/// <summary>Returns the value of the deleted key</summary>
/// <param name="node"></param>
/// <param name="keyAndValue"></param>
/// <returns></returns>
/// <exception cref="System.Exception">System.Exception</exception>
protected virtual object InternalDelete(NeoDatis.Btree.IBTreeNode node, NeoDatis.Btree.IKeyAndValue
keyAndValue)
{
int position = node.GetPositionOfKey(keyAndValue.GetKey());
bool keyIsHere = position > 0;
int realPosition = -1;
NeoDatis.Btree.IBTreeNode leftNode = null;
NeoDatis.Btree.IBTreeNode rightNode = null;
try
{
if (node.IsLeaf())
{
if (keyIsHere)
{
object deletedValue = node.DeleteKeyForLeafNode(keyAndValue);
GetPersister().SaveNode(node);
return(deletedValue);
}
// key does not exist
return(null);
}
if (!keyIsHere)
{
// descend
realPosition = -position - 1;
NeoDatis.Btree.IBTreeNode child = node.GetChildAt(realPosition, true);
if (child.GetNbKeys() == degree - 1)
{
node = PrepareForDelete(node, child, realPosition);
return(InternalDelete(node, keyAndValue));
}
return(InternalDelete(child, keyAndValue));
}
// Here,the node is not a leaf and contains the key
realPosition = position - 1;
System.IComparable currentKey = node.GetKeyAt(realPosition);
object currentValue = node.GetValueAsObjectAt(realPosition);
// case 2a
leftNode = node.GetChildAt(realPosition, true);
if (leftNode.GetNbKeys() >= degree)
{
NeoDatis.Btree.IKeyAndValue prev = GetBiggest(leftNode, true);
node.SetKeyAndValueAt(prev, realPosition);
NeoDatis.Btree.Tool.BTreeValidator.ValidateNode(node, node == root);
GetPersister().SaveNode(node);
return(currentValue);
}
// case 2b
rightNode = node.GetChildAt(realPosition + 1, true);
if (rightNode.GetNbKeys() >= degree)
{
NeoDatis.Btree.IKeyAndValue next = GetSmallest(rightNode, true);
node.SetKeyAndValueAt(next, realPosition);
NeoDatis.Btree.Tool.BTreeValidator.ValidateNode(node, node == root);
GetPersister().SaveNode(node);
return(currentValue);
}
// case 2c
// Here, both left and right part have degree-1 keys
// remove the element to be deleted from node (shifting left all
// right
// elements, link to right link does not exist anymore)
// insert the key to be deleted in left child and merge the 2 nodes.
// rightNode should be deleted
// if node is root, then leftNode becomes the new root and node
// should be deleted
//
node.DeleteKeyAndValueAt(realPosition, true);
leftNode.InsertKeyAndValue(currentKey, currentValue);
leftNode.MergeWith(rightNode);
// If node is the root and is empty
if (!node.HasParent() && node.GetNbKeys() == 0)
{
persister.DeleteNode(node);
root = leftNode;
leftNode.SetParent(null);
// The height has been decreased. No need to save btree here.
// The calling delete method will save it.
height--;
}
else
{
node.SetChildAt(leftNode, realPosition);
// Node must only be validated if it is not the root
NeoDatis.Btree.Tool.BTreeValidator.ValidateNode(node, node == root);
}
persister.DeleteNode(rightNode);
NeoDatis.Btree.Tool.BTreeValidator.ValidateNode(leftNode, leftNode == root);
GetPersister().SaveNode(node);
GetPersister().SaveNode(leftNode);
return(InternalDelete(leftNode, keyAndValue));
}
finally
{
}
}