Hasql.Pool

Pool

data Pool

A pool of connections to DB.

acquire :: Int -> Settings -> IO Pool

Given the pool-size and connection settings create a connection-pool.

No connections actually get established by this function. It is delegated to use.

acquireDynamically :: Int -> IO Settings -> IO Pool

Given the pool-size and connection settings constructor action create a connection-pool.

No connections actually get established by this function. It is delegated to use.

In difference to acquire new settings get fetched each time a connection is created. This may be useful for some security models.

release :: Pool -> IO ()

Release all the connections in the pool.

use :: Pool -> Session a -> IO (Either UsageError a)

Use a connection from the pool to run a session and return the connection to the pool, when finished.

Session failing with a ClientError gets interpreted as a loss of connection. In such case the connection does not get returned to the pool and a slot gets freed up for a new connection to be established the next time one is needed. The error still gets returned from this function.

Errors

data UsageError

Union over all errors that use can result in.

Constructors

ConnectionUsageError ConnectionError

Attempt to establish a connection failed.

SessionUsageError QueryError

Session execution failed.

PoolIsReleasedUsageError

Attempt to use a pool, which has already been called release upon.

Instances

Eq UsageError

Defined in Hasql.Pool

Methods

(==) :: UsageError -> UsageError -> Bool

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

Show UsageError

Defined in Hasql.Pool

Methods

showsPrec :: Int -> UsageError -> ShowS

show :: UsageError -> String

showList :: [UsageError] -> ShowS

Exception UsageError

Defined in Hasql.Pool

Methods

toException :: UsageError -> SomeException

fromException :: SomeException -> Maybe UsageError

displayException :: UsageError -> String