事务保存点
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@@ -28,5 +28,5 @@
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- 改动说明只在交流中记录。
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## 当前重点
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- 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。
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- 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。
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- 进度与计数见 `agent_credientials/project-plan.txt`，限制与风险见 `agent_credientials/known-issues.txt`。
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@@ -137,6 +137,9 @@ runStatementUncheckedM _ ShowDatabases = runStatementM ShowDatabases
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runStatementUncheckedM _ BeginTransaction = pure (Left "BEGIN is executed by the session")
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runStatementUncheckedM _ CommitTransaction = pure (Left "COMMIT is executed by the session")
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runStatementUncheckedM _ RollbackTransaction = pure (Left "ROLLBACK is executed by the session")
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runStatementUncheckedM _ Savepoint{} = pure (Left "SAVEPOINT is executed by the session")
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runStatementUncheckedM _ RollbackToSavepoint{} = pure (Left "ROLLBACK TO is executed by the session")
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runStatementUncheckedM _ ReleaseSavepoint{} = pure (Left "RELEASE is executed by the session")
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-- | 只有需要读全表才能判断约束时才扫表
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existingRows :: (MonadStorage m) => String -> Table -> m (Either String [Row])
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@@ -437,6 +437,10 @@ checkResolvedWith db outer q = case q of
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BeginTransaction -> Right ()
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CommitTransaction -> Right ()
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RollbackTransaction -> Right ()
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-- | 保存点名字只是会话层的记号，不做列检查
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Savepoint _ -> Right ()
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RollbackToSavepoint _ -> Right ()
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ReleaseSavepoint _ -> Right ()
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where
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tableCols' = map fst . tableCols
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@@ -59,6 +59,12 @@ data Statement
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| CommitTransaction
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-- | 回滚事务
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| RollbackTransaction
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-- | 建保存点：SAVEPOINT 名字
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| Savepoint String
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-- | 回滚到保存点：ROLLBACK TO [SAVEPOINT] 名字
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| RollbackToSavepoint String
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-- | 释放保存点：RELEASE [SAVEPOINT] 名字
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| ReleaseSavepoint String
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deriving (Show, Eq)
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-- | 连接类型：内连接与左外连接
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@@ -619,7 +619,14 @@ transactionStatement =
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try (BeginTransaction <$ (keyword "start" *> keyword "transaction"))
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<|> (BeginTransaction <$ (keyword "begin" *> optional (keyword "transaction")))
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<|> (CommitTransaction <$ (keyword "commit" *> optional (keyword "transaction")))
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<|> try (RollbackToSavepoint <$> rollbackToName)
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<|> (RollbackTransaction <$ (keyword "rollback" *> optional (keyword "transaction")))
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<|> (Savepoint <$> (keyword "savepoint" *> identifier))
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<|> (ReleaseSavepoint <$> (keyword "release" *> optional (keyword "savepoint") *> identifier))
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where
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-- | ROLLBACK TO [SAVEPOINT] 名字
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rollbackToName =
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keyword "rollback" *> keyword "to" *> optional (keyword "savepoint") *> identifier
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-- | 解析总入口
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parseStatement :: String -> Either String Statement
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@@ -286,6 +286,17 @@ main = hspec $ do
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parseStatement "COMMIT TRANSACTION" `shouldBe` Right CommitTransaction
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parseStatement "ROLLBACK" `shouldBe` Right RollbackTransaction
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parseStatement "rollback transaction" `shouldBe` Right RollbackTransaction
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parseStatement "SAVEPOINT spot" `shouldBe` Right (Savepoint "spot")
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parseStatement "savepoint spot" `shouldBe` Right (Savepoint "spot")
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parseStatement "ROLLBACK TO spot" `shouldBe` Right (RollbackToSavepoint "spot")
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parseStatement "ROLLBACK TO SAVEPOINT spot" `shouldBe` Right (RollbackToSavepoint "spot")
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parseStatement "RELEASE spot" `shouldBe` Right (ReleaseSavepoint "spot")
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parseStatement "RELEASE SAVEPOINT spot" `shouldBe` Right (ReleaseSavepoint "spot")
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it "requires a name on savepoint statements" $ do
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parseStatement "SAVEPOINT" `shouldSatisfy` isLeft
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parseStatement "ROLLBACK TO" `shouldSatisfy` isLeft
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parseStatement "RELEASE" `shouldSatisfy` isLeft
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it "parses the bare words only as whole words" $ do
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parseStatement "BEGINNER" `shouldSatisfy` isLeft
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@@ -297,7 +308,7 @@ main = hspec $ do
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(runStatement [("users", users)] =<< parseStatement sql)
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`shouldSatisfy` either (isInfixOf "executed by the session") (const False)
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)
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["BEGIN", "COMMIT", "ROLLBACK"]
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["BEGIN", "COMMIT", "ROLLBACK", "SAVEPOINT spot", "ROLLBACK TO spot", "RELEASE spot"]
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it "puts transaction errors under the protocol category" $ do
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errorCode "BEGIN is executed by the session" `shouldBe` "query_error"
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@@ -69,10 +69,11 @@ data Session = Session
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, ssTransaction :: IORef (Maybe Transaction)
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}
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-- | 一条会话里的显式事务：开事务时的快照与事务内改到的状态
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-- | 一条会话里的显式事务：开事务时的快照、事务内改到的状态与保存点栈
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data Transaction = Transaction
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{ txBase :: Database
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, txStaged :: Database
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, txSavepoints :: [(String, Database)]
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}
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-- | 开一个会话：账号与角色服务、配置策略都和 Web 端一致
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@@ -191,6 +192,9 @@ runStatementCoded session sql = case parseStatement (T.unpack sql) of
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Right BeginTransaction -> beginTransaction session
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Right CommitTransaction -> commitTransaction session
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Right RollbackTransaction -> rollbackTransaction session
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Right (Savepoint name) -> savepointTransaction session (T.pack name)
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Right (RollbackToSavepoint name) -> rollbackToSavepoint session (T.pack name)
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Right (ReleaseSavepoint name) -> releaseSavepoint session (T.pack name)
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Right statement
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| Just command <- accountCommand statement -> runAccount session command
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| Just command <- privilegeCommand statement -> runPrivilege session command
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@@ -249,7 +253,7 @@ beginTransaction session = do
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case snapshotResult of
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Left err -> pure (Left (engineErrorCode err))
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Right db -> do
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writeIORef (ssTransaction session) (Just (Transaction db db))
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writeIORef (ssTransaction session) (Just (Transaction db db []))
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pure (Right (emptyResult (Just current)))
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-- | 提交：把快照差分交给存储层应用，成功才结束事务
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@@ -285,6 +289,54 @@ rollbackTransaction session = do
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writeIORef (ssTransaction session) Nothing
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pure (Right (emptyResult (Just current)))
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-- | 建保存点：把事务当前状态压进保存点栈
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savepointTransaction :: Session -> Text -> IO (Either SessionError QueryResult)
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savepointTransaction session name = do
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current <- readIORef (ssCurrent session)
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existing <- readIORef (ssTransaction session)
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case existing of
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Nothing -> pure (Left (SessionError "query_error" "no transaction in progress"))
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Just transaction -> do
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let stack = txSavepoints transaction ++ [(T.unpack name, txStaged transaction)]
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writeIORef (ssTransaction session) (Just transaction {txSavepoints = stack})
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pure (Right (emptyResult (Just current)))
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-- | 回滚到保存点：事务状态退回保存点，该保存点保留
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rollbackToSavepoint :: Session -> Text -> IO (Either SessionError QueryResult)
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rollbackToSavepoint session name = do
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current <- readIORef (ssCurrent session)
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existing <- readIORef (ssTransaction session)
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case existing of
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Nothing -> pure (Left (SessionError "query_error" "no transaction in progress"))
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Just transaction -> case savepointIndex name (txSavepoints transaction) of
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Nothing -> pure (Left (SessionError "query_error" ("no such savepoint: " <> name)))
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Just index -> do
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let (_, staged) = txSavepoints transaction !! index
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writeIORef
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(ssTransaction session)
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(Just transaction {txStaged = staged, txSavepoints = take (index + 1) (txSavepoints transaction)})
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pure (Right (emptyResult (Just current)))
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-- | 释放保存点：该保存点与它之后的保存点一起丢掉
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releaseSavepoint :: Session -> Text -> IO (Either SessionError QueryResult)
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releaseSavepoint session name = do
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current <- readIORef (ssCurrent session)
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existing <- readIORef (ssTransaction session)
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case existing of
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Nothing -> pure (Left (SessionError "query_error" "no transaction in progress"))
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Just transaction -> case savepointIndex name (txSavepoints transaction) of
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Nothing -> pure (Left (SessionError "query_error" ("no such savepoint: " <> name)))
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Just index -> do
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writeIORef (ssTransaction session) (Just transaction {txSavepoints = take index (txSavepoints transaction)})
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pure (Right (emptyResult (Just current)))
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-- | 最近一次同名保存点的下标
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savepointIndex :: Text -> [(String, Database)] -> Maybe Int
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savepointIndex name entries =
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case [index | (index, (label, _)) <- zip [0 ..] entries, T.pack label == name] of
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[] -> Nothing
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hits -> Just (last hits)
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-- | 事务里跑一条数据语句：只动内存快照，不碰存储层
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runInTransaction :: Session -> Statement -> IO (Either SessionError QueryResult)
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runInTransaction session statement = do
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@@ -788,6 +788,66 @@ transactionSpec = describe "server transactions" $ do
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ids <- sessionIds second
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ids `shouldMatchList` [1, 2, 3, 5]
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it "keeps the work before a savepoint and drops the work after it" $ withMemorySession $ \session -> do
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_ <- mustSql session "begin"
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_ <- mustSql session "update users set age = 31 where id = 1"
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_ <- mustSql session "savepoint spot"
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_ <- mustSql session "insert into users (id, name, age) values (6, 'six', 26)"
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_ <- mustSql session "delete from users where id = 2"
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_ <- mustSql session "rollback to spot"
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inside <- sessionIds session
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inside `shouldMatchList` [1, 2, 3, 4, 5]
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sessionAge session 1 `shouldReturn` Just 31
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_ <- mustSql session "commit"
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ids <- sessionIds session
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ids `shouldMatchList` [1, 2, 3, 4, 5]
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sessionAge session 1 `shouldReturn` Just 31
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it "lets a savepoint be used again after rolling back to it" $ withMemorySession $ \session -> do
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_ <- mustSql session "begin"
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_ <- mustSql session "insert into users (id, name, age) values (6, 'six', 26)"
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_ <- mustSql session "savepoint spot"
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_ <- mustSql session "insert into users (id, name, age) values (7, 'seven', 27)"
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_ <- mustSql session "rollback to spot"
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_ <- mustSql session "insert into users (id, name, age) values (8, 'eight', 28)"
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ids <- sessionIds session
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ids `shouldMatchList` [1, 2, 3, 4, 5, 6, 8]
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it "drops the savepoints above the one rolled back to" $ withMemorySession $ \session -> do
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_ <- mustSql session "begin"
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_ <- mustSql session "savepoint one"
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_ <- mustSql session "savepoint two"
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_ <- mustSql session "rollback to one"
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missing <- runStatementCoded session "rollback to two"
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failureMessage missing `shouldBe` "no such savepoint: two"
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it "drops a released savepoint and the ones after it" $ withMemorySession $ \session -> do
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_ <- mustSql session "begin"
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_ <- mustSql session "savepoint one"
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_ <- mustSql session "savepoint two"
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released <- mustSql session "release one"
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qrRowCount released `shouldBe` 0
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first <- runStatementCoded session "rollback to one"
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failureMessage first `shouldBe` "no such savepoint: one"
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second <- runStatementCoded session "rollback to two"
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failureMessage second `shouldBe` "no such savepoint: two"
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it "clears the savepoints on COMMIT" $ withMemorySession $ \session -> do
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_ <- mustSql session "begin"
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_ <- mustSql session "savepoint spot"
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_ <- mustSql session "commit"
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missing <- runStatementCoded session "rollback to spot"
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failureMessage missing `shouldBe` "no transaction in progress"
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it "needs a transaction and a known name for savepoints" $ withMemorySession $ \session -> do
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outside <- runStatementCoded session "savepoint spot"
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failureMessage outside `shouldBe` "no transaction in progress"
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_ <- mustSql session "begin"
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unknown <- runStatementCoded session "rollback to nowhere"
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failureMessage unknown `shouldBe` "no such savepoint: nowhere"
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gone <- runStatementCoded session "release nowhere"
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failureMessage gone `shouldBe` "no such savepoint: nowhere"
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it "needs a current database to start" $ do
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db <- newMVar testDb
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settings <- tempSettingsPath "transaction-bare"
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@@ -882,6 +942,26 @@ ipcConcurrencySpec = describe "server backend on the real storage" $ do
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rows <- rowsOf (beStatement alpha "SELECT id FROM t")
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intColumn "id" rows `shouldBe` [1]
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it "rolls back to a savepoint on the real storage" $ withIpcStorage $ do
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base <- ipcBackend
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mustRun (beStatement base "CREATE DATABASE alpha")
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let alpha = beWithDatabase base "alpha"
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settings <- tempSettingsPath "transaction-ipc-savepoint"
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removeIfExists settings
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session <- newSession alpha (T.pack testDatabaseName) settings
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_ <- mustSql session "use alpha"
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_ <- mustSql session "create table t (id int)"
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_ <- mustSql session "begin"
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_ <- mustSql session "insert into t (id) values (1)"
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_ <- mustSql session "savepoint spot"
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_ <- mustSql session "insert into t (id) values (2)"
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_ <- mustSql session "rollback to spot"
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inside <- mustSql session "select * from t"
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intValues (qrRows inside) `shouldBe` [1]
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_ <- mustSql session "commit"
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rows <- rowsOf (beStatement alpha "SELECT id FROM t")
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intColumn "id" rows `shouldBe` [1]
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it "refuses the second COMMIT on the real storage" $ withIpcStorage $ do
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base <- ipcBackend
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mustRun (beStatement base "CREATE DATABASE alpha")
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@@ -49,7 +49,7 @@ chusql-server
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语句里的库前缀和表限定符由引擎在语义层解析：存储层只接受精确的表名键，因此 `FROM sales.orders` 与选定 `sales` 后的 `FROM orders` 指向同一张表。
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显式事务在会话层实现：`BEGIN` 把当前数据库整库读成内存快照，事务内的语句都在快照上执行；`COMMIT` 先把快照、基线与库里现值按行 `id` 逐键比对，检测到写写冲突就报 `serialization_failure` 并保留事务；没有冲突才把差分用一条 `apply_transaction` 请求交给存储层应用；`ROLLBACK` 直接丢弃快照。因此隔离级别是快照读加原子提交：事务里看不到别的事务未提交或后来提交的改动，提交对外一次性可见，冲突由调用方回滚或重试。
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显式事务在会话层实现：`BEGIN` 把当前数据库整库读成内存快照，事务内的语句都在快照上执行；`SAVEPOINT` 把当前快照压进会话里的保存点栈，`ROLLBACK TO` 退回该点并保留它，`RELEASE` 丢掉该点与其后的保存点；`COMMIT` 先把快照、基线与库里现值按行 `id` 逐键比对，检测到写写冲突就报 `serialization_failure` 并保留事务；没有冲突才把差分用一条 `apply_transaction` 请求交给存储层应用；`ROLLBACK` 直接丢弃快照。因此隔离级别是快照读加原子提交：事务里看不到别的事务未提交或后来提交的改动，提交对外一次性可见，冲突由调用方回滚或重试。
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WAL 负责崩溃恢复：每条记录带自增 LSN，一组写操作与一条提交标记一次落盘；每组提交在数据和字典都刷盘之后把 `wal.checkpoint` 推进到这条提交的 LSN，含义是「到此为止的改动都已落盘」，再按这个边界丢掉日志前缀——所以日志里通常只有当组在飞的记录。进程重启时只重放检查点之后的记录，按标记分组取已提交的组、丢弃没有标记的整组，重放前逐条做幂等检查作为第二道保险，结束后再把检查点推到最后一条提交。LSN 从检查点与文件尾里较大的那个续号，跨重启单调，`SystemStatus` 应答里的 `last_lsn` 报告该检查点 LSN。建表、删表、建索引、删索引与数据改动走同一条 WAL，恢复时一并重放。
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+3
-1
@@ -48,10 +48,12 @@ csql -f json -e "SELECT count(*) FROM orders"
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事务：
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- `BEGIN`（或 `START TRANSACTION`）开始显式事务，`COMMIT` 提交，`ROLLBACK` 回滚。
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- `SAVEPOINT 名字` 在事务里记一个回滚点，`ROLLBACK TO 名字`（可写 `ROLLBACK TO SAVEPOINT 名字`）退回该点但保留它，`RELEASE 名字` 丢掉该点与它之后的回滚点。
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- 事务内只允许数据语句；DDL 与 `USE` 会被拒绝，`SHOW DATABASES` 这类不碰表数据的语句照常可用。
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- 事务里的读都看开事务那一刻的快照：别的连接在事务期间提交的改动不会出现在事务里，本会话未提交的改动别的连接也看不见。
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- 同一连接同时只能有一个事务，没有保存点与嵌套事务；开事务前要先选好数据库。
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- 同一连接同时只能有一个事务，没有嵌套事务；回滚点只在事务内有效，事务结束就没了。开事务前要先选好数据库。
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- 提交时按行 `id` 写回本事务改动过的行，事务没碰过的行不受影响；没有整数 `id` 的表按整表替换提交。
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- 提交前会比对基线：本事务改过的行如果已被别的连接改掉或删掉，提交报 `serialization_failure` 并保留事务，由调用方 `ROLLBACK` 或重试。
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- 提交是持久的：整批改动与一条提交标记一次落盘，提交后进程被强杀也会在重启时重放；提交前崩溃则整批丢弃，不会只落一半。
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### 交互模式
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