c96a43d · typeable/postgresql-simple

git.iko.soy/typeable/postgresql-simple

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Change withTransactionModeRetry to allow the user to determine when to retry

c96a43dOliver Charles14 years ago

src/Database/PostgreSQL/Simple.hs+19−13

compare with master

unifiedsplit

@@ -663,6 +663,15 @@ withTransactionSerializable =

663 { isolationLevel = Serializable

664 , readWriteMode = ReadWrite

665 }

666+ retryOnNotSerializable

667+ where

668+ retryOnNotSerializable exception =

669+ case exception of

670+ SqlError{..} | sqlState == serialization_failure

671+ -> True

672+ _ -> False

673+ -- http://www.postgresql.org/docs/current/static/errcodes-appendix.html

674+ serialization_failure = "40001"

666

675

667-- | Execute an action inside a SQL transaction with a given isolation level.

676-- | Execute an action inside a SQL transaction with a given isolation level.

668withTransactionLevel :: IsolationLevel -> Connection -> IO a -> IO a

677withTransactionLevel :: IsolationLevel -> Connection -> IO a -> IO a

@@ -678,14 +687,15 @@ withTransactionMode mode conn act =

678 commit conn

687 commit conn

679 return r

688 return r

680

689

681−-- | Like 'withTransactionMode', but if a 'SqlError' arises whose 'sqlState' is

690+-- | Like 'withTransactionMode', but also takes a custom callback to

682−-- @\"40001\"@ (@serialization_failure@), this will issue a @ROLLBACK@, then

691+-- determine if a transaction should be retried if an 'SqlError' occurs.

683−-- try the action again. If any other exception arises, this will issue a

692+-- If the callback returns True, then the transaction will be retried.

684−-- @ROLLBACK@, but will propagate the exception instead of retrying.

693+-- If the callback returns False, or an exception other than an 'SqlError'

694+-- occurs then the transaction will be rolled back and the exception rethrown.

685--

695--

686-- This is used to implement 'withTransactionSerializable'.

696-- This is used to implement 'withTransactionSerializable'.

687−withTransactionModeRetry :: TransactionMode -> Connection -> IO a -> IO a

697+withTransactionModeRetry :: TransactionMode -> (SqlError -> Bool) -> Connection -> IO a -> IO a

688−withTransactionModeRetry mode conn act =

698+withTransactionModeRetry mode shouldRetry conn act =

689 mask $ \restore ->

699 mask $ \restore ->

690 retryLoop $ try $ do

700 retryLoop $ try $ do

691 a <- restore act

701 a <- restore act

@@ -699,16 +709,12 @@ withTransactionModeRetry mode conn act =

699 case r of

709 case r of

700 Left e -> do

710 Left e -> do

701 rollback conn

711 rollback conn

702− case fromException e of

712+ case fmap shouldRetry (fromException e) of

703− Just SqlError{..} | sqlState == serialization_failure

704− -> retryLoop act'

713+ Just True -> retryLoop act'

705− _ -> throwIO e

714+ _ -> throwIO e

706 Right a ->

715 Right a ->

707 return a

716 return a

708

717

709− -- http://www.postgresql.org/docs/current/static/errcodes-appendix.html

710− serialization_failure = "40001"

711−

712-- | Rollback a transaction.

718-- | Rollback a transaction.

713rollback :: Connection -> IO ()

719rollback :: Connection -> IO ()

714rollback conn = execute_ conn "ABORT" >> return ()

720rollback conn = execute_ conn "ABORT" >> return ()