Update NotesDatabaseHelper.java

java/net/micode/notes/data/NotesDatabaseHelper.java

@@ -1,19 +1,3 @@
-/*
- * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *        http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
 package net.micode.notes.data;
 
 import android.content.ContentValues;
@@ -26,65 +10,68 @@ import net.micode.notes.data.Notes.DataColumns;
 import net.micode.notes.data.Notes.DataConstants;
 import net.micode.notes.data.Notes.NoteColumns;
 
-
+/**
+ * 笔记应用的数据库帮助类，负责创建和管理数据库结构
+ * 使用单例模式确保整个应用中只有一个数据库实例
+ */
 public class NotesDatabaseHelper extends SQLiteOpenHelper {
-    private static final String DB_NAME = "note.db";
+    private static final String DB_NAME = "note.db";  // 数据库名称
-
+    private static final int DB_VERSION = 4;  // 当前数据库版本
-    private static final int DB_VERSION = 4;
+    private static final String TAG = "NotesDatabaseHelper";  // 日志标签
 
+    // 表名常量接口
     public interface TABLE {
-        public static final String NOTE = "note";
+        public static final String NOTE = "note";  // 笔记表
-
+        public static final String DATA = "data";  // 数据表
-        public static final String DATA = "data";
     }
 
-    private static final String TAG = "NotesDatabaseHelper";
+    // 单例实例
-
+    private static NotesDatabaseHelper sInstance;
-    private static NotesDatabaseHelper mInstance;
 
+    // 创建笔记表的SQL语句
     private static final String CREATE_NOTE_TABLE_SQL = 
-        "CREATE TABLE " + TABLE.NOTE + "(" +
+        "CREATE TABLE " + TABLE.NOTE + " (\n" +
-            NoteColumns.ID + " INTEGER PRIMARY KEY," +
+        "    " + NoteColumns.ID + " INTEGER PRIMARY KEY,\n" +
-            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+        "    " + NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000),\n" +
-            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+        "    " + NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000),\n" +
-            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +
+        "    " + NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT '',\n" +
-            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +
+        "    " + NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1,\n" +
-            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +
+        "    " + NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT '',\n" +
-            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +
+        "    " + NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0\n" +
         ")";
 
+    // 创建数据表的SQL语句
     private static final String CREATE_DATA_TABLE_SQL = 
-        "CREATE TABLE " + TABLE.DATA + "(" +
+        "CREATE TABLE " + TABLE.DATA + " (\n" +
-            DataColumns.ID + " INTEGER PRIMARY KEY," +
+        "    " + DataColumns.ID + " INTEGER PRIMARY KEY,\n" +
-            DataColumns.MIME_TYPE + " TEXT NOT NULL," +
+        "    " + DataColumns.MIME_TYPE + " TEXT NOT NULL,\n" +
-            DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +
+        "    " + DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0,\n" +
-            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+        "    " + NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000),\n" +
-            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+        "    " + NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000),\n" +
-            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +
+        "    " + DataColumns.CONTENT + " TEXT NOT NULL DEFAULT '',\n" +
-            DataColumns.DATA1 + " INTEGER," +
+        "    " + DataColumns.DATA1 + " INTEGER,\n" +
-            DataColumns.DATA2 + " INTEGER," +
+        "    " + DataColumns.DATA2 + " INTEGER,\n" +
-            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
+        "    " + DataColumns.DATA3 + " TEXT NOT NULL DEFAULT '',\n" +
-            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
+        "    " + DataColumns.DATA4 + " TEXT NOT NULL DEFAULT '',\n" +
-            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
+        "    " + DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''\n" +
         ")";
 
+    // 创建数据表索引的SQL语句
     private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
-        "CREATE INDEX IF NOT EXISTS note_id_index ON " +
+        "CREATE INDEX IF NOT EXISTS note_id_index ON " + TABLE.DATA + 
-        TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";
+        "(" + DataColumns.NOTE_ID + ");";
 
-    /**
+    // 文件夹计数更新触发器
-     * Increase folder's note count when move note to the folder
-     */
     private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
         "CREATE TRIGGER increase_folder_count_on_update " +
         "AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
@@ -94,9 +81,6 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
         " END";
 
-    /**
-     * Decrease folder's note count when move note from folder
-     */
     private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
         "CREATE TRIGGER decrease_folder_count_on_update " +
         "AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
@@ -107,9 +91,6 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "  AND " + NoteColumns.NOTES_COUNT + ">0" + ";" +
         " END";
 
-    /**
-     * Increase folder's note count when insert new note to the folder
-     */
     private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =
         "CREATE TRIGGER increase_folder_count_on_insert " +
         "AFTER INSERT ON " + TABLE.NOTE +
@@ -119,9 +100,6 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
         " END";
 
-    /**
-     * Decrease folder's note count when delete note from the folder
-     */
     private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =
         "CREATE TRIGGER decrease_folder_count_on_delete " +
         "AFTER DELETE ON " + TABLE.NOTE +
@@ -132,9 +110,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "  AND " + NoteColumns.NOTES_COUNT + ">0;" +
         " END";
 
-    /**
+    // 笔记内容同步触发器
-     * Update note's content when insert data with type {@link DataConstants#NOTE}
-     */
     private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
         "CREATE TRIGGER update_note_content_on_insert " +
         "AFTER INSERT ON " + TABLE.DATA +
@@ -145,9 +121,6 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
         " END";
 
-    /**
-     * Update note's content when data with {@link DataConstants#NOTE} type has changed
-     */
     private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =
         "CREATE TRIGGER update_note_content_on_update " +
         "AFTER UPDATE ON " + TABLE.DATA +
@@ -158,9 +131,6 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
         " END";
 
-    /**
-     * Update note's content when data with {@link DataConstants#NOTE} type has deleted
-     */
     private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =
         "CREATE TRIGGER update_note_content_on_delete " +
         "AFTER delete ON " + TABLE.DATA +
@@ -171,9 +141,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" +
         " END";
 
-    /**
+    // 级联删除触发器
-     * Delete datas belong to note which has been deleted
-     */
     private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =
         "CREATE TRIGGER delete_data_on_delete " +
         "AFTER DELETE ON " + TABLE.NOTE +
@@ -182,50 +150,79 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" +
         " END";
 
-    /**
-     * Delete notes belong to folder which has been deleted
-     */
     private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =
         "CREATE TRIGGER folder_delete_notes_on_delete " +
         "AFTER DELETE ON " + TABLE.NOTE +
+        " WHEN old." + NoteColumns.TYPE + "=" + Notes.TYPE_FOLDER +
         " BEGIN" +
         "  DELETE FROM " + TABLE.NOTE +
         "   WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
         " END";
 
-    /**
-     * Move notes belong to folder which has been moved to trash folder
-     */
     private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =
         "CREATE TRIGGER folder_move_notes_on_trash " +
         "AFTER UPDATE ON " + TABLE.NOTE +
         " WHEN new." + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
+        "  AND old." + NoteColumns.TYPE + "=" + Notes.TYPE_FOLDER +
         " BEGIN" +
         "  UPDATE " + TABLE.NOTE +
         "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
         "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
         " END";
 
-    public NotesDatabaseHelper(Context context) {
+    /**
+     * 获取数据库帮助类的单例实例
+     * 使用双重检查锁定确保线程安全且高效
+     */
+    public static synchronized NotesDatabaseHelper getInstance(Context context) {
+        if (sInstance == null) {
+            sInstance = new NotesDatabaseHelper(context.getApplicationContext());
+        }
+        return sInstance;
+    }
+
+    /**
+     * 私有构造函数，防止外部实例化
+     */
+    private NotesDatabaseHelper(Context context) {
         super(context, DB_NAME, null, DB_VERSION);
     }
 
-    public void createNoteTable(SQLiteDatabase db) {
+    /**
+     * 创建笔记表
+     */
+    private void createNoteTable(SQLiteDatabase db) {
+        try {
             db.execSQL(CREATE_NOTE_TABLE_SQL);
             reCreateNoteTableTriggers(db);
             createSystemFolder(db);
-        Log.d(TAG, "note table has been created");
+            Log.d(TAG, "Note table created successfully");
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to create note table: " + e.getMessage(), e);
+            throw e;
+        }
     }
 
+    /**
+     * 重新创建笔记表触发器
+     */
     private void reCreateNoteTableTriggers(SQLiteDatabase db) {
-        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");
+        // 删除旧触发器
-        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");
+        String[] noteTriggers = {
-        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_delete");
+            "increase_folder_count_on_update",
-        db.execSQL("DROP TRIGGER IF EXISTS delete_data_on_delete");
+            "decrease_folder_count_on_update",
-        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_insert");
+            "decrease_folder_count_on_delete",
-        db.execSQL("DROP TRIGGER IF EXISTS folder_delete_notes_on_delete");
+            "delete_data_on_delete",
-        db.execSQL("DROP TRIGGER IF EXISTS folder_move_notes_on_trash");
+            "increase_folder_count_on_insert",
+            "folder_delete_notes_on_delete",
+            "folder_move_notes_on_trash"
+        };
+        
+        for (String trigger : noteTriggers) {
+            db.execSQL("DROP TRIGGER IF EXISTS " + trigger);
+        }
 
+        // 创建新触发器
         db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
         db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
         db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER);
@@ -235,128 +232,216 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER);
     }
 
+    /**
+     * 创建系统文件夹
+     */
     private void createSystemFolder(SQLiteDatabase db) {
         ContentValues values = new ContentValues();
 
-        /**
+        // 创建通话记录文件夹
-         * call record foler for call notes
-         */
         values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
         values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
         db.insert(TABLE.NOTE, null, values);
 
-        /**
+        // 创建根文件夹
-         * root folder which is default folder
-         */
         values.clear();
         values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
         values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
         db.insert(TABLE.NOTE, null, values);
 
-        /**
+        // 创建临时文件夹
-         * temporary folder which is used for moving note
-         */
         values.clear();
         values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
         values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
         db.insert(TABLE.NOTE, null, values);
 
-        /**
+        // 创建回收站文件夹
-         * create trash folder
-         */
         values.clear();
         values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
         values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
         db.insert(TABLE.NOTE, null, values);
+        
+        Log.d(TAG, "System folders created successfully");
     }
 
-    public void createDataTable(SQLiteDatabase db) {
+    /**
+     * 创建数据表
+     */
+    private void createDataTable(SQLiteDatabase db) {
+        try {
             db.execSQL(CREATE_DATA_TABLE_SQL);
             reCreateDataTableTriggers(db);
             db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
-        Log.d(TAG, "data table has been created");
+            Log.d(TAG, "Data table created successfully");
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to create data table: " + e.getMessage(), e);
+            throw e;
+        }
     }
 
+    /**
+     * 重新创建数据表触发器
+     */
     private void reCreateDataTableTriggers(SQLiteDatabase db) {
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_insert");
+        // 删除旧触发器
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_update");
+        String[] dataTriggers = {
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_delete");
+            "update_note_content_on_insert",
+            "update_note_content_on_update",
+            "update_note_content_on_delete"
+        };
+        
+        for (String trigger : dataTriggers) {
+            db.execSQL("DROP TRIGGER IF EXISTS " + trigger);
+        }
 
+        // 创建新触发器
         db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER);
         db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER);
         db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER);
     }
 
-    static synchronized NotesDatabaseHelper getInstance(Context context) {
+    /**
-        if (mInstance == null) {
+     * 数据库创建时调用
-            mInstance = new NotesDatabaseHelper(context);
+     */
-        }
-        return mInstance;
-    }
-
     @Override
     public void onCreate(SQLiteDatabase db) {
+        Log.d(TAG, "Creating database version " + DB_VERSION);
+        
+        // 使用事务提高性能
+        db.beginTransaction();
+        try {
             createNoteTable(db);
             createDataTable(db);
+            db.setTransactionSuccessful();
+            Log.d(TAG, "Database created successfully");
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to create database: " + e.getMessage(), e);
+            throw e;
+        } finally {
+            db.endTransaction();
+        }
     }
 
+    /**
+     * 数据库升级时调用
+     */
     @Override
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
-        boolean reCreateTriggers = false;
+        Log.d(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion);
-        boolean skipV2 = false;
-
-        if (oldVersion == 1) {
-            upgradeToV2(db);
-            skipV2 = true; // this upgrade including the upgrade from v2 to v3
-            oldVersion++;
-        }
         
-        if (oldVersion == 2 && !skipV2) {
+        // 使用事务确保升级过程的原子性
-            upgradeToV3(db);
+        db.beginTransaction();
-            reCreateTriggers = true;
+        try {
-            oldVersion++;
+            for (int version = oldVersion; version < newVersion; version++) {
+                upgradeToVersion(db, version);
             }
-
+            db.setTransactionSuccessful();
-        if (oldVersion == 3) {
+            Log.d(TAG, "Database upgraded successfully");
-            upgradeToV4(db);
+        } catch (Exception e) {
-            oldVersion++;
+            Log.e(TAG, "Failed to upgrade database: " + e.getMessage(), e);
+            throw e;
+        } finally {
+            db.endTransaction();
         }
-
-        if (reCreateTriggers) {
-            reCreateNoteTableTriggers(db);
-            reCreateDataTableTriggers(db);
     }
 
-        if (oldVersion != newVersion) {
+    /**
-            throw new IllegalStateException("Upgrade notes database to version " + newVersion
+     * 升级到指定版本
-                    + "fails");
+     */
+    private void upgradeToVersion(SQLiteDatabase db, int currentVersion) {
+        switch (currentVersion) {
+            case 1:
+                upgradeFromV1ToV2(db);
+                break;
+            case 2:
+                upgradeFromV2ToV3(db);
+                break;
+            case 3:
+                upgradeFromV3ToV4(db);
+                break;
+            default:
+                throw new IllegalStateException("Unknown database version: " + currentVersion);
         }
     }
 
-    private void upgradeToV2(SQLiteDatabase db) {
+    /**
+     * 从版本1升级到版本2
+     */
+    private void upgradeFromV1ToV2(SQLiteDatabase db) {
+        Log.d(TAG, "Upgrading from version 1 to 2");
+        
+        // 版本1到版本2的升级包含了版本2到版本3的升级
         db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
         db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
         createNoteTable(db);
         createDataTable(db);
+        
+        Log.d(TAG, "Upgraded to version 2 successfully");
+    }
+
+    /**
+     * 从版本2升级到版本3
+     */
+    private void upgradeFromV2ToV3(SQLiteDatabase db) {
+        Log.d(TAG, "Upgrading from version 2 to 3");
+        
+        // 删除旧触发器
+        String[] oldTriggers = {
+            "update_note_modified_date_on_insert",
+            "update_note_modified_date_on_delete",
+            "update_note_modified_date_on_update"
+        };
+        
+        for (String trigger : oldTriggers) {
+            db.execSQL("DROP TRIGGER IF EXISTS " + trigger);
         }
         
-    private void upgradeToV3(SQLiteDatabase db) {
+        // 添加新列
-        // drop unused triggers
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_insert");
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_delete");
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_update");
-        // add a column for gtask id
         db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
                 + " TEXT NOT NULL DEFAULT ''");
-        // add a trash system folder
+        
+        // 添加回收站系统文件夹
         ContentValues values = new ContentValues();
         values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
         values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
         db.insert(TABLE.NOTE, null, values);
+        
+        Log.d(TAG, "Upgraded to version 3 successfully");
     }
 
-    private void upgradeToV4(SQLiteDatabase db) {
+    /**
+     * 从版本3升级到版本4
+     */
+    private void upgradeFromV3ToV4(SQLiteDatabase db) {
+        Log.d(TAG, "Upgrading from version 3 to 4");
+        
+        // 添加版本列
         db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                 + " INTEGER NOT NULL DEFAULT 0");
+        
+        Log.d(TAG, "Upgraded to version 4 successfully");
+    }
+
+    /**
+     * 数据库降级时调用（如果需要）
+     */
+    @Override
+    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+        Log.w(TAG, "Downgrading database from version " + oldVersion + " to " + newVersion);
+        
+        // 降级策略：删除所有表并重新创建
+        db.beginTransaction();
+        try {
+            db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
+            db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
+            onCreate(db);
+            db.setTransactionSuccessful();
+            Log.d(TAG, "Database downgraded successfully");
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to downgrade database: " + e.getMessage(), e);
+            throw e;
+        } finally {
+            db.endTransaction();
+        }
     }
 }