比较运算符

AGENTS.md

@@ -28,5 +28,5 @@
 - 改动说明只在交流中记录。
 
 ## 当前重点
-- 主线已完成：高级优化器 → 并行查询 → M1 会话隔离 → M2 快照事务 → M3 WAL 与崩溃恢复 → M4 表结构进 WAL → M5 系统表统一命名 → M6 检查点按 LSN 部分截断 → M7 事务写写冲突检测 → M8 事务保存点 → M9 角色继承 → M10 转授权 → M11 FROM 派生表与投影别名 → M12 `WITH` / CTE。
+- 主线已完成：高级优化器 → 并行查询 → M1 会话隔离 → M2 快照事务 → M3 WAL 与崩溃恢复 → M4 表结构进 WAL → M5 系统表统一命名 → M6 检查点按 LSN 部分截断 → M7 事务写写冲突检测 → M8 事务保存点 → M9 角色继承 → M10 转授权 → M11 FROM 派生表与投影别名 → M12 `WITH` / CTE → M13 比较运算符补全。
 - 进度与计数见 `agent_credientials/project-plan.txt`，限制与风险见 `agent_credientials/known-issues.txt`。

chusql-core/engine/src/ChuSQL/Core/Engine/Algebra/Eval.hs

@@ -327,6 +327,9 @@ substSubqueries db e env = case e of
     Gt a b -> bin Gt a b
     Lt a b -> bin Lt a b
     Eq a b -> bin Eq a b
+    GtE a b -> bin GtE a b
+    LtE a b -> bin LtE a b
+    NotEq a b -> bin NotEq a b
     And a b -> bin And a b
     Or a b -> bin Or a b
     IsNull a -> un IsNull a

chusql-core/engine/src/ChuSQL/Core/Engine/Algebra/Expr.hs

@@ -28,6 +28,9 @@ evalExpr (Neg a) row = do
 evalExpr (Gt a b) row = liftOperator OpGt a b row
 evalExpr (Lt a b) row = liftOperator OpLt a b row
 evalExpr (Eq a b) row = liftOperator OpEq a b row
+evalExpr (GtE a b) row = liftOperator OpGtE a b row
+evalExpr (LtE a b) row = liftOperator OpLtE a b row
+evalExpr (NotEq a b) row = liftOperator OpNe a b row
 evalExpr (And a b) row = liftOperator OpAnd a b row
 evalExpr (Or a b) row = liftOperator OpOr a b row
 evalExpr (IsNull a) row = do
@@ -61,6 +64,9 @@ colsInExpr (Neg a) = colsInExpr a
 colsInExpr (Gt a b) = colsInExpr a ++ colsInExpr b
 colsInExpr (Lt a b) = colsInExpr a ++ colsInExpr b
 colsInExpr (Eq a b) = colsInExpr a ++ colsInExpr b
+colsInExpr (GtE a b) = colsInExpr a ++ colsInExpr b
+colsInExpr (LtE a b) = colsInExpr a ++ colsInExpr b
+colsInExpr (NotEq a b) = colsInExpr a ++ colsInExpr b
 colsInExpr (And a b) = colsInExpr a ++ colsInExpr b
 colsInExpr (Or a b) = colsInExpr a ++ colsInExpr b
 colsInExpr (IsNull a) = colsInExpr a
@@ -87,6 +93,9 @@ hasDivision e = case e of
     Gt a b -> both a b
     Lt a b -> both a b
     Eq a b -> both a b
+    GtE a b -> both a b
+    LtE a b -> both a b
+    NotEq a b -> both a b
     And a b -> both a b
     Or a b -> both a b
     _ -> False
@@ -109,6 +118,9 @@ hasSubquery e = case e of
     Gt a b -> both a b
     Lt a b -> both a b
     Eq a b -> both a b
+    GtE a b -> both a b
+    LtE a b -> both a b
+    NotEq a b -> both a b
     And a b -> both a b
     Or a b -> both a b
     IsNull a -> hasSubquery a
@@ -140,6 +152,9 @@ aggregatesIn e = case e of
     Gt a b -> both a b
     Lt a b -> both a b
     Eq a b -> both a b
+    GtE a b -> both a b
+    LtE a b -> both a b
+    NotEq a b -> both a b
     And a b -> both a b
     Or a b -> both a b
     IsNull a -> aggregatesIn a
@@ -165,6 +180,9 @@ bareColumns e = case e of
     Gt a b -> both a b
     Lt a b -> both a b
     Eq a b -> both a b
+    GtE a b -> both a b
+    LtE a b -> both a b
+    NotEq a b -> both a b
     And a b -> both a b
     Or a b -> both a b
     IsNull a -> bareColumns a

chusql-core/engine/src/ChuSQL/Core/Engine/Algebra/JoinOrder.hs

@@ -62,6 +62,9 @@ scaleRows db p x rows = case p of
         _ -> quarter
     Gt _ _ -> quarter
     Lt _ _ -> quarter
+    GtE _ _ -> quarter
+    LtE _ _ -> quarter
+    NotEq _ _ -> quarter
     And a b -> max 1 (min (scaleRows db a x rows) (scaleRows db b x rows))
     _ -> quarter
   where

chusql-core/engine/src/ChuSQL/Core/Engine/Algebra/Optimize.hs

@@ -144,6 +144,9 @@ foldConstants (Neg a) = foldNode (Neg (foldConstants a))
 foldConstants (Gt a b) = foldNode (Gt (foldConstants a) (foldConstants b))
 foldConstants (Lt a b) = foldNode (Lt (foldConstants a) (foldConstants b))
 foldConstants (Eq a b) = foldNode (Eq (foldConstants a) (foldConstants b))
+foldConstants (GtE a b) = foldNode (GtE (foldConstants a) (foldConstants b))
+foldConstants (LtE a b) = foldNode (LtE (foldConstants a) (foldConstants b))
+foldConstants (NotEq a b) = foldNode (NotEq (foldConstants a) (foldConstants b))
 foldConstants (And a b) = foldNode (And (foldConstants a) (foldConstants b))
 foldConstants (Or a b) = foldNode (Or (foldConstants a) (foldConstants b))
 foldConstants e = e
@@ -180,6 +183,32 @@ rewriteNode db (Filter (Lt (Col k) (LitInt v)) (Scan mAlias t Nothing))
     | worthRange db t (unqualify mAlias k) = Range mAlias t (unqualify mAlias k) Nothing (Just (VInt v, False))
 rewriteNode db (Filter (Lt (Col k) (LitStr v)) (Scan mAlias t Nothing))
     | worthRange db t (unqualify mAlias k) = Range mAlias t (unqualify mAlias k) Nothing (Just (VStr v, False))
+rewriteNode db (Filter (And (GtE (Col k1) (LitInt lo)) (LtE (Col k2) (LitInt hi))) (Scan mAlias t Nothing))
+    | k1 == k2 && worthRange db t (unqualify mAlias k1) =
+        Range mAlias t (unqualify mAlias k1) (Just (VInt lo, True)) (Just (VInt hi, True))
+rewriteNode db (Filter (And (GtE (Col k1) (LitInt lo)) (Lt (Col k2) (LitInt hi))) (Scan mAlias t Nothing))
+    | k1 == k2 && worthRange db t (unqualify mAlias k1) =
+        Range mAlias t (unqualify mAlias k1) (Just (VInt lo, True)) (Just (VInt hi, False))
+rewriteNode db (Filter (And (Gt (Col k1) (LitInt lo)) (LtE (Col k2) (LitInt hi))) (Scan mAlias t Nothing))
+    | k1 == k2 && worthRange db t (unqualify mAlias k1) =
+        Range mAlias t (unqualify mAlias k1) (Just (VInt lo, False)) (Just (VInt hi, True))
+rewriteNode db (Filter (And (GtE (Col k1) (LitStr lo)) (LtE (Col k2) (LitStr hi))) (Scan mAlias t Nothing))
+    | k1 == k2 && worthRange db t (unqualify mAlias k1) =
+        Range mAlias t (unqualify mAlias k1) (Just (VStr lo, True)) (Just (VStr hi, True))
+rewriteNode db (Filter (And (GtE (Col k1) (LitStr lo)) (Lt (Col k2) (LitStr hi))) (Scan mAlias t Nothing))
+    | k1 == k2 && worthRange db t (unqualify mAlias k1) =
+        Range mAlias t (unqualify mAlias k1) (Just (VStr lo, True)) (Just (VStr hi, False))
+rewriteNode db (Filter (And (Gt (Col k1) (LitStr lo)) (LtE (Col k2) (LitStr hi))) (Scan mAlias t Nothing))
+    | k1 == k2 && worthRange db t (unqualify mAlias k1) =
+        Range mAlias t (unqualify mAlias k1) (Just (VStr lo, False)) (Just (VStr hi, True))
+rewriteNode db (Filter (GtE (Col k) (LitInt v)) (Scan mAlias t Nothing))
+    | worthRange db t (unqualify mAlias k) = Range mAlias t (unqualify mAlias k) (Just (VInt v, True)) Nothing
+rewriteNode db (Filter (GtE (Col k) (LitStr v)) (Scan mAlias t Nothing))
+    | worthRange db t (unqualify mAlias k) = Range mAlias t (unqualify mAlias k) (Just (VStr v, True)) Nothing
+rewriteNode db (Filter (LtE (Col k) (LitInt v)) (Scan mAlias t Nothing))
+    | worthRange db t (unqualify mAlias k) = Range mAlias t (unqualify mAlias k) Nothing (Just (VInt v, True))
+rewriteNode db (Filter (LtE (Col k) (LitStr v)) (Scan mAlias t Nothing))
+    | worthRange db t (unqualify mAlias k) = Range mAlias t (unqualify mAlias k) Nothing (Just (VStr v, True))
 rewriteNode db (Filter p (Join kind l r c))
     | not (hasDivision p || planHasDivision (Join kind l r c)) =
         case kind of

chusql-core/engine/src/ChuSQL/Core/Engine/Algebra/Planner.hs

@@ -44,6 +44,9 @@ rewriteAggs aggs e = case [label | (label, agg) <- aggs, agg == e] of
         Gt a b -> Gt (go a) (go b)
         Lt a b -> Lt (go a) (go b)
         Eq a b -> Eq (go a) (go b)
+        GtE a b -> GtE (go a) (go b)
+        LtE a b -> LtE (go a) (go b)
+        NotEq a b -> NotEq (go a) (go b)
         And a b -> And (go a) (go b)
         Or a b -> Or (go a) (go b)
         IsNull a -> IsNull (go a)

chusql-core/engine/src/ChuSQL/Core/Engine/Builtin.hs

@@ -137,6 +137,9 @@ data Operator
     | OpGt
     | OpLt
     | OpEq
+    | OpGtE
+    | OpLtE
+    | OpNe
     | OpAnd
     | OpOr
     deriving (Show, Eq, Enum, Bounded)
@@ -151,6 +154,9 @@ operatorSymbol OpNeg = "-"
 operatorSymbol OpGt = ">"
 operatorSymbol OpLt = "<"
 operatorSymbol OpEq = "="
+operatorSymbol OpGtE = ">="
+operatorSymbol OpLtE = "<="
+operatorSymbol OpNe = "<>"
 operatorSymbol OpAnd = "AND"
 operatorSymbol OpOr = "OR"
 
@@ -164,6 +170,9 @@ operatorOfExpr (Neg _) = Just OpNeg
 operatorOfExpr (Gt _ _) = Just OpGt
 operatorOfExpr (Lt _ _) = Just OpLt
 operatorOfExpr (Eq _ _) = Just OpEq
+operatorOfExpr (GtE _ _) = Just OpGtE
+operatorOfExpr (LtE _ _) = Just OpLtE
+operatorOfExpr (NotEq _ _) = Just OpNe
 operatorOfExpr (And _ _) = Just OpAnd
 operatorOfExpr (Or _ _) = Just OpOr
 operatorOfExpr _ = Nothing
@@ -175,6 +184,9 @@ executeOperator op vs = case (op, vs) of
     (OpGt, [x, y]) -> compareValues (== GT) x y
     (OpLt, [x, y]) -> compareValues (< EQ) x y
     (OpEq, [x, y]) -> compareValues (== EQ) x y
+    (OpGtE, [x, y]) -> compareValues (>= EQ) x y
+    (OpLtE, [x, y]) -> compareValues (<= EQ) x y
+    (OpNe, [x, y]) -> compareValues (/= EQ) x y
     (OpAnd, [x, y]) -> andValues x y
     (OpOr, [x, y]) -> orValues x y
     (_, [x, y]) | Just a <- arithOf op -> evalArith a x y

chusql-core/engine/src/ChuSQL/Core/Engine/Semantic.hs

@@ -137,6 +137,9 @@ inferExpr db place env (Neg a) = do
 inferExpr db place env (Gt a b) = comparison db place env a b
 inferExpr db place env (Lt a b) = comparison db place env a b
 inferExpr db place env (Eq a b) = comparison db place env a b
+inferExpr db place env (GtE a b) = comparison db place env a b
+inferExpr db place env (LtE a b) = comparison db place env a b
+inferExpr db place env (NotEq a b) = comparison db place env a b
 inferExpr db place env (And a b) = boolean db place env a b
 inferExpr db place env (Or a b) = boolean db place env a b
 inferExpr db place env (IsNull a) = inferExpr db place env a >> Right (InferType CBool)
@@ -597,6 +600,9 @@ resolveExpr db env outer f e = case e of
     Gt a b -> binary Gt a b
     Lt a b -> binary Lt a b
     Eq a b -> binary Eq a b
+    GtE a b -> binary GtE a b
+    LtE a b -> binary LtE a b
+    NotEq a b -> binary NotEq a b
     And a b -> binary And a b
     Or a b -> binary Or a b
     IsNull a -> IsNull <$> resolveExpr db env outer f a

chusql-core/engine/src/ChuSQL/Core/Engine/Syntax/AST.hs

@@ -107,6 +107,9 @@ data Expr
     | Gt Expr Expr
     | Lt Expr Expr
     | Eq Expr Expr
+    | GtE Expr Expr
+    | LtE Expr Expr
+    | NotEq Expr Expr
     | And Expr Expr
     | Or Expr Expr
     | IsNull Expr

chusql-core/engine/src/ChuSQL/Core/Engine/Syntax/Parser.hs

@@ -112,7 +112,10 @@ operatorTable =
     [ [Prefix (Neg <$ symbol "-")]
     , [InfixL (Mul <$ symbol "*"), InfixL (Div <$ symbol "/")]
     , [InfixL (Add <$ symbol "+"), InfixL (Sub <$ symbol "-")]
-    , [ InfixN (Gt <$ symbol ">")
+    , [ InfixN (NotEq <$ try (symbol "<>" <|> symbol "!="))
+        , InfixN (GtE <$ try (symbol ">="))
+        , InfixN (LtE <$ try (symbol "<="))
+        , InfixN (Gt <$ symbol ">")
         , InfixN (Lt <$ symbol "<")
         , InfixN (Eq <$ symbol "=")
         ]
@@ -695,6 +698,9 @@ expandExpr env e = case e of
     Gt a b -> Gt <$> go a <*> go b
     Lt a b -> Lt <$> go a <*> go b
     Eq a b -> Eq <$> go a <*> go b
+    GtE a b -> GtE <$> go a <*> go b
+    LtE a b -> LtE <$> go a <*> go b
+    NotEq a b -> NotEq <$> go a <*> go b
     And a b -> And <$> go a <*> go b
     Or a b -> Or <$> go a <*> go b
     Neg a -> Neg <$> go a

chusql-core/engine/test/Spec.hs

@@ -518,6 +518,90 @@ main = hspec $ do
         it "reports an unknown table for a name that is not a CTE" $ do
             sql "WITH t AS (SELECT name FROM users) SELECT x.name FROM x" `shouldSatisfy` isLeft
 
+    describe "ChuSQL.Core.Engine (比较运算符)" $ do
+        -- sql：在默认库上跑 SQL 取结果行
+        let sql input = parseStatement input >>= rowsOf . runStatement testDB
+            -- values：只取结果里的值
+            values input = fmap (map (map snd)) (sql input)
+
+        it "parses >= into GtE" $ do
+            parseStatement "SELECT name FROM users WHERE age >= 18"
+                `shouldBe` Right (Select ["name"] (FromTable Nothing "users") (Just (GtE (Col "age") (LitInt 18))) [] [] Nothing)
+
+        it "parses <= into LtE" $ do
+            parseStatement "SELECT name FROM users WHERE age <= 30"
+                `shouldBe` Right (Select ["name"] (FromTable Nothing "users") (Just (LtE (Col "age") (LitInt 30))) [] [] Nothing)
+
+        it "parses <> and != into the same node" $ do
+            sql "SELECT name FROM users WHERE age <> 17"
+                `shouldBe` sql "SELECT name FROM users WHERE age != 17"
+            values "SELECT name FROM users WHERE age <> 17 ORDER BY name"
+                `shouldBe` Right [[VStr "Alice"], [VStr "Carol"]]
+
+        it "runs >= and <=" $ do
+            values "SELECT name FROM users WHERE age >= 25 ORDER BY name"
+                `shouldBe` Right [[VStr "Alice"], [VStr "Carol"]]
+            values "SELECT name FROM users WHERE age <= 20" `shouldBe` Right [[VStr "Bob"]]
+
+        it "keeps comparisons with NULL three-valued" $ do
+            executeOperator OpGtE [VNull, VInt 1] `shouldBe` Right VNull
+            executeOperator OpLtE [VInt 1, VNull] `shouldBe` Right VNull
+            executeOperator OpNe [VNull, VInt 1] `shouldBe` Right VNull
+            executeOperator OpGtE [VInt 1, VFloat 1.0] `shouldBe` Right (VBool True)
+            executeOperator OpNe [VInt 1, VFloat 1.0] `shouldBe` Right (VBool False)
+
+        it "rewrites >= and <= into an inclusive index range" $ do
+            let stat rows distinct indexes = TableMeta rows [(c, d, False) | (c, d) <- distinct] indexes
+                dbWith m = [("users", Table "users" [("id", TInt), ("name", TStr)] [] (Just m))]
+                indexed = dbWith (stat 10000 [("id", 10000)] ["id"])
+                low = Filter (GtE (Col "id") (LitInt 2)) (Scan Nothing "users" Nothing)
+                both = Filter (And (GtE (Col "id") (LitInt 1)) (LtE (Col "id") (LitInt 3))) (Scan Nothing "users" Nothing)
+                halfOpenTop = Filter (And (GtE (Col "id") (LitInt 1)) (Lt (Col "id") (LitInt 3))) (Scan Nothing "users" Nothing)
+                halfOpenBottom = Filter (And (Gt (Col "id") (LitInt 1)) (LtE (Col "id") (LitInt 3))) (Scan Nothing "users" Nothing)
+            optimize indexed low `shouldBe` Range Nothing "users" "id" (Just (VInt 2, True)) Nothing
+            optimize indexed both
+                `shouldBe` Range Nothing "users" "id" (Just (VInt 1, True)) (Just (VInt 3, True))
+            -- 开区间那一端标记取反
+            optimize indexed halfOpenTop
+                `shouldBe` Range Nothing "users" "id" (Just (VInt 1, True)) (Just (VInt 3, False))
+            optimize indexed halfOpenBottom
+                `shouldBe` Range Nothing "users" "id" (Just (VInt 1, False)) (Just (VInt 3, True))
+            optimize indexed (Filter (LtE (Col "id") (LitInt 9)) (Scan Nothing "users" Nothing))
+                `shouldBe` Range Nothing "users" "id" Nothing (Just (VInt 9, True))
+            -- 统计说索引不划算时保持原样，交给全表扫
+            optimize (dbWith (stat 10000 [("id", 10000)] [])) low `shouldBe` low
+
+        it "uses an inclusive range on the real storage" $ do
+            withTestSession $ \srv -> withServerEnv srv $ do
+                _ <- runIPCStorage (runStatementM (CreateTable "rng_t" [("id", TInt), ("code", TInt)]))
+                _ <-
+                    runIPCStorage
+                        ( runStatementM
+                            ( Insert
+                                "rng_t"
+                                ["id", "code"]
+                                [ [LitInt 1, LitInt 500]
+                                , [LitInt 2, LitInt 501]
+                                , [LitInt 3, LitInt 502]
+                                , [LitInt 4, LitInt 503]
+                                ]
+                            )
+                        )
+                _ <- runIPCStorage (runStatementM (CreateIndex "rng_t" "code"))
+                -- ids：按条件取 id，只比较值
+                let ids cond =
+                        fmap (map (map snd))
+                            <$> runIPCStorage (runStatementM (makeSelect ["id"] "rng_t" (Just cond)))
+                ids (And (GtE (Col "code") (LitInt 501)) (LtE (Col "code") (LitInt 502)))
+                    `shouldReturn` Right [[VInt 2], [VInt 3]]
+                -- 闭端含边界、开端不含边界
+                ids (And (Gt (Col "code") (LitInt 501)) (LtE (Col "code") (LitInt 502)))
+                    `shouldReturn` Right [[VInt 3]]
+                ids (And (GtE (Col "code") (LitInt 501)) (Lt (Col "code") (LitInt 502)))
+                    `shouldReturn` Right [[VInt 2]]
+                ids (And (Gt (Col "code") (LitInt 501)) (Lt (Col "code") (LitInt 502)))
+                    `shouldReturn` Right []
+
     describe "ChuSQL.Core.Engine (SELECT)" $ do
         -- sql：在默认库上跑 SQL 取结果行
         let sql input = parseStatement input >>= rowsOf . runStatement testDB
@@ -2660,6 +2744,7 @@ planTables op = case op of
     Sort _ x -> planTables x
     Limit _ x -> planTables x
     Join _ l r _ -> planTables l ++ planTables r
+    Derived _ x -> planTables x
     Unit -> []
 
 -- | 计划里每个 Join 节点是不是 LEFT JOIN（先序）
@@ -2671,6 +2756,7 @@ leftJoinKinds (Aggregate _ _ x) = leftJoinKinds x
 leftJoinKinds (Filter _ x) = leftJoinKinds x
 leftJoinKinds (Sort _ x) = leftJoinKinds x
 leftJoinKinds (Limit _ x) = leftJoinKinds x
+leftJoinKinds (Derived _ x) = leftJoinKinds x
 leftJoinKinds _ = []
 
 -- | 取计划里第一个过滤条件
@@ -2688,6 +2774,7 @@ firstFilterCond (Join _ l r _) = case firstFilterCond l of
 firstFilterCond (Scan _ _ _) = Nothing
 firstFilterCond (Lookup _ _ _ _) = Nothing
 firstFilterCond (Range _ _ _ _ _) = Nothing
+firstFilterCond (Derived _ x) = firstFilterCond x
 
 -- | 判断计划里是否还有过滤节点
 anyFilter :: RelOp -> Bool
@@ -2702,6 +2789,7 @@ anyFilter (Join _ l r _) = anyFilter l || anyFilter r
 anyFilter (Scan _ _ _) = False
 anyFilter (Lookup _ _ _ _) = False
 anyFilter (Range _ _ _ _ _) = False
+anyFilter (Derived _ x) = anyFilter x
 
 -- | 去掉计划里的投影节点
 stripProjects :: RelOp -> RelOp
@@ -2716,6 +2804,7 @@ stripProjects (Join k l r c) = Join k (stripProjects l) (stripProjects r) c
 stripProjects (Scan a t _) = Scan a t Nothing
 stripProjects (Lookup a t c k) = Lookup a t c k
 stripProjects (Range a t c lo hi) = Range a t c lo hi
+stripProjects (Derived a x) = Derived a (stripProjects x)
 
 -- | 解析并做投影下推，返回计划
 projectedPlan :: String -> Either String RelOp

chusql-server/src/ChuSQL/Server/Backend.hs

@@ -300,6 +300,9 @@ exprTables expr = case expr of
     Gt a b -> both a b
     Lt a b -> both a b
     Eq a b -> both a b
+    GtE a b -> both a b
+    LtE a b -> both a b
+    NotEq a b -> both a b
     And a b -> both a b
     Or a b -> both a b
     Neg a -> exprTables a

chusql-server/test/Spec.hs

@@ -661,6 +661,15 @@ privilegeSpec = describe "server privileges" $ do
         authorizeSql service (Ordinary testAccount) "WITH d AS (SELECT product FROM orders) SELECT d.product FROM d"
             `shouldReturn` Left (PrivilegeError "forbidden" "permission denied: SELECT ON orders")
 
+    it "requires the privilege on the table inside a comparison subquery" $ withPrivileges $ \service root -> do
+        _ <- runPrivilegeCommand service root testDatabase (CreateRoleCommand "reader")
+        _ <- runPrivilegeCommand service root testDatabase (GrantPrivilegesCommand ["select"] "users" "reader" False)
+        _ <- runPrivilegeCommand service root testDatabase (GrantRoleCommand "reader" ["alice"])
+        authorizeSql service (Ordinary testAccount) "SELECT name FROM users WHERE id >= (SELECT id FROM users)"
+            `shouldReturn` Right ()
+        authorizeSql service (Ordinary testAccount) "SELECT name FROM users WHERE id >= (SELECT id FROM orders)"
+            `shouldReturn` Left (PrivilegeError "forbidden" "permission denied: SELECT ON orders")
+
     it "keeps the role tables on the real storage" $ withIpcStorage $ do
         base <- ipcBackend
         service <- newPrivileges base

docs/commands.md

@@ -52,6 +52,12 @@ csql -f json -e "SELECT count(*) FROM orders"
 - 投影列可以起别名：`SELECT count(*) AS total FROM orders`，别名就是结果集的列名。`ORDER BY` 仍按来源列解析，要引用派生表的列得写限定名（如 `ORDER BY d.total`）。
 - 鉴权覆盖整棵来源树：查派生表时内层表也要有权限，只有外层引用的表有权限不够。
 
+比较运算符：
+
+- 支持 `=`、`<>`（也可写 `!=`）、`>`、`>=`、`<`、`<=`；`<>` 与 `!=` 是同一个运算符。
+- `>`、`>=`、`<`、`<=` 在列上有索引时会改写成索引范围扫描；`>=` / `<=` 是闭区间，端点值本身也在结果里。
+- 任一操作数为 `NULL` 时比较结果是 `NULL`，`WHERE` 只保留结果为真的行。
+
 公共表表达式：
 
 - `WITH 名字 AS (SELECT …), 另一个 AS (SELECT …) SELECT … FROM 名字` 先定义再引用，名字可以带列清单（`WITH t(who) AS (SELECT name FROM users) …`）。