[feat]CsvDb支持事务，开启事务后加速数据操作，提交事务时再写入磁盘

NewLife.Core/IO/CsvDb.cs

@@ -10,11 +10,15 @@ namespace NewLife.IO;
 /// <summary>Csv文件轻量级数据库</summary>
 /// <remarks>
 /// 文档 https://newlifex.com/core/csv_db
-/// 适用于大量数据需要快速存储、快速查找，很少修改和删除的场景。
+/// 适用于大量数据需要快速追加、快速查找，很少修改和删除的场景。
 /// 在桌面客户端中，关系型数据库SQLite很容易因非法关机而损坏，本数据库能跳过损坏行，自动恢复。
+/// 
+/// 中间插入和删除时，需要移动尾部数据，性能较差。
+/// 
+/// 本设计不支持线程安全，务必确保单线程操作。
 /// </remarks>
 /// <typeparam name="T"></typeparam>
-public class CsvDb<T> where T : new()
+public class CsvDb<T> : DisposeBase where T : new()
 {
     #region 属性
     /// <summary>文件名</summary>
@@ -34,14 +38,43 @@ namespace NewLife.IO;
     /// <summary>实例化Csv文件数据库</summary>
     /// <param name="comparer"></param>
     public CsvDb(Func<T?, T?, Boolean> comparer) => Comparer = new MyComparer(comparer);
+
+    /// <summary>销毁</summary>
+    /// <param name="disposing"></param>
+    protected override void Dispose(Boolean disposing)
+    {
+        base.Dispose(disposing);
+
+        Commit();
+    }
+    #endregion
+
+    #region 基础方法
+    private List<T>? _cache;
+    /// <summary>开启事务，便于批量处理数据</summary>
+    public void BeginTransaction()
+    {
+        _cache ??= FindAll().ToList();
+    }
+
+    /// <summary>提交事务，把缓存数据写入磁盘</summary>
+    public void Commit()
+    {
+        if (_cache == null) return;
+
+        Write(_cache, false);
+        _cache = null;
+    }
     #endregion
 
-    #region 方法
-    /// <summary>强行写入数据</summary>
+    #region 添删改查
+    /// <summary>批量写入数据（高性能）</summary>
     /// <param name="models">要写入的数据</param>
-    /// <param name="append">是否附加在尾部</param>
+    /// <param name="append">是否附加在尾部。为false时从头写入，覆盖已有数据</param>
     public void Write(IEnumerable<T> models, Boolean append)
     {
+        if (!models.Any() && append) return;
+
         var file = GetFile();
         file.EnsureDirectory(true);
 
@@ -70,11 +103,23 @@ public void Write(IEnumerable<T> models, Boolean append)
 
     /// <summary>尾部插入数据，性能极好</summary>
     /// <param name="model"></param>
-    public void Add(T model) => Add([model]);
+    public void Add(T model)
+    {
+        if (_cache != null)
+            _cache.Add(model);
+        else
+            Write([model], true);
+    }
 
     /// <summary>尾部插入数据，性能极好</summary>
     /// <param name="models"></param>
-    public void Add(IEnumerable<T> models) => Write(models, true);
+    public void Add(IEnumerable<T> models)
+    {
+        if (_cache != null)
+            _cache.AddRange(models);
+        else
+            Write(models, true);
+    }
 
     /// <summary>删除数据，性能很差，全部读取剔除后保存</summary>
     /// <param name="model"></param>
@@ -101,6 +146,8 @@ public Int32 Remove(Func<T, Boolean> predicate)
 
         lock (this)
         {
+            if (_cache != null) return _cache.RemoveAll(x => predicate(x));
+
             var list = FindAll();
             if (list.Count == 0) return 0;
 
@@ -119,7 +166,13 @@ public Int32 Remove(Func<T, Boolean> predicate)
     }
 
     /// <summary>清空数据。只写头部</summary>
-    public void Clear() => Write([], false);
+    public void Clear()
+    {
+        if (_cache != null)
+            _cache.Clear();
+        else
+            Write([], false);
+    }
 
     /// <summary>更新指定数据行，性能很差，全部读取替换后保存</summary>
     /// <param name="model"></param>
@@ -137,7 +190,7 @@ private Boolean Set(T model, Boolean add)
 
         lock (this)
         {
-            var list = FindAll();
+            var list = _cache ?? FindAll();
             if (!add && list.Count == 0) return false;
 
             // 找到目标数据行，并替换
@@ -159,7 +212,10 @@ private Boolean Set(T model, Boolean add)
             }
 
             // 重新写回去
-            Write(list, false);
+            if (_cache == null)
+            {
+                Write(list, false);
+            }
 
             return true;
         }
@@ -182,22 +238,36 @@ private Boolean Set(T model, Boolean add)
 
     /// <summary>获取所有数据行</summary>
     /// <returns></returns>
-    public IList<T> FindAll() => Query(null).ToList();
+    public IList<T> FindAll() => _cache?.ToList() ?? Query(null).ToList();
 
     /// <summary>获取满足条件的数据行，性能好，顺序查找</summary>
     /// <param name="predicate"></param>
     /// <param name="count"></param>
     /// <returns></returns>
     public IEnumerable<T> Query(Func<T, Boolean>? predicate, Int32 count = -1)
     {
+        // 开启事务时，直接返回缓存数据
+        if (_cache != null)
+        {
+            foreach (var item in _cache)
+            {
+                if (predicate == null || predicate(item))
+                {
+                    yield return item;
+
+                    if (--count == 0) break;
+                }
+            }
+            yield break;
+        }
+
         var file = GetFile();
         if (!File.Exists(file)) yield break;
 
         lock (this)
         {
             using var csv = new CsvFile(file, false) { Encoding = Encoding };
 
-            //var list = new List<T>();
             var headers = new Dictionary<String, Int32>();
             var pis = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
             while (true)
@@ -236,7 +306,6 @@ public IEnumerable<T> Query(Func<T, Boolean>? predicate, Int32 count = -1)
 
                         if (predicate == null || predicate(model))
                         {
-                            //list.Add(model);
                             flag = true;
                         }
                     }
@@ -254,15 +323,15 @@ public IEnumerable<T> Query(Func<T, Boolean>? predicate, Int32 count = -1)
                     if (--count == 0) break;
                 }
             }
-
-            //return list;
         }
     }
 
     /// <summary>获取数据行数，性能极好，文件行数（除头部）</summary>
     /// <returns></returns>
     public Int32 FindCount()
     {
+        if (_cache != null) return _cache!.Count;
+
         lock (this)
         {
             var file = GetFile();