Database.Persist.Class

PersistStore

class MonadIO m => PersistStore m where

Minimal complete definition

get, insert, insertKey, repsert, replace, delete

Associated Types

type PersistMonadBackend m

Methods

get :: (PersistMonadBackend m ~ PersistEntityBackend val, PersistEntity val) => Key val -> m (Maybe val)

Get a record by identifier, if available.

insert :: (PersistMonadBackend m ~ PersistEntityBackend val, PersistEntity val) => val -> m (Key val)

Create a new record in the database, returning an automatically created key (in SQL an auto-increment id).

insert_ :: (PersistMonadBackend m ~ PersistEntityBackend val, PersistEntity val) => val -> m ()

Same as insert, but doesn't return a Key.

insertMany :: (PersistMonadBackend m ~ PersistEntityBackend val, PersistEntity val) => [val] -> m [Key val]

Create multiple records in the database. SQL backends currently use the slow default implementation of mapM insert

insertKey :: (PersistMonadBackend m ~ PersistEntityBackend val, PersistEntity val) => Key val -> val -> m ()

Create a new record in the database using the given key.

repsert :: (PersistMonadBackend m ~ PersistEntityBackend val, PersistEntity val) => Key val -> val -> m ()

Put the record in the database with the given key. Unlike replace, if a record with the given key does not exist then a new record will be inserted.

replace :: (PersistMonadBackend m ~ PersistEntityBackend val, PersistEntity val) => Key val -> val -> m ()

Replace the record in the database with the given key. Note that the result is undefined if such record does not exist, so you must use 'insertKey or repsert in these cases.

delete :: (PersistMonadBackend m ~ PersistEntityBackend val, PersistEntity val) => Key val -> m ()

Delete a specific record by identifier. Does nothing if record does not exist.

Instances

PersistStore m => PersistStore (MaybeT m)

PersistStore m => PersistStore (LoggingT m)

PersistStore m => PersistStore (ListT m)

PersistStore m => PersistStore (ResourceT m)

PersistStore m => PersistStore (IdentityT m)

(MonadResource m, MonadLogger m) => PersistStore (SqlPersistT m)

(Monoid w, PersistStore m) => PersistStore (WriterT w m)

(Monoid w, PersistStore m) => PersistStore (WriterT w m)

PersistStore m => PersistStore (StateT s m)

PersistStore m => PersistStore (StateT s m)

PersistStore m => PersistStore (ReaderT r m)

(Error e, PersistStore m) => PersistStore (ErrorT e m)

PersistStore m => PersistStore (ContT r m)

PersistStore m => PersistStore (ExceptT e m)

PersistStore m => PersistStore (ConduitM i o m)

(Monoid w, PersistStore m) => PersistStore (RWST r w s m)

(Monoid w, PersistStore m) => PersistStore (RWST r w s m)

PersistStore m => PersistStore (Pipe l i o u m)

getJust :: (PersistStore m, PersistEntity val, Show (Key val), PersistMonadBackend m ~ PersistEntityBackend val) => Key val -> m val

Same as get, but for a non-null (not Maybe) foreign key Unsafe unless your database is enforcing that the foreign key is valid

belongsTo :: (PersistStore m, PersistEntity ent1, PersistEntity ent2, PersistMonadBackend m ~ PersistEntityBackend ent2) => (ent1 -> Maybe (Key ent2)) -> ent1 -> m (Maybe ent2)

curry this to make a convenience function that loads an associated model > foreign = belongsTo foeignId

belongsToJust :: (PersistStore m, PersistEntity ent1, PersistEntity ent2, PersistMonadBackend m ~ PersistEntityBackend ent2) => (ent1 -> Key ent2) -> ent1 -> m ent2

same as belongsTo, but uses getJust and therefore is similarly unsafe

PersistUnique

class PersistStore m => PersistUnique m where

Queries against unique keys (other than the id).

Please read the general Persistent documentation to learn how to create Unique keys. SQL backends automatically create uniqueness constraints, but for MongoDB you must manually place a unique index on the field.

Some functions in this module (insertUnique, insertBy, and replaceUnique) first query the unique indexes to check for conflicts. You could instead optimistically attempt to perform the operation (e.g. replace instead of replaceUnique). However,

• there is some fragility to trying to catch the correct exception and determing the column of failure.
• an exception will automatically abort the current SQL transaction

Minimal complete definition

getBy, deleteBy

Methods

getBy :: (PersistEntityBackend val ~ PersistMonadBackend m, PersistEntity val) => Unique val -> m (Maybe (Entity val))

Get a record by unique key, if available. Returns also the identifier.

deleteBy :: (PersistEntityBackend val ~ PersistMonadBackend m, PersistEntity val) => Unique val -> m ()

Delete a specific record by unique key. Does nothing if no record matches.

insertUnique :: (PersistEntityBackend val ~ PersistMonadBackend m, PersistEntity val) => val -> m (Maybe (Key val))

Like insert, but returns Nothing when the record couldn't be inserted because of a uniqueness constraint.

Instances

PersistUnique m => PersistUnique (MaybeT m)

PersistUnique m => PersistUnique (LoggingT m)

PersistUnique m => PersistUnique (ListT m)

PersistUnique m => PersistUnique (ResourceT m)

PersistUnique m => PersistUnique (IdentityT m)

(MonadResource m, MonadLogger m) => PersistUnique (SqlPersistT m)

(Monoid w, PersistUnique m) => PersistUnique (WriterT w m)

(Monoid w, PersistUnique m) => PersistUnique (WriterT w m)

PersistUnique m => PersistUnique (StateT s m)

PersistUnique m => PersistUnique (StateT s m)

PersistUnique m => PersistUnique (ReaderT r m)

(Error e, PersistUnique m) => PersistUnique (ErrorT e m)

PersistUnique m => PersistUnique (ContT r m)

PersistUnique m => PersistUnique (ExceptT e m)

(Monoid w, PersistUnique m) => PersistUnique (RWST r w s m)

(Monoid w, PersistUnique m) => PersistUnique (RWST r w s m)

PersistUnique m => PersistUnique (Pipe l i o u m)

getByValue :: (PersistEntity value, PersistUnique m, PersistEntityBackend value ~ PersistMonadBackend m) => value -> m (Maybe (Entity value))

A modification of getBy, which takes the PersistEntity itself instead of a Unique value. Returns a value matching one of the unique keys. This function makes the most sense on entities with a single Unique constructor.

insertBy :: (PersistEntity val, PersistUnique m, PersistEntityBackend val ~ PersistMonadBackend m) => val -> m (Either (Entity val) (Key val))

Insert a value, checking for conflicts with any unique constraints. If a duplicate exists in the database, it is returned as Left. Otherwise, the new 'Key is returned as Right.

replaceUnique :: (Eq record, Eq (Unique record), PersistEntityBackend record ~ PersistMonadBackend m, PersistEntity record, PersistStore m, PersistUnique m) => Key record -> record -> m (Maybe (Unique record))

Attempt to replace the record of the given key with the given new record. First query the unique fields to make sure the replacement maintains uniqueness constraints. Return Nothing if the replacement was made. If uniqueness is violated, return a Just with the Unique violation

Since 1.2.2.0

PersistQuery

class PersistStore m => PersistQuery m where

Minimal complete definition

update, updateWhere, deleteWhere, selectSource, selectKeys, count

Methods

update :: (PersistEntity val, PersistEntityBackend val ~ PersistMonadBackend m) => Key val -> [Update val] -> m ()

Update individual fields on a specific record.

updateGet :: (PersistEntity val, PersistMonadBackend m ~ PersistEntityBackend val) => Key val -> [Update val] -> m val

Update individual fields on a specific record, and retrieve the updated value from the database.

Note that this function will throw an exception if the given key is not found in the database.

updateWhere :: (PersistEntity val, PersistEntityBackend val ~ PersistMonadBackend m) => [Filter val] -> [Update val] -> m ()

Update individual fields on any record matching the given criterion.

deleteWhere :: (PersistEntity val, PersistEntityBackend val ~ PersistMonadBackend m) => [Filter val] -> m ()

Delete all records matching the given criterion.

selectSource :: (PersistEntity val, PersistEntityBackend val ~ PersistMonadBackend m) => [Filter val] -> [SelectOpt val] -> Source m (Entity val)

Get all records matching the given criterion in the specified order. Returns also the identifiers.

selectFirst :: (PersistEntity val, PersistEntityBackend val ~ PersistMonadBackend m) => [Filter val] -> [SelectOpt val] -> m (Maybe (Entity val))

get just the first record for the criterion

selectKeys :: (PersistEntity val, PersistEntityBackend val ~ PersistMonadBackend m) => [Filter val] -> [SelectOpt val] -> Source m (Key val)

Get the Keys of all records matching the given criterion.

count :: (PersistEntity val, PersistEntityBackend val ~ PersistMonadBackend m) => [Filter val] -> m Int

The total number of records fulfilling the given criterion.

Instances

PersistQuery m => PersistQuery (MaybeT m)

PersistQuery m => PersistQuery (LoggingT m)

PersistQuery m => PersistQuery (ListT m)

PersistQuery m => PersistQuery (ResourceT m)

PersistQuery m => PersistQuery (IdentityT m)

(MonadResource m, MonadLogger m) => PersistQuery (SqlPersistT m)

(Monoid w, PersistQuery m) => PersistQuery (WriterT w m)

(Monoid w, PersistQuery m) => PersistQuery (WriterT w m)

PersistQuery m => PersistQuery (StateT s m)

PersistQuery m => PersistQuery (StateT s m)

PersistQuery m => PersistQuery (ReaderT r m)

(Error e, PersistQuery m) => PersistQuery (ErrorT e m)

PersistQuery m => PersistQuery (ContT r m)

PersistQuery m => PersistQuery (ExceptT e m)

PersistQuery m => PersistQuery (ConduitM i o m)

(Monoid w, PersistQuery m) => PersistQuery (RWST r w s m)

(Monoid w, PersistQuery m) => PersistQuery (RWST r w s m)

PersistQuery m => PersistQuery (Pipe l i o u m)

selectList :: (PersistEntity val, PersistQuery m, PersistEntityBackend val ~ PersistMonadBackend m) => [Filter val] -> [SelectOpt val] -> m [Entity val]

Call selectSource but return the result as a list.

selectKeysList :: (PersistEntity val, PersistQuery m, PersistEntityBackend val ~ PersistMonadBackend m) => [Filter val] -> [SelectOpt val] -> m [Key val]

Call selectKeys but return the result as a list.

DeleteCascade

class (PersistStore m, PersistEntity a, PersistEntityBackend a ~ PersistMonadBackend m) => DeleteCascade a m where

Methods

deleteCascade :: Key a -> m ()

deleteCascadeWhere :: (DeleteCascade a m, PersistQuery m) => [Filter a] -> m ()

PersistEntity

class PersistEntity record where

Persistent serialized Haskell records to the database. A Database Entity (A row in SQL, a document in MongoDB, etc) corresponds to a Key plus a Haskell record.

For every Haskell record type stored in the database there is a corresponding PersistEntity instance. An instance of PersistEntity contains meta-data for the record. PersistEntity also helps abstract over different record types. That way the same query interface can return a PersistEntity, with each query returning different types of Haskell records.

Some advanced type system capabilities are used to make this process type-safe. Persistent users usually don't need to understand the class associated data and functions.

Associated Types

data EntityField record :: * -> *

An EntityField is parameterised by the Haskell record it belongs to and the additional type of that field

type PersistEntityBackend record

Persistent allows multiple different backends

data Unique record

Unique keys besided the Key

Methods

persistFieldDef :: EntityField record typ -> FieldDef SqlType

return meta-data for a given EntityField

entityDef :: Monad m => m record -> EntityDef SqlType

retrieve the EntityDef meta-data for the record

toPersistFields :: record -> [SomePersistField]

Get the database fields of a record

fromPersistValues :: [PersistValue] -> Either Text record

Convert from database values to a Haskell record

persistUniqueToFieldNames :: Unique record -> [(HaskellName, DBName)]

persistUniqueToValues :: Unique record -> [PersistValue]

persistUniqueKeys :: record -> [Unique record]

persistIdField :: EntityField record (Key record)

fieldLens :: EntityField record field -> forall f. Functor f => (field -> f field) -> Entity record -> f (Entity record)

PersistField

class PersistField a where

A value which can be marshalled to and from a PersistValue.

Methods

toPersistValue :: a -> PersistValue

fromPersistValue :: PersistValue -> Either Text a

Instances

PersistField Bool

PersistField Double

PersistField Int

PersistField Int8

PersistField Int16

PersistField Int32

PersistField Int64

PersistField Rational

PersistField Word

PersistField Word8

PersistField Word16

PersistField Word32

PersistField Word64

PersistField String

PersistField ByteString

PersistField Text

PersistField UTCTime

PersistField Text

PersistField Html

PersistField ZonedTime

PersistField TimeOfDay

PersistField Day

PersistField PersistValue

PersistField Checkmark

PersistField SomePersistField

PersistField a => PersistField [a]

PersistField a => PersistField (Maybe a)

HasResolution a => PersistField (Fixed a)

(Ord a, PersistField a) => PersistField (Set a)

PersistField entity => PersistField (Entity entity)

(PersistField a, PersistField b) => PersistField (a, b)

PersistField v => PersistField (Map Text v)

PersistField (KeyBackend backend entity)

PersistConfig

class PersistConfig c where

Represents a value containing all the configuration options for a specific backend. This abstraction makes it easier to write code that can easily swap backends.

Minimal complete definition

loadConfig, createPoolConfig, runPool

Associated Types

type PersistConfigBackend c :: (* -> *) -> * -> *

type PersistConfigPool c

Methods

loadConfig :: Value -> Parser c

Load the config settings from a Value, most likely taken from a YAML config file.

applyEnv :: c -> IO c

Modify the config settings based on environment variables.

createPoolConfig :: c -> IO (PersistConfigPool c)

Create a new connection pool based on the given config settings.

runPool :: (MonadBaseControl IO m, MonadIO m) => c -> PersistConfigBackend c m a -> PersistConfigPool c -> m a

Run a database action by taking a connection from the pool.

Instances

(PersistConfig c1, PersistConfig c2, (~) * (PersistConfigPool c1) (PersistConfigPool c2), (~) ((* -> *) -> * -> *) (PersistConfigBackend c1) (PersistConfigBackend c2)) => PersistConfig (Either c1 c2)

JSON utilities

keyValueEntityToJSON :: ToJSON e => Entity e -> Value

Predefined toJSON. The resulting JSON looks like {"key": 1, "value": {"name": ...}}.

The typical usage is:

  instance ToJSON User where
      toJSON = keyValueEntityToJSON

keyValueEntityFromJSON :: FromJSON e => Value -> Parser (Entity e)

Predefined parseJSON. The input JSON looks like {"key": 1, "value": {"name": ...}}.

The typical usage is:

  instance FromJSON User where
      parseJSON = keyValueEntityFromJSON

entityIdToJSON :: ToJSON e => Entity e -> Value

Predefined toJSON. The resulting JSON looks like {"id": 1, "name": ...}.

The typical usage is:

  instance ToJSON User where
      toJSON = entityIdToJSON

entityIdFromJSON :: FromJSON e => Value -> Parser (Entity e)

Predefined parseJSON. The input JSON looks like {"id": 1, "name": ...}.

The typical usage is:

  instance FromJSON User where
      parseJSON = entityIdFromJSON