persistent-2.0.5: Type-safe, multi-backend data serialization.

Safe HaskellNone

Database.Persist.Class

Contents

Synopsis

PersistStore

class (Show (BackendKey backend), Read (BackendKey backend), Eq (BackendKey backend), Ord (BackendKey backend), PersistField (BackendKey backend), ToJSON (BackendKey backend), FromJSON (BackendKey backend)) => PersistStore backend whereSource

Associated Types

data BackendKey backend Source

Methods

get :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => Key val -> ReaderT backend m (Maybe val)Source

Get a record by identifier, if available.

insert :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => val -> ReaderT backend m (Key val)Source

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

insert_ :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => val -> ReaderT backend m ()Source

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

insertMany :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => [val] -> ReaderT backend m [Key val]Source

Create multiple records in the database.

If you don't need the inserted Keys, use insertMany_

SQL backends currently use the slow default implementation of mapM insert

insertMany_ :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => [val] -> ReaderT backend m ()Source

Same as insertMany, but doesn't return any Keys.

SQL backends currently use an efficient implementation for this unlike insertMany.

insertKey :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => Key val -> val -> ReaderT backend m ()Source

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

repsert :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => Key val -> val -> ReaderT backend m ()Source

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 :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => Key val -> val -> ReaderT backend m ()Source

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 :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => Key val -> ReaderT backend m ()Source

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

update :: (MonadIO m, PersistEntity val, backend ~ PersistEntityBackend val) => Key val -> [Update val] -> ReaderT backend m ()Source

Update individual fields on a specific record.

updateGet :: (MonadIO m, PersistEntity val, backend ~ PersistEntityBackend val) => Key val -> [Update val] -> ReaderT backend m valSource

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.

getJust :: (PersistStore backend, PersistEntity val, Show (Key val), backend ~ PersistEntityBackend val, MonadIO m) => Key val -> ReaderT backend m valSource

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 backend, PersistEntity ent1, PersistEntity ent2, backend ~ PersistEntityBackend ent2, MonadIO m) => (ent1 -> Maybe (Key ent2)) -> ent1 -> ReaderT backend m (Maybe ent2)Source

curry this to make a convenience function that loads an associated model

 foreign = belongsTo foerignId

belongsToJust :: (PersistStore backend, PersistEntity ent1, PersistEntity ent2, backend ~ PersistEntityBackend ent2, MonadIO m) => (ent1 -> Key ent2) -> ent1 -> ReaderT backend m ent2Source

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

PersistUnique

class PersistStore backend => PersistUnique backend whereSource

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

Methods

getBy :: (MonadIO m, backend ~ PersistEntityBackend val, PersistEntity val) => Unique val -> ReaderT backend m (Maybe (Entity val))Source

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

deleteBy :: (MonadIO m, PersistEntityBackend val ~ backend, PersistEntity val) => Unique val -> ReaderT backend m ()Source

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

insertUnique :: (MonadIO m, PersistEntityBackend val ~ backend, PersistEntity val) => val -> ReaderT backend m (Maybe (Key val))Source

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

upsertSource

Arguments

:: (MonadIO m, PersistEntityBackend val ~ backend, PersistEntity val) 
=> val

new record to insert

-> [Update val]

updates to perform if the record already exists. leaving this empty is the equivalent of performing a repsert on a unique key.

-> ReaderT backend m (Entity val)

the record in the database after the operation

update based on a uniquness constraint or insert

insert the new record if it does not exist update the existing record that matches the uniqueness contraint

Throws an exception if there is more than 1 uniqueness contraint

getByValue :: (MonadIO m, PersistEntity value, PersistUnique backend, PersistEntityBackend value ~ backend) => value -> ReaderT backend m (Maybe (Entity value))Source

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 :: (MonadIO m, PersistEntity val, PersistUnique backend, PersistEntityBackend val ~ backend) => val -> ReaderT backend m (Either (Entity val) (Key val))Source

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 :: (MonadIO m, Eq record, Eq (Unique record), PersistEntityBackend record ~ backend, PersistEntity record, PersistUnique backend) => Key record -> record -> ReaderT backend m (Maybe (Unique record))Source

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

checkUnique :: (MonadIO m, PersistEntityBackend record ~ backend, PersistEntity record, PersistUnique backend) => record -> ReaderT backend m (Maybe (Unique record))Source

Check whether there are any conflicts for unique keys with this entity and existing entities in the database.

Returns Nothing if the entity would be unique, and could thus safely be inserted. on a conflict returns the conflicting key

onlyUnique :: (MonadIO m, PersistEntity val, PersistUnique backend, PersistEntityBackend val ~ backend) => val -> ReaderT backend m (Unique val)Source

Return the single unique key for a record

PersistQuery

class PersistStore backend => PersistQuery backend whereSource

Methods

updateWhere :: (MonadIO m, PersistEntity val, backend ~ PersistEntityBackend val) => [Filter val] -> [Update val] -> ReaderT backend m ()Source

Update individual fields on any record matching the given criterion.

deleteWhere :: (MonadIO m, PersistEntity val, backend ~ PersistEntityBackend val) => [Filter val] -> ReaderT backend m ()Source

Delete all records matching the given criterion.

selectSourceRes :: (PersistEntity val, PersistEntityBackend val ~ backend, MonadIO m1, MonadIO m2) => [Filter val] -> [SelectOpt val] -> ReaderT backend m1 (Acquire (Source m2 (Entity val)))Source

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

selectFirst :: (MonadIO m, PersistEntity val, backend ~ PersistEntityBackend val) => [Filter val] -> [SelectOpt val] -> ReaderT backend m (Maybe (Entity val))Source

get just the first record for the criterion

selectKeysRes :: (MonadIO m1, MonadIO m2, PersistEntity val, backend ~ PersistEntityBackend val) => [Filter val] -> [SelectOpt val] -> ReaderT backend m1 (Acquire (Source m2 (Key val)))Source

Get the Keys of all records matching the given criterion.

count :: (MonadIO m, PersistEntity val, backend ~ PersistEntityBackend val) => [Filter val] -> ReaderT backend m IntSource

The total number of records fulfilling the given criterion.

selectSource :: (PersistQuery backend, MonadResource m, PersistEntity val, PersistEntityBackend val ~ backend, MonadReader env m, HasPersistBackend env backend) => [Filter val] -> [SelectOpt val] -> Source m (Entity val)Source

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

selectKeys :: (PersistQuery backend, MonadResource m, PersistEntity val, backend ~ PersistEntityBackend val, MonadReader env m, HasPersistBackend env backend) => [Filter val] -> [SelectOpt val] -> Source m (Key val)Source

Get the Keys of all records matching the given criterion.

selectList :: (MonadIO m, PersistEntity val, PersistQuery backend, PersistEntityBackend val ~ backend) => [Filter val] -> [SelectOpt val] -> ReaderT backend m [Entity val]Source

Call selectSource but return the result as a list.

selectKeysList :: (MonadIO m, PersistEntity val, PersistQuery backend, PersistEntityBackend val ~ backend) => [Filter val] -> [SelectOpt val] -> ReaderT backend m [Key val]Source

Call selectKeys but return the result as a list.

DeleteCascade

class (PersistStore backend, PersistEntity record, backend ~ PersistEntityBackend record) => DeleteCascade record backend whereSource

Methods

deleteCascade :: MonadIO m => Key record -> ReaderT backend m ()Source

deleteCascadeWhere :: (MonadIO m, DeleteCascade record backend, PersistQuery backend) => [Filter record] -> ReaderT backend m ()Source

PersistEntity

class (PersistField (Key record), ToJSON (Key record), FromJSON (Key record), Show (Key record), Read (Key record), Eq (Key record), Ord (Key record)) => PersistEntity record whereSource

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

type PersistEntityBackend record Source

Persistent allows multiple different backends (databases)

data Key record Source

By default, a backend will automatically generate the key Instead you can specify a Primary key made up of unique values.

data EntityField record :: * -> *Source

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

data Unique record Source

Unique keys besided the Key

Methods

keyToValues :: Key record -> [PersistValue]Source

a lower-level key operation

keyFromValues :: [PersistValue] -> Either Text (Key record)Source

a lower-level key operation

persistIdField :: EntityField record (Key record)Source

a meta-operation to retrieve the Key EntityField

entityDef :: Monad m => m record -> EntityDefSource

retrieve the EntityDef meta-data for the record

persistFieldDef :: EntityField record typ -> FieldDefSource

return meta-data for a given EntityField

toPersistFields :: record -> [SomePersistField]Source

A meta-operation to get the database fields of a record

fromPersistValues :: [PersistValue] -> Either Text recordSource

A lower-level operation to convert from database values to a Haskell record

persistUniqueKeys :: record -> [Unique record]Source

A meta operation to retrieve all the Unique keys

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

A lower level operation

persistUniqueToValues :: Unique record -> [PersistValue]Source

A lower level operation

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

Use a PersistField as a lens

PersistField

PersistConfig

class PersistConfig c whereSource

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.

Associated Types

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

type PersistConfigPool c Source

Methods

loadConfig :: Value -> Parser cSource

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

applyEnv :: c -> IO cSource

Modify the config settings based on environment variables.

createPoolConfig :: c -> IO (PersistConfigPool c)Source

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 aSource

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) 

Lifting

class HasPersistBackend env backend | env -> backend whereSource

Methods

persistBackend :: env -> backendSource

liftPersist :: (MonadReader env m, HasPersistBackend env backend, MonadIO m) => ReaderT backend IO a -> m aSource

JSON utilities

keyValueEntityToJSON :: (PersistEntity record, ToJSON record, ToJSON (Key record)) => Entity record -> ValueSource

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

The typical usage is:

   instance ToJSON User where
       toJSON = keyValueEntityToJSON

keyValueEntityFromJSON :: (PersistEntity record, FromJSON record, FromJSON (Key record)) => Value -> Parser (Entity record)Source

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

The typical usage is:

   instance FromJSON User where
       parseJSON = keyValueEntityFromJSON

entityIdToJSON :: (PersistEntity record, ToJSON record, ToJSON (Key record)) => Entity record -> ValueSource

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

The typical usage is:

   instance ToJSON User where
       toJSON = entityIdToJSON

entityIdFromJSON :: (PersistEntity record, FromJSON record, FromJSON (Key record)) => Value -> Parser (Entity record)Source

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

The typical usage is:

   instance FromJSON User where
       parseJSON = entityIdFromJSON