bug: 无法完成 drop 和 drop all，停止开发这两个功能

src/main/java/top/guoziyang/mydb/backend/dm/pageCache/PageCacheImpl.java

@@ -55,7 +55,7 @@ public int newPage(byte[] initData) {
     }
 
     public Page getPage(int pgno) throws Exception {
-        return get((long)pgno);
+        return get(pgno);
     }
 
     /**

src/main/java/top/guoziyang/mydb/backend/im/BPlusTree.java

@@ -241,4 +241,36 @@ public void close() {
     static class InsertRes {
         long newNode, newKey;
     }
+
+    /**
+     * 删除键值
+     * @param key 键值
+     */
+    public void delete(long key) throws Exception {
+        long rootUid = rootUid();
+        delete(rootUid, key);
+    }
+
+    /**
+     * 递归删除键值
+     * @param nodeUid 节点 UID
+     * @param key 键值
+     */
+    private void delete(long nodeUid, long key) throws Exception {
+        Node node = Node.loadNode(this, nodeUid);
+        boolean isLeaf = node.isLeaf();
+        node.release();
+
+        if (isLeaf) {
+            Node leaf = Node.loadNode(this, nodeUid);
+            leaf.remove(key);
+            leaf.release();
+        } else {
+            long next = searchNext(nodeUid, key);
+            delete(next, key);
+            Node internalNode = Node.loadNode(this, nodeUid);
+            internalNode.remove(key);
+            internalNode.release();
+        }
+    }
 }

src/main/java/top/guoziyang/mydb/backend/im/Node.java

@@ -355,4 +355,67 @@ static class SplitRes {
         long newSon, newKey;
     }
 
+    /**
+     * 从节点中删除指定的键值
+     * @param key 要删除的键值
+     * @return 返回是否成功删除
+     */
+    public boolean remove(long key) throws Exception {
+        dataItem.before();
+        try {
+            boolean result = removeKey(key);
+            if (result && needMerge()) {
+                merge();
+            }
+            return result;
+        } finally {
+            dataItem.after(TransactionManagerImpl.SUPER_XID);
+        }
+    }
+
+    /**
+     * 从节点中删除指定的键值，并重新排列节点
+     * @param key 要删除的键值
+     * @return 返回是否成功删除
+     */
+    private boolean removeKey(long key) {
+        int noKeys = getRawNoKeys(raw);
+        int kth = 0;
+        while (kth < noKeys) {
+            long ik = getRawKthKey(raw, kth);
+            if (ik == key) {
+                break;
+            }
+            kth++;
+        }
+        if (kth == noKeys || getRawKthKey(raw, kth) != key) {
+            return false;
+        }
+
+        if (getRawIfLeaf(raw)) {
+            shiftRawKth(raw, kth);
+            setRawNoKeys(raw, noKeys - 1);
+        } else {
+            shiftRawKth(raw, kth);
+            setRawNoKeys(raw, noKeys - 1);
+        }
+        return true;
+    }
+
+    /**
+     * 判断是否需要合并节点
+     * @return 是否需要合并
+     */
+    private boolean needMerge() {
+        return getRawNoKeys(raw) < BALANCE_NUMBER / 2;
+    }
+
+    /**
+     * 合并当前节点
+     * @throws Exception
+     */
+    private void merge() throws Exception {
+        // Implement the merge logic here
+    }
+
 }

src/main/java/top/guoziyang/mydb/backend/parser/Parser.java

@@ -291,7 +291,12 @@ private static boolean isLogicOp(String op) {
         return ("and".equals(op) || "or".equals(op));
     }
 
-    private static Drop parseDrop(Tokenizer tokenizer) throws Exception {
+    private static Object parseDrop(Tokenizer tokenizer) throws Exception {
+        if ("all".equals(tokenizer.peek())) {
+            tokenizer.pop();
+            return new DropAll();
+        }
+
         if (!"table".equals(tokenizer.peek())) {
             throw Error.InvalidCommandException;
         }
@@ -313,6 +318,14 @@ private static Drop parseDrop(Tokenizer tokenizer) throws Exception {
         return drop;
     }
 
+    private static DropAll parseDropAll(Tokenizer tokenizer) throws Exception {
+        tokenizer.pop();
+        if ("all".equals(tokenizer.peek())) {
+            return new DropAll();
+        }
+        throw Error.InvalidCommandException;
+    }
+
     private static Create parseCreate(Tokenizer tokenizer) throws Exception {
         if (!"table".equals(tokenizer.peek())) {
             throw Error.InvalidCommandException;

src/main/java/top/guoziyang/mydb/backend/parser/statement/DropAll.java

@@ -0,0 +1,5 @@
+package top.guoziyang.mydb.backend.parser.statement;
+
+public class DropAll {
+
+}

src/main/java/top/guoziyang/mydb/backend/server/Executor.java

@@ -92,6 +92,12 @@ private byte[] execute2(Object stat) throws Exception {
                 res = tbm.showTables(xid);
             } else if (stat instanceof Create) {
                 res = tbm.create(xid, (Create) stat);
+            } else if (stat instanceof Drop) {
+                res = "COMMAND IS UNSUPPORTED".getBytes();
+//                res = tbm.drop(xid, (Drop) stat);
+            } else if (stat instanceof DropAll) {
+                res = "COMMAND IS UNSUPPORTED".getBytes();
+//                res = tbm.dropAll(xid, (DropAll) stat);
             } else if (stat instanceof Select) {
                 res = tbm.read(xid, (Select) stat);
             } else if (stat instanceof Insert) {

src/main/java/top/guoziyang/mydb/backend/tbm/Field.java

@@ -27,7 +27,7 @@ public class Field {
     String fieldType;
     private final Table tb;
     private long index;
-    private BPlusTree bt;
+    BPlusTree bt;
 
     public Field(long uid, Table tb) {
         this.uid = uid;

src/main/java/top/guoziyang/mydb/backend/tbm/Table.java

@@ -1,6 +1,8 @@
 package top.guoziyang.mydb.backend.tbm;
 
 import com.google.common.primitives.Bytes;
+import top.guoziyang.mydb.backend.dm.page.Page;
+import top.guoziyang.mydb.backend.dm.pageCache.PageCache;
 import top.guoziyang.mydb.backend.parser.statement.*;
 import top.guoziyang.mydb.backend.tbm.Field.ParseValueRes;
 import top.guoziyang.mydb.backend.tm.TransactionManagerImpl;
@@ -302,4 +304,17 @@ class CalWhereRes {
         long l0, r0, l1, r1;
         boolean single;
     }
+
+
+    private PageCache pageCache;  // 页面缓存对象
+    private int maxPageNumber;    // 该表的最大页号
+
+
+    public PageCache getPageCache() {
+        return pageCache;
+    }
+
+    public int getMaxPageNumber() {
+        return maxPageNumber;
+    }
 }

src/main/java/top/guoziyang/mydb/backend/tbm/TableManager.java

@@ -52,6 +52,12 @@ static TableManager open(String path, VersionManager vm, DataManager dm) {
     // 创建一个新的表
     byte[] create(long xid, Create create) throws Exception;
 
+    // 删除一张表
+    byte[] drop(long xid, Drop drop) throws Exception;
+
+    // 删除所有表
+    byte[] dropAll(long xid, DropAll drop) throws Exception;
+
     // 插入新的记录
     byte[] insert(long xid, Insert insert) throws Exception;