Safe Haskell | None |
---|---|
Language | Haskell2010 |
Database.PostgreSQL.PQTypes.Class
Documentation
class (Applicative m, Monad m) => MonadDB m where #
Minimal complete definition
runQuery, getLastQuery, getConnectionStats, getQueryResult, clearQueryResult, getTransactionSettings, setTransactionSettings, getNotification, withNewConnection
Methods
runQuery :: IsSQL sql => sql -> m Int #
Run SQL query and return number of affected/returned rows. Note that
for a given connection, only one thread may be executing runQuery
at
a given time. If simultaneous call is made from another thread, it
will block until currently running runQuery
finishes.
getLastQuery :: m SomeSQL #
Get last SQL query that was executed.
getConnectionStats :: m ConnectionStats #
Get current connection statistics.
getQueryResult :: FromRow row => m (Maybe (QueryResult row)) #
Get current query result.
clearQueryResult :: m () #
Clear current query result.
getTransactionSettings :: m TransactionSettings #
Get current transaction settings.
setTransactionSettings :: TransactionSettings -> m () #
Set transaction settings to supplied ones. Note that it won't change any properties of currently running transaction, only the subsequent ones.
getNotification :: Int -> m (Maybe Notification) #
Attempt to receive a notification from the server. This function waits until a notification arrives or specified number of microseconds has passed. If a negative number of microseconds is passed as an argument, it will wait indefinitely. In addition, there are a couple of things to be aware of:
- A lock on the underlying database connection is acquired for the duration of the function.
- Notifications can be received only between transactions
(see http://www.postgresql.org/docs/current/static/sql-notify.html
for further info), therefore calling this function within
a transaction block will return
Just
only if notifications were received before the transaction began.
withNewConnection :: m a -> m a #
Execute supplied monadic action with new connection using current connection source and transaction settings.
Particularly useful when you want to spawn a new thread, but do not want the connection in child thread to be shared with the parent one.
Instances
(Applicative (t m), Monad (t m), MonadTrans t, MonadTransControl t, MonadDB m) => MonadDB (t m) # | Generic, overlapping instance. |
((~) (* -> *) m n, MonadBase IO m, MonadMask m) => MonadDB (DBT_ m n) # | |