feature: 增加了一个新的关键词：show tables，可以查看当前数据库中所有的表！

01Petard · Sep 16, 2024 · ece32cb · ece32cb
1 parent b8c8f4d
commit ece32cb
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Showing 7 changed files with 53 additions and 8 deletions.
diff --git a/src/main/java/top/guoziyang/mydb/backend/parser/Parser.java b/src/main/java/top/guoziyang/mydb/backend/parser/Parser.java
@@ -75,11 +75,12 @@ public static Object Parse(byte[] statement) throws Exception {
         return stat;
     }
 
-    private static Show parseShow(Tokenizer tokenizer) throws Exception {
-        tokenizer.pop();
-        if ("tables".equals(tokenizer.peek())) {
-            tokenizer.pop();
+    private static Object parseShow(Tokenizer tokenizer) throws Exception {
+        if ("".equals(tokenizer.peek())) {
             return new Show();
+        } else if ("tables".equals(tokenizer.peek())) {
+            tokenizer.pop();
+            return new ShowTables();
         }
         throw Error.InvalidCommandException;
     }

diff --git a/src/main/java/top/guoziyang/mydb/backend/parser/statement/ShowTables.java b/src/main/java/top/guoziyang/mydb/backend/parser/statement/ShowTables.java
@@ -0,0 +1,4 @@
+package top.guoziyang.mydb.backend.parser.statement;
+
+public class ShowTables {
+}
diff --git a/src/main/java/top/guoziyang/mydb/backend/server/Executor.java b/src/main/java/top/guoziyang/mydb/backend/server/Executor.java
@@ -88,6 +88,8 @@ private byte[] execute2(Object stat) throws Exception {
             byte[] res = null;
             if (stat instanceof Show) {
                 res = tbm.show(xid);
+            } else if (stat instanceof ShowTables) {
+                res = tbm.showTables(xid);
             } else if (stat instanceof Create) {
                 res = tbm.create(xid, (Create) stat);
             } else if (stat instanceof Select) {

diff --git a/src/main/java/top/guoziyang/mydb/backend/tbm/Field.java b/src/main/java/top/guoziyang/mydb/backend/tbm/Field.java
@@ -13,7 +13,7 @@
 import java.util.List;
 
 /**
- * 表示字段信息
+ * 管理表和字段的结构数据，例如表名、表字段信息和字段索引等
  * 二进制格式为：
  * [FieldName][TypeName][IndexUid]
  * 如果field无索引，IndexUid为0

diff --git a/src/main/java/top/guoziyang/mydb/backend/tbm/TableManager.java b/src/main/java/top/guoziyang/mydb/backend/tbm/TableManager.java
@@ -5,6 +5,9 @@
 import top.guoziyang.mydb.backend.utils.Parser;
 import top.guoziyang.mydb.backend.vm.VersionManager;
 
+/**
+ * 表管理器接口
+ */
 public interface TableManager {
     /**
      * 创建一个新的表管理器实例
@@ -43,6 +46,9 @@ static TableManager open(String path, VersionManager vm, DataManager dm) {
     // 显示事务的状态
     byte[] show(long xid);
 
+    // 查看数据库中的所有表
+    byte[] showTables(long xid) throws Exception;
+
     // 创建一个新的表
     byte[] create(long xid, Create create) throws Exception;
 

diff --git a/src/main/java/top/guoziyang/mydb/backend/tbm/TableManagerImpl.java b/src/main/java/top/guoziyang/mydb/backend/tbm/TableManagerImpl.java
@@ -13,6 +13,9 @@
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
+/**
+ * 直接被最外层 Server 调用，直接返回执行的结果
+ */
 public class TableManagerImpl implements TableManager {
     VersionManager vm;
     DataManager dm;
@@ -32,7 +35,7 @@ public class TableManagerImpl implements TableManager {
     }
 
     /**
-     * 启动时，
+     * 启动时
      */
     private void loadTables() {
         long uid = firstTableUid();
@@ -95,6 +98,24 @@ public byte[] show(long xid) {
         }
     }
 
+    @Override
+    public byte[] showTables(long xid) throws Exception {
+        lock.lock();
+        try {
+            StringBuilder sb = new StringBuilder();
+            if (tableCache.isEmpty()) {
+                return "No tables found.".getBytes(); // 如果没有表，返回提示信息
+            }
+            for (String tableName : tableCache.keySet()) {
+                sb.append(tableName).append("\n"); // 将每个表名追加到字符串
+            }
+            return sb.toString().getBytes(); // 返回字节数组
+        } finally {
+            lock.unlock();
+        }
+    }
+
+
     @Override
     public byte[] create(long xid, Create create) throws Exception {
         lock.lock();

diff --git a/src/test/java/top/guoziyang/mydb/backend/parser/ParserTest.java b/src/test/java/top/guoziyang/mydb/backend/parser/ParserTest.java
@@ -78,11 +78,11 @@ public void testDelete() throws Exception {
 
     @Test
     public void testShow() throws Exception {
-        String stat = "show tables";
+        String stat = "show";
         Object res = Parser.Parse(stat.getBytes());
         Show show = (Show)res;
         Gson gson = new Gson();
-        System.out.println("Show Tables");
+        System.out.println("Show");
         System.out.println(gson.toJson(show));
         System.out.println("======================");
     }
@@ -98,6 +98,17 @@ public void testUpdate() throws Exception {
         System.out.println("======================");
     }
 
+    @Test
+    public void testShowTable() throws Exception {
+        String stat = "show tables";
+        Object res = Parser.Parse(stat.getBytes());
+        ShowTables showTables = (ShowTables)res;
+        Gson gson = new Gson();
+        System.out.println("Show Tables");
+        System.out.println(gson.toJson(showTables));
+        System.out.println("======================");
+    }
+
     @Test
     public void testHelp() throws Exception {
         String stat = "help";