public virtual IKeyAndValue GetSmallest(IBTreeNode node, bool delete) { if (!node.IsLeaf()) { var childTreeNode = node.GetChildAt(0, true); if (childTreeNode.GetNbKeys() == _degree - 1) { node = PrepareForDelete(node, childTreeNode, 0); } childTreeNode = node.GetChildAt(0, true); return(GetSmallest(childTreeNode, delete)); } var keyAndValue = node.GetKeyAndValueAt(0); if (delete) { node.DeleteKeyAndValueAt(0, true); _persister.SaveNode(node); } return(keyAndValue); }
public virtual IKeyAndValue GetBiggest(IBTreeNode node, bool delete) { var lastKeyIndex = node.GetNbKeys() - 1; var lastChildIndex = node.GetNbChildren() - 1; if (lastChildIndex > lastKeyIndex) { var child = node.GetChildAt(lastChildIndex, true); if (child.GetNbKeys() == _degree - 1) { node = PrepareForDelete(node, child, lastChildIndex); } lastChildIndex = node.GetNbChildren() - 1; child = node.GetChildAt(lastChildIndex, true); return(GetBiggest(child, delete)); } var kav = node.GetKeyAndValueAt(lastKeyIndex); if (delete) { node.DeleteKeyAndValueAt(lastKeyIndex, false); _persister.SaveNode(node); } return(kav); }
private IBTreeNode PrepareForDelete(IBTreeNode parent, IBTreeNode child, int childIndex) { BTreeValidator.ValidateNode(parent); BTreeValidator.ValidateNode(child); // case 3a IBTreeNode leftSibling = null; IBTreeNode rightSibling = null; if (childIndex > 0 && parent.GetNbChildren() > 0) { leftSibling = parent.GetChildAt(childIndex - 1, false); } if (childIndex < parent.GetNbChildren() - 1) { rightSibling = parent.GetChildAt(childIndex + 1, false); } // case 3a left if (leftSibling != null && leftSibling.GetNbKeys() >= _degree) { var elementToMoveDown = parent.GetKeyAndValueAt(childIndex - 1); var elementToMoveUp = leftSibling.GetLastKeyAndValue(); parent.SetKeyAndValueAt(elementToMoveUp, childIndex - 1); child.InsertKeyAndValue(elementToMoveDown.GetKey(), elementToMoveDown.GetValue()); if (leftSibling.GetNbChildren() > leftSibling.GetNbKeys()) { // Take the last child of the left sibling and set it the // first child of the 'child' (incoming parameter) // child.setChildAt(leftSibling.getChildAt(leftSibling.getNbChildren() // - 1, true), 0); child.SetChildAt(leftSibling, leftSibling.GetNbChildren() - 1, 0, true); child.IncrementNbChildren(); } leftSibling.DeleteKeyAndValueAt(leftSibling.GetNbKeys() - 1, false); if (!leftSibling.IsLeaf()) { leftSibling.DeleteChildAt(leftSibling.GetNbChildren() - 1); } _persister.SaveNode(parent); _persister.SaveNode(child); _persister.SaveNode(leftSibling); if (OdbConfiguration.IsBTreeValidationEnabled()) { BTreeValidator.ValidateNode(parent, parent == _root); BTreeValidator.ValidateNode(child, false); BTreeValidator.ValidateNode(leftSibling, false); BTreeValidator.CheckDuplicateChildren(leftSibling, child); } return(parent); } // case 3a right if (rightSibling != null && rightSibling.GetNbKeys() >= _degree) { var elementToMoveDown = parent.GetKeyAndValueAt(childIndex); var elementToMoveUp = rightSibling.GetKeyAndValueAt(0); parent.SetKeyAndValueAt(elementToMoveUp, childIndex); child.InsertKeyAndValue(elementToMoveDown.GetKey(), elementToMoveDown.GetValue()); if (rightSibling.GetNbChildren() > 0) { // Take the first child of the right sibling and set it the // last child of the 'child' (incoming parameter) child.SetChildAt(rightSibling, 0, child.GetNbChildren(), true); child.IncrementNbChildren(); } rightSibling.DeleteKeyAndValueAt(0, true); _persister.SaveNode(parent); _persister.SaveNode(child); _persister.SaveNode(rightSibling); if (OdbConfiguration.IsBTreeValidationEnabled()) { BTreeValidator.ValidateNode(parent, parent == _root); BTreeValidator.ValidateNode(child, false); BTreeValidator.ValidateNode(rightSibling, false); BTreeValidator.CheckDuplicateChildren(rightSibling, child); } return(parent); } // case 3b var isCase3B = (leftSibling != null && leftSibling.GetNbKeys() == _degree - 1) || (rightSibling != null && rightSibling.GetNbKeys() >= _degree - 1); var parentWasSetToNull = false; if (isCase3B) { // choose left sibling to execute merge if (leftSibling != null) { var elementToMoveDown = parent.GetKeyAndValueAt(childIndex - 1); leftSibling.InsertKeyAndValue(elementToMoveDown.GetKey(), elementToMoveDown.GetValue()); leftSibling.MergeWith(child); parent.DeleteKeyAndValueAt(childIndex - 1, true); if (parent.GetNbKeys() == 0) { // this is the root if (!parent.HasParent()) { _root = leftSibling; _root.SetParent(null); _height--; parentWasSetToNull = true; } else { const string errorMessage = "Unexpected empty node that is node the root!"; throw new BTreeNodeValidationException(errorMessage); } } else { parent.SetChildAt(leftSibling, childIndex - 1); } if (parentWasSetToNull) { _persister.DeleteNode(parent); } else { _persister.SaveNode(parent); BTreeValidator.ValidateNode(parent, parent == _root); } // child was merged with another node it must be deleted _persister.DeleteNode(child); _persister.SaveNode(leftSibling); // Validator.validateNode(child, child == root); BTreeValidator.ValidateNode(leftSibling, leftSibling == _root); // Validator.checkDuplicateChildren(leftSibling, child); return(parentWasSetToNull ? _root : parent); } // choose right sibling to execute merge { var elementToMoveDown = parent.GetKeyAndValueAt(childIndex); child.InsertKeyAndValue(elementToMoveDown.GetKey(), elementToMoveDown.GetValue()); child.MergeWith(rightSibling); parent.DeleteKeyAndValueAt(childIndex, true); if (parent.GetNbKeys() == 0) { // this is the root if (!parent.HasParent()) { _root = child; _root.SetParent(null); _height--; parentWasSetToNull = true; } else { throw new BTreeNodeValidationException("Unexpected empty root node!"); } } else { parent.SetChildAt(child, childIndex); } if (parentWasSetToNull) { _persister.DeleteNode(parent); } else { _persister.SaveNode(parent); BTreeValidator.ValidateNode(parent, parent == _root); } _persister.DeleteNode(rightSibling); _persister.SaveNode(child); BTreeValidator.ValidateNode(child, child == _root); // Validator.validateNode(rightSibling, rightSibling == // root); // Validator.checkDuplicateChildren(rightSibling, child); return(parentWasSetToNull ? _root : parent); } } throw new BTreeNodeValidationException("Unexpected case in executing prepare for delete"); }
/// <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> private object InternalDelete(IBTreeNode node, IKeyAndValue keyAndValue) { var positionOfKey = node.GetPositionOfKey(keyAndValue.GetKey()); var keyIsHere = positionOfKey > 0; if (node.IsLeaf()) { if (keyIsHere) { var deletedValue = node.DeleteKeyForLeafNode(keyAndValue); GetPersister().SaveNode(node); return(deletedValue); } // key does not exist return(null); } int realPosition; if (!keyIsHere) { // descend realPosition = -positionOfKey - 1; var childTreeNode = node.GetChildAt(realPosition, true); if (childTreeNode.GetNbKeys() == _degree - 1) { node = PrepareForDelete(node, childTreeNode, realPosition); return(InternalDelete(node, keyAndValue)); } return(InternalDelete(childTreeNode, keyAndValue)); } // Here,the node is not a leaf and contains the key realPosition = positionOfKey - 1; var currentKey = node.GetKeyAt(realPosition); var currentValue = node.GetValueAsObjectAt(realPosition); // case 2a var leftNode = node.GetChildAt(realPosition, true); if (leftNode.GetNbKeys() >= _degree) { var prevKeyAndValue = GetBiggest(leftNode, true); node.SetKeyAndValueAt(prevKeyAndValue, realPosition); BTreeValidator.ValidateNode(node, node == _root); GetPersister().SaveNode(node); return(currentValue); } // case 2b var rightNode = node.GetChildAt(realPosition + 1, true); if (rightNode.GetNbKeys() >= _degree) { var nextKeyAndValue = GetSmallest(rightNode, true); node.SetKeyAndValueAt(nextKeyAndValue, realPosition); 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 BTreeValidator.ValidateNode(node, node == _root); } _persister.DeleteNode(rightNode); BTreeValidator.ValidateNode(leftNode, leftNode == _root); GetPersister().SaveNode(node); GetPersister().SaveNode(leftNode); return(InternalDelete(leftNode, keyAndValue)); }