完成查询优化：谓词下推、投影下推和常量折叠，配置好了benchmark

benchmark/chusql-engine/chusql-bench.cabal

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+cabal-version: 2.4
+
+name:           chusql-bench
+version:        1.0.0
+synopsis:       ChuSQL 查询优化基准测试（对比开/关优化器）
+build-type:     Simple
+
+executable chusql-bench
+    main-is:          Main.hs
+    hs-source-dirs:   src
+    build-depends:    base >= 4.14 && < 5
+                    , chusql-engine
+    default-language: Haskell2010
+    ghc-options:      -O2 -Wall

benchmark/chusql-engine/src/Main.hs

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+module Main where
+
+import ChuSQL.Algebra.Eval (evalRelOp)
+import ChuSQL.Algebra.Optimize (optimize)
+import ChuSQL.Algebra.Planner (translate)
+import ChuSQL.Model
+import ChuSQL.SQLSyntax.Parser (parseQuery)
+import Control.Exception (evaluate)
+import System.CPUTime (getCPUTime)
+import System.Environment (getArgs)
+import Text.Printf (printf)
+
+mkUsers :: Int -> Table
+mkUsers n =
+    Table
+        { tableName = "users"
+        , tableCols = ["id", "name", "age"]
+        , tableRows =
+            [ [("id", VInt i), ("name", VStr ("user" ++ show i)), ("age", VInt (i `mod` 100))]
+            | i <- [1 .. n]
+            ]
+        }
+
+mkOrders :: Int -> Int -> Table
+mkOrders n m =
+    Table
+        { tableName = "orders"
+        , tableCols = ["id", "user_id", "product"]
+        , tableRows =
+            [ [("id", VInt j), ("user_id", VInt (1 + (j - 1) `mod` n)), ("product", VStr ("item" ++ show (j `mod` 50)))]
+            | j <- [1 .. m]
+            ]
+        }
+
+checksum :: Either String [Row] -> Int
+checksum (Left _) = -1
+checksum (Right rows) = go 0 rows
+  where
+    go acc [] = acc
+    go acc (r : rs) = go (acc + length r) rs
+
+rowCount :: Either String [Row] -> Int
+rowCount (Left _) = -1
+rowCount (Right rows) = length rows
+
+runOnce :: Database -> String -> Bool -> IO Int
+runOnce db sql useOpt = do
+    let result = case parseQuery sql >>= translate db of
+            Left e -> Left e
+            Right plan -> evalRelOp db (if useOpt then optimize db plan else plan)
+    forced <- evaluate (checksum result)
+    return forced
+
+resultRows :: Database -> String -> Bool -> IO Int
+resultRows db sql useOpt = do
+    let result = case parseQuery sql >>= translate db of
+            Left e -> Left e
+            Right plan -> evalRelOp db (if useOpt then optimize db plan else plan)
+    _ <- evaluate (checksum result)
+    return (rowCount result)
+
+timed :: IO a -> IO Double
+timed act = do
+    t0 <- getCPUTime
+    _ <- act
+    t1 <- getCPUTime
+    return (fromIntegral (t1 - t0) / 1e12)
+
+benchOp :: Double -> IO Int -> IO (Double, Int)
+benchOp target act = loop 1
+  where
+    loop k = do
+        t <- timed (mapM_ (const act) [1 .. k])
+        if t < target then loop (k * 2) else return (t / fromIntegral k, k)
+
+report :: Database -> Double -> String -> IO ()
+report db target sql = do
+    nUn <- resultRows db sql False
+    nOp <- resultRows db sql True
+    (tUn, kUn) <- benchOp target (runOnce db sql False)
+    (tOp, kOp) <- benchOp target (runOnce db sql True)
+    let speedup = if tOp <= 0 then 0 else tUn / tOp
+        mismatch = if nUn == nOp then "" else "   <<< 结果不一致！"
+    printf "%s\n" sql
+    printf
+        "    结果行数 %-6d | 未优化 %9.3f ms | 优化后 %9.3f ms | 加速 %6.1fx%s\n"
+        nOp
+        (tUn * 1000)
+        (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
+
+queries :: [String]
+queries =
+    [ "SELECT u.name FROM users u JOIN orders o ON u.id = o.user_id WHERE u.age > 90"
+    , "SELECT u.name, o.product FROM users u JOIN orders o ON u.id = o.user_id"
+    , "SELECT u.name FROM users u JOIN orders o ON u.id = o.user_id WHERE u.age > 90 ORDER BY o.product LIMIT 10"
+    , "SELECT name FROM users WHERE age > 90"
+    ]
+
+warmupSql :: String
+warmupSql = "SELECT name FROM users"
+
+main :: IO ()
+main = do
+    args <- getArgs
+    let pick i d = if length args > i then read (args !! i) else d
+        n = pick 0 500
+        m = pick 1 500
+        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 "（先跑一遍预热，避免把首次构造数据的开销算进去）\n\n"
+    _ <- runOnce db warmupSql False
+    _ <- runOnce db warmupSql True
+    mapM_ (report db target) queries

benchmark/chusql-engine/stack.yaml

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+resolver: lts-24.59
+
+packages:
+    - .
+    - ../../chusql-engine

benchmark/chusql-engine/stack.yaml.lock

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+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/topics/lock_files
+
+packages: []
+snapshots:
+- completed:
+    sha256: 0f728e30e843d7f00460ad56858b995a3b227fca683659c7df9f2fc3988a3ce1
+    size: 732465
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/24/59.yaml
+  original: lts-24.59