Hasql.Transaction

Transaction settings

data Mode

Constructors

Read

Read-only. No writes possible.

Write

Write and commit.

WriteWithoutCommitting

Write without committing. Useful for testing, allowing you to modify your database, producing some result based on your changes, and letting Hasql roll all the changes back on the exit from the transaction.

Instances

Bounded Mode

Methods

minBound :: Mode

maxBound :: Mode

Enum Mode

Methods

succ :: Mode -> Mode

pred :: Mode -> Mode

toEnum :: Int -> Mode

fromEnum :: Mode -> Int

enumFrom :: Mode -> [Mode]

enumFromThen :: Mode -> Mode -> [Mode]

enumFromTo :: Mode -> Mode -> [Mode]

enumFromThenTo :: Mode -> Mode -> Mode -> [Mode]

Eq Mode

Methods

(==) :: Mode -> Mode -> Bool

(/=) :: Mode -> Mode -> Bool

Ord Mode

Methods

compare :: Mode -> Mode -> Ordering

(<) :: Mode -> Mode -> Bool

(<=) :: Mode -> Mode -> Bool

(>) :: Mode -> Mode -> Bool

(>=) :: Mode -> Mode -> Bool

max :: Mode -> Mode -> Mode

min :: Mode -> Mode -> Mode

Show Mode

Methods

showsPrec :: Int -> Mode -> ShowS

show :: Mode -> String

showList :: [Mode] -> ShowS

data IsolationLevel

For reference see the Postgres' documentation.

Constructors

ReadCommitted

RepeatableRead

Serializable

Instances

Bounded IsolationLevel

Methods

minBound :: IsolationLevel

maxBound :: IsolationLevel

Enum IsolationLevel

Methods

succ :: IsolationLevel -> IsolationLevel

pred :: IsolationLevel -> IsolationLevel

toEnum :: Int -> IsolationLevel

fromEnum :: IsolationLevel -> Int

enumFrom :: IsolationLevel -> [IsolationLevel]

enumFromThen :: IsolationLevel -> IsolationLevel -> [IsolationLevel]

enumFromTo :: IsolationLevel -> IsolationLevel -> [IsolationLevel]

enumFromThenTo :: IsolationLevel -> IsolationLevel -> IsolationLevel -> [IsolationLevel]

Eq IsolationLevel

Methods

(==) :: IsolationLevel -> IsolationLevel -> Bool

(/=) :: IsolationLevel -> IsolationLevel -> Bool

Ord IsolationLevel

Methods

compare :: IsolationLevel -> IsolationLevel -> Ordering

(<) :: IsolationLevel -> IsolationLevel -> Bool

(<=) :: IsolationLevel -> IsolationLevel -> Bool

(>) :: IsolationLevel -> IsolationLevel -> Bool

(>=) :: IsolationLevel -> IsolationLevel -> Bool

max :: IsolationLevel -> IsolationLevel -> IsolationLevel

min :: IsolationLevel -> IsolationLevel -> IsolationLevel

Show IsolationLevel

Methods

showsPrec :: Int -> IsolationLevel -> ShowS

show :: IsolationLevel -> String

showList :: [IsolationLevel] -> ShowS

Transaction monad

data Transaction a

A composable abstraction over the retryable transactions.

Executes multiple queries under the specified mode and isolation level, while automatically retrying the transaction in case of conflicts. Thus this abstraction closely reproduces the behaviour of STM.

Instances

Monad Transaction

Methods

(>>=) :: Transaction a -> (a -> Transaction b) -> Transaction b

(>>) :: Transaction a -> Transaction b -> Transaction b

return :: a -> Transaction a

fail :: String -> Transaction a

Functor Transaction

Methods

fmap :: (a -> b) -> Transaction a -> Transaction b

(<$) :: a -> Transaction b -> Transaction a

Applicative Transaction

Methods

pure :: a -> Transaction a

(<*>) :: Transaction (a -> b) -> Transaction a -> Transaction b

(*>) :: Transaction a -> Transaction b -> Transaction b

(<*) :: Transaction a -> Transaction b -> Transaction a

run :: Transaction a -> IsolationLevel -> Mode -> Session a

Execute the transaction using the provided isolation level and mode.

sql :: ByteString -> Transaction ()

Possibly a multi-statement query, which however cannot be parameterized or prepared, nor can any results of it be collected.

query :: a -> Query a b -> Transaction b

Parameters and a specification of the parametric query to apply them to.