diff --git a/README.md b/README.md
index 6df3814..342d116 100644
--- a/README.md
+++ b/README.md
@@ -43,16 +43,16 @@
 > 如果找到了较好的Rust+Haskell集成方法也会及时替换
 
 # 性能基准
-
 **测试环境**：Windows / GHC 9.10.3 / `-O2`
 **数据规模**：`users`、`orders` 各 500 行，两表配对共 25 万对
-**计时方式**：CPU 时间，自适应批量（累计超过 0.3 秒后折算成单次耗时）
+**计时方式**：CPU 时间；每批至少 8 次迭代、累计超过 0.3 秒后固定批次，取 3 批中位数（避开时钟量化误差）
 
 | 查询                                       | 结果行数 |   未优化 |      优化后 |      加速 |
 | ------------------------------------------ | -------: | -------: | ----------: | --------: |
-| `JOIN` + `WHERE u.age > 90`                |       45 | 242.2 ms | **16.6 ms** | **14.6x** |
-| `JOIN`（无 WHERE，只有投影）               |      500 | 210.9 ms |    195.3 ms |      1.1x |
-| `JOIN` + `WHERE` + `ORDER BY` + `LIMIT 10` |       10 | 164.1 ms | **14.2 ms** | **11.6x** |
-| 单表 `WHERE age > 90`（对照组）            |       45 | 0.175 ms |    0.290 ms |      0.6x |
+| `JOIN` + `WHERE u.age > 90`                |       45 | 156.3 ms | **12.2 ms** | **12.8x** |
+| `JOIN`（无 WHERE，只有投影）               |      500 | 169.9 ms |    146.5 ms |      1.2x |
+| `JOIN` + `WHERE` + `ORDER BY` + `LIMIT 10` |       10 | 175.8 ms | **13.7 ms** | **12.9x** |
+| 单表 `WHERE age > 90`（对照组）            |       45 | 0.183 ms |    0.275 ms |      0.7x |
 
-> 最近更新：2026-09-22
+> 跑法：`cd benchmark/chusql-engine && stack run`（可选参数：`用户行数 订单数 单批目标秒数`，默认 `500 500 0.3`）
+> 最近更新：2026-09-24
diff --git a/benchmark/chusql-engine/src/Main.hs b/benchmark/chusql-engine/src/Main.hs
index 44f1fa9..0448db3 100644
--- a/benchmark/chusql-engine/src/Main.hs
+++ b/benchmark/chusql-engine/src/Main.hs
@@ -7,6 +7,7 @@ import ChuSQL.Model
 import ChuSQL.Syntax.Parser (parseStatement)
 import Control.Exception (evaluate)
 import Data.IORef (IORef, newIORef, readIORef)
+import Data.List (sort)
 import System.CPUTime (getCPUTime)
 import System.Environment (getArgs)
 import Text.Printf (printf)
@@ -79,14 +80,33 @@ timed act = do
     t1 <- getCPUTime
     return (fromIntegral (t1 - t0) / 1e12)
 
--- | 加倍批量次数再折算单次
+-- | 每批至少跑几次（减少 CPU 时钟量化误差）
+minBatch :: Int
+minBatch = 8
+
+-- | 取几批中位数
+rounds :: Int
+rounds = 3
+
+-- | 跑一批 k 次，返回总耗时
+timeBatch :: Int -> IO Int -> IO Double
+timeBatch k act = timed (mapM_ (const act) [1 .. k])
+
+-- | 中位数
+median :: [Double] -> Double
+median xs = sort xs !! (length xs `div` 2)
+
+-- | 自适应批量（够长且至少 8 次），取 3 批中位数
 benchOp :: Double -> IO Int -> IO (Double, Int)
-benchOp target act = loop 1
+benchOp target act = do
+    k <- pickBatch 1
+    ts <- mapM (const (timeBatch k act)) [1 .. rounds]
+    return (median ts / fromIntegral k, k)
   where
-    -- \| 批次翻倍直到超过目标
-    loop k = do
-        t <- timed (mapM_ (const act) [1 .. k])
-        if t < target then loop (k * 2) else return (t / fromIntegral k, k)
+    -- \| 批次翻倍直到累计超过目标
+    pickBatch k = do
+        t <- timeBatch k act
+        if t < target || k < minBatch then pickBatch (k * 2) else return k
 
 -- | 打印一个用例的对比
 report :: IORef String -> Database -> Double -> String -> IO ()
@@ -105,7 +125,12 @@ report saltRef db target sql = do
         (tOp * 1000)
         speedup
         mismatch
-    printf "    （实测批次：未优化 %d 次/批，优化后 %d 次/批）\n\n" kUn kOp
+    printf
+        "    （%d 次/批 × %d 批取中位数：未优化 %d 次/批，优化后 %d 次/批）\n\n"
+        minBatch
+        rounds
+        kUn
+        kOp
 
 queries :: [String]
 queries =
@@ -128,7 +153,7 @@ main = do
         target = pick 2 (0.3 :: Double)
         db = [("users", mkUsers n), ("orders", mkOrders n m)]
     printf "数据规模：users = %d 行，orders = %d 行\n" n m
-    printf "计时方式：CPU 时间；每个用例自动加倍批量次数，直到一批累计耗时超过 %.2f 秒，再折算成单次耗时\n" target
+    printf "计时方式：CPU 时间；每批至少 %d 次迭代、累计超过 %.2f 秒后固定批次，取 %d 批中位数\n" minBatch target rounds
     printf "（先跑一遍预热，避免把首次构造数据的开销算进去）\n\n"
     saltRef <- newIORef ""
     _ <- runOnce saltRef db warmupSql False
diff --git a/chusql-engine/src/ChuSQL/Algebra/Eval.hs b/chusql-engine/src/ChuSQL/Algebra/Eval.hs
index 714a309..9db8993 100644
--- a/chusql-engine/src/ChuSQL/Algebra/Eval.hs
+++ b/chusql-engine/src/ChuSQL/Algebra/Eval.hs
@@ -6,11 +6,12 @@ import ChuSQL.Algebra.Sort (sortRows)
 import ChuSQL.Model
 import ChuSQL.Storage (MonadStorage (..))
 import ChuSQL.Syntax.AST (Expr (..))
-import Control.Monad (filterM)
+import Control.Monad (filterM, foldM)
 
 -- 执行：按算子树算出结果行（Scan 阶段会加别名前缀）。
 
 -- * 工具
+
 -- | 只保留清单里的列
 project :: [String] -> Row -> Row
 project ["*"] row = row
@@ -31,7 +32,21 @@ evalScan db mAlias tbl = do
     let prefix = maybe "" (++ ".") mAlias
     Right (map (addPrefix prefix) (tableRows table))
 
+-- | 把两边的行按条件配对（边配边筛，不先建整张积表）
+filterPairs :: (Row -> Either String Bool) -> [Row] -> [Row] -> Either String [Row]
+filterPairs cond lrows rrows = go lrows []
+  where
+    go [] acc = Right (reverse acc)
+    go (l : ls) acc = do
+        acc' <- foldM (keep l) acc rrows
+        go ls acc'
+    keep l acc r = do
+        let row = l ++ r
+        ok <- cond row
+        pure (if ok then row : acc else acc)
+
 -- * 求值
+
 -- | 纯求值（不需要存储）
 evalRelOp :: Database -> RelOp -> Either String [Row]
 evalRelOp db (Scan mAlias tbl) = evalScan db mAlias tbl
@@ -53,37 +68,41 @@ evalRelOp db (Limit n op) = do
 evalRelOp db (Join left right cond) = do
     lrows <- evalRelOp db left
     rrows <- evalRelOp db right
-    let cross = [l ++ r | l <- lrows, r <- rrows]
-    filterM (evalCondForRow cond) cross
+    filterPairs (evalCondForRow cond) lrows rrows
 
 -- | 单子求值：Lookup 问存储
-evalRelOpM :: (MonadStorage m) => Database -> RelOp -> m (Either String [Row])
-evalRelOpM db (Scan a t) = pure (evalScan db a t)
-evalRelOpM _ (Lookup t k) = do
+evalRelOpM :: (MonadStorage m) => RelOp -> m (Either String [Row])
+evalRelOpM (Scan mAlias t) = do
+    result <- scan t
+    pure $ do
+        rows <- result
+        case mAlias of
+            Nothing -> Right rows
+            Just a -> Right (map (addPrefix (a ++ ".")) rows)
+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 (Filter p x) = do
-    result <- evalRelOpM db x
+        Right (Just row) -> Right [row]
+evalRelOpM (Filter p x) = do
+    result <- evalRelOpM 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
+evalRelOpM (Project cols x) = do
+    result <- evalRelOpM x
+    pure (fmap (map (project cols)) result)
+evalRelOpM (Sort spec x) = do
+    result <- evalRelOpM x
+    pure (fmap (sortRows spec) result)
+evalRelOpM (Limit n x) = do
+    result <- evalRelOpM x
+    pure (fmap (take n) result)
+evalRelOpM (Join l r cond) = do
+    ls <- evalRelOpM l
+    rs <- evalRelOpM r
     pure $ do
-        leftRows <- ls
-        rightRows <- rs
-        let cross = [x ++ y | x <- leftRows, y <- rightRows]
-        filterM (evalCondForRow c) cross
+        left <- ls
+        right <- rs
+        filterPairs (evalCondForRow cond) left right
diff --git a/chusql-engine/src/ChuSQL/Algebra/Sort.hs b/chusql-engine/src/ChuSQL/Algebra/Sort.hs
index 0dbb3a0..5e64cd7 100644
--- a/chusql-engine/src/ChuSQL/Algebra/Sort.hs
+++ b/chusql-engine/src/ChuSQL/Algebra/Sort.hs
@@ -19,21 +19,26 @@ compareValue (VStr a) (VStr b) = compare a b
 compareValue (VBool a) (VBool b) = compare a b
 compareValue _ _ = EQ
 
--- | 按排序要求比较两行
-compareRows :: [(String, SortDir)] -> Row -> Row -> Ordering
-compareRows [] _ _ = EQ
-compareRows ((col, dir) : rest) r1 r2 =
-    case (lookup col r1, lookup col r2) of
+-- | 取出排序键（按 spec 顺序，每行只查一次）
+sortKey :: [(String, SortDir)] -> Row -> [Maybe Value]
+sortKey spec row = [lookup col row | (col, _) <- spec]
+
+-- | 比较两个排序键
+compareKeys :: [(String, SortDir)] -> [Maybe Value] -> [Maybe Value] -> Ordering
+compareKeys [] _ _ = EQ
+compareKeys ((_, dir) : rest) (a : as) (b : bs) =
+    case (a, b) of
         (Just v1, Just v2) ->
             case compareValue v1 v2 of
-                EQ -> compareRows rest r1 r2
-                o ->
-                    if dir == Desc
-                        then flipOrdering o
-                        else o
-        _ -> compareRows rest r1 r2
+                EQ -> compareKeys rest as bs
+                o -> if dir == Desc then flipOrdering o else o
+        _ -> compareKeys rest as bs
+compareKeys _ _ _ = EQ
 
--- | 排序若干行
+-- | 排序若干行（先取键再排，避免每次比较都查列）
 sortRows :: [(String, SortDir)] -> [Row] -> [Row]
 sortRows [] rows = rows
-sortRows spec rows = sortBy (compareRows spec) rows
+sortRows spec rows = map snd (sortBy cmp (map decorate rows))
+  where
+    decorate row = (sortKey spec row, row)
+    cmp (k1, _) (k2, _) = compareKeys spec k1 k2
diff --git a/chusql-engine/src/ChuSQL/Engine.hs b/chusql-engine/src/ChuSQL/Engine.hs
index 03caff6..892fab5 100644
--- a/chusql-engine/src/ChuSQL/Engine.hs
+++ b/chusql-engine/src/ChuSQL/Engine.hs
@@ -14,6 +14,7 @@ import Control.Monad (filterM)
 -- 引擎入口：语义检查 + 分发执行，以及内存实现与泛型版本。
 
 -- * 对外入口
+
 -- | 跑一条语句（内存实现）
 runStatement :: Database -> Statement -> Either String (Database, [Row])
 runStatement db q = do
@@ -25,35 +26,36 @@ runStatement db q = do
 rowsOf :: Either String (Database, [Row]) -> Either String [Row]
 rowsOf = fmap snd
 
-
 -- | 泛型入口：先检查再执行
 runStatementM :: (MonadStorage m) => Statement -> m (Either String [Row])
 runStatementM q = do
     db <- snapshot
     case check db q of
         Left err -> pure (Left err)
-        Right _ -> runStatementUncheckedM q
+        Right _ -> runStatementUncheckedM db q
 
 -- * 分发执行
+
 -- | 按语句类型分发（已检查过）
-runStatementUncheckedM :: (MonadStorage m) => Statement -> m (Either String [Row])
-runStatementUncheckedM q@Select{} = do
-    db <- snapshot
+runStatementUncheckedM :: (MonadStorage m) => Database -> Statement -> m (Either String [Row])
+runStatementUncheckedM db q@Select{} =
     case translate q of
         Left e -> pure (Left e)
-        Right relOp -> evalRelOpM db (optimize db relOp)
-
-runStatementUncheckedM (Insert tbl cols vals) =
+        Right relOp -> evalRelOpM (optimize db relOp)
+runStatementUncheckedM _ (Insert tbl cols vals) =
     case mapM (\e -> evalExpr e []) vals of
         Left err -> pure (Left err)
         Right values
             | length cols /= length values ->
                 pure (Left "column count does not match value count")
             | otherwise -> do
-                result <- insert tbl (zip cols values)
+                let row = zip cols values
+                    key = case lookup "id" row of
+                        Just (VInt k) -> Just k
+                        _ -> Nothing
+                result <- insert tbl row key
                 pure (result >> Right [])
-
-runStatementUncheckedM (Delete tbl mWhere) = do
+runStatementUncheckedM _ (Delete tbl mWhere) = do
     rowsResult <- scan tbl
     case rowsResult of
         Left err -> pure (Left err)
@@ -70,8 +72,7 @@ runStatementUncheckedM (Delete tbl mWhere) = do
     -- \| 保留 = 条件不成立
     shouldKeep :: Expr -> Row -> Either String Bool
     shouldKeep e row = not <$> evalCondForRow e row
-
-runStatementUncheckedM (Update tbl assigns mWhere) = do
+runStatementUncheckedM _ (Update tbl assigns mWhere) = do
     rowsResult <- scan tbl
     case rowsResult of
         Left err -> pure (Left err)
@@ -90,15 +91,15 @@ runStatementUncheckedM (Update tbl assigns mWhere) = do
             Nothing -> Right True
             Just e -> evalCondForRow e row
         if keep then applyUpdates asgns row else Right row
-
-runStatementUncheckedM (CreateTable name cols) = do
+runStatementUncheckedM _ (CreateTable name cols) = do
     result <- createTable name cols
     pure (result >> Right [])
-runStatementUncheckedM (DropTable name) = do
+runStatementUncheckedM _ (DropTable name) = do
     result <- dropTable name
     pure (result >> Right [])
 
 -- * 更新辅助
+
 -- | 依次求值并覆盖列
 applyUpdates :: [(String, Expr)] -> Row -> Either String Row
 applyUpdates [] row = Right row
diff --git a/chusql-engine/src/ChuSQL/Storage.hs b/chusql-engine/src/ChuSQL/Storage.hs
index 8ee9a26..b06a0e5 100644
--- a/chusql-engine/src/ChuSQL/Storage.hs
+++ b/chusql-engine/src/ChuSQL/Storage.hs
@@ -12,7 +12,7 @@ class (Monad m) => MonadStorage m where
     scan :: String -> m (Either String [Row])
 
     -- \| 追加一行
-    insert :: String -> Row -> m (Either String ())
+    insert :: String -> Row -> Maybe Int -> m (Either String ())
 
     -- \| 整表替换
     replaceAll :: String -> [Row] -> m (Either String ())
diff --git a/chusql-engine/src/ChuSQL/Storage/IPC.hs b/chusql-engine/src/ChuSQL/Storage/IPC.hs
index facf87c..3f31e00 100644
--- a/chusql-engine/src/ChuSQL/Storage/IPC.hs
+++ b/chusql-engine/src/ChuSQL/Storage/IPC.hs
@@ -7,17 +7,19 @@ module ChuSQL.Storage.IPC (
     Response (..),
     SchemaColumn (..),
     sendRequest,
+    closeConnection,
     doListTables,
     doLookupByKey,
-    doInsertKeyed,
+    doInsertWith,
     doDescribeTable,
-    doCreateTable,
     doDropTable,
+    doListCatalog,
 ) where
 
 import ChuSQL.Model
 import ChuSQL.Storage
-import Control.Exception (IOException, bracket, try)
+import Control.Concurrent.MVar (MVar, modifyMVar, modifyMVar_, newMVar)
+import Control.Exception (IOException, try)
 import Data.Aeson (FromJSON (..), ToJSON (..), eitherDecodeStrict, encode, object, withObject, (.:), (.=))
 import Data.Aeson qualified as A
 import Data.Aeson.Key qualified as K
@@ -25,15 +27,16 @@ import Data.Aeson.KeyMap qualified as KM
 import Data.Aeson.Types (Parser)
 import Data.ByteString.Char8 qualified as BSC
 import Data.ByteString.Lazy qualified as BL
-import Data.List (nub)
 import Data.Scientific (floatingOrInteger)
 import Data.Text qualified as T
 import System.Environment (lookupEnv)
 import System.IO
+import System.IO.Unsafe (unsafePerformIO)
 
 -- IPC 存储实现：每个存储方法翻成管道上的一条 JSON 请求。
 
 -- * 存储实现
+
 -- | 命名管道上的存储
 newtype IPCStorage a = IPCStorage
     { runIPCStorage :: IO a
@@ -54,45 +57,80 @@ instance Monad IPCStorage where
         a <- m
         runIPCStorage (k a)
 
+-- * 全局连接缓存
+
+-- | 全局句柄缓存：按管道路径缓存，路径变了就换连接。
+{-# NOINLINE connectionRef #-}
+connectionRef :: MVar (Maybe (FilePath, Handle))
+connectionRef = unsafePerformIO (newMVar Nothing)
+
+-- | 打开管道
+openPipe :: FilePath -> IO Handle
+openPipe path = do
+    h <- openFile path ReadWriteMode
+    hSetBuffering h LineBuffering
+    hSetNewlineMode h noNewlineTranslation
+    pure h
+
+-- | 关掉缓存里的句柄（没有就什么都不做）
+closeCached :: Maybe (FilePath, Handle) -> IO ()
+closeCached Nothing = pure ()
+closeCached (Just (_, h)) = hClose h
+
+-- | 拿一个可用句柄；路径没变就复用，变了就换。
+getConnection :: FilePath -> IO Handle
+getConnection path = modifyMVar connectionRef $ \cached -> case cached of
+    Just (p, h)
+        | p == path -> pure (Just (p, h), h)
+    _ -> do
+        _ <- try (closeCached cached) :: IO (Either IOException ())
+        h <- openPipe path
+        pure (Just (path, h), h)
+
+-- | 丢掉缓存的连接（出错后调用，下次会重连）
+dropConnection :: IO ()
+dropConnection = modifyMVar_ connectionRef $ \cached -> do
+    _ <- try (closeCached cached) :: IO (Either IOException ())
+    pure Nothing
+
+-- | 关闭并清空连接。可选，进程退出前调用。
+closeConnection :: IO ()
+closeConnection = dropConnection
+
 -- * 管道
+
 -- | 管道路径
 pipePath :: IO String
 pipePath = do
     name <- maybe "chusql-storage" id <$> lookupEnv "CHUSQL_PIPE"
     pure ("\\\\.\\pipe\\" ++ name)
 
--- | 开管道跑闭包
-withPipe :: (Handle -> IO a) -> IO a
-withPipe = bracket openPipe hClose
-  where
-    -- \| 打开管道句柄
-    openPipe = do
-        path <- pipePath
-        h <- openFile path ReadWriteMode
-        hSetBuffering h LineBuffering
-        hSetNewlineMode h noNewlineTranslation
-        pure h
-
--- | 发一条请求读一条响应
+-- | 发一条请求读一条响应；管道不通就回 RespError，并丢掉缓存等下次重连。
 sendRequest :: Request -> IO Response
 sendRequest req = do
-    result <- try (withPipe roundTrip) :: IO (Either IOException Response)
-    pure $ case result of
-        Left e -> RespError ("pipe error: " ++ show e)
-        Right r -> r
-  where
-    roundTrip h = do
-        BL.hPutStr h (encode req)
-        BSC.hPutStr h "\n"
-        hFlush h
-        line <- BSC.hGetLine h
-        let cleaned = BSC.dropWhileEnd (== '\r') line
-        case eitherDecodeStrict cleaned of
-            Left err -> pure (RespError ("decode: " ++ err))
-            Right r -> pure r
+    path <- pipePath
+    result <- try (roundTrip req path) :: IO (Either IOException Response)
+    case result of
+        Left e -> do
+            dropConnection
+            pure (RespError ("pipe error: " ++ show e))
+        Right r -> pure r
 
+-- | 一条请求-响应往返（复用缓存里的句柄）
+roundTrip :: Request -> FilePath -> IO Response
+roundTrip req path = do
+    h <- getConnection path
+    BL.hPutStr h (encode req)
+    BSC.hPutStr h "\n"
+    hFlush h
+    line <- BSC.hGetLine h
+    let cleaned = BSC.dropWhileEnd (== '\r') line
+    case eitherDecodeStrict cleaned of
+        Left err -> pure (RespError ("decode: " ++ err))
+        Right r -> pure r
 
 -- * 编解码
+
 -- | 一列的 schema
 data SchemaColumn = SchemaColumn
     { scName :: String
@@ -112,6 +150,7 @@ instance FromJSON SchemaColumn where
         pure (SchemaColumn n t)
 
 -- * 请求
+
 -- | 请求类型
 data Request
     = ReqPing
@@ -123,6 +162,7 @@ data Request
     | ReqDescribeTable String
     | ReqCreateTable String [SchemaColumn]
     | ReqDropTable String
+    | ReqListCatalog
 
 -- | 请求编码
 instance ToJSON Request where
@@ -163,7 +203,7 @@ instance ToJSON Request where
             ]
     toJSON (ReqDropTable t) =
         object ["method" .= ("drop_table" :: T.Text), "table" .= t]
-
+    toJSON ReqListCatalog = object ["method" .= ("list_catalog" :: T.Text)]
 
 -- | 响应类型
 data Response
@@ -173,6 +213,7 @@ data Response
     | RespSchema [SchemaColumn] Int
     | RespOk
     | RespError String
+    | RespCatalog [(String, [SchemaColumn], Int)]
 
 -- | 响应解码
 instance FromJSON Response where
@@ -188,7 +229,18 @@ instance FromJSON Response where
                 cols <- o .: "columns"
                 cnt <- o .: "row_count"
                 pure (RespSchema cols cnt)
+            "catalog" -> do
+                xs <- o .: "schemas"
+                parsed <- mapM parseTableSchema xs
+                pure (RespCatalog parsed)
             other -> fail ("unknown status: " ++ T.unpack other)
+      where
+        -- \| 解析一条 list_catalog 记录。
+        parseTableSchema = withObject "TableSchema" $ \o -> do
+            t <- o .: "table"
+            cols <- o .: "columns"
+            cnt <- o .: "row_count"
+            pure (t, cols, cnt)
 
 -- | 值编码成 JSON
 valueToJSON :: Value -> A.Value
@@ -221,8 +273,8 @@ rowFromJSON (A.Object o) = mapM toPair (KM.toList o)
         pure (K.toString k, val)
 rowFromJSON _ = fail "row must be a JSON object"
 
-
 -- * 内部封装
+
 -- | 发 Scan
 doScan :: String -> IO (Either String [Row])
 doScan t = do
@@ -232,25 +284,10 @@ doScan t = do
         RespError e -> Left e
         _ -> Left "unexpected response to scan"
 
--- | 发 Insert（带 id 键）
-doInsert :: String -> Row -> IO (Either String ())
-doInsert t r = do
-    resp <- sendRequest (ReqInsert t r (rowKey r))
-    pure $ case resp of
-        RespOk -> Right ()
-        RespError e -> Left e
-        _ -> Left "unexpected response to insert"
-
--- | 取行里的 id 作索引键
-rowKey :: Row -> Maybe Int
-rowKey r = case lookup "id" r of
-    Just (VInt k) -> Just k
-    _ -> Nothing
-
--- | 发 Insert（指定键）
-doInsertKeyed :: String -> Row -> Int -> IO (Either String ())
-doInsertKeyed t r k = do
-    resp <- sendRequest (ReqInsert t r (Just k))
+-- | 发 Insert，可带索引键。
+doInsertWith :: String -> Row -> Maybe Int -> IO (Either String ())
+doInsertWith t r mk = do
+    resp <- sendRequest (ReqInsert t r mk)
     pure $ case resp of
         RespOk -> Right ()
         RespError e -> Left e
@@ -274,6 +311,15 @@ doListTables = do
         RespError e -> Left e
         _ -> Left "unexpected response to list_tables"
 
+-- | 一次拿全库 schema（表名 + 列 + 行数）。
+doListCatalog :: IO (Either String [(String, [SchemaColumn], Int)])
+doListCatalog = do
+    resp <- sendRequest ReqListCatalog
+    pure $ case resp of
+        RespCatalog xs -> Right xs
+        RespError e -> Left e
+        _ -> Left "unexpected response to list_catalog"
+
 -- | 发 LookupByIndex
 doLookupByKey :: String -> Int -> IO (Either String (Maybe Row))
 doLookupByKey t k = do
@@ -312,6 +358,7 @@ doDropTable t = do
         _ -> Left "unexpected response to drop_table"
 
 -- * 表结构
+
 -- | 线上 schema 转本地列
 schemaToColumns :: [SchemaColumn] -> [(String, Column)]
 schemaToColumns = map go
@@ -321,45 +368,15 @@ schemaToColumns = map go
     go (SchemaColumn n "bool") = (n, TBool)
     go (SchemaColumn n _) = (n, TStr)
 
--- | 从行推断列和类型
-inferColumns :: [Row] -> [(String, Column)]
-inferColumns rows = [(n, inferType n) | n <- names]
-  where
-    -- \| 出现过的列名
-    names = nub (concatMap (map fst) rows)
-
-    -- \| 按第一个值推断类型
-    inferType n = case [v | r <- rows, Just v <- [lookup n r]] of
-        (VInt _ : _) -> TInt
-        (VStr _ : _) -> TStr
-        (VBool _ : _) -> TBool
-        [] -> TStr
-
--- | 扫一张表拼成 Table
-loadTable :: String -> IO Table
-loadTable t = do
-    schemaR <- doDescribeTable t
-    case schemaR of
-        Right (cols, _n) -> do
-            rowsR <- doScan t
-            case rowsR of
-                Right rows -> pure (Table t (schemaToColumns cols) rows)
-                Left _ -> pure (Table t (schemaToColumns cols) [])
-        Left _ -> do
-            rowsR <- doScan t
-            case rowsR of
-                Right rows -> pure (Table t (inferColumns rows) rows)
-                Left _ -> pure (Table t [] [])
-
-
 -- * MonadStorage 实例
+
 -- | 存储方法全走管道
 instance MonadStorage IPCStorage where
     -- \| 发 Scan
     scan t = IPCStorage (doScan t)
 
     -- \| 发 Insert
-    insert t r = IPCStorage (doInsert t r)
+    insert t r mk = IPCStorage (doInsertWith t r mk)
 
     -- \| 发 ReplaceAll
     replaceAll t rs = IPCStorage (doReplaceAll t rs)
@@ -380,12 +397,12 @@ instance MonadStorage IPCStorage where
 
     -- \| 列表 + 逐表扫描拼库
     snapshot = IPCStorage $ do
-        result <- doListTables
+        result <- doListCatalog
         case result of
             Left _ -> pure []
-            Right ts -> mapM loadDbEntry ts
+            Right xs -> mapM loadEntry xs
       where
-        -- \| 加载一个 (表名, 表) 对
-        loadDbEntry t = do
-            tbl <- loadTable t
-            pure (t, tbl)
+        -- \| 加载一张表（schema 来自 catalog，行来自 scan）
+        loadEntry (t, cols, _n) = do
+            rows <- doScan t
+            pure (t, Table t (schemaToColumns cols) (either (const []) id rows))
diff --git a/chusql-engine/src/ChuSQL/Storage/Memory.hs b/chusql-engine/src/ChuSQL/Storage/Memory.hs
index 0e9b46f..41f1bf1 100644
--- a/chusql-engine/src/ChuSQL/Storage/Memory.hs
+++ b/chusql-engine/src/ChuSQL/Storage/Memory.hs
@@ -2,10 +2,12 @@ module ChuSQL.Storage.Memory (MemoryStorage (runMemoryStorage)) where
 
 import ChuSQL.Model
 import ChuSQL.Storage
+import Data.List (find)
 
 -- 内存实现：状态是 Database，错误通道是 Either String。
 
 -- * 实例
+
 -- | 内存存储：Database 上的状态
 newtype MemoryStorage a = MemoryStorage {runMemoryStorage :: Database -> Either String (a, Database)}
 
@@ -37,7 +39,7 @@ instance MonadStorage MemoryStorage where
         Right (Right (tableRows tbl), db)
 
     -- \| 追加一行
-    insert t r = MemoryStorage $ \db -> do
+    insert t r _ = MemoryStorage $ \db -> do
         tbl <- lookupTable db t
         Right (Right (), replaceTable t tbl{tableRows = tableRows tbl ++ [r]} db)
 
@@ -67,11 +69,10 @@ instance MonadStorage MemoryStorage where
     snapshot = MemoryStorage $ \db -> Right (db, db)
 
 -- * 工具
+
 -- | 按 id 列找一行
 findRow :: Table -> Int -> Maybe Row
-findRow tbl k = case filter matches (tableRows tbl) of
-    (r : _) -> Just r
-    [] -> Nothing
+findRow tbl k = find matches (tableRows tbl)
   where
     -- \| 这行的 id 是否等于 k
     matches r = lookup "id" r == Just (VInt k)
diff --git a/chusql-engine/src/ChuSQL/Syntax/AST.hs b/chusql-engine/src/ChuSQL/Syntax/AST.hs
index 7dff886..9398e35 100644
--- a/chusql-engine/src/ChuSQL/Syntax/AST.hs
+++ b/chusql-engine/src/ChuSQL/Syntax/AST.hs
@@ -5,6 +5,7 @@ import ChuSQL.Model (Column (..))
 -- 语法树：语句、数据来源、条件表达式、排序方向。
 
 -- * 语句
+
 -- | 一条语句：查 / 加 / 删 / 改 / 建表 / 删表
 data Statement
     = Select
@@ -28,6 +29,7 @@ data FromClause
     deriving (Show, Eq)
 
 -- * 表达式
+
 -- | 条件表达式
 data Expr
     = Col String
@@ -42,6 +44,7 @@ data Expr
     deriving (Show, Eq)
 
 -- * 排序
+
 -- | 排序方向
 data SortDir
     = Asc
@@ -49,6 +52,7 @@ data SortDir
     deriving (Show, Eq)
 
 -- * 构造
+
 -- | 造一个最简单的 SELECT
 makeSelect :: [String] -> String -> Maybe Expr -> Statement
 makeSelect cols tbl w =
diff --git a/chusql-engine/test/Spec.hs b/chusql-engine/test/Spec.hs
index f377aea..b899f85 100644
--- a/chusql-engine/test/Spec.hs
+++ b/chusql-engine/test/Spec.hs
@@ -11,8 +11,9 @@ import ChuSQL.Storage.IPC (IPCStorage (runIPCStorage), Request (ReqPing), Respon
 import ChuSQL.Syntax.AST
 import ChuSQL.Syntax.Parser
 import Control.Concurrent (threadDelay)
-import Control.Exception (IOException, bracket, try)
+import Control.Exception (IOException, bracket, finally, try)
 import Data.List (isInfixOf, sortOn)
+import Data.Unique (hashUnique, newUnique)
 import System.CPUTime (getCPUTime)
 import System.Directory (createDirectoryIfMissing, doesDirectoryExist, doesFileExist, getTemporaryDirectory, removePathForcibly)
 import System.Environment (getEnvironment, lookupEnv, setEnv, unsetEnv)
@@ -340,7 +341,12 @@ main = hspec $ do
         it "returns Left when a value has the wrong type for comparison" $ do
             runStatement testDB (Insert "users" ["name"] [Col "other"])
                 `shouldSatisfy` isLeft
-
+        it "writes id column to index and queries it back" $ do
+            case parseStatement "INSERT INTO users (id, name, age) VALUES (42, 'Zoe', 20)" >>= runStatement testDB of
+                Left err -> expectationFailure err
+                Right (db', _) -> do
+                    rowsOf (parseStatement "SELECT name FROM users WHERE id = 42" >>= runStatement db')
+                        `shouldBe` Right [[("name", VStr "Zoe")]]
     describe "ChuSQL.Engine (DELETE)" $ do
         it "parses DELETE with WHERE" $ do
             parseStatement "DELETE FROM users WHERE age < 18"
@@ -1102,7 +1108,7 @@ main = hspec $ do
         it "scan returns rows with all three value types after insert" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
                 let row = [("id", VInt 7), ("name", VStr "Alice"), ("flag", VBool True)]
-                runIPCStorage (insert "users" row) `shouldReturn` Right ()
+                runIPCStorage (insert "users" row (Just 7)) `shouldReturn` Right ()
                 rows <- runIPCStorage (scan "users")
                 (map sortRow <$> rows) `shouldBe` Right [sortRow row]
 
@@ -1113,7 +1119,7 @@ main = hspec $ do
 
         it "scan returns all 20 inserted rows in order" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                mapM_ (\i -> runIPCStorage (insert "many" [("id", VInt i)])) [1 .. 20 :: Int]
+                mapM_ (\i -> runIPCStorage (insert "many" [("id", VInt i)] (Just i))) [1 .. 20 :: Int]
                 rows <- runIPCStorage (scan "many")
                 fmap length rows `shouldBe` Right 20
                 fmap (sortOn show . map (lookup "id")) rows
@@ -1121,7 +1127,7 @@ main = hspec $ do
 
         it "replaceAll leaves only the new rows" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                runIPCStorage (insert "t" [("id", VInt 1)]) `shouldReturn` Right ()
+                runIPCStorage (insert "t" [("id", VInt 1)] (Just 1)) `shouldReturn` Right ()
                 runIPCStorage (replaceAll "t" [[("id", VInt 9)], [("id", VInt 8)]]) `shouldReturn` Right ()
                 rows <- runIPCStorage (scan "t")
                 fmap (sortOn show . map (lookup "id")) rows
@@ -1130,7 +1136,7 @@ main = hspec $ do
         it "lookupByKey finds a row inserted with an id over the pipe" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
                 let row = [("id", VInt 7), ("name", VStr "Zoe")]
-                runIPCStorage (insert "keyed" row) `shouldReturn` Right ()
+                runIPCStorage (insert "keyed" row (Just 7)) `shouldReturn` Right ()
                 found <- runIPCStorage (lookupByKey "keyed" 7)
                 fmap (fmap sortRow) found `shouldBe` Right (Just (sortRow row))
                 missing <- runIPCStorage (lookupByKey "keyed" 8)
@@ -1138,7 +1144,7 @@ main = hspec $ do
 
         it "replaceAll rebuilds the index over the pipe" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                runIPCStorage (insert "rb" [("id", VInt 1)]) `shouldReturn` Right ()
+                runIPCStorage (insert "rb" [("id", VInt 1)] (Just 1)) `shouldReturn` Right ()
                 runIPCStorage (replaceAll "rb" [[("id", VInt 9), ("name", VStr "Zoe")]]) `shouldReturn` Right ()
                 old <- runIPCStorage (lookupByKey "rb" 1)
                 old `shouldBe` Right Nothing
@@ -1148,8 +1154,8 @@ main = hspec $ do
 
         it "snapshot lists tables and scans each one to build the database" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                runIPCStorage (insert "a" [("id", VInt 1)]) `shouldReturn` Right ()
-                runIPCStorage (insert "b" [("id", VInt 2)]) `shouldReturn` Right ()
+                runIPCStorage (insert "a" [("id", VInt 1)] (Just 1)) `shouldReturn` Right ()
+                runIPCStorage (insert "b" [("id", VInt 2)] (Just 2)) `shouldReturn` Right ()
                 db <- runIPCStorage snapshot
                 map fst db `shouldBe` ["a", "b"]
                 map (length . tableRows . snd) db `shouldBe` [1, 1]
@@ -1157,8 +1163,8 @@ main = hspec $ do
 
         it "doListTables returns the tables that exist" $ do
             withTestServer $ \srv -> withServerEnv srv $ do
-                runIPCStorage (insert "t1" [("id", VInt 1)]) `shouldReturn` Right ()
-                runIPCStorage (insert "t2" [("id", VInt 2)]) `shouldReturn` Right ()
+                runIPCStorage (insert "t1" [("id", VInt 1)] (Just 1)) `shouldReturn` Right ()
+                runIPCStorage (insert "t2" [("id", VInt 2)] (Just 2)) `shouldReturn` Right ()
                 doListTables `shouldReturn` Right ["t1", "t2"]
 
         it "rows survive a restart on the same data directory" $ do
@@ -1168,7 +1174,7 @@ main = hspec $ do
                 Right bin -> do
                     srv1 <- startServer bin
                     let dir = dataDir srv1
-                    withServerEnv srv1 $ runIPCStorage (insert "persist" [("id", VInt 42)]) `shouldReturn` Right ()
+                    withServerEnv srv1 $ runIPCStorage (insert "persist" [("id", VInt 42)] (Just 42)) `shouldReturn` Right ()
                     stopServer srv1
                     srv2 <- startServerAt bin dir
                     rows <- withServerEnv srv2 $ runIPCStorage (scan "persist")
@@ -1180,6 +1186,31 @@ main = hspec $ do
             withPipeName "chusql-no-such-server" $ do
                 result <- runIPCStorage (scan "users")
                 result `shouldSatisfy` isLeft
+        it "INSERT then SELECT WHERE id = k via IPC" $ do
+            withTestServer $ \srv -> withServerEnv srv $ do
+                _ <-
+                    runIPCStorage
+                        ( runStatementM
+                            (CreateTable "ipc_idx" [("id", TInt), ("name", TStr)])
+                        )
+                _ <-
+                    runIPCStorage
+                        ( runStatementM
+                            (Insert "ipc_idx" ["id", "name"] [LitInt 42, LitStr "Zoe"])
+                        )
+                result <-
+                    runIPCStorage
+                        ( runStatementM
+                            ( Select
+                                { selectCols = ["name"]
+                                , selectFrom = FromTable Nothing "ipc_idx"
+                                , selectWhere = Just (Eq (Col "id") (LitInt 42))
+                                , selectOrderBy = []
+                                , selectLimit = Nothing
+                                }
+                            )
+                        )
+                result `shouldBe` Right [[("name", VStr "Zoe")]]
         it "parses CREATE TABLE with two columns" $ do
             parseStatement "CREATE TABLE users (id INT, name TEXT)"
                 `shouldBe` Right (CreateTable "users" [("id", TInt), ("name", TStr)])
@@ -1280,7 +1311,7 @@ locateServer = do
 
 startServer :: FilePath -> IO IPCServer
 startServer bin = do
-    stamp <- show <$> getCPUTime
+    stamp <- uniqueStamp
     tmp <- getTemporaryDirectory
     let dir = tmp </> "chusql-hs-IPC" </> stamp
     createDirectoryIfMissing True dir
@@ -1288,7 +1319,7 @@ startServer bin = do
 
 startServerAt :: FilePath -> FilePath -> IO IPCServer
 startServerAt bin dir = do
-    stamp <- show <$> getCPUTime
+    stamp <- uniqueStamp
     let name = "chusql-hs-test-" ++ stamp
     parentEnv <- getEnvironment
     (_, _, _, ph) <-
@@ -1302,6 +1333,13 @@ startServerAt bin dir = do
     waitUntilReady srv 100
     pure srv
 
+-- | 每次调用都不同的后缀：CPU 时间精度不够，再加上一个唯一编号。
+uniqueStamp :: IO String
+uniqueStamp = do
+    cpu <- getCPUTime
+    u <- hashUnique <$> newUnique
+    pure (show cpu ++ "-" ++ show u)
+
 waitUntilReady :: IPCServer -> Int -> IO ()
 waitUntilReady srv tries = do
     probe <- try (withServerEnv srv (sendRequest ReqPing)) :: IO (Either IOException Response)
@@ -1337,10 +1375,9 @@ withServerEnv srv act = do
     oldDir <- lookupEnv "CHUSQL_DATA_DIR"
     setEnv "CHUSQL_PIPE" (pipeName srv)
     setEnv "CHUSQL_DATA_DIR" (dataDir srv)
-    r <- act
-    restore "CHUSQL_PIPE" oldPipe
-    restore "CHUSQL_DATA_DIR" oldDir
-    pure r
+    act `finally` do
+        restore "CHUSQL_PIPE" oldPipe
+        restore "CHUSQL_DATA_DIR" oldDir
   where
     restore k = maybe (unsetEnv k) (setEnv k)
 
diff --git a/chusql-storage/src/bin/server.rs b/chusql-storage/src/bin/server.rs
index a4387b9..18c397b 100644
--- a/chusql-storage/src/bin/server.rs
+++ b/chusql-storage/src/bin/server.rs
@@ -9,7 +9,7 @@ use chusql_storage::catalog::Catalog;
 use chusql_storage::config::{self, Config, Loaded};
 use chusql_storage::heap::HeapTable;
 use chusql_storage::log;
-use chusql_storage::protocol::{Request, Response, SchemaColumn};
+use chusql_storage::protocol::{Request, Response, SchemaColumn, TableSchemaWire};
 use chusql_storage::wal::{Wal, WalOp};
 use chusql_storage::{log_debug, log_error, log_info, log_warn};
 use interprocess::local_socket::{
@@ -28,20 +28,22 @@ struct Server {
     cfg: Config,
     tables: Mutex<HashMap<String, Arc<Mutex<HeapTable>>>>,
     write_lock: Mutex<()>,
+    catalog: Mutex<Catalog>,
 }
 
 impl Server {
     /// 新建服务器状态
     fn new(cfg: Config) -> std::io::Result<Self> {
         std::fs::create_dir_all(&cfg.data_dir)?;
+        let catalog = Catalog::load(cfg.data_dir.join("catalog.json"))?;
         Ok(Server {
             cfg,
             tables: Mutex::new(HashMap::new()),
             write_lock: Mutex::new(()),
+            catalog: Mutex::new(catalog),
         })
     }
 
-
 // 路径
     /// 表名 -> 数据文件
     fn table_path(&self, table: &str) -> PathBuf {
@@ -125,7 +127,9 @@ impl Server {
         table: &str,
         f: impl FnOnce(&mut HeapTable) -> std::io::Result<R>,
     ) -> std::io::Result<R> {
-        if !self.table_exists(table) {
+        // 已经在缓存里的表不用再查磁盘（省一次 metadata 系统调用）
+        let cached = self.tables.lock().unwrap().contains_key(table);
+        if !cached && !self.table_exists(table) {
             return Err(std::io::Error::new(
                 std::io::ErrorKind::NotFound,
                 format!("unknown table: {}", table),
@@ -143,19 +147,21 @@ impl Server {
                     None => self.with_table(table, |t| t.insert(row))?,
                     Some(k) => self.with_indexed_table(table, |t| t.insert_keyed(row, *k))?,
                 }
-                let mut c = Catalog::load(self.catalog_path())?;
                 let row: chusql_storage::protocol::Row = row.clone().into_iter().collect();
-                c.record_insert(table, &row);
-                c.save(self.catalog_path())?;
+                let mut c = self.catalog.lock().unwrap();
+                if c.record_insert(table, &row) {
+                    c.save(self.catalog_path())?;
+                }
                 Ok(())
             }
             WalOp::ReplaceAll { table, rows } => {
                 self.with_indexed_table(table, |t| t.replace_all(rows))?;
-                let mut c = Catalog::load(self.catalog_path())?;
                 let rows: Vec<chusql_storage::protocol::Row> =
                     rows.iter().map(|r| r.clone().into_iter().collect()).collect();
-                c.record_replace_all(table, &rows);
-                c.save(self.catalog_path())?;
+                let mut c = self.catalog.lock().unwrap();
+                if c.record_replace_all(table, &rows) {
+                    c.save(self.catalog_path())?;
+                }
                 Ok(())
             }
         }
@@ -298,6 +304,21 @@ impl Server {
                 }
             }
 
+            Request::ListCatalog => {
+                log_debug!(pipe, "list_catalog");
+                let c = self.catalog.lock().unwrap();
+                let schemas: Vec<TableSchemaWire> = c
+                    .all_tables()
+                    .into_iter()
+                    .map(|(name, ts)| TableSchemaWire {
+                        table: name.to_string(),
+                        columns: ts.columns.clone(),
+                        row_count: ts.row_count,
+                    })
+                    .collect();
+                Response::Catalog { schemas }
+            }
+
             Request::DescribeTable { table } => {
                 log_debug!(pipe, "describe_table table={}", table);
                 match self.describe_table(&table) {
@@ -317,18 +338,13 @@ impl Server {
             Request::CreateTable { table, columns } => {
                 log_debug!(pipe, "create_table table={} cols={}", table, columns.len());
 
-                let mut c = match Catalog::load(self.catalog_path()) {
-                    Ok(c) => c,
-                    Err(e) => {
+                {
+                    let c = self.catalog.lock().unwrap();
+                    if c.describe(&table).is_some() {
                         return Response::Error {
-                            message: format!("create_table {}: catalog: {}", table, e),
-                        }
+                            message: format!("create_table {}: table already exists", table),
+                        };
                     }
-                };
-                if c.describe(&table).is_some() {
-                    return Response::Error {
-                        message: format!("create_table {}: table already exists", table),
-                    };
                 }
 
                 if let Err(e) = self.with_table(&table, |_t| Ok(())) {
@@ -337,6 +353,7 @@ impl Server {
                     };
                 }
 
+                let mut c = self.catalog.lock().unwrap();
                 if let Err(e) = c.create_table(&table, columns) {
                     return Response::Error {
                         message: format!("create_table {}: {}", table, e),
@@ -347,31 +364,27 @@ impl Server {
                         message: format!("create_table {}: catalog save: {}", table, e),
                     };
                 }
-
                 Response::Ok
             }
+
             Request::DropTable { table } => {
                 log_debug!(pipe, "drop_table table={}", table);
 
-                let mut c = match Catalog::load(self.catalog_path()) {
-                    Ok(c) => c,
-                    Err(e) => return Response::Error {
-                        message: format!("drop_table {}: catalog: {}", table, e),
-                    },
-                };
-                if let Err(e) = c.drop_table(&table) {
-                    return Response::Error {
-                        message: format!("drop_table {}: {}", table, e),
-                    };
-                }
-                if let Err(e) = c.save(self.catalog_path()) {
-                    return Response::Error {
-                        message: format!("drop_table {}: catalog save: {}", table, e),
-                    };
+                {
+                    let mut c = self.catalog.lock().unwrap();
+                    if let Err(e) = c.drop_table(&table) {
+                        return Response::Error {
+                            message: format!("drop_table {}: {}", table, e),
+                        };
+                    }
+                    if let Err(e) = c.save(self.catalog_path()) {
+                        return Response::Error {
+                            message: format!("drop_table {}: catalog save: {}", table, e),
+                        };
+                    }
                 }
 
                 self.tables.lock().unwrap().remove(&table);
-
                 let _ = std::fs::remove_file(self.table_path(&table));
                 let _ = std::fs::remove_file(self.index_path(&table));
 
@@ -384,12 +397,12 @@ impl Server {
     /// 表名：catalog 与目录取并集
     fn list_tables(&self) -> std::io::Result<Vec<String>> {
         let mut names = BTreeSet::new();
-
-        let c = Catalog::load(self.catalog_path())?;
-        for t in c.table_names() {
-            names.insert(t);
+        {
+            let c = self.catalog.lock().unwrap();
+            for t in c.table_names() {
+                names.insert(t);
+            }
         }
-
         let dir = &self.cfg.data_dir;
         if dir.exists() {
             for entry in std::fs::read_dir(dir)? {
@@ -400,19 +413,17 @@ impl Server {
                 }
             }
         }
-
         Ok(names.into_iter().collect())
     }
 
     /// 查一张表的 schema
     fn describe_table(&self, table: &str) -> std::io::Result<(Vec<SchemaColumn>, u64)> {
-        let c = Catalog::load(self.catalog_path())?;
+        let c = self.catalog.lock().unwrap();
         if let Some(schema) = c.describe(table) {
             return Ok((schema.columns.clone(), schema.row_count));
         }
-        if self.tables.lock().unwrap().contains_key(table)
-            || std::fs::metadata(self.table_path(table)).is_ok()
-        {
+        drop(c);
+        if std::fs::metadata(self.table_path(table)).is_ok() {
             return Ok((Vec::new(), 0));
         }
         Err(std::io::Error::new(
@@ -422,6 +433,14 @@ impl Server {
     }
 }
 
+impl Drop for Server {
+    fn drop(&mut self) {
+        if let Ok(c) = self.catalog.lock() {
+            let _ = c.save(self.catalog_path());
+        }
+    }
+}
+
 
 // 连接
 /// 处理一条连接
diff --git a/chusql-storage/src/btree.rs b/chusql-storage/src/btree.rs
index 5d4e536..a9e06b5 100644
--- a/chusql-storage/src/btree.rs
+++ b/chusql-storage/src/btree.rs
@@ -250,16 +250,14 @@ impl DiskBTree {
 
     /// 读根页号
     fn root(&mut self) -> io::Result<Option<PageId>> {
-        let meta = self.file.read_page(META_PAGE)?;
-        let r = read_u64(&meta, OFF_META_ROOT);
+        let r = self.file.with_page(META_PAGE, |p| read_u64(p, OFF_META_ROOT))?;
         Ok(if r == 0 { None } else { Some(r) })
     }
 
     /// 写根页号
     fn set_root(&mut self, r: Option<PageId>) -> io::Result<()> {
-        let mut meta = self.file.read_page(META_PAGE)?;
-        write_u64(&mut meta, OFF_META_ROOT, r.unwrap_or(0));
-        self.file.write_page(&meta)
+        self.file
+            .update_page(META_PAGE, |p| write_u64(p, OFF_META_ROOT, r.unwrap_or(0)))
     }
 
     /// 分配新页
@@ -292,8 +290,8 @@ impl DiskBTree {
 
     /// 递归查找
     fn get_rec(&mut self, page_id: PageId, key: i64) -> io::Result<Option<u64>> {
-        let p = self.file.read_page(page_id)?;
-        match read_node(&p, self.order) {
+        let order = self.order;
+        match self.file.with_page(page_id, |p| read_node(p, order))? {
             NodeData::Leaf { keys, values, .. } => {
                 Ok(keys.binary_search(&key).ok().map(|i| values[i]))
             }
@@ -345,9 +343,10 @@ impl DiskBTree {
         key: i64,
         value: u64,
     ) -> io::Result<(PageId, Option<(i64, PageId)>)> {
-        let p = self.file.read_page(page_id)?;
-        let limit = max_keys(self.order);
-        match read_node(&p, self.order) {
+        let order = self.order;
+        let node = self.file.with_page(page_id, |p| read_node(p, order))?;
+        let limit = max_keys(order);
+        match node {
             NodeData::Leaf { mut keys, mut values, next } => {
                 match keys.binary_search(&key) {
                     Ok(i) => values[i] = value,
@@ -357,9 +356,9 @@ impl DiskBTree {
                     }
                 }
                 if keys.len() <= limit {
-                    let mut p2 = self.new_page(page_id);
-                    write_node(&mut p2, &NodeData::Leaf { keys, values, next }, self.order);
-                    self.file.write_page(&p2)?;
+                    self.file.update_page(page_id, |p| {
+                        write_node(p, &NodeData::Leaf { keys, values, next }, order)
+                    })?;
                     Ok((page_id, None))
                 } else {
                     let mid = keys.len() / 2;
@@ -372,17 +371,13 @@ impl DiskBTree {
                     write_node(
                         &mut rp,
                         &NodeData::Leaf { keys: rkeys, values: rvalues, next },
-                        self.order,
+                        order,
                     );
                     self.file.write_page(&rp)?;
 
-                    let mut lp = self.new_page(page_id);
-                    write_node(
-                        &mut lp,
-                        &NodeData::Leaf { keys, values, next: right_id },
-                        self.order,
-                    );
-                    self.file.write_page(&lp)?;
+                    self.file.update_page(page_id, |p| {
+                        write_node(p, &NodeData::Leaf { keys, values, next: right_id }, order)
+                    })?;
 
                     Ok((page_id, Some((sep, right_id))))
                 }
@@ -394,22 +389,18 @@ impl DiskBTree {
                 children[i] = new_child;
                 match split {
                     None => {
-                        let mut p2 = self.new_page(page_id);
-                        write_node(&mut p2, &NodeData::Internal { keys, children }, self.order);
-                        self.file.write_page(&p2)?;
+                        self.file.update_page(page_id, |p| {
+                            write_node(p, &NodeData::Internal { keys, children }, order)
+                        })?;
                         Ok((page_id, None))
                     }
                     Some((sep, right_id)) => {
                         keys.insert(i, sep);
                         children.insert(i + 1, right_id);
                         if keys.len() <= limit {
-                            let mut p2 = self.new_page(page_id);
-                            write_node(
-                                &mut p2,
-                                &NodeData::Internal { keys, children },
-                                self.order,
-                            );
-                            self.file.write_page(&p2)?;
+                            self.file.update_page(page_id, |p| {
+                                write_node(p, &NodeData::Internal { keys, children }, order)
+                            })?;
                             Ok((page_id, None))
                         } else {
                             let mid = keys.len() / 2;
@@ -423,17 +414,13 @@ impl DiskBTree {
                             write_node(
                                 &mut rp,
                                 &NodeData::Internal { keys: rkeys, children: rchildren },
-                                self.order,
+                                order,
                             );
                             self.file.write_page(&rp)?;
 
-                            let mut lp = self.new_page(page_id);
-                            write_node(
-                                &mut lp,
-                                &NodeData::Internal { keys, children },
-                                self.order,
-                            );
-                            self.file.write_page(&lp)?;
+                            self.file.update_page(page_id, |p| {
+                                write_node(p, &NodeData::Internal { keys, children }, order)
+                            })?;
 
                             Ok((page_id, Some((up, right_id))))
                         }
@@ -454,8 +441,8 @@ impl DiskBTree {
 
     /// 中序遍历
     fn walk(&mut self, page_id: PageId, out: &mut Vec<(i64, u64)>) -> io::Result<()> {
-        let p = self.file.read_page(page_id)?;
-        match read_node(&p, self.order) {
+        let order = self.order;
+        match self.file.with_page(page_id, |p| read_node(p, order))? {
             NodeData::Leaf { keys, values, .. } => {
                 for i in 0..keys.len() {
                     out.push((keys[i], values[i]));
diff --git a/chusql-storage/src/catalog.rs b/chusql-storage/src/catalog.rs
index 5188b9a..076a403 100644
--- a/chusql-storage/src/catalog.rs
+++ b/chusql-storage/src/catalog.rs
@@ -39,6 +39,11 @@ impl Catalog {
         serde_json::from_slice(&bytes).map_err(io::Error::other)
     }
 
+    /// 返回所有表的 (表名, schema)。
+    pub fn all_tables(&self) -> Vec<(&str, &TableSchema)> {
+        self.tables.iter().map(|(k, v)| (k.as_str(), v)).collect()
+    }
+
     /// 写回文件
     pub fn save<P: AsRef<Path>>(&self, path: P) -> io::Result<()> {
         let bytes = serde_json::to_vec_pretty(self).map_err(io::Error::other)?;
@@ -98,22 +103,27 @@ impl Catalog {
         }
     }
     /// 记一次插入：补列 + 行数 +1
-    pub fn record_insert(&mut self, table: &str, row: &Row) {
+    pub fn record_insert(&mut self, table: &str, row: &Row) -> bool {
         let entry = self.tables.entry(table.to_string()).or_default();
+        let mut changed = false;
         for (k, v) in row {
             if entry.columns.iter().any(|c| &c.name == k) {
                 continue;
             }
             if let Some(ty) = infer_type(v) {
                 entry.columns.push(SchemaColumn { name: k.clone(), ty });
+                changed = true;
             }
         }
         entry.row_count += 1;
+        changed
     }
 
+
     /// 记一次整表替换：列照补，行数重置
-    pub fn record_replace_all(&mut self, table: &str, rows: &[Row]) {
+    pub fn record_replace_all(&mut self, table: &str, rows: &[Row]) -> bool {
         let entry = self.tables.entry(table.to_string()).or_default();
+        let mut changed = false;
         for r in rows {
             for (k, v) in r {
                 if entry.columns.iter().any(|c| &c.name == k) {
@@ -121,10 +131,12 @@ impl Catalog {
                 }
                 if let Some(ty) = infer_type(v) {
                     entry.columns.push(SchemaColumn { name: k.clone(), ty });
+                    changed = true;
                 }
             }
         }
         entry.row_count = rows.len() as u64;
+        changed
     }
 
     /// 删表
diff --git a/chusql-storage/src/config.rs b/chusql-storage/src/config.rs
index 1a3893f..5da95fb 100644
--- a/chusql-storage/src/config.rs
+++ b/chusql-storage/src/config.rs
@@ -11,7 +11,7 @@ use crate::log::Level;
 pub const DEFAULT_CONFIG_PATH: &str = "chusql-storage.toml";
 
 /// 默认池容量（页数）
-pub const DEFAULT_POOL_SIZE: usize = 64;
+pub const DEFAULT_POOL_SIZE: usize = 1024;
 /// 默认页大小
 pub const DEFAULT_PAGE_SIZE: usize = 4096;
 /// 默认 B+ 树 order
diff --git a/chusql-storage/src/heap.rs b/chusql-storage/src/heap.rs
index ebb6733..f7cc6df 100644
--- a/chusql-storage/src/heap.rs
+++ b/chusql-storage/src/heap.rs
@@ -177,10 +177,12 @@ impl HeapTable {
         let n = self.file.num_pages()?;
         if n > 0 {
             let last_id = n - 1;
-            let mut p = self.file.read_page(last_id)?;
-            if let Some(slot) = HeapPage::insert_tuple(&mut p, &tuple) {
-                self.file.write_page(&p)?;
-                return Ok((last_id, slot));
+            let mut slot = None;
+            self.file.update_page(last_id, |p| {
+                slot = HeapPage::insert_tuple(p, &tuple);
+            })?;
+            if let Some(s) = slot {
+                return Ok((last_id, s));
             }
         }
 
@@ -215,8 +217,8 @@ impl HeapTable {
 
     /// 按位置读一行
     pub fn read_at(&mut self, page_id: PageId, slot: u16) -> io::Result<Option<Row>> {
-        let p = self.file.read_page(page_id)?;
-        match HeapPage::get_tuple(&p, slot) {
+        let bytes = self.file.with_page(page_id, |p| HeapPage::get_tuple(p, slot))?;
+        match bytes {
             None => Ok(None),
             Some(bytes) => {
                 let row: Row = serde_json::from_slice(&bytes).map_err(io::Error::other)?;
@@ -230,13 +232,18 @@ impl HeapTable {
         let n = self.file.num_pages()?;
         let mut rows = Vec::new();
         for i in 0..n {
-            let p = self.file.read_page(i)?;
-            for slot in HeapPage::iter_slots(&p) {
-                if let Some(bytes) = HeapPage::get_tuple(&p, slot) {
-                    let row: Row = serde_json::from_slice(&bytes)
-                        .map_err(io::Error::other)?;
-                    rows.push(row);
+            let tuples = self.file.with_page(i, |p| {
+                let mut out = Vec::new();
+                for slot in HeapPage::iter_slots(p) {
+                    if let Some(bytes) = HeapPage::get_tuple(p, slot) {
+                        out.push(bytes);
+                    }
                 }
+                out
+            })?;
+            for bytes in tuples {
+                let row: Row = serde_json::from_slice(&bytes).map_err(io::Error::other)?;
+                rows.push(row);
             }
         }
         Ok(rows)
diff --git a/chusql-storage/src/page.rs b/chusql-storage/src/page.rs
index 763ad3c..f2f51f7 100644
--- a/chusql-storage/src/page.rs
+++ b/chusql-storage/src/page.rs
@@ -1,4 +1,4 @@
-use std::collections::{HashMap, HashSet, VecDeque};
+use std::collections::{HashMap, HashSet};
 use std::fs::{File, OpenOptions};
 use std::io::{self, Read, Seek, SeekFrom, Write};
 use std::path::Path;
@@ -41,7 +41,8 @@ pub struct PageFile {
     page_size: usize,
     capacity: usize,
     cache: HashMap<PageId, Page>,
-    order: VecDeque<PageId>,
+    last_used: HashMap<PageId, u64>,
+    clock: u64,
     dirty: HashSet<PageId>,
     hits: u64,
     misses: u64,
@@ -70,7 +71,8 @@ impl PageFile {
             page_size,
             capacity,
             cache: HashMap::new(),
-            order: VecDeque::new(),
+            last_used: HashMap::new(),
+            clock: 0,
             dirty: HashSet::new(),
             hits: 0,
             misses: 0,
@@ -116,26 +118,28 @@ impl PageFile {
 
     /// 标记为最近使用
     fn touch(&mut self, id: PageId) {
-        if let Some(pos) = self.order.iter().position(|&x| x == id) {
-            self.order.remove(pos);
-        }
-        self.order.push_back(id);
+        self.clock += 1;
+        self.last_used.insert(id, self.clock);
     }
 
     /// 淘汰一个最冷的页
     fn evict_one(&mut self) -> io::Result<bool> {
-        while let Some(victim) = self.order.pop_front() {
-            if let Some(p) = self.cache.get(&victim) {
-                if self.dirty.contains(&victim) {
-                    let p = p.clone();
-                    self.write_raw(&p)?;
-                    self.dirty.remove(&victim);
-                }
-                self.cache.remove(&victim);
-                return Ok(true);
-            }
+        let victim = self
+            .cache
+            .keys()
+            .min_by_key(|id| self.last_used.get(id).copied().unwrap_or(0))
+            .copied();
+        let Some(victim) = victim else {
+            return Ok(false);
+        };
+        if self.dirty.contains(&victim) {
+            let p = self.cache[&victim].clone();
+            self.write_raw(&p)?;
+            self.dirty.remove(&victim);
         }
-        Ok(false)
+        self.cache.remove(&victim);
+        self.last_used.remove(&victim);
+        Ok(true)
     }
 
     /// 直接写文件
@@ -166,20 +170,38 @@ impl PageFile {
 
     /// 读一页（走缓存）
     pub fn read_page(&mut self, id: PageId) -> io::Result<Page> {
-        if let Some(p) = self.cache.get(&id) {
-            let p = p.clone();
+        self.note_access(id)?;
+        Ok(self.cache[&id].clone())
+    }
+
+    /// 只读地用一页（走缓存，不整页拷贝）
+    pub fn with_page<R>(&mut self, id: PageId, f: impl FnOnce(&Page) -> R) -> io::Result<R> {
+        self.note_access(id)?;
+        Ok(f(&self.cache[&id]))
+    }
+
+    /// 就地改一页（走缓存，不整页拷贝）
+    pub fn update_page<R>(&mut self, id: PageId, f: impl FnOnce(&mut Page) -> R) -> io::Result<R> {
+        self.note_access(id)?;
+        let r = f(self.cache.get_mut(&id).expect("cached above"));
+        self.dirty.insert(id);
+        Ok(r)
+    }
+
+    /// 记一次访问：命中加 hits，未命中读进来并记 misses
+    fn note_access(&mut self, id: PageId) -> io::Result<()> {
+        if self.cache.contains_key(&id) {
             self.hits += 1;
-            self.touch(id);
-            return Ok(p);
+        } else {
+            self.misses += 1;
+            let p = self.read_raw(id)?;
+            if self.cache.len() >= self.capacity {
+                self.evict_one()?;
+            }
+            self.cache.insert(id, p);
         }
-        self.misses += 1;
-        let p = self.read_raw(id)?;
-        if self.cache.len() >= self.capacity {
-            self.evict_one()?;
-        }
-        self.cache.insert(id, p.clone());
-        self.order.push_back(id);
-        Ok(p)
+        self.touch(id);
+        Ok(())
     }
 
     /// 写一页（走缓存）
@@ -257,7 +279,7 @@ impl PageFile {
     /// 清空文件
     pub fn truncate(&mut self) -> io::Result<()> {
         self.cache.clear();
-        self.order.clear();
+        self.last_used.clear();
         self.dirty.clear();
         self.file.set_len(0)?;
         self.file.seek(SeekFrom::Start(0))?;
diff --git a/chusql-storage/src/protocol.rs b/chusql-storage/src/protocol.rs
index 44e6bac..7af16eb 100644
--- a/chusql-storage/src/protocol.rs
+++ b/chusql-storage/src/protocol.rs
@@ -43,6 +43,7 @@ pub enum Request {
         columns: Vec<SchemaColumn>,
     },
     DropTable { table: String },
+    ListCatalog
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -59,4 +60,13 @@ pub enum Response {
     },
     Ok,
     Error { message: String },
+    Catalog { schemas: Vec<TableSchemaWire> },
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TableSchemaWire {
+    pub table: String,
+    pub columns: Vec<SchemaColumn>,
+    #[serde(default)]
+    pub row_count: u64,
 }
diff --git a/chusql-storage/src/wal.rs b/chusql-storage/src/wal.rs
index 5f7251e..2b2afab 100644
--- a/chusql-storage/src/wal.rs
+++ b/chusql-storage/src/wal.rs
@@ -63,7 +63,7 @@ impl Wal {
             .append(true)
             .open(&self.path)?;
         f.write_all(&bytes)?;
-        f.sync_all()?;
+        f.sync_data()?;
         Ok(())
     }