootGraph(Key leftKey, NodeId id)
{
// The node being returned
TreeReportNode node;
// Open the area
IArea area = nodeStore.GetArea(ToInt64StoreAddress(id));
// What type of node is this?
short nodeType = area.ReadInt2();
// The version
short ver = area.ReadInt2();
if (nodeType == StoreLeafType)
{
// Read the reference count,
long refCount = area.ReadInt4();
// The number of bytes in the leaf
int leafSize = area.ReadInt4();
// Set up the leaf node object
node = new TreeReportNode("leaf", id);
node.SetProperty("VER", ver);
node.SetProperty("key", leftKey.ToString());
node.SetProperty("reference_count", refCount);
node.SetProperty("leaf_size", leafSize);
}
else if (nodeType == StoreBranchType)
{
// The data size area containing the children information
int childDataSize = area.ReadInt4();
long[] dataArr = new long[childDataSize];
for (int i = 0; i < childDataSize; ++i)
{
dataArr[i] = area.ReadInt8();
}
// Create the TreeBranch object to query it
TreeBranch branch = new TreeBranch(id, dataArr, childDataSize);
// Set up the branch node object
node = new TreeReportNode("branch", id);
node.SetProperty("VER", ver);
node.SetProperty("key", leftKey.ToString());
node.SetProperty("branch_size", branch.ChildCount);
// Recursively add each child into the tree
for (int i = 0; i < branch.ChildCount; ++i)
{
NodeId childId = branch.GetChild(i);
// If the id is a special node, skip it
if (childId.IsSpecial)
{
// Should we record special nodes?
}
else
{
Key newLeftKey = (i > 0) ? branch.GetKey(i) : leftKey;
TreeReportNode bn = new TreeReportNode("child_meta", id);
bn.SetProperty("extent", branch.GetChildLeafElementCount(i));
node.ChildNodes.Add(bn);
node.ChildNodes.Add(CreateDiagnosticRootGraph(newLeftKey, childId));
}
}
}
else
{
throw new IOException("Unknown node type: " + nodeType);
}
return(node);
}
private TreeReportNode CreateDiagnosticRootGraph(Key leftKey, NodeId id)
{
// The node being returned
TreeReportNode node;
// Open the area
IArea area = nodeStore.GetArea(ToInt64StoreAddress(id));
// What type of node is this?
short nodeType = area.ReadInt2();
// The version
short ver = area.ReadInt2();
if (nodeType == StoreLeafType) {
// Read the reference count,
long refCount = area.ReadInt4();
// The number of bytes in the leaf
int leafSize = area.ReadInt4();
// Set up the leaf node object
node = new TreeReportNode("leaf", id);
node.SetProperty("VER", ver);
node.SetProperty("key", leftKey.ToString());
node.SetProperty("reference_count", refCount);
node.SetProperty("leaf_size", leafSize);
} else if (nodeType == StoreBranchType) {
// The data size area containing the children information
int childDataSize = area.ReadInt4();
long[] dataArr = new long[childDataSize];
for (int i = 0; i < childDataSize; ++i) {
dataArr[i] = area.ReadInt8();
}
// Create the TreeBranch object to query it
TreeBranch branch = new TreeBranch(id, dataArr, childDataSize);
// Set up the branch node object
node = new TreeReportNode("branch", id);
node.SetProperty("VER", ver);
node.SetProperty("key", leftKey.ToString());
node.SetProperty("branch_size", branch.ChildCount);
// Recursively add each child into the tree
for (int i = 0; i < branch.ChildCount; ++i) {
NodeId childId = branch.GetChild(i);
// If the id is a special node, skip it
if (childId.IsSpecial) {
// Should we record special nodes?
} else {
Key newLeftKey = (i > 0) ? branch.GetKey(i) : leftKey;
TreeReportNode bn = new TreeReportNode("child_meta", id);
bn.SetProperty("extent", branch.GetChildLeafElementCount(i));
node.ChildNodes.Add(bn);
node.ChildNodes.Add(CreateDiagnosticRootGraph(newLeftKey, childId));
}
}
} else {
throw new IOException("Unknown node type: " + nodeType);
}
return node;
}