Add deleteCount and updateCount (fixes #10).

esqueleto.cabal

@@ -55,7 +55,7 @@ library
   build-depends:
       base                 >= 4.5    && < 4.7
     , text                 == 0.11.*
-    , persistent           == 1.1.*
+    , persistent           >= 1.1.5  && < 1.2
     , transformers         >= 0.2
     , unordered-containers >= 0.2
 

src/Database/Esqueleto.hs

@@ -48,7 +48,9 @@ module Database.Esqueleto
   , selectSource
   , selectDistinctSource
   , delete
+  , deleteCount
   , update
+  , updateCount
 
     -- * Helpers
   , valkey

src/Database/Esqueleto/Internal/Sql.hs

@@ -20,7 +20,9 @@ module Database.Esqueleto.Internal.Sql
   , selectDistinct
   , selectDistinctSource
   , delete
+  , deleteCount
   , update
+  , updateCount
     -- * The guts
   , unsafeSqlBinOp
   , unsafeSqlValue
@@ -38,7 +40,7 @@ module Database.Esqueleto.Internal.Sql
 import Control.Applicative (Applicative(..), (<$>), (<$))
 import Control.Arrow ((***), first)
 import Control.Exception (throw, throwIO)
-import Control.Monad ((>=>), ap, MonadPlus(..))
+import Control.Monad ((>=>), ap, void, MonadPlus(..))
 import Control.Monad.IO.Class (MonadIO(..))
 import Control.Monad.Logger (MonadLogger)
 import Control.Monad.Trans.Class (lift)
@@ -49,7 +51,7 @@ import Data.Monoid (Monoid(..), (<>))
 import Database.Persist.EntityDef
 import Database.Persist.GenericSql
 import Database.Persist.GenericSql.Internal (Connection(escapeName, noLimit))
-import Database.Persist.GenericSql.Raw (execute, SqlBackend, withStmt)
+import Database.Persist.GenericSql.Raw (executeCount, SqlBackend, withStmt)
 import Database.Persist.Store hiding (delete)
 import qualified Control.Monad.Trans.Reader as R
 import qualified Control.Monad.Trans.State as S
@@ -589,10 +591,10 @@ rawExecute :: ( MonadLogger m
               , MonadResourceBase m )
            => Mode
            -> SqlQuery ()
-           -> SqlPersist m ()
+           -> SqlPersist m Int64
 rawExecute mode query = do
   conn <- SqlPersist R.ask
-  uncurry execute $
+  uncurry executeCount $
     first builderToText $
     toRawSql mode conn query
 
@@ -623,7 +625,15 @@ delete :: ( MonadLogger m
           , MonadResourceBase m )
        => SqlQuery ()
        -> SqlPersist m ()
-delete = rawExecute DELETE
+delete = void . deleteCount
+
+
+-- | Same as 'delete', but returns the number of rows affected.
+deleteCount :: ( MonadLogger m
+               , MonadResourceBase m )
+            => SqlQuery ()
+            -> SqlPersist m Int64
+deleteCount = rawExecute DELETE
 
 
 -- | Execute an @esqueleto@ @UPDATE@ query inside @persistent@'s
@@ -643,7 +653,16 @@ update :: ( MonadLogger m
           , SqlEntity val )
        => (SqlExpr (Entity val) -> SqlQuery ())
        -> SqlPersist m ()
-update = rawExecute UPDATE . from
+update = void . updateCount
+
+
+-- | Same as 'update', but returns the number of rows affected.
+updateCount :: ( MonadLogger m
+               , MonadResourceBase m
+               , SqlEntity val )
+            => (SqlExpr (Entity val) -> SqlQuery ())
+            -> SqlPersist m Int64
+updateCount = rawExecute UPDATE . from
 
 
 ----------------------------------------------------------------------

test/Test.hs

@@ -434,19 +434,22 @@ main = do
           p1e <- insert' p1
           p2e <- insert' p2
           p3e <- insert' p3
-          ret1 <- select $
-                  from $ \p -> do
-                  orderBy [asc (p ^. PersonName)]
-                  return p
+          let getAll = select $
+                       from $ \p -> do
+                       orderBy [asc (p ^. PersonName)]
+                       return p
+          ret1 <- getAll
           liftIO $ ret1 `shouldBe` [ p1e, p3e, p2e ]
           ()   <- delete $
                   from $ \p ->
                   where_ (p ^. PersonName ==. val (personName p1))
-          ret2 <- select $
-                  from $ \p -> do
-                  orderBy [asc (p ^. PersonName)]
-                  return p
+          ret2 <- getAll
           liftIO $ ret2 `shouldBe` [ p3e, p2e ]
+          n    <- deleteCount $
+                  from $ \p ->
+                  return ((p :: SqlExpr (Entity Person)) `seq` ())
+          ret3 <- getAll
+          liftIO $ (n, ret3) `shouldBe` (2, [])
 
     describe "update" $ do
       it "works on a simple example" $
@@ -459,12 +462,16 @@ main = do
                  set p [ PersonName =. val anon
                        , PersonAge *=. just (val 2) ]
                  where_ (p ^. PersonName !=. val "Mike")
+          n   <- updateCount $ \p -> do
+                 set p [ PersonAge +=. just (val 1) ]
+                 where_ (p ^. PersonName !=. val "Mike")
           ret <- select $
                  from $ \p -> do
                  orderBy [ asc (p ^. PersonName), asc (p ^. PersonAge) ]
                  return p
+          liftIO $ n `shouldBe` 2
           liftIO $ ret `shouldBe` [ Entity p2k (Person anon Nothing)
-                                  , Entity p1k (Person anon (Just 72))
+                                  , Entity p1k (Person anon (Just 73))
                                   , Entity p3k p3 ]
 
       it "works with a subexpression having COUNT(*)" $