import java.util.ArrayList;
import java.util.List;
// 模拟Oracle中的ROWID，唯一标识表中的一行数据
class RowId {
private String dataFile; // 数据文件号
private int blockNumber; // 块号
private int rowNumber; // 行号
public RowId(String dataFile, int blockNumber, int rowNumber) {
this.dataFile = dataFile;
this.blockNumber = blockNumber;
this.rowNumber = rowNumber;
}
@Override
public String toString() {
return dataFile + ":" + blockNumber + ":" + rowNumber;
}
}
// B树索引的叶子节点
class LeafNode {
private int key; // 索引键值
private RowId rowId; // 对应的行ID
private LeafNode prev; // 左指针，指向前一个叶子节点
private LeafNode next; // 右指针，指向后一个叶子节点
public LeafNode(int key, RowId rowId) {
this.key = key;
this.rowId = rowId;
}
// getter和setter方法
public int getKey() {
return key;
}
public RowId getRowId() {
return rowId;
}
public LeafNode getPrev() {
return prev;
}
public void setPrev(LeafNode prev) {
this.prev = prev;
}
public LeafNode getNext() {
return next;
}
public void setNext(LeafNode next) {
this.next = next;
}
@Override
public String toString() {
return "Key: " + key + ", ROWID: " + rowId;
}
}
// 模拟B树索引的叶子节点双向链表
public class BTreeLeafNodes {
public static void main(String[] args) {
// 创建几个叶子节点
LeafNode node1 = new LeafNode(10, new RowId("f1", 100, 5));
LeafNode node2 = new LeafNode(20, new RowId("f1", 102, 3));
LeafNode node3 = new LeafNode(30, new RowId("f2", 50, 8));
LeafNode node4 = new LeafNode(40, new RowId("f2", 55, 2));
// 构建双向链表
connectNodes(node1, node2);
connectNodes(node2, node3);
connectNodes(node3, node4);
// 从头部遍历链表
System.out.println("从头部遍历叶子节点:");
LeafNode current = node1;
while (current != null) {
System.out.println(current);
current = current.getNext();
}
// 从尾部遍历链表
System.out.println("\n从尾部遍历叶子节点:");
current = node4;
while (current != null) {
System.out.println(current);
current = current.getPrev();
}
// 模拟范围查询 (key between 20 and 30)
System.out.println("\n范围查询结果 (key between 20 and 30):");
List<LeafNode> result = rangeQuery(node1, 20, 30);
for (LeafNode node : result) {
System.out.println(node);
}
}
// 连接两个叶子节点，建立双向关系
private static void connectNodes(LeafNode prevNode, LeafNode nextNode) {
prevNode.setNext(nextNode);
nextNode.setPrev(prevNode);
}
// 模拟范围查询，利用双向链表特性
private static List<LeafNode> rangeQuery(LeafNode head, int minKey, int maxKey) {
List<LeafNode> result = new ArrayList<>();
LeafNode current = head;
// 找到起始节点
while (current != null && current.getKey() < minKey) {
current = current.getNext();
}
// 收集范围内的节点
while (current != null && current.getKey() <= maxKey) {
result.add(current);
current = current.getNext();
}
return result;
}
}