c77e338 · typeable/postgresql-simple

git.iko.soy/typeable/postgresql-simple

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Add support for isolation levels

c77e338Leon P Smith15 years ago

src/Database/PostgreSQL/Simple.hs+39−18

compare with master

unifiedsplit

@@ -85,8 +85,11 @@ module Database.PostgreSQL.Simple

85-- , Base.insertID

86 -- * Transaction handling

87 , withTransaction

88+ , withTransactionLevel

89+ , IsolationLevel(..)

88-- , Base.autocommit

90-- , Base.autocommit

89 , begin

91 , begin

92+ , beginLevel

90 , commit

93 , commit

91 , rollback

94 , rollback

92 -- * Helper functions

95 -- * Helper functions

@@ -332,12 +335,14 @@ data FetchQuantity

332 = Automatic

335 = Automatic

333 | Fixed !Int

336 | Fixed !Int

334

337

335−newtype FoldOptions

338+data FoldOptions

336 = FoldOptions {

339 = FoldOptions {

337− fetchQuantity :: FetchQuantity

340+ fetchQuantity :: !FetchQuantity,

341+ isolationLevel :: !IsolationLevel

338 }

342 }

339

343

340−defaultFoldOptions = FoldOptions { fetchQuantity = Automatic }

344+defaultFoldOptions = FoldOptions { fetchQuantity = Automatic

345+ , isolationLevel = ReadCommitted }

341

346

342foldWithOptions :: ( QueryResults row, QueryParams params )

347foldWithOptions :: ( QueryResults row, QueryParams params )

343 => FoldOptions

348 => FoldOptions

@@ -379,10 +384,10 @@ doFold :: ( QueryResults row )

379 -> a

384 -> a

380 -> (a -> row -> IO a)

385 -> (a -> row -> IO a)

381 -> IO a

386 -> IO a

382−doFold opts conn _template q a f = do

387+doFold FoldOptions{..} conn _template q a f = do

383 stat <- withConnection conn PQ.transactionStatus

388 stat <- withConnection conn PQ.transactionStatus

384 case stat of

389 case stat of

385− PQ.TransIdle -> withTransaction conn go

390+ PQ.TransIdle -> withTransactionLevel isolationLevel conn go

386 PQ.TransInTrans -> go

391 PQ.TransInTrans -> go

387 PQ.TransActive -> fail "foldWithOpts FIXME: PQ.TransActive"

392 PQ.TransActive -> fail "foldWithOpts FIXME: PQ.TransActive"

388 -- This _shouldn't_ occur in the current incarnation of

393 -- This _shouldn't_ occur in the current incarnation of

@@ -409,7 +414,7 @@ doFold opts conn _template q a f = do

409-- are of highly variable size.

414-- are of highly variable size.

410-- A refinement of this technique is to pick this number adaptively

415-- A refinement of this technique is to pick this number adaptively

411-- as results are read in from the database.

416-- as results are read in from the database.

412− chunkSize = case fetchQuantity opts of

417+ chunkSize = case fetchQuantity of

413 Automatic -> 256

418 Automatic -> 256

414 Fixed n -> n

419 Fixed n -> n

415 loop a = do

420 loop a = do

@@ -473,6 +478,17 @@ finishQuery conn q result = do

473 , sqlErrorMsg = B.concat [ "query: ", statusmsg

478 , sqlErrorMsg = B.concat [ "query: ", statusmsg

474 , ": ", errormsg ]}

479 , ": ", errormsg ]}

475

480

481+-- | Of the four isolation levels defined by the SQL standard,

482+-- these are the three levels distinguished by PostgreSQL as of version 9.0.

483+-- See <http://www.postgresql.org/docs/9.1/static/transaction-iso.html>

484+-- for more information.

485+

486+data IsolationLevel

487+ = ReadCommitted

488+ | RepeatableRead

489+ | Serializable

490+ deriving (Show, Eq, Ord, Enum, Bounded)

491+

476-- | Execute an action inside a SQL transaction.

492-- | Execute an action inside a SQL transaction.

477--

493--

478-- This function initiates a transaction with a \"@begin

494-- This function initiates a transaction with a \"@begin

@@ -484,8 +500,12 @@ finishQuery conn q result = do

484-- PostgreSQL-related exception), the transaction will be rolled back using

500-- PostgreSQL-related exception), the transaction will be rolled back using

485-- 'rollback', then the exception will be rethrown.

501-- 'rollback', then the exception will be rethrown.

486withTransaction :: Connection -> IO a -> IO a

502withTransaction :: Connection -> IO a -> IO a

487−withTransaction conn act = do

503+withTransaction = withTransactionLevel ReadCommitted

488− _ <- begin conn

504+

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

506+withTransactionLevel :: IsolationLevel -> Connection -> IO a -> IO a

507+withTransactionLevel isolationLevel conn act = do

508+ beginLevel isolationLevel conn

489 r <- act `onException` rollback conn

509 r <- act `onException` rollback conn

490 commit conn

510 commit conn

491 return r

511 return r

@@ -493,22 +513,23 @@ withTransaction conn act = do

493-- | Rollback a transaction.

513-- | Rollback a transaction.

494-- rollback :: (MonadCatchIO m,MonadIO m) => Connection -> m ()

514-- rollback :: (MonadCatchIO m,MonadIO m) => Connection -> m ()

495rollback :: Connection -> IO ()

515rollback :: Connection -> IO ()

496−rollback conn = do

497− _ <- execute_ conn "ABORT"

516+rollback conn = execute_ conn "ABORT" >> return ()

498− return ()

499

517

500-- | Commit a transaction.

518-- | Commit a transaction.

501−-- commit :: (MonadCatchIO m,MonadIO m) => Connection -> m ()

502commit :: Connection -> IO ()

519commit :: Connection -> IO ()

503−commit conn = do

504− _ <- execute_ conn "COMMIT"

520+commit conn = execute_ conn "COMMIT" >> return ()

505− return ()

506

521

507-- | Begin a transaction.

522-- | Begin a transaction.

508−-- begin :: (MonadCatchIO m,MonadIO m) => Connection -> m ()

509begin :: Connection -> IO ()

523begin :: Connection -> IO ()

510−begin conn = do

524+begin = beginLevel ReadCommitted

525+

526+-- | Begin a transaction with a given isolation level

527+beginLevel :: IsolationLevel -> Connection -> IO ()

528+beginLevel isolationLevel conn = do

511− _ <- execute_ conn "BEGIN"

529+ execute_ conn $! case isolationLevel of

530+ ReadCommitted -> "BEGIN"

531+ RepeatableRead -> "BEGIN ISOLATION LEVEL REPEATABLE READ"

532+ Serializable -> "BEGIN ISOLATION LEVEL SERIALIZABLE"

512 return ()

533 return ()

513

534

514fmtError :: String -> Query -> [Action] -> a

535fmtError :: String -> Query -> [Action] -> a