private void relocate(BPlusTreeNode parentNode)
{
// this node has outgrown its allotted space.
// we need to move it to the end of the file and update everybody who points to it
// so have to update the following:
// 1. Parent node's pointer
// 2. Left sibling's pointer
// 3. Right sibling's pointer
// 4. All children's parent pointer (which points at this node)
_tree.Log("------------ BEGIN Relocating node ------------");
_tree.Log("BEGIN Relocating node -> ".PadRight(50) + ToString());
// get an abandoned node (or the end of the file, whichever comes first)
BPlusAbandonedNode abandonedNode = _tree.GetNextAvailableNodeLocation(this);
// mark this node as abandoned in the file (and remove from cache)
_tree.AbandonNode(this);
//if (this.IsRoot) {
// // we're relocating the root.
// _tree.Log("TODO: what to do here, if anything?");
//}
if (!IsLeaf)
{
// only leaf nodes should track left/right siblings.
LeftSiblingFileOffset = -1;
RightSiblingFileOffset = -1;
}
if (LeftSiblingFileOffset > -1)
{
BPlusTreeNode originalLeftSibling = BPlusTreeNode.Read(_tree, this.LeftSiblingFileOffset, true);
originalLeftSibling.RightSiblingFileOffset = originalLeftSibling.IsLeaf ? abandonedNode.FileOffset : -1;
_tree.Log(("Updating left sibling node @ " + originalLeftSibling.FileOffset + " -> ").PadRight(50) + originalLeftSibling.ToString());
originalLeftSibling.Write(null);
}
if (RightSiblingFileOffset > -1)
{
BPlusTreeNode originalRightSibling = BPlusTreeNode.Read(_tree, this.RightSiblingFileOffset, true);
originalRightSibling.LeftSiblingFileOffset = originalRightSibling.IsLeaf ? abandonedNode.FileOffset : -1;
_tree.Log(("Updating right sibling node @ " + originalRightSibling.FileOffset + " -> ").PadRight(50) + originalRightSibling.ToString());
originalRightSibling.Write(null);
}
if (this.IsRoot)
{
// special case! no parent means this is the root node.
// update the int at the very beginning of the file to point at the new root node
_tree.WriteRootNodeOffset(abandonedNode.FileOffset);
}
else
{
if (parentNode != null)
{
for (int i = 0; i < parentNode.KeywordCount + 1; i++)
{
if (parentNode.ChildrenByteOffsets[i] == FileOffset)
{
parentNode.ChildrenByteOffsets[i] = abandonedNode.FileOffset;
_tree.Log(("Updating parent node @ " + parentNode.FileOffset + " -> ").PadRight(50) + parentNode.ToString());
parentNode.Write(null);
// the Root node is cached in the tree object -- udpate it if need be
if (parentNode.IsRoot)
{
_tree.Root = parentNode;
}
break;
}
}
}
}
_tree.Writer.BaseStream.Position = abandonedNode.FileOffset;
FileOffset = abandonedNode.FileOffset;
//_chunkSize = abandonedNode.ByteCount;
_tree.Log("END Relocating node (not written yet) -> ".PadRight(50) + ToString());
_tree.Log("------------ END Relocating node ------------");
}
// here's the vernacular:
// The _keywords array represents all the keywords in this node.
// The _byteRanges array represents all the file offsets in this node for either (a) a keyword or (b) the data itself.
// a. If it is located in an index node (i.e. non-Leaf), the byte range represents the start/end offsets in the index file (used for traversing to other nodes)
// b. If it is located in a Leaf node, the byte range represents the start/end offsets in the data file (for looking up associated hit(s))
// Think ByteRange = pointer to next node or data, Keyword = item we're searching by
// So we always have 1 more pointer (or byterange, BR) than search item (or keyword, K):
//
// |-------- Node ---------|
// | go pi |
// | / | | | \ |
// | BR1 K1 BR2 K2 BR3 |
// |-----------------------|
/// <summary>
/// Creates a new root node for the tree and makes the original root the first child of the new root.
/// </summary>
/// <param name="tree"></param>
/// <returns></returns>
internal static BPlusTreeNode ReplaceRoot(BPlusTree tree, BPlusTreeNode originalRoot, string keyword, long dataByteOffset)
{
// NOTE: This is a very special case.
// replacing the root involves creating 2 new nodes:
// 1. the new root node
// 2. splitting the existing root node into 2 nodes, one of which is a new one
BPlusTreeNode newRoot = null;
// create a new root node, mark it as not a leaf, put it in exact same spot as original root
newRoot = new BPlusTreeNode {
IsLeaf = false,
_tree = tree,
Keywords = new string[tree.Fanout],
ChildrenByteOffsets = new long[tree.Fanout + 1],
KeywordCount = 0,
FileOffset = -1,
LeftSiblingFileOffset = -1,
RightSiblingFileOffset = -1,
};
tree.Log("------------ BEGIN Replacing root ------------");
tree.Log("BEGIN Replacing root. original node -> ".PadRight(50) + originalRoot.ToString());
tree.Log("BEGIN Replacing root. new node -> ".PadRight(50) + newRoot.ToString());
// add our new root to file, update the root node pointer
BPlusAbandonedNode abandoned = tree.GetNextAvailableNodeLocation(originalRoot);
newRoot.FileOffset = abandoned.FileOffset;
newRoot.Write(null);
tree.WriteRootNodeOffset(newRoot.FileOffset);
// trickle-down insert the new keyword/data
if (!String.IsNullOrEmpty(keyword))
{
// split the original
BPlusTreeNode newChild = newRoot.SplitChild(0, originalRoot, null);
tree.Log("CONTINUE Replacing root. new child node -> ".PadRight(50) + originalRoot.ToString());
if (newRoot.Insert(keyword, dataByteOffset, null))
{
// the new root was relocated during insertion (outgrew its allotted space)
// the insert should take care of it
// re-read it in just in case
newRoot = BPlusTreeNode.Read(tree, newRoot.FileOffset, true);
}
}
else
{
newRoot = BPlusTreeNode.Read(tree, newRoot.FileOffset, true);
}
tree.Log("END Replacing root. original node -> ".PadRight(50) + originalRoot.ToString());
// _tree.Log("END Replacing root. new child node -> ".PadRight(50) + newChild.ToString());
tree.Log("END Replacing root. new root -> ".PadRight(50) + newRoot.ToString());
tree.Log("------------ END Replacing root ------------");
return(newRoot);
}
