Merge pull request #1 from bergey/master

use foldr in combineParts, addressing the TODO item

Author: 3noch

benchmarks/Benchmarks.hs

@@ -0,0 +1,44 @@
+module Benchmarks where
+
+import Database.PostgreSQL.Simple.SqlQQ.Interpolated
+import Database.PostgreSQL.Simple.SqlQQ.Interpolated.Parser
+
+import Data.List (foldl')
+import Criterion
+import Criterion.Main
+import Language.Haskell.TH
+
+main = defaultMain
+    [ bench "combineParts foldl' length 2" $
+        nf combinePartsL' sql2
+    , bench "combineParts foldl' length 100" $
+        nf combinePartsL' sql100
+    , bench "combineParts foldr length 2" $ nf combinePartsR sql2
+    , bench "combineParts foldr length 100" $ nf combinePartsR sql100
+    ]
+
+
+sql2 :: [Either String Int]
+sql2 =
+    [ Left "SELECT field FROM table WHERE name = "
+    , Right 1
+    , Left " LIMIT "
+    , Right 2
+    ]
+
+sql100 :: [Either String Int]
+sql100 = concat [ [Left " ", Right n ] | n <- [1..100]]
+
+-- | The same as combineParts in the library, using foldl'
+combinePartsL' :: [Either String Int] -> (String, [Int])
+combinePartsL' = foldl' step ("", [])
+  where
+    step (s, exprs) subExpr = case subExpr of
+      Left str -> (s <> str, exprs)
+      Right e -> (s <> "?", exprs <> [e]) -- TODO: Make this not slow
+
+combinePartsR :: [Either String Int] -> (String, [Int])
+combinePartsR = foldr step ("", [])
+  where step subExpr (s, exprs) = case subExpr of
+            Left str -> (str <> s, exprs)
+            Right e -> ("?" <> s, e : exprs)

postgresql-simple-interpolate.cabal

@@ -29,3 +29,14 @@ library
     postgresql-simple >= 0.1,
     template-haskell
   ghc-options: -Wall -O2
+
+benchmark criterion
+    hs-source-dirs: benchmarks
+    main-is: Benchmarks.hs
+    ghc-options: -O2 -Wall -rtsopts
+    build-depends: postgresql-simple-interpolate
+                 , base
+                 , criterion
+    default-language:    Haskell2010
+    type: exitcode-stdio-1.0
+    

src/Database/PostgreSQL/Simple/SqlQQ/Interpolated.hs

@@ -5,7 +5,6 @@ module Database.PostgreSQL.Simple.SqlQQ.Interpolated (isql, quoteInterpolatedSql
 
 import Language.Haskell.TH (Exp, Q, appE, listE, sigE, tupE, varE)
 import Language.Haskell.TH.Quote (QuasiQuoter (..))
-import Data.List (foldl')
 import Database.PostgreSQL.Simple.ToField (Action, toField)
 import Database.PostgreSQL.Simple.SqlQQ (sql)
 import Text.Parsec (ParseError)
@@ -48,12 +47,12 @@ isql = QuasiQuoter
   }
 
 combineParts :: [StringPart] -> (String, [Q Exp])
-combineParts = foldl' step ("", [])
+combineParts = foldr step ("", [])
   where
-    step (s, exprs) subExpr = case subExpr of
-      Lit str -> (s <> str, exprs)
-      Esc c -> (s <> [c], exprs)
-      Anti e -> (s <> "?", exprs <> [e]) -- TODO: Make this not slow
+    step subExpr (s, exprs) = case subExpr of
+      Lit str -> (str <> s, exprs)
+      Esc c -> (c : s, exprs)
+      Anti e -> ('?' : s, e : exprs)
 
 applySql :: [StringPart] -> Q Exp
 applySql parts =