Safe Haskell	None
Language	Haskell2010

Hasql

Contents

Session
- Session Settings
Transaction
- Transaction Settings
Statement Quasi-Quoter
Statement Execution
Results Stream
Row parser
Error

Description

This is the API of the "hasql" library. For an introduction to the package and links to more documentation please refer to the package's index page.

Synopsis

Session

type Session b = ReaderT (Pool (Connection b)) Source

A monad transformer, which executes transactions.

session :: (Backend b, MonadBaseControl IO m) => b -> SessionSettings -> Session b m r -> m r Source

Given backend settings, session settings, and a session monad transformer, execute it in the inner monad.

Session Settings

data SessionSettings Source

Settings of a session.

sessionSettings Source

Arguments

:: Word32	The maximum number of connections to keep open. The smallest acceptable value is 1. Requests for connections will block if this limit is reached.
-> NominalDiffTime	The amount of time for which an unused connection is kept open. The smallest acceptable value is 0.5 seconds.
-> Maybe SessionSettings	Maybe session settings, if they are correct.

A smart constructor for session settings.

Transaction

data Tx b s r Source

A transaction specialized for backend b, running on an anonymous state-thread s and producing a result r.

Instances

Monad (Tx b s)
Functor (Tx b s)
Applicative (Tx b s)

tx :: (Backend b, MonadBase IO m) => Mode -> (forall s. Tx b s r) -> Session b m r Source

Execute a transaction in a session.

Transaction Settings

type Mode = Maybe (IsolationLevel, Bool) Source

A transaction mode defining how a transaction should be executed.

Just (isolationLevel, write) indicates that a database transaction should be established with a specified isolation level and a boolean, defining, whether it would perform any modification operations.
Nothing indicates that there should be no database transaction established on the backend and therefore it should be executed with no ACID guarantees, but also without any induced overhead.

data IsolationLevel :: *

For reference see the Wikipedia info.

Constructors

Serializable
RepeatableReads
ReadCommitted
ReadUncommitted

Statement Quasi-Quoter

q :: QuasiQuoter Source

Produces a lambda-expression, which takes as many parameters as there are placeholders in the quoted text and results in a Statement.

E.g.:

selectFive :: 'Backend.Statement' c
selectFive = [q|SELECT (? + ?)|] 2 3

Statement Execution

unit :: Backend b => Statement b -> Tx b s () Source

Execute a statement, which produces no result.

count :: (Backend b, Mapping b Word64) => Statement b -> Tx b s Word64 Source

Execute a statement and count the amount of affected rows. Useful for resolving how many rows were updated or deleted.

single :: (Backend b, RowParser b r) => Statement b -> Tx b s (Maybe r) Source

Execute a statement, which produces a single result row: a SELECT or an INSERT, which produces a generated value (e.g., an auto-incremented id).

list :: (Backend b, RowParser b r) => Statement b -> Tx b s [r] Source

Execute a SELECT statement, and produce a list of results.

stream :: (Backend b, RowParser b r) => Statement b -> TxListT s (Tx b s) r Source

Execute a SELECT statement with a cursor, and produce a results stream.

Cursor allows you to fetch virtually limitless results in a constant memory at a cost of a small overhead. Note that in most databases cursors require establishing a database transaction, so a NotInTransaction error will be raised if you run it improperly.

Results Stream

data TxListT s m r Source

A stream of results, which fetches only those that you reach.

It's a wrapper around ListT, which uses the same trick as the ST monad to associate with the context transaction and become impossible to be used outside of it. This lets the library ensure that it is safe to automatically release all the resources associated with this stream.

All the functions of the "list-t" library are applicable to this type, amongst which are head, toList, fold, traverse_.

Instances

ListTrans (TxListT s)
MonadTrans (TxListT s)
(Monad m, Functor m) => Alternative (TxListT s m)
Monad m => Monad (TxListT s m)
Functor m => Functor (TxListT s m)
Monad m => MonadPlus (TxListT s m)
(Monad m, Functor m) => Applicative (TxListT s m)
Monad m => ListMonad (TxListT s m)
Monad m => Monoid (TxListT s m r)

Row parser

class RowParser b r where Source

Methods

parseRow :: Vector (Result b) -> Either Text r Source

Instances

RowParser b ()
Mapping b v => RowParser b (Identity v)
(Mapping b v1, Mapping b v2) => RowParser b (v1, v2)
(Mapping b v1, Mapping b v2, Mapping b v3) => RowParser b (v1, v2, v3)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4) => RowParser b (v1, v2, v3, v4)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5) => RowParser b (v1, v2, v3, v4, v5)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6) => RowParser b (v1, v2, v3, v4, v5, v6)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7) => RowParser b (v1, v2, v3, v4, v5, v6, v7)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16, Mapping b v17) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16, Mapping b v17, Mapping b v18) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16, Mapping b v17, Mapping b v18, Mapping b v19) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18, v19)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16, Mapping b v17, Mapping b v18, Mapping b v19, Mapping b v20) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18, v19, v20)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16, Mapping b v17, Mapping b v18, Mapping b v19, Mapping b v20, Mapping b v21) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18, v19, v20, v21)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16, Mapping b v17, Mapping b v18, Mapping b v19, Mapping b v20, Mapping b v21, Mapping b v22) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18, v19, v20, v21, v22)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16, Mapping b v17, Mapping b v18, Mapping b v19, Mapping b v20, Mapping b v21, Mapping b v22, Mapping b v23) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18, v19, v20, v21, v22, v23)
(Mapping b v1, Mapping b v2, Mapping b v3, Mapping b v4, Mapping b v5, Mapping b v6, Mapping b v7, Mapping b v8, Mapping b v9, Mapping b v10, Mapping b v11, Mapping b v12, Mapping b v13, Mapping b v14, Mapping b v15, Mapping b v16, Mapping b v17, Mapping b v18, Mapping b v19, Mapping b v20, Mapping b v21, Mapping b v22, Mapping b v23, Mapping b v24) => RowParser b (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18, v19, v20, v21, v22, v23, v24)

Error

data Error Source

The only exception type that this API can raise.

Constructors

CantConnect Text	Cannot connect to a server.
ConnectionLost Text	The connection got interrupted.
ErroneousResult Text	An error returned from the database.
UnexpectedResult Text	Unexpected result structure. Indicates usage of inappropriate statement executor.
UnparsableTemplate Text	Incorrect statement template.
NotInTransaction	An operation, which requires a database transaction was executed without one.
UnparsableRow Text	Attempt to parse a row into an incompatible type. Indicates either a mismatching schema or an incorrect query.

Instances

Eq Error
Ord Error
Show Error
Exception Error
Typeable * Error