06df1a1 · typeable/postgresql-simple

git.iko.soy/typeable/postgresql-simple

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Merge remote-tracking branch 'ocharles/general-transaction-retrying' into 0.3

06df1a1Leon P Smith14 years ago

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

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unifiedsplit

@@ -667,6 +667,15 @@ withTransactionSerializable =

667 { isolationLevel = Serializable

668 , readWriteMode = ReadWrite

669 }

670+ retryOnNotSerializable

671+ where

672+ retryOnNotSerializable exception =

673+ case exception of

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

675+ -> True

676+ _ -> False

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

678+ serialization_failure = "40001"

670

679

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

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

672withTransactionLevel :: IsolationLevel -> Connection -> IO a -> IO a

681withTransactionLevel :: IsolationLevel -> Connection -> IO a -> IO a

@@ -682,14 +691,15 @@ withTransactionMode mode conn act =

682 commit conn

691 commit conn

683 return r

692 return r

684

693

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

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

686−-- @\"40001\"@ (@serialization_failure@), this will issue a @ROLLBACK@, then

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

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

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

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

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

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

689--

699--

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

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

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

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

692−withTransactionModeRetry mode conn act =

702+withTransactionModeRetry mode shouldRetry conn act =

693 mask $ \restore ->

703 mask $ \restore ->

694 retryLoop $ try $ do

704 retryLoop $ try $ do

695 a <- restore act

705 a <- restore act

@@ -703,16 +713,12 @@ withTransactionModeRetry mode conn act =

703 case r of

713 case r of

704 Left e -> do

714 Left e -> do

705 rollback conn

715 rollback conn

706− case fromException e of

716+ case fmap shouldRetry (fromException e) of

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

708− -> retryLoop act'

717+ Just True -> retryLoop act'

709− _ -> throwIO e

718+ _ -> throwIO e

710 Right a ->

719 Right a ->

711 return a

720 return a

712

721

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

714− serialization_failure = "40001"

715−

716-- | Rollback a transaction.

722-- | Rollback a transaction.

717rollback :: Connection -> IO ()

723rollback :: Connection -> IO ()

718rollback conn = execute_ conn "ABORT" >> return ()

724rollback conn = execute_ conn "ABORT" >> return ()