{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE ViewPatterns #-}
{-|
This snaplet makes it simple to use a PostgreSQL database from your Snap
application and is based on the excellent postgresql-simple library
(<http://hackage.haskell.org/package/postgresql-simple>) by Leon Smith
(adapted from Bryan O\'Sullivan\'s mysql-simple). Now, adding a database
to your web app takes just two simple steps.
First, include this snaplet in your application's state.
> data App = App
> { ... -- Other state needed in your app
> , _db :: Snaplet Postgres
> }
Next, call the pgsInit from your application's initializer.
> appInit = makeSnaplet ... $ do
> ...
> d <- nestSnaplet "db" db pgsInit
> return $ App ... d
Now you can use any of the postgresql-simple wrapper functions defined in this
module anywhere in your application handlers. For instance:
> postHandler :: Handler App App ()
> postHandler = do
> posts <- with db $ query_ "select * from blog_post"
> ...
Optionally, if you find yourself doing many database queries, you can eliminate some of the boilerplate by defining a HasPostgres instance for your application.
> instance HasPostgres (Handler b App) where
> getPostgresState = with db get
> setLocalPostgresState s = local (set (db . snapletValue) s)
With this code, our postHandler example no longer requires the 'with' function:
> postHandler :: Handler App App ()
> postHandler = do
> posts <- query_ "select * from blog_post"
> ...
If you have code that runs multiple queries but you want to make sure that you only use one database connection then you can use the withPG function, like so:
> postHandler :: Handler App App ()
> postHandler = withPG $ do
> posts <- query_ "select * from blog_post"
> links <- query_ "select * from links"
> ...
The first time you run an application with the postgresql-simple snaplet, a
configuration file @devel.cfg@ is created in the @snaplets/postgresql-simple@
directory underneath your project root. It specifies how to connect to your
PostgreSQL server and what user, password, and database to use. Edit this
file and modify the values appropriately and you'll be off and running.
If you want to have out-of-the-box authentication, look at the documentation
for the "Snap.Snaplet.Auth.Backends.PostgresqlSimple" module.
-}
module Snap.Snaplet.PostgresqlSimple (
-- * The Snaplet
Postgres(..)
, HasPostgres(..)
, PGSConfig(..)
, pgsDefaultConfig
, mkPGSConfig
, pgsInit
, pgsInit'
, getConnectionString
, withPG
, P.Connection
, liftPG
, liftPG'
-- * Wrappers and re-exports
, query
, query_
, fold
, foldWithOptions
, fold_
, foldWithOptions_
, forEach
, forEach_
, execute
, execute_
, executeMany
, returning
, withTransaction
, withTransactionLevel
, withTransactionMode
, formatMany
, formatQuery
-- Re-exported from postgresql-simple
, P.Query
, P.In(..)
, P.Binary(..)
, P.Only(..)
, P.SqlError(..)
, P.FormatError(..)
, P.QueryError(..)
, P.ResultError(..)
, P.TransactionMode(..)
, P.IsolationLevel(..)
, P.ReadWriteMode(..)
, P.begin
, P.beginLevel
, P.beginMode
, P.rollback
, P.commit
, (P.:.)(..)
, ToRow(..)
, FromRow(..)
, P.defaultConnectInfo
, P.defaultTransactionMode
, P.defaultIsolationLevel
, P.defaultReadWriteMode
, field
) where
import Control.Applicative
import qualified Control.Exception as E
import Control.Lens (set, (^#))
import Control.Monad (liftM)
import Control.Monad.IO.Class (MonadIO, liftIO)
import Control.Monad.Reader (ReaderT, ask, asks,
local)
import Control.Monad.State (get)
import Control.Monad.Trans.Control (MonadBaseControl,
liftBaseWith, restoreM)
import Data.ByteString (ByteString)
import qualified Data.Configurator as C
import qualified Data.Configurator.Types as C
import Data.Int (Int64)
import Data.Monoid (Monoid (..), (<>))
import Data.Pool (createPool)
import Data.Ratio (denominator, numerator)
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
import qualified Data.Text.Lazy as TL
import qualified Data.Text.Lazy.Builder as TB
import qualified Data.Text.Lazy.Builder.Int as TB
import qualified Data.Text.Lazy.Builder.RealFloat as TB
import qualified Database.PostgreSQL.Simple as P
import Database.PostgreSQL.Simple.FromRow
import Database.PostgreSQL.Simple.ToRow
import qualified Database.PostgreSQL.Simple.Transaction as P
import Paths_snaplet_postgresql_simple
import Prelude hiding ((++))
import qualified Snap as Snap
import Snap.Snaplet.PostgresqlSimple.Internal
------------------------------------------------------------------------------
-- | Default instance
instance HasPostgres (Snap.Handler b Postgres) where
getPostgresState = get
setLocalPostgresState s = local (const s)
------------------------------------------------------------------------------
-- | A convenience instance to make it easier to use this snaplet in the
-- Initializer monad like this:
--
-- > d <- nestSnaplet "db" db pgsInit
-- > count <- liftIO $ runReaderT (execute "INSERT ..." params) d
instance {-# OVERLAPPING #-} (MonadIO m, MonadBaseControl IO m)
=> HasPostgres (ReaderT (Snap.Snaplet Postgres) m) where
getPostgresState = asks (^# Snap.snapletValue)
setLocalPostgresState s = local (set Snap.snapletValue s)
------------------------------------------------------------------------------
-- | A convenience instance to make it easier to use functions written for
-- this snaplet in non-snaplet contexts.
instance {-# OVERLAPPING #-} (MonadIO m, MonadBaseControl IO m)
=> HasPostgres (ReaderT Postgres m) where
getPostgresState = ask
setLocalPostgresState s = local (const s)
------------------------------------------------------------------------------
-- | Produce a connection string from a config
getConnectionString :: C.Config -> IO ByteString
getConnectionString config = do
let params =
[ ["host"]
, ["hostaddr"]
, ["port"]
, ["dbname","db"]
, ["user"]
, ["password","pass"]
, ["connection_timeout"]
, ["client_encoding"]
, ["options"]
, ["application_name"]
, ["fallback_application_name"]
, ["keepalives"]
, ["keepalives_idle"]
, ["keepalives_interval"]
, ["keepalives_count"]
, ["sslmode"]
, ["sslcompression"]
, ["sslcert"]
, ["sslkey"]
, ["sslrootcert"]
, ["sslcrl"]
, ["requirepeer"]
, ["krbsrvname"]
, ["gsslib"]
, ["service"]
]
connstr <- fmap mconcat $ mapM showParam params
extra <- fmap TB.fromText $ C.lookupDefault "" config "connectionString"
return $! T.encodeUtf8 (TL.toStrict (TB.toLazyText (connstr <> extra)))
where
qt = TB.singleton '\''
bs = TB.singleton '\\'
sp = TB.singleton ' '
eq = TB.singleton '='
lookupConfig = foldr (\name names -> do
mval <- C.lookup config name
case mval of
Nothing -> names
Just _ -> return mval)
(return Nothing)
showParam [] = undefined
showParam names@(name:_) = do
mval :: Maybe C.Value <- lookupConfig names
let key = TB.fromText name <> eq
case mval of
Nothing -> return mempty
Just (C.Bool x) -> return (key <> showBool x <> sp)
Just (C.String x) -> return (key <> showText x <> sp)
Just (C.Number x) -> return (key <> showNum x <> sp)
Just (C.List _) -> return mempty
showBool x = TB.decimal (fromEnum x)
nd ratio = (numerator ratio, denominator ratio)
showNum (nd -> (n,1)) = TB.decimal n
showNum x = TB.formatRealFloat TB.Fixed Nothing
( fromIntegral (numerator x)
/ fromIntegral (denominator x) :: Double )
showText x = qt <> loop x
where
loop (T.break escapeNeeded -> (a,b))
= TB.fromText a <>
case T.uncons b of
Nothing -> qt
Just (c,b') -> escapeChar c <> loop b'
escapeNeeded c = c == '\'' || c == '\\'
escapeChar c = case c of
'\'' -> bs <> qt
'\\' -> bs <> bs
_ -> TB.singleton c
description :: T.Text
description = "PostgreSQL abstraction"
datadir :: Maybe (IO FilePath)
datadir = Just $ liftM (<>"/resources/db") getDataDir
------------------------------------------------------------------------------
-- | Initialize the snaplet
pgsInit :: Snap.SnapletInit b Postgres
pgsInit = Snap.makeSnaplet "postgresql-simple" description datadir $ do
config <- mkPGSConfig =<< Snap.getSnapletUserConfig
initHelper config
------------------------------------------------------------------------------
-- | Initialize the snaplet using a specific configuration.
pgsInit' :: PGSConfig -> Snap.SnapletInit b Postgres
pgsInit' config = Snap.makeSnaplet "postgresql-simple" description Nothing $
initHelper config
------------------------------------------------------------------------------
-- | Builds a PGSConfig object from a configurator Config object. This
-- function uses getConnectionString to construct the connection string. The
-- rest of the PGSConfig fields are obtained from \"numStripes\",
-- \"idleTime\", and \"maxResourcesPerStripe\".
mkPGSConfig :: MonadIO m => C.Config -> m PGSConfig
mkPGSConfig config = liftIO $ do
connstr <- getConnectionString config
stripes <- C.lookupDefault 1 config "numStripes"
idle <- C.lookupDefault 5 config "idleTime"
resources <- C.lookupDefault 20 config "maxResourcesPerStripe"
return $ PGSConfig connstr stripes idle resources
initHelper :: MonadIO m => PGSConfig -> m Postgres
initHelper PGSConfig{..} = do
pool <- liftIO $ createPool (P.connectPostgreSQL pgsConnStr) P.close
pgsNumStripes (realToFrac pgsIdleTime)
pgsResources
return $ PostgresPool pool
------------------------------------------------------------------------------
-- | See 'P.query'
query :: (HasPostgres m, ToRow q, FromRow r)
=> P.Query -> q -> m [r]
query q params = liftPG' (\c -> P.query c q params)
------------------------------------------------------------------------------
-- | See 'P.query_'
query_ :: (HasPostgres m, FromRow r) => P.Query -> m [r]
query_ q = liftPG' (`P.query_` q)
------------------------------------------------------------------------------
-- | See 'P.returning'
returning :: (HasPostgres m, ToRow q, FromRow r)
=> P.Query -> [q] -> m [r]
returning q params = liftPG' (\c -> P.returning c q params)
------------------------------------------------------------------------------
-- |
fold :: (HasPostgres m,
FromRow row,
ToRow params)
=> P.Query -> params -> b -> (b -> row -> IO b) -> m b
fold template qs a f = liftPG' (\c -> P.fold c template qs a f)
------------------------------------------------------------------------------
-- |
foldWithOptions :: (HasPostgres m,
FromRow row,
ToRow params)
=> P.FoldOptions
-> P.Query
-> params
-> b
-> (b -> row -> IO b)
-> m b
foldWithOptions opts template qs a f =
liftPG' (\c -> P.foldWithOptions opts c template qs a f)
------------------------------------------------------------------------------
-- |
fold_ :: (HasPostgres m,
FromRow row)
=> P.Query -> b -> (b -> row -> IO b) -> m b
fold_ template a f = liftPG' (\c -> P.fold_ c template a f)
------------------------------------------------------------------------------
-- |
foldWithOptions_ :: (HasPostgres m,
FromRow row)
=> P.FoldOptions
-> P.Query
-> b
-> (b -> row -> IO b)
-> m b
foldWithOptions_ opts template a f =
liftPG' (\c -> P.foldWithOptions_ opts c template a f)
------------------------------------------------------------------------------
-- |
forEach :: (HasPostgres m,
FromRow r,
ToRow q)
=> P.Query -> q -> (r -> IO ()) -> m ()
forEach template qs f = liftPG' (\c -> P.forEach c template qs f)
------------------------------------------------------------------------------
-- |
forEach_ :: (HasPostgres m,
FromRow r)
=> P.Query -> (r -> IO ()) -> m ()
forEach_ template f = liftPG' (\c -> P.forEach_ c template f)
------------------------------------------------------------------------------
-- |
execute :: (HasPostgres m, ToRow q)
=> P.Query -> q -> m Int64
execute template qs = liftPG' (\c -> P.execute c template qs)
------------------------------------------------------------------------------
-- |
execute_ :: (HasPostgres m)
=> P.Query -> m Int64
execute_ template = liftPG' (`P.execute_` template)
------------------------------------------------------------------------------
-- |
executeMany :: (HasPostgres m, ToRow q)
=> P.Query -> [q] -> m Int64
executeMany template qs = liftPG' (\c -> P.executeMany c template qs)
------------------------------------------------------------------------------
-- | Be careful that you do not call Snap's `finishWith` function anywhere
-- inside the function that you pass to `withTransaction`. Doing so has been
-- known to cause DB connection leaks.
withTransaction :: (HasPostgres m)
=> m a -> m a
withTransaction = withTransactionMode P.defaultTransactionMode
------------------------------------------------------------------------------
-- | Be careful that you do not call Snap's `finishWith` function anywhere
-- inside the function that you pass to `withTransactionLevel`. Doing so has
-- been known to cause DB connection leaks.
withTransactionLevel :: (HasPostgres m)
=> P.IsolationLevel -> m a -> m a
withTransactionLevel lvl =
withTransactionMode P.defaultTransactionMode { P.isolationLevel = lvl }
------------------------------------------------------------------------------
-- | Be careful that you do not call Snap's `finishWith` function anywhere
-- inside the function that you pass to `withTransactionMode`. Doing so has
-- been known to cause DB connection leaks.
withTransactionMode :: (HasPostgres m)
=> P.TransactionMode -> m a -> m a
withTransactionMode mode act = withPG $ do
pg <- getPostgresState
r <- liftBaseWith $ \run -> E.mask
$ \unmask -> withConnection pg
$ \con -> do
P.beginMode mode con
r <- unmask (run act) `E.onException` P.rollback con
P.commit con
return r
restoreM r
formatMany :: (ToRow q, HasPostgres m)
=> P.Query -> [q] -> m ByteString
formatMany q qs = liftPG' (\c -> P.formatMany c q qs)
formatQuery :: (ToRow q, HasPostgres m)
=> P.Query -> q -> m ByteString
formatQuery q qs = liftPG' (\c -> P.formatQuery c q qs)