release: v0.4.1 — Aria 级联/ALTER/clearAll + 流式查询/派生表 + 正确性加固

新增：
- AriaEngine 外键级联（CASCADE/SET NULL/RESTRICT）+ clearAll() 重置 API
- 引擎级 alterTable：Aria DROP COLUMN 重写存储行 + schema 持久化
- 流式查询 queryStream / findStream（LSM 惰性扫描不物化）
- FROM 派生表 / 多列 ON 哈希连接 / COUNT(DISTINCT) / NULLS FIRST/LAST
- 普通列别名 + ORDER BY 别名 + 无表查询 + 字符串常量列
- 演示页引擎切换器（Memory/Aria）+ 预设自动重置

修复：
- Aria WAL DROP_TABLE 崩溃恢复（删表复活）+ 恢复后 WAL 截断
- Memory update/delete 索引维护（unique 约束绕过）
- 关联 EXISTS 绑定失效 / HAVING 标量子查询 / INSERT SELECT 位置错位
- 裸布尔列条件（WHERE done / CASE WHEN done）
- Aria $in 重复行 / JOIN 主表 WHERE 下推 / DROP INDEX 报错
- ORDER BY/GROUP BY/SELECT 表前缀列 + SQL '' 标准转义

质量：894 测试 · 47 套件 · 81.5% 覆盖率

src/sql/parser.ts

@@ -212,18 +212,37 @@ export class Parser {
       columns.push(...this.parseColumnList());
     }
 
-    // FROM
-    this.expect(TokenType.FROM);
-    const tableName = this.expectIdentifier('table name');
-
-    // 表别名（可选）
+    // FROM（v0.4.0 可选：SELECT 1 / SELECT 'lit' 无表查询）
+    let fromSubquery: SelectStatement | SelectUnionStatement | undefined;
+    let tableName = '';
     let alias: string | undefined;
-    if (this.curTokenIs(TokenType.AS)) {
-      this.nextToken();
-      alias = this.expectIdentifier('alias');
-    } else if (this.curToken.type === TokenType.IDENTIFIER && !this._isReservedAfterFrom()) {
-      alias = this.curToken.value;
+    if (this.curTokenIs(TokenType.FROM)) {
       this.nextToken();
+
+      // v0.4.0: FROM (SELECT ...) AS alias 派生表
+      if (this.curTokenIs(TokenType.LPAREN)) {
+        this.nextToken();
+        fromSubquery = this.parseSelect();
+        this.expect(TokenType.RPAREN);
+        if (this.curTokenIs(TokenType.AS)) {
+          this.nextToken();
+          alias = this.expectIdentifier('alias');
+        } else if (this.curToken.type === TokenType.IDENTIFIER && !this._isReservedAfterFrom()) {
+          alias = this.curToken.value;
+          this.nextToken();
+        }
+      } else {
+        tableName = this.expectIdentifier('table name');
+
+        // 表别名（可选）
+        if (this.curTokenIs(TokenType.AS)) {
+          this.nextToken();
+          alias = this.expectIdentifier('alias');
+        } else if (this.curToken.type === TokenType.IDENTIFIER && !this._isReservedAfterFrom()) {
+          alias = this.curToken.value;
+          this.nextToken();
+        }
+      }
     }
 
     const stmt: SelectStatement = {
@@ -234,6 +253,9 @@ export class Parser {
       alias,
       where: {},
     };
+    if (fromSubquery) {
+      stmt.fromSubquery = fromSubquery;
+    }
 
     // JOIN 子句（可选，支持多个）
     const joins = this.parseJoinClauses();
@@ -824,6 +846,17 @@ export class Parser {
       return result;
     }
 
+    // v0.4.1: 裸布尔列条件（WHERE done / CASE WHEN done THEN）— 列后直接是终止符时视为真值判断
+    if (
+      this.curTokenIs(TokenType.AND) || this.curTokenIs(TokenType.OR) ||
+      this.curTokenIs(TokenType.RPAREN) || this.curTokenIs(TokenType.EOF) ||
+      (this.curToken.type === TokenType.IDENTIFIER && ['THEN', 'END', 'ELSE', 'NULLS', 'LIMIT', 'OFFSET', 'ORDER', 'GROUP', 'HAVING', 'UNION', 'WHERE'].includes(this.curToken.value.toUpperCase()))
+    ) {
+      const result: WhereCondition = {};
+      result[column] = { $eq: true };
+      return result;
+    }
+
     // 比较运算符
     const op = this.parseComparisonOp();
 
@@ -897,15 +930,30 @@ export class Parser {
 
   private parseColumnList(): string[] {
     const cols: string[] = [];
-    cols.push(this.parseColumnRef());
+    cols.push(this.parseColumnWithAlias());
     while (this.curTokenIs(TokenType.COMMA)) {
       this.nextToken();
-      cols.push(this.parseColumnRef());
+      cols.push(this.parseColumnWithAlias());
     }
     return cols;
   }
 
-  /** 解析列引用：支持 'col'、'table.col'、'COUNT(*)'/'SUM(col)'、数字常量列（SELECT 1）和 CASE WHEN 表达式（v0.3.1） */
+  /** v0.3.3: 解析列（支持 `col AS alias` 显式别名与 `col alias` 隐式别名） */
+  private parseColumnWithAlias(): string {
+    let col = this.parseColumnRef();
+    if (this.curTokenIs(TokenType.AS)) {
+      this.nextToken();
+      const alias = this.expectIdentifier('alias');
+      col = `${col} AS ${alias}`;
+    } else if (this.curToken.type === TokenType.IDENTIFIER && !this._isReservedAfterFrom() && !this._isJoinKeyword()) {
+      const alias = this.curToken.value;
+      this.nextToken();
+      col = `${col} AS ${alias}`;
+    }
+    return col;
+  }
+
+  /** 解析列引用：支持 'col'、'table.col'、'COUNT(*)'/'SUM(col)'、数字常量列（SELECT 1）、字符串常量列（SELECT 'x'，v0.4.0）和 CASE WHEN 表达式（v0.3.1） */
   private parseColumnRef(): string {
     // CASE WHEN 表达式（v0.3.1）
     if (this.curTokenIs(TokenType.CASE)) {
@@ -919,6 +967,13 @@ export class Parser {
       return value;
     }
 
+    // v0.4.0: 字符串常量列：SELECT 'value' FROM t
+    if (this.curTokenIs(TokenType.STRING)) {
+      const value = this.curToken.value;
+      this.nextToken();
+      return `'${value}'`;
+    }
+
     // 聚合函数?
     if (
       this.curTokenIs(TokenType.COUNT) ||
@@ -973,11 +1028,19 @@ export class Parser {
     return text;
   }
 
-  /** 解析聚合函数调用: COUNT(*), SUM(col), AVG(col), MIN(col), MAX(col) */  private parseAggregateCall(): string {
+  /** 解析聚合函数调用: COUNT(*), SUM(col), AVG(col), MIN(col), MAX(col)，v0.4.0 支持 COUNT(DISTINCT col) */
+  private parseAggregateCall(): string {
     const func = this.curToken.value.toUpperCase();
     this.nextToken();
     this.expect(TokenType.LPAREN);
 
+    // v0.4.0: COUNT(DISTINCT col) 等去重聚合
+    let distinct = false;
+    if (this.curTokenIs(TokenType.DISTINCT)) {
+      distinct = true;
+      this.nextToken();
+    }
+
     let arg: string;
     if (this.curTokenIs(TokenType.STAR)) {
       arg = '*';
@@ -998,10 +1061,11 @@ export class Parser {
       this.nextToken();
     }
 
+    const inner = distinct ? `DISTINCT ${arg}` : arg;
     if (alias) {
-      return `${func}(${arg}) AS ${alias}`;
+      return `${func}(${inner}) AS ${alias}`;
     }
-    return `${func}(${arg})`;
+    return `${func}(${inner})`;
   }
 
   private _isAggregateAlias(): boolean {
@@ -1010,10 +1074,10 @@ export class Parser {
 
   private parseIdentifierList(): string[] {
     const ids: string[] = [];
-    ids.push(this.expectIdentifier('identifier'));
+    ids.push(this.parseIdentifierWithDot());
     while (this.curTokenIs(TokenType.COMMA)) {
       this.nextToken();
-      ids.push(this.expectIdentifier('identifier'));
+      ids.push(this.parseIdentifierWithDot());
     }
     return ids;
   }
@@ -1039,7 +1103,7 @@ export class Parser {
   }
 
   private parseOrderBy(): OrderBy {
-    const column = this.expectIdentifier('column name');
+    const column = this.parseIdentifierWithDot();
     let direction: SortDirection = 'asc';
     if (this.curTokenIs(TokenType.ASC)) {
       this.nextToken();
@@ -1047,7 +1111,29 @@ export class Parser {
       direction = 'desc';
       this.nextToken();
     }
-    return { column, direction };
+    // v0.4.0: NULLS FIRST / NULLS LAST
+    let nulls: 'first' | 'last' | undefined;
+    if (this.curTokenIs(TokenType.IDENTIFIER) && this.curToken.value.toUpperCase() === 'NULLS') {
+      this.nextToken();
+      if (this.curTokenIs(TokenType.IDENTIFIER) && this.curToken.value.toUpperCase() === 'FIRST') {
+        nulls = 'first';
+        this.nextToken();
+      } else if (this.curTokenIs(TokenType.IDENTIFIER) && this.curToken.value.toUpperCase() === 'LAST') {
+        nulls = 'last';
+        this.nextToken();
+      }
+    }
+    return { column, direction, ...(nulls ? { nulls } : {}) };
+  }
+
+  /** v0.4.0: 标识符（支持 'table.column' 带表前缀引用，用于 ORDER BY / GROUP BY） */
+  private parseIdentifierWithDot(): string {
+    const first = this.expectIdentifier('identifier');
+    if (this.curTokenIs(TokenType.DOT)) {
+      this.nextToken();
+      return `${first}.${this.expectIdentifier('identifier')}`;
+    }
+    return first;
   }
 
   /** 解析字面量值 */