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Reimplement Backend
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Nikita Volkov
parent
e877f2b986
commit
e940079a4c
@ -56,6 +56,7 @@ library
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text == 1.1.*,
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hashable == 1.2.*,
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-- control:
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errors == 1.4.*,
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list-t >= 0.2.1 && < 0.3,
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mmorph == 1.0.*,
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monad-control == 0.3.*,
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@ -2,108 +2,83 @@
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-- An open API for implementation of specific backend drivers.
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module HighSQL.Backend where
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import HighSQL.Prelude hiding (Error)
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import HighSQL.Prelude
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import qualified Data.Text as Text
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import qualified Language.Haskell.TH as TH
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import qualified Data.Decimal as Decimal
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-- |
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-- A database interface.
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--
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-- Implementations are provided by driver libraries.
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data Backend =
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Backend {
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connect :: IO Connection
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}
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data Connection =
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forall s.
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Connection {
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-- |
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-- Start a transaction in a write mode if the flag is true.
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beginTransaction :: Bool -> IO (),
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-- |
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-- Finish the transaction,
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-- while releasing all the resources acquired with 'executeAndStream'.
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--
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-- The boolean defines whether to commit the updates,
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-- otherwise it rolls back.
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finishTransaction :: Bool -> IO (),
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-- |
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-- If the backend supports statement preparation,
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-- this function compiles a bytestring statement
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-- with placeholders if it's not compiled already,
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-- and otherwise returns the cached already compiled statement.
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-- IOW, it implements memoization.
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--
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-- If the backend does not support this,
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-- then this function should simply be implemented as a 'return'.
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prepare :: ByteString -> IO s,
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-- |
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-- Execute a statement with values for placeholders.
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execute :: s -> [Value] -> IO (),
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-- |
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-- Execute a statement with values for placeholders,
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-- returning the amount of affected rows.
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executeCountingEffects :: s -> [Value] -> IO Integer,
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-- |
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-- Execute a statement with values for placeholders,
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-- returning the possibly generated auto-incremented value.
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executeIncrementing :: s -> [Value] -> IO (Maybe Integer),
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-- |
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-- Execute a statement with values and an expected results stream size.
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-- The expected stream size can be used by the backend to determine
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-- an optimal fetching method.
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executeStreaming :: s -> [Value] -> Maybe Integer -> IO ResultSet,
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-- |
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-- Close the connection.
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disconnect :: IO ()
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}
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data Error =
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data Failure b =
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-- |
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-- A transaction failed and should be retried.
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TransactionError |
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TransactionFailure |
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-- |
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-- Cannot connect to a server
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-- or the connection got interrupted.
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ConnectionError Text |
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-- |
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-- A free-form backend-specific exception.
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BackendError SomeException
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deriving (Show, Typeable)
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ConnectionFailure Text
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instance Exception Error
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type M b =
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ExceptT (Failure b) IO
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-- |
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-- A row width and a stream of values.
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-- The length of the stream must be a multiple of the row width.
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type ResultSet =
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(Int, ListT IO Value)
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-- A width of a row and a stream of serialized values.
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type ResultsStream =
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(Int, ListT IO ByteString)
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class Backend b where
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-- |
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-- An argument prepared for a statement.
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type StatementArgument b
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-- |
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-- A raw value returned from the database.
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data Result b
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type Connection b
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-- |
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-- Open a connection using the backend's settings.
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connect :: b -> M b (Connection b)
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-- |
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-- Close the connection.
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disconnect :: Connection b -> M b ()
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-- |
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-- If the backend supports statement preparation,
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-- this function compiles a bytestring statement
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-- with placeholders if it's not compiled already,
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-- and otherwise returns the cached already compiled statement.
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-- IOW, it implements memoization.
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--
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-- If the backend does not support this,
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-- then this function should simply be implemented as a 'return'.
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prepare :: ByteString -> Connection b -> M b s
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-- |
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-- Execute a statement with values for placeholders.
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execute :: ByteString -> [StatementArgument b] -> Connection b -> M b ()
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-- |
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-- Execute a statement with values for placeholders
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-- and an expected results stream size.
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-- The expected stream size can be used by the backend to determine
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-- an optimal fetching method.
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executeStreaming :: ByteString -> [StatementArgument b] -> Maybe Integer -> Connection b -> ListT (M b) r
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-- |
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-- Execute a statement with values for placeholders,
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-- returning the amount of affected rows.
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executeCountingEffects :: s -> [StatementArgument b] -> Connection b -> M b Integer
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-- |
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-- Start a transaction in a write mode if the flag is true.
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beginTransaction :: Bool -> Connection b -> M b ()
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-- |
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-- Finish the transaction,
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-- while releasing all the resources acquired with 'executeAndStream'.
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--
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-- The boolean defines whether to commit the updates,
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-- otherwise it rolls back.
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finishTransaction :: Bool -> Connection b -> M b ()
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class Backend b => Value v b where
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renderArgument :: v -> StatementArgument b
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parseResult :: Result b -> Maybe v
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data Value =
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Text !Text |
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ByteString !ByteString |
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Word32 !Word32 |
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Word64 !Word64 |
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Int32 !Int32 |
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Int64 !Int64 |
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Integer !Integer |
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Char !Char |
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Bool !Bool |
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Double !Double |
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Rational !Rational |
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Day !Day |
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LocalTime !LocalTime |
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TimeOfDay !TimeOfDay |
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ZonedTime !ZonedTime |
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UTCTime !UTCTime |
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NominalDiffTime !NominalDiffTime |
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-- | Yes, this encodes @NULL@s.
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Maybe !(Maybe Value)
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deriving (Show, Data, Typeable, Generic)
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@ -9,7 +9,7 @@ where
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-- base-prelude
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-------------------------
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import BasePrelude as Exports hiding (left, right, tryJust, bool)
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import BasePrelude as Exports hiding (left, right, tryJust, bool, isRight, isLeft)
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-- mtl-prelude
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-------------------------
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@ -19,6 +19,10 @@ import MTLPrelude as Exports hiding (shift)
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-------------------------
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import Control.Monad.Morph as Exports
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-- errors
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-------------------------
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import Control.Error as Exports
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-- list-t
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-------------------------
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import ListT as Exports (ListT)
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