| Copyright |
(c) 2011-2013 Leon P Smith
(c) 2013 Joey Adams |
|---|---|
| License | BSD3 |
| Maintainer | Leon P Smith <leon@melding-monads.com> |
| Safe Haskell | None |
| Language | Haskell2010 |
Database.PostgreSQL.Simple.Transaction
Description
Synopsis
- withTransaction :: Connection -> IO a -> IO a
- withTransactionLevel :: IsolationLevel -> Connection -> IO a -> IO a
- withTransactionMode :: TransactionMode -> Connection -> IO a -> IO a
- withTransactionModeRetry :: TransactionMode -> ( SqlError -> Bool ) -> Connection -> IO a -> IO a
- withTransactionModeRetry' :: forall a e. Exception e => TransactionMode -> (e -> Bool ) -> Connection -> IO a -> IO a
- withTransactionSerializable :: Connection -> IO a -> IO a
- data TransactionMode = TransactionMode { }
- data IsolationLevel
- data ReadWriteMode
- defaultTransactionMode :: TransactionMode
- defaultIsolationLevel :: IsolationLevel
- defaultReadWriteMode :: ReadWriteMode
- begin :: Connection -> IO ()
- beginLevel :: IsolationLevel -> Connection -> IO ()
- beginMode :: TransactionMode -> Connection -> IO ()
- commit :: Connection -> IO ()
- rollback :: Connection -> IO ()
- withSavepoint :: Connection -> IO a -> IO a
- data Savepoint
- newSavepoint :: Connection -> IO Savepoint
- releaseSavepoint :: Connection -> Savepoint -> IO ()
- rollbackToSavepoint :: Connection -> Savepoint -> IO ()
- rollbackToAndReleaseSavepoint :: Connection -> Savepoint -> IO ()
- isSerializationError :: SqlError -> Bool
- isNoActiveTransactionError :: SqlError -> Bool
- isFailedTransactionError :: SqlError -> Bool
Transaction handling
withTransaction :: Connection -> IO a -> IO a Source #
Execute an action inside a SQL transaction.
This function initiates a transaction with a "
begin
transaction
" statement, then executes the supplied action. If
the action succeeds, the transaction will be completed with
commit
before this function returns.
If the action throws
any
kind of exception (not just a
PostgreSQL-related exception), the transaction will be rolled back using
rollback
, then the exception will be rethrown.
For nesting transactions, see
withSavepoint
.
withTransactionLevel :: IsolationLevel -> Connection -> IO a -> IO a Source #
Execute an action inside a SQL transaction with a given isolation level.
withTransactionMode :: TransactionMode -> Connection -> IO a -> IO a Source #
Execute an action inside a SQL transaction with a given transaction mode.
withTransactionModeRetry :: TransactionMode -> ( SqlError -> Bool ) -> Connection -> IO a -> IO a Source #
withTransactionModeRetry'
but with the exception type pinned to
SqlError
.
withTransactionModeRetry' :: forall a e. Exception e => TransactionMode -> (e -> Bool ) -> Connection -> IO a -> IO a Source #
Like
withTransactionMode
, but also takes a custom callback to
determine if a transaction should be retried if an exception occurs.
If the callback returns
True
, then the transaction will be retried.
If the callback returns
False
, or an exception other than an
e
occurs then the transaction will be rolled back and the exception rethrown.
This is used to implement
withTransactionSerializable
.
withTransactionSerializable :: Connection -> IO a -> IO a Source #
Execute an action inside of a
Serializable
transaction. If a
serialization failure occurs, roll back the transaction and try again.
Be warned that this may execute the IO action multiple times.
A
Serializable
transaction creates the illusion that your program has
exclusive access to the database. This means that, even in a concurrent
setting, you can perform queries in sequence without having to worry about
what might happen between one statement and the next.
Think of it as STM, but without
retry
.
data TransactionMode Source #
Constructors
| TransactionMode | |
|
Fields |
|
Instances
| Eq TransactionMode Source # | |
|
Defined in Database.PostgreSQL.Simple.Transaction Methods (==) :: TransactionMode -> TransactionMode -> Bool Source # (/=) :: TransactionMode -> TransactionMode -> Bool Source # |
|
| Show TransactionMode Source # | |
|
Defined in Database.PostgreSQL.Simple.Transaction |
|
data IsolationLevel Source #
Of the four isolation levels defined by the SQL standard,
these are the three levels distinguished by PostgreSQL as of version 9.0.
See
https://www.postgresql.org/docs/9.5/static/transaction-iso.html
for more information. Note that prior to PostgreSQL 9.0,
RepeatableRead
was equivalent to
Serializable
.
Constructors
| DefaultIsolationLevel |
the isolation level will be taken from
PostgreSQL's per-connection
|
| ReadCommitted | |
| RepeatableRead | |
| Serializable |
Instances
data ReadWriteMode Source #
Constructors
| DefaultReadWriteMode |
the read-write mode will be taken from
PostgreSQL's per-connection
|
| ReadWrite | |
| ReadOnly |
Instances
begin :: Connection -> IO () Source #
Begin a transaction.
beginLevel :: IsolationLevel -> Connection -> IO () Source #
Begin a transaction with a given isolation level
beginMode :: TransactionMode -> Connection -> IO () Source #
Begin a transaction with a given transaction mode
commit :: Connection -> IO () Source #
Commit a transaction.
rollback :: Connection -> IO () Source #
Rollback a transaction.
Savepoint
withSavepoint :: Connection -> IO a -> IO a Source #
Create a savepoint, and roll back to it if an error occurs. This may only be used inside of a transaction, and provides a sort of "nested transaction".
See https://www.postgresql.org/docs/9.5/static/sql-savepoint.html
Instances
| Eq Savepoint Source # | |
| Ord Savepoint Source # | |
|
Defined in Database.PostgreSQL.Simple.Types Methods compare :: Savepoint -> Savepoint -> Ordering Source # (<) :: Savepoint -> Savepoint -> Bool Source # (<=) :: Savepoint -> Savepoint -> Bool Source # (>) :: Savepoint -> Savepoint -> Bool Source # (>=) :: Savepoint -> Savepoint -> Bool Source # |
|
| Read Savepoint Source # | |
| Show Savepoint Source # | |
newSavepoint :: Connection -> IO Savepoint Source #
Create a new savepoint. This may only be used inside of a transaction.
releaseSavepoint :: Connection -> Savepoint -> IO () Source #
Destroy a savepoint, but retain its effects.
Warning: this will throw a
SqlError
matching
isFailedTransactionError
if
the transaction is aborted due to an error.
commit
would merely warn and
roll back.
rollbackToSavepoint :: Connection -> Savepoint -> IO () Source #
Roll back to a savepoint. This will not release the savepoint.
rollbackToAndReleaseSavepoint :: Connection -> Savepoint -> IO () Source #
Roll back to a savepoint and release it. This is like calling
rollbackToSavepoint
followed by
releaseSavepoint
, but avoids a
round trip to the database server.
Error predicates
isSerializationError :: SqlError -> Bool Source #