项目 6 数据存储：仿冒 SqlClient（T-SQL 转写成 SQLite）、数据库页面、DataGridView、DateTimePicker

- 每个学生一套数据库，长期保存（data/databases/<用户编号>/库名.db）；学生程序运行时挂进沙箱可读写
- Sim.Data：SqlConnection / SqlCommand / SqlDataReader / SqlDataAdapter / SqlCommandBuilder / SqlParameter；
  连接字符串只按库名打开学生自己的库；ScriptDom 解析 T-SQL 后按白名单转写成 SQLite 语句，
  STRICT 表 + 元数据表还原 SQL Server 的列类型，报错编号和中文信息与 SQL Server 一致；
  INSERT 不写列名时跳过自增列，日期统一格式（书上 DateTime.ToString() 拼接的日期能正确比较）
- 常驻 SQL 服务（Sim.Runner sql-server）：数据库页面的查询、对象资源管理器，评分前按实验 database.sql 建库
- 数据库页面（代替 SSMS）：对象资源管理器、查询窗口、编辑前 200 行、表设计器、恢复实验初始数据
- DataGridView（绑定 DataView/DataTable/DataSet，单元格修改写回 DataTable）、DateTimePicker；设计器工具箱加入
- 评分：每个检查项一份新建的实验库；新增点 / 修改表格单元格、选日期、表格里有 / 没有某行的检查
- 示例：项目 6 任务 2、3；时间格式改成和中文 Windows 一致（9:05:03）；异常堆栈不暴露服务器路径
- 测试：数据库端到端、接口（每人只看到自己的库、恢复实验数据）、评分出错情况、T-SQL 生成

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

runtime/Sim.Data/Engine/Session.cs

@@ -0,0 +1,243 @@
+using System;
+using System.Collections.Generic;
+using System.Data.SqlClient;
+using System.Linq;
+using System.Text.RegularExpressions;
+using Microsoft.Data.Sqlite;
+using Microsoft.SqlServer.TransactSql.ScriptDom;
+
+namespace Sim.Data.Engine;
+
+/// <summary>结果集的一列：名字、T-SQL 类型（表达式列为 null），以及来自哪张表的哪一列（SqlCommandBuilder 生成语句时要用）</summary>
+internal sealed record ResultColumn(string Name, TSqlType? Type, string? BaseTable, string? BaseColumn, bool IsKey, bool IsIdentity, bool AllowNull)
+{
+    public Type ClrType => Type?.ClrType is { } t && t != typeof(object) ? t : typeof(object);
+}
+
+/// <summary>一个结果集（读完放在内存里）</summary>
+internal sealed record QueryResult(IReadOnlyList<ResultColumn> Columns, List<object[]> Rows);
+
+/// <summary>一批语句的执行结果：各个结果集和受影响的行数（只有增删改时才算，否则为 -1）</summary>
+internal sealed record BatchResult(List<QueryResult> Results, int RecordsAffected);
+
+/// <summary>
+/// 一个打开的数据库连接：当前库（USE 可以切换）、事务，执行一批 T-SQL。
+/// SqlConnection 和数据库页面的查询窗口都用它。
+/// </summary>
+internal sealed class Session : IDisposable
+{
+    private SqliteTransaction? _transaction;
+    private long _deadline = long.MaxValue;
+
+    public Session(DatabaseStore store, string database, TimeSpan? timeLimit = null)
+    {
+        Store = store;
+        TimeLimit = timeLimit;
+        Connection = Open(database);
+        Database = store.Resolve(database)!;
+    }
+
+    /// <summary>每批语句最长执行时间（数据库页面的查询窗口用；学生程序里由沙箱的 CPU 时间限制兜底）</summary>
+    public TimeSpan? TimeLimit { get; }
+
+    private SqliteConnection Open(string database)
+    {
+        var connection = Store.Open(database);
+        if (TimeLimit != null)
+        {
+            // 每执行一千条虚拟机指令检查一次，超时就中断（SQLite 报 interrupted）
+            SQLitePCL.raw.sqlite3_progress_handler(connection.Handle, 1000, _ => Environment.TickCount64 > _deadline ? 1 : 0, null);
+        }
+        return connection;
+    }
+
+    public DatabaseStore Store { get; }
+    public SqliteConnection Connection { get; private set; }
+    public string Database { get; private set; }
+    public bool InTransaction => _transaction != null;
+
+    public TableInfo? Lookup(string table) => DatabaseStore.GetTable(Connection, table);
+
+    public void ChangeDatabase(string name)
+    {
+        if (Store.Resolve(name) == null) throw SqlException.DatabaseNotFound(name);
+        if (_transaction != null) throw new SqlException(226, "在多语句事务内不允许使用 USE 语句。");
+        var next = Open(name);
+        Connection.Dispose();
+        Connection = next;
+        Database = Store.Resolve(name)!;
+    }
+
+    public void BeginTransaction()
+    {
+        if (_transaction != null) throw new InvalidOperationException("SqlConnection 不支持并行事务。");
+        _transaction = Connection.BeginTransaction();
+    }
+
+    public void Commit()
+    {
+        _transaction?.Commit();
+        _transaction = null;
+    }
+
+    public void Rollback()
+    {
+        _transaction?.Rollback();
+        _transaction = null;
+    }
+
+    /// <summary>执行一批语句；parameter 按名字（带不带 @ 都行）取参数值</summary>
+    public BatchResult Execute(string sql, Func<string, (bool Found, object? Value)> parameter)
+    {
+        var statements = Translator.Parse(sql);
+        if (TimeLimit is { } limit) _deadline = Environment.TickCount64 + (long)limit.TotalMilliseconds;
+        var results = new List<QueryResult>();
+        var affected = -1;
+        foreach (var parsed in statements)
+        {
+            var statement = Translate(parsed);
+            switch (statement)
+            {
+                case CreateDatabase create:
+                    Store.Create(create.Name);
+                    break;
+                case DropDatabases drop:
+                    foreach (var name in drop.Names)
+                    {
+                        if (string.Equals(Store.Resolve(name), Database, StringComparison.OrdinalIgnoreCase)) throw SqlException.DatabaseInUse(name);
+                        Store.Drop(name);
+                    }
+                    break;
+                case UseDatabase use:
+                    ChangeDatabase(use.Name);
+                    break;
+                case SqliteStatement run:
+                    var (result, changes) = Run(run, parameter);
+                    if (result != null) results.Add(result);
+                    else if (changes >= 0) affected = Math.Max(affected, 0) + changes;
+                    break;
+            }
+        }
+        return new BatchResult(results, affected);
+    }
+
+    private Statement Translate(TSqlStatement statement)
+    {
+        try
+        {
+            return Translator.Translate(statement, Lookup);
+        }
+        catch (SqliteException ex)
+        {
+            throw Map(ex);
+        }
+    }
+
+    private (QueryResult? Result, int Changes) Run(SqliteStatement statement, Func<string, (bool Found, object? Value)> parameter)
+    {
+        using var command = Connection.CreateCommand();
+        command.Transaction = _transaction;
+        command.CommandText = statement.Sql;
+        foreach (var name in statement.Parameters)
+        {
+            var (found, value) = parameter(name);
+            if (!found) throw SqlException.UndeclaredVariable(name);
+            command.Parameters.AddWithValue(name, Values.ToStorage(value) ?? DBNull.Value);
+        }
+
+        // 建表等语句和元数据一起提交；已经在学生的事务里时就用那个事务
+        var own = _transaction == null && statement.AfterExecute != null ? Connection.BeginTransaction() : null;
+        if (own != null) command.Transaction = own;
+        try
+        {
+            QueryResult? result = null;
+            int changes;
+            if (statement.IsQuery)
+            {
+                result = Read(command);
+                changes = -1;
+            }
+            else
+            {
+                changes = command.ExecuteNonQuery();
+                statement.AfterExecute?.Invoke(Connection);
+                if (statement.AfterExecute != null) changes = -1;
+            }
+            own?.Commit();
+            return (result, changes);
+        }
+        catch (SqliteException ex)
+        {
+            own?.Rollback();
+            throw Map(ex);
+        }
+        finally
+        {
+            own?.Dispose();
+        }
+    }
+
+    private QueryResult Read(SqliteCommand command)
+    {
+        using var reader = command.ExecuteReader();
+        var schema = reader.GetSchemaTable();
+        var tables = new Dictionary<string, TableInfo?>(StringComparer.OrdinalIgnoreCase);
+        var columns = new List<ResultColumn>();
+        for (var i = 0; i < reader.FieldCount; i++)
+        {
+            var row = schema.Rows[i];
+            var baseTable = row["BaseTableName"] as string;
+            var baseColumn = row["BaseColumnName"] as string;
+            ColumnInfo? info = null;
+            if (!string.IsNullOrEmpty(baseTable) && !string.IsNullOrEmpty(baseColumn))
+            {
+                if (!tables.TryGetValue(baseTable, out var table)) tables[baseTable] = table = Lookup(baseTable);
+                info = table?.Find(baseColumn);
+            }
+            columns.Add(new ResultColumn(reader.GetName(i), info?.Type, info != null ? baseTable : null, info?.Name,
+                info?.PrimaryKey ?? false, info?.Identity ?? false, info?.Nullable ?? true));
+        }
+        var rows = new List<object[]>();
+        while (reader.Read())
+        {
+            var values = new object[reader.FieldCount];
+            reader.GetValues(values);
+            for (var i = 0; i < values.Length; i++) values[i] = Values.FromStorage(values[i], columns[i].Type);
+            rows.Add(values);
+        }
+        return new QueryResult(columns, rows);
+    }
+
+    /// <summary>SQLite 的报错转成 SQL Server 的错误号和中文信息</summary>
+    private SqlException Map(SqliteException ex)
+    {
+        if (Functions.TakePending() is { } pending) return pending;
+        var message = ex.Message;
+        Match m;
+        if ((m = Regex.Match(message, @"no such table: (?:main\.)?(.+?)'?$")).Success) return SqlException.InvalidObject(m.Groups[1].Value);
+        // SQLite 对写错的列名会附带"是不是想写字符串"的提示，只取列名本身
+        if ((m = Regex.Match(message, @"no such column: ""?([^""\s']+)")).Success) return SqlException.InvalidColumn(m.Groups[1].Value);
+        if ((m = Regex.Match(message, @"ambiguous column name: (.+?)'?$")).Success) return SqlException.AmbiguousColumn(m.Groups[1].Value);
+        if ((m = Regex.Match(message, @"UNIQUE constraint failed: (\w+)\.")).Success) return SqlException.DuplicateKey(m.Groups[1].Value);
+        if ((m = Regex.Match(message, @"NOT NULL constraint failed: (.+?)\.(.+?)'?$")).Success)
+            return SqlException.NullNotAllowed(m.Groups[2].Value, $"{Database}.dbo.{m.Groups[1].Value}");
+        if (message.Contains("CHECK constraint failed: trunc:")) return SqlException.Truncated();
+        if ((m = Regex.Match(message, @"CHECK constraint failed: bit:(.+?)'?$")).Success) return new SqlException(245, $"列 '{m.Groups[1].Value}' 是 bit 类型，只能保存 0、1 或 NULL。");
+        if ((m = Regex.Match(message, @"cannot store (\w+) value in (\w+) column (.+?)\.(.+?)'?$")).Success)
+        {
+            var type = Lookup(m.Groups[3].Value)?.Find(m.Groups[4].Value)?.Type.Name ?? m.Groups[2].Value.ToLowerInvariant();
+            return new SqlException(245, $"将数据插入列 '{m.Groups[4].Value}' 时，无法把值转换成数据类型 {type}。");
+        }
+        if (message.Contains("database or disk is full")) return new SqlException(1105, "数据库已满：每个数据库最多约 50 MB。");
+        if (message.Contains("misuse of aggregate")) return new SqlException(147, "聚合不应出现在 WHERE 子句中，除非该聚合位于 HAVING 子句或选择列表所包含的子查询中。");
+        if (message.Contains("interrupted")) return new SqlException(-2, $"执行超时：查询超过 {TimeLimit?.TotalSeconds ?? 0} 秒，已停止。检查是否缺少 WHERE 条件或连接条件。");
+        if (message.Contains("database is locked")) return new SqlException(1222, "已超过了锁请求超时时段：数据库正被其他程序修改，请稍后再试。");
+        return new SqlException(50000, "执行出错：" + message.Replace("SQLite Error ", "").Trim());
+    }
+
+    public void Dispose()
+    {
+        _transaction?.Dispose();
+        Connection.Dispose();
+    }
+}