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{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}
module Database.Persist.Query.Internal
( -- re-exported as public
PersistQuery (..)
, selectList
-- just Internal
, SelectOpt (..)
, limitOffsetOrder
, Filter (..)
, PersistUpdate (..)
, Update (..)
, updateFieldDef
, deleteCascadeWhere
) where
import Database.Persist.Store
import Database.Persist.EntityDef
import Control.Monad.Trans.Class (lift)
import qualified Data.Conduit as C
import qualified Data.Conduit.List as CL
class PersistStore b m => PersistQuery b m where
-- | Update individual fields on a specific record.
update :: PersistEntity val => Key b val -> [Update val] -> b m ()
-- | Update individual fields on any record matching the given criterion.
updateWhere :: PersistEntity val => [Filter val] -> [Update val] -> b m ()
-- | Delete all records matching the given criterion.
deleteWhere :: PersistEntity val => [Filter val] -> b m ()
-- | Get all records matching the given criterion in the specified order.
-- Returns also the identifiers.
selectSource
:: (PersistEntity val, PersistEntityBackend val ~ b)
=> [Filter val]
-> [SelectOpt val]
-> C.Source (C.ResourceT (b m)) (Entity val)
-- | get just the first record for the criterion
selectFirst :: (PersistEntity val, PersistEntityBackend val ~ b)
=> [Filter val]
-> [SelectOpt val]
-> b m (Maybe (Entity val))
selectFirst filts opts = C.runResourceT
$ selectSource filts ((LimitTo 1):opts) C.$$ CL.head
-- | Get the 'Key's of all records matching the given criterion.
selectKeys :: PersistEntity val
=> [Filter val]
-> C.Source (C.ResourceT (b m)) (Key b val)
-- | The total number of records fulfilling the given criterion.
count :: PersistEntity val => [Filter val] -> b m Int
-- | Filters which are available for 'select', 'updateWhere' and
-- 'deleteWhere'. Each filter constructor specifies the field being
-- filtered on, the type of comparison applied (equals, not equals, etc)
-- and the argument for the comparison.
data Filter v = forall typ. PersistField typ => Filter
{ filterField :: EntityField v typ
, filterValue :: Either typ [typ] -- FIXME
, filterFilter :: PersistFilter -- FIXME
}
| FilterAnd [Filter v] -- ^ convenient for internal use, not needed for the API
| FilterOr [Filter v]
data SelectOpt v = forall typ. Asc (EntityField v typ)
| forall typ. Desc (EntityField v typ)
| OffsetBy Int
| LimitTo Int
-- | Call 'select' but return the result as a list.
selectList :: (PersistEntity val, PersistQuery b m, PersistEntityBackend val ~ b)
=> [Filter val]
-> [SelectOpt val]
-> b m [Entity val]
selectList a b = C.runResourceT $ selectSource a b C.$$ CL.consume
data PersistUpdate = Assign | Add | Subtract | Multiply | Divide -- FIXME need something else here
deriving (Read, Show, Enum, Bounded)
data Update v = forall typ. PersistField typ => Update
{ updateField :: EntityField v typ
, updateValue :: typ
, updateUpdate :: PersistUpdate -- FIXME Replace with expr down the road
}
limitOffsetOrder :: PersistEntity val => [SelectOpt val] -> (Int, Int, [SelectOpt val])
limitOffsetOrder opts =
foldr go (0, 0, []) opts
where
go (LimitTo l) (_, b, c) = (l, b ,c)
go (OffsetBy o) (a, _, c) = (a, o, c)
go x (a, b, c) = (a, b, x : c)
updateFieldDef :: PersistEntity v => Update v -> FieldDef
updateFieldDef (Update f _ _) = persistFieldDef f
deleteCascadeWhere :: (DeleteCascade a b m, PersistQuery b m)
=> [Filter a] -> b m ()
deleteCascadeWhere filts = do
C.runResourceT $ selectKeys filts C.$$ CL.mapM_ (lift . deleteCascade)
|
