rust部分推进：进程间通信（Windows平台命名管线）、内存页表、B+树、WAL恢复系统、动态配置

chusql-engine/src/ChuSQL/Algebra/Eval.hs

@@ -1,25 +1,41 @@
-module ChuSQL.Algebra.Eval (evalRelOp) where
+module ChuSQL.Algebra.Eval (evalRelOp, evalRelOpM) where
 
 import ChuSQL.Algebra.Expr (evalCondForRow)
 import ChuSQL.Algebra.Op
 import ChuSQL.Algebra.Sort (sortRows)
 import ChuSQL.Model
+import ChuSQL.Storage (MonadStorage (..))
+import ChuSQL.Syntax.AST (Expr (..))
 import Control.Monad (filterM)
 
--- 投影
+-- 执行：按关系算子树真正算出结果行（Scan 阶段会给列名加上别名前缀）。
+
+-- 投影：只保留清单里的列；哨兵 "*" 表示全部列。
 project :: [String] -> Row -> Row
 project ["*"] row = row
 project cs row = [(c, v) | (c, v) <- row, c `elem` cs]
 
--- 执行关系代数运算
+-- 给一行里的每个列名加上别名前缀（如 "u."）。
 addPrefix :: String -> Row -> Row
 addPrefix prefix = map (\(k, v) -> (prefix ++ k, v))
 
-evalRelOp :: Database -> RelOp -> Either String [Row]
-evalRelOp db (Scan mAlias tbl) = do
+-- 索引查找的约定：主键列名是 "id"（优化器只在这种情况下才把过滤改写成 Lookup）。
+keyCondition :: Int -> Expr
+keyCondition k = Eq (Col "id") (LitInt k)
+
+-- 扫描一张表；有别名就给每个列名加上前缀，JOIN 两边同名列靠它区分。
+evalScan :: Database -> Maybe String -> String -> Either String [Row]
+evalScan db mAlias tbl = do
     table <- lookupTable db tbl
     let prefix = maybe "" (++ ".") mAlias
     Right (map (addPrefix prefix) (tableRows table))
+
+-- 执行关系代数运算：Scan / Lookup / Filter / Project / Sort / Limit / Join 各一支。
+evalRelOp :: Database -> RelOp -> Either String [Row]
+evalRelOp db (Scan mAlias tbl) = evalScan db mAlias tbl
+evalRelOp db (Lookup tbl k) = do
+    rows <- evalScan db Nothing tbl
+    filterM (evalCondForRow (keyCondition k)) rows
 evalRelOp db (Filter e op) = do
     rows <- evalRelOp db op
     filterM (evalCondForRow e) rows
@@ -37,3 +53,35 @@ evalRelOp db (Join left right cond) = do
     rrows <- evalRelOp db right
     let cross = [l ++ r | l <- lrows, r <- rrows] -- 笛卡尔积
     filterM (evalCondForRow cond) cross
+
+-- | Monadic 版本：Lookup 直接问存储要一行（走索引），其余算子照原样递归。
+evalRelOpM :: (MonadStorage m) => Database -> RelOp -> m (Either String [Row])
+evalRelOpM _ (Lookup t k) = do
+    result <- lookupByKey t k
+    pure $ case result of
+        Left e -> Left e
+        Right Nothing -> Right []
+        Right (Just r) -> Right [r]
+evalRelOpM db (Scan a t) = pure (evalScan db a t)
+evalRelOpM db (Filter p x) = do
+    result <- evalRelOpM db x
+    pure $ do
+        rows <- result
+        filterM (evalCondForRow p) rows
+evalRelOpM db (Project cols x) = do
+    result <- evalRelOpM db x
+    pure (map (project cols) <$> result)
+evalRelOpM db (Sort specs x) = do
+    result <- evalRelOpM db x
+    pure (sortRows specs <$> result)
+evalRelOpM db (Limit n x) = do
+    result <- evalRelOpM db x
+    pure (take n <$> result)
+evalRelOpM db (Join l r c) = do
+    ls <- evalRelOpM db l
+    rs <- evalRelOpM db r
+    pure $ do
+        leftRows <- ls
+        rightRows <- rs
+        let cross = [x ++ y | x <- leftRows, y <- rightRows]
+        filterM (evalCondForRow c) cross