void CBPlusTree::recursive_remove(CNode* parentNode, KeyType key, DataType& dataValue)
{
int keyIndex = parentNode->getKeyIndex(key);
int childIndex= parentNode->getChildIndex(key, keyIndex); // 孩子结点指针索引
if (parentNode->getType()==LEAF)// 找到目标叶子节点
{
if (key==m_MaxKey&&keyIndex>0)
{
m_MaxKey = parentNode->getKeyValue(keyIndex-1);
}
dataValue = ((CLeafNode*)parentNode)->getData(keyIndex);
parentNode->removeKey(keyIndex, childIndex); // 直接删除
// 如果键值在内部结点中存在，也要相应的替换内部结点
if (childIndex==0 && m_Root->getType()!=LEAF && parentNode!=m_DataHead)
{
changeKey(m_Root, key, parentNode->getKeyValue(0));
}
}
else // 内结点
{
CNode *pChildNode = ((CInternalNode*)parentNode)->getChild(childIndex); //包含key的子树根节点
if (pChildNode->getKeyNum()==MINNUM_KEY) // 包含关键字达到下限值，进行相关操作
{
CNode *pLeft = childIndex>0 ? ((CInternalNode*)parentNode)->getChild(childIndex-1) : NULL; //左兄弟节点
CNode *pRight = childIndex<parentNode->getKeyNum() ? ((CInternalNode*)parentNode)->getChild(childIndex+1) : NULL;//右兄弟节点
// 先考虑从兄弟结点中借
if (pLeft && pLeft->getKeyNum()>MINNUM_KEY)// 左兄弟结点可借
{
pChildNode->borrowFrom(pLeft, parentNode, childIndex-1, LEFT);
}
else if (pRight && pRight->getKeyNum()>MINNUM_KEY)//右兄弟结点可借
{
pChildNode->borrowFrom(pRight, parentNode, childIndex, RIGHT);
}
//左右兄弟节点都不可借，考虑合并
else if (pLeft) //与左兄弟合并
{
pLeft->mergeChild(parentNode, pChildNode, childIndex-1);
pChildNode = pLeft;
}
else if (pRight) //与右兄弟合并
{
pChildNode->mergeChild(parentNode, pRight, childIndex);
}
}
recursive_remove(pChildNode, key, dataValue);
}
}
