// replaceNode cuts a node away form its parent, substituting a new node or
// nil. The updated new node is returned. Note that this does not in fact alter
// the old node in any way, but only the old node's parent and the new node.
func (tc *treeContext) replaceNode(oldNode, newNode *roachpb.RangeTreeNode) (*roachpb.RangeTreeNode, *roachpb.Error) {
if oldNode.ParentKey == nil {
if newNode == nil {
return nil, roachpb.NewErrorf("cannot replace the root node with nil")
}
// Update the root key if this was the root.
tc.setRootKey(newNode.Key)
} else {
oldParent, pErr := tc.getNode(oldNode.ParentKey)
if pErr != nil {
return nil, pErr
}
if oldParent.LeftKey != nil && oldNode.Key.Equal(oldParent.LeftKey) {
if newNode == nil {
oldParent.LeftKey = nil
} else {
oldParent.LeftKey = newNode.Key
}
} else {
if newNode == nil {
oldParent.RightKey = nil
} else {
oldParent.RightKey = newNode.Key
}
}
tc.setNode(oldParent)
}
if newNode != nil {
newNode.ParentKey = oldNode.ParentKey
tc.setNode(newNode)
}
return newNode, nil
}
// insert performs the insertion of a new node into the tree. It walks the tree
// until it finds the correct location. It will fail if the node already exists
// as that case should not occur. After inserting the node, it checks all insert
// cases to ensure the tree is balanced and adjusts it if needed.
func (tc *treeContext) insert(node *roachpb.RangeTreeNode) *roachpb.Error {
if tc.tree.RootKey == nil {
tc.setRootKey(node.Key)
} else {
// Walk the tree to find the right place to insert the new node.
currentKey := tc.tree.RootKey
for {
currentNode, pErr := tc.getNode(currentKey)
if pErr != nil {
return pErr
}
if node.Key.Equal(currentNode.Key) {
return roachpb.NewErrorf("key %s already exists in the range tree", node.Key)
}
if node.Key.Less(currentNode.Key) {
if currentNode.LeftKey == nil {
currentNode.LeftKey = node.Key
tc.setNode(currentNode)
break
} else {
currentKey = currentNode.LeftKey
}
} else {
if currentNode.RightKey == nil {
currentNode.RightKey = node.Key
tc.setNode(currentNode)
break
} else {
currentKey = currentNode.RightKey
}
}
}
node.ParentKey = currentKey
tc.setNode(node)
}
return tc.insertCase1(node)
}
// rotateRight performs a right rotation around the node.
func (tc *treeContext) rotateRight(node *roachpb.RangeTreeNode) (*roachpb.RangeTreeNode, *roachpb.Error) {
left, pErr := tc.getNode(node.LeftKey)
if pErr != nil {
return nil, pErr
}
left, pErr = tc.replaceNode(node, left)
if pErr != nil {
return nil, pErr
}
node.LeftKey = left.RightKey
if left.RightKey != nil {
leftRight, pErr := tc.getNode(left.RightKey)
if pErr != nil {
return nil, pErr
}
leftRight.ParentKey = node.Key
tc.setNode(leftRight)
}
left.RightKey = node.Key
node.ParentKey = left.Key
tc.setNode(left)
tc.setNode(node)
return left, nil
}
// rotateLeft performs a left rotation around the node.
func (tc *treeContext) rotateLeft(node *roachpb.RangeTreeNode) (*roachpb.RangeTreeNode, *roachpb.Error) {
right, pErr := tc.getNode(node.RightKey)
if pErr != nil {
return nil, pErr
}
right, pErr = tc.replaceNode(node, right)
if pErr != nil {
return nil, pErr
}
node.RightKey = right.LeftKey
if right.LeftKey != nil {
rightLeft, pErr := tc.getNode(right.LeftKey)
if pErr != nil {
return nil, pErr
}
rightLeft.ParentKey = node.Key
tc.setNode(rightLeft)
}
right.LeftKey = node.Key
node.ParentKey = right.Key
tc.setNode(right)
tc.setNode(node)
return right, nil
}