| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Database.Persist.Class
Description
This module exports all of the type classes in
persistent
for operating
on the database backends.
persistent
offers methods that are abstract in the specific
backend
type.
For SQL databases, this wil be
SqlBackend
.
Other database backends will define their own types.
Methods and functions in this module have examples documented under an "Example Usage" thing, that you need to click on to expand.
Synopsis
- type PersistStore a = PersistStoreWrite a
- class ( Show ( BackendKey backend), Read ( BackendKey backend), Eq ( BackendKey backend), Ord ( BackendKey backend), PersistCore backend, PersistField ( BackendKey backend), ToJSON ( BackendKey backend), FromJSON ( BackendKey backend)) => PersistStoreRead backend where
-
class
(
Show
(
BackendKey
backend),
Read
(
BackendKey
backend),
Eq
(
BackendKey
backend),
Ord
(
BackendKey
backend),
PersistStoreRead
backend,
PersistField
(
BackendKey
backend),
ToJSON
(
BackendKey
backend),
FromJSON
(
BackendKey
backend)) =>
PersistStoreWrite
backend
where
- insert :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m ( Key record)
- insert_ :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m ()
- insertMany :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [record] -> ReaderT backend m [ Key record]
- insertMany_ :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [record] -> ReaderT backend m ()
- insertEntityMany :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [ Entity record] -> ReaderT backend m ()
- insertKey :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> record -> ReaderT backend m ()
- repsert :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> record -> ReaderT backend m ()
- repsertMany :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [( Key record, record)] -> ReaderT backend m ()
- replace :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> record -> ReaderT backend m ()
- delete :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> ReaderT backend m ()
- update :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> [ Update record] -> ReaderT backend m ()
- updateGet :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> [ Update record] -> ReaderT backend m record
- type PersistRecordBackend record backend = ( PersistEntity record, PersistEntityBackend record ~ BaseBackend backend)
- getJust :: forall record backend m. ( PersistStoreRead backend, PersistRecordBackend record backend, MonadIO m) => Key record -> ReaderT backend m record
- getJustEntity :: forall record backend m. ( PersistEntityBackend record ~ BaseBackend backend, MonadIO m, PersistEntity record, PersistStoreRead backend) => Key record -> ReaderT backend m ( Entity record)
- getEntity :: forall e backend m. ( PersistStoreRead backend, PersistRecordBackend e backend, MonadIO m) => Key e -> ReaderT backend m ( Maybe ( Entity e))
- belongsTo :: forall ent1 ent2 backend m. ( PersistStoreRead backend, PersistEntity ent1, PersistRecordBackend ent2 backend, MonadIO m) => (ent1 -> Maybe ( Key ent2)) -> ent1 -> ReaderT backend m ( Maybe ent2)
- belongsToJust :: forall ent1 ent2 backend m. ( PersistStoreRead backend, PersistEntity ent1, PersistRecordBackend ent2 backend, MonadIO m) => (ent1 -> Key ent2) -> ent1 -> ReaderT backend m ent2
- insertEntity :: forall e backend m. ( PersistStoreWrite backend, PersistRecordBackend e backend, MonadIO m) => e -> ReaderT backend m ( Entity e)
- insertRecord :: forall record backend m. ( PersistEntityBackend record ~ BaseBackend backend, PersistEntity record, MonadIO m, PersistStoreWrite backend) => record -> ReaderT backend m record
- type PersistUnique a = PersistUniqueWrite a
- class PersistStoreRead backend => PersistUniqueRead backend where
-
class
(
PersistUniqueRead
backend,
PersistStoreWrite
backend) =>
PersistUniqueWrite
backend
where
- deleteBy :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Unique record -> ReaderT backend m ()
- insertUnique :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m ( Maybe ( Key record))
- upsert :: forall record m. ( MonadIO m, PersistRecordBackend record backend, OnlyOneUniqueKey record) => record -> [ Update record] -> ReaderT backend m ( Entity record)
- upsertBy :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Unique record -> record -> [ Update record] -> ReaderT backend m ( Entity record)
- putMany :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [record] -> ReaderT backend m ()
-
class
PersistEntity
record =>
OnlyOneUniqueKey
record
where
- onlyUniqueP :: record -> Unique record
-
class
PersistEntity
record =>
AtLeastOneUniqueKey
record
where
- requireUniquesP :: record -> NonEmpty ( Unique record)
- onlyOneUniqueDef :: ( OnlyOneUniqueKey record, Monad proxy) => proxy record -> UniqueDef
- type NoUniqueKeysError ty = ((' Text "The entity " :<>: ' ShowType ty) :<>: ' Text " does not have any unique keys.") :$$: (' Text "The function you are trying to call requires a unique key " :<>: ' Text "to be defined on the entity.")
- type MultipleUniqueKeysError ty = (((' Text "The entity " :<>: ' ShowType ty) :<>: ' Text " has multiple unique keys.") :$$: (' Text "The function you are trying to call requires only a single " :<>: ' Text "unique key.")) :$$: ((' Text "There is probably a variant of the function with 'By' " :<>: ' Text "appended that will allow you to select a unique key ") :<>: ' Text "for the operation.")
- getByValue :: forall record m backend. ( MonadIO m, PersistUniqueRead backend, PersistRecordBackend record backend, AtLeastOneUniqueKey record) => record -> ReaderT backend m ( Maybe ( Entity record))
- insertBy :: forall record backend m. ( MonadIO m, PersistUniqueWrite backend, PersistRecordBackend record backend, AtLeastOneUniqueKey record) => record -> ReaderT backend m ( Either ( Entity record) ( Key record))
- insertUniqueEntity :: forall record backend m. ( MonadIO m, PersistRecordBackend record backend, PersistUniqueWrite backend) => record -> ReaderT backend m ( Maybe ( Entity record))
- replaceUnique :: forall record backend m. ( MonadIO m, Eq ( Unique record), PersistRecordBackend record backend, PersistUniqueWrite backend) => Key record -> record -> ReaderT backend m ( Maybe ( Unique record))
- checkUnique :: forall record backend m. ( MonadIO m, PersistRecordBackend record backend, PersistUniqueRead backend) => record -> ReaderT backend m ( Maybe ( Unique record))
- checkUniqueUpdateable :: forall record backend m. ( MonadIO m, PersistRecordBackend record backend, PersistUniqueRead backend) => Entity record -> ReaderT backend m ( Maybe ( Unique record))
- onlyUnique :: forall record backend m. ( MonadIO m, PersistUniqueWrite backend, PersistRecordBackend record backend, OnlyOneUniqueKey record) => record -> ReaderT backend m ( Unique record)
- selectList :: forall record backend m. ( MonadIO m, PersistQueryRead backend, PersistRecordBackend record backend) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m [ Entity record]
- selectKeys :: forall record backend m. ( PersistQueryRead backend, MonadResource m, PersistRecordBackend record backend, MonadReader backend m) => [ Filter record] -> [ SelectOpt record] -> ConduitM () ( Key record) m ()
- type PersistQuery a = PersistQueryWrite a
-
class
(
PersistCore
backend,
PersistStoreRead
backend) =>
PersistQueryRead
backend
where
- selectSourceRes :: ( PersistRecordBackend record backend, MonadIO m1, MonadIO m2) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m1 ( Acquire ( ConduitM () ( Entity record) m2 ()))
- selectFirst :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m ( Maybe ( Entity record))
- selectKeysRes :: ( MonadIO m1, MonadIO m2, PersistRecordBackend record backend) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m1 ( Acquire ( ConduitM () ( Key record) m2 ()))
- count :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> ReaderT backend m Int
- exists :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> ReaderT backend m Bool
-
class
(
PersistQueryRead
backend,
PersistStoreWrite
backend) =>
PersistQueryWrite
backend
where
- updateWhere :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> [ Update record] -> ReaderT backend m ()
- deleteWhere :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> ReaderT backend m ()
- selectSource :: forall record backend m. ( PersistQueryRead backend, MonadResource m, PersistRecordBackend record backend, MonadReader backend m) => [ Filter record] -> [ SelectOpt record] -> ConduitM () ( Entity record) m ()
- selectKeysList :: forall record backend m. ( MonadIO m, PersistQueryRead backend, PersistRecordBackend record backend) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m [ Key record]
-
class
(
PersistStoreWrite
backend,
PersistEntity
record,
BaseBackend
backend ~
PersistEntityBackend
record) =>
DeleteCascade
record backend
where
- deleteCascade :: MonadIO m => Key record -> ReaderT backend m ()
- deleteCascadeWhere :: forall record backend m. ( MonadIO m, DeleteCascade record backend, PersistQueryWrite backend) => [ Filter record] -> ReaderT backend m ()
-
class
(
PersistField
(
Key
record),
ToJSON
(
Key
record),
FromJSON
(
Key
record),
Show
(
Key
record),
Read
(
Key
record),
Eq
(
Key
record),
Ord
(
Key
record)) =>
PersistEntity
record
where
- type PersistEntityBackend record
- data Key record
- data EntityField record :: Type -> Type
- data Unique record
- keyToValues :: Key record -> [ PersistValue ]
- keyFromValues :: [ PersistValue ] -> Either Text ( Key record)
- persistIdField :: EntityField record ( Key record)
- entityDef :: proxy record -> EntityDef
- persistFieldDef :: EntityField record typ -> FieldDef
- toPersistFields :: record -> [ SomePersistField ]
- fromPersistValues :: [ PersistValue ] -> Either Text record
- persistUniqueKeys :: record -> [ Unique record]
- persistUniqueToFieldNames :: Unique record -> NonEmpty ( FieldNameHS , FieldNameDB )
- persistUniqueToValues :: Unique record -> [ PersistValue ]
- fieldLens :: EntityField record field -> forall f. Functor f => (field -> f field) -> Entity record -> f ( Entity record)
- keyFromRecordM :: Maybe (record -> Key record)
-
class
SymbolToField
(sym ::
Symbol
) rec typ | sym rec -> typ
where
- symbolToField :: EntityField rec typ
-
class
PersistField
a
where
- toPersistValue :: a -> PersistValue
- fromPersistValue :: PersistValue -> Either Text a
-
class
PersistConfig
c
where
- type PersistConfigBackend c :: ( Type -> Type ) -> Type -> Type
- type PersistConfigPool c
- loadConfig :: Value -> Parser c
- applyEnv :: c -> IO c
- createPoolConfig :: c -> IO ( PersistConfigPool c)
- runPool :: MonadUnliftIO m => c -> PersistConfigBackend c m a -> PersistConfigPool c -> m a
- entityValues :: PersistEntity record => Entity record -> [ PersistValue ]
-
class
HasPersistBackend
backend
where
- type BaseBackend backend
- persistBackend :: backend -> BaseBackend backend
- withBaseBackend :: HasPersistBackend backend => ReaderT ( BaseBackend backend) m a -> ReaderT backend m a
- class HasPersistBackend backend => IsPersistBackend backend
- liftPersist :: ( MonadIO m, MonadReader backend m) => ReaderT backend IO b -> m b
-
class
BackendCompatible
sup sub
where
- projectBackend :: sub -> sup
- withCompatibleBackend :: BackendCompatible sup sub => ReaderT sup m a -> ReaderT sub m a
-
class
PersistCore
backend
where
- data BackendKey backend
-
class
(
PersistEntity
record,
PersistEntityBackend
record ~ backend,
PersistCore
backend) =>
ToBackendKey
backend record
where
- toBackendKey :: Key record -> BackendKey backend
- fromBackendKey :: BackendKey backend -> Key record
- keyValueEntityToJSON :: ( PersistEntity record, ToJSON record) => Entity record -> Value
- keyValueEntityFromJSON :: ( PersistEntity record, FromJSON record) => Value -> Parser ( Entity record)
- entityIdToJSON :: ( PersistEntity record, ToJSON record) => Entity record -> Value
- entityIdFromJSON :: ( PersistEntity record, FromJSON record) => Value -> Parser ( Entity record)
- toPersistValueJSON :: ToJSON a => a -> PersistValue
- fromPersistValueJSON :: FromJSON a => PersistValue -> Either Text a
PersistStore
The
PersistStore
,
PersistStoreRead
, and
PersistStoreWrite
type
classes are used to define basic operations on the database. A database
that implements these classes is capable of being used as a simple
key-value store.
All the examples present here will be explained based on these schemas, datasets and functions:
schema-1
share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistLowerCase|
User
name String
age Int
deriving Show
|]
dataset-1
+----+-------+-----+ | id | name | age | +----+-------+-----+ | 1 | SPJ | 40 | +----+-------+-----+ | 2 | Simon | 41 | +----+-------+-----+
type PersistStore a = PersistStoreWrite a Source #
A backwards-compatible alias for those that don't care about distinguishing between read and write queries. It signifies the assumption that, by default, a backend can write as well as read.
class ( Show ( BackendKey backend), Read ( BackendKey backend), Eq ( BackendKey backend), Ord ( BackendKey backend), PersistCore backend, PersistField ( BackendKey backend), ToJSON ( BackendKey backend), FromJSON ( BackendKey backend)) => PersistStoreRead backend where Source #
Minimal complete definition
Methods
get :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> ReaderT backend m ( Maybe record) Source #
Get a record by identifier, if available.
Example usage
getMany :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [ Key record] -> ReaderT backend m ( Map ( Key record) record) Source #
Get many records by their respective identifiers, if available.
Example usage
getUsers :: MonadIO m => ReaderT SqlBackend m (Map (Key User) User) getUsers = getMany allkeys
musers <- getUsers
The above query when applied on dataset-1 , will get these records:
+----+-------+-----+ | id | name | age | +----+-------+-----+ | 1 | SPJ | 40 | +----+-------+-----+ | 2 | Simon | 41 | +----+-------+-----+
Since: 2.8.1
Instances
class ( Show ( BackendKey backend), Read ( BackendKey backend), Eq ( BackendKey backend), Ord ( BackendKey backend), PersistStoreRead backend, PersistField ( BackendKey backend), ToJSON ( BackendKey backend), FromJSON ( BackendKey backend)) => PersistStoreWrite backend where Source #
Methods
insert :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m ( Key record) Source #
Create a new record in the database, returning an automatically created key (in SQL an auto-increment id).
Example usage
Using
schema-1
and
dataset-1
, let's insert a new user
John
.
insertJohn :: MonadIO m => ReaderT SqlBackend m (Key User) insertJohn = insert $ User "John" 30
johnId <- insertJohn
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |John |30 | +-----+------+-----+
insert_ :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m () Source #
Same as
insert
, but doesn't return a
Key
.
Example usage
insertJohn :: MonadIO m => ReaderT SqlBackend m (Key User) insertJohn = insert_ $ User "John" 30
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |John |30 | +-----+------+-----+
insertMany :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [record] -> ReaderT backend m [ Key record] Source #
Create multiple records in the database and return their
Key
s.
If you don't need the inserted
Key
s, use
insertMany_
.
The MongoDB and PostgreSQL backends insert all records and retrieve their keys in one database query.
The SQLite and MySQL backends use the slow, default implementation of
mapM insert
.
Example usage
insertUsers :: MonadIO m => ReaderT SqlBackend m [Key User] insertUsers = insertMany [User "John" 30, User "Nick" 32, User "Jane" 20]
userIds <- insertUsers
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |John |30 | +-----+------+-----+ |4 |Nick |32 | +-----+------+-----+ |5 |Jane |20 | +-----+------+-----+
insertMany_ :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [record] -> ReaderT backend m () Source #
Same as
insertMany
, but doesn't return any
Key
s.
The MongoDB, PostgreSQL, SQLite and MySQL backends insert all records in one database query.
Example usage
insertUsers_ :: MonadIO m => ReaderT SqlBackend m () insertUsers_ = insertMany_ [User "John" 30, User "Nick" 32, User "Jane" 20]
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |John |30 | +-----+------+-----+ |4 |Nick |32 | +-----+------+-----+ |5 |Jane |20 | +-----+------+-----+
insertEntityMany :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [ Entity record] -> ReaderT backend m () Source #
Same as
insertMany_
, but takes an
Entity
instead of just a record.
Useful when migrating data from one entity to another and want to preserve ids.
The MongoDB, PostgreSQL, SQLite and MySQL backends insert all records in one database query.
Example usage
insertUserEntityMany :: MonadIO m => ReaderT SqlBackend m () insertUserEntityMany = insertEntityMany [SnakeEntity, EvaEntity]
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |Snake |38 | +-----+------+-----+ |4 |Eva |38 | +-----+------+-----+
insertKey :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> record -> ReaderT backend m () Source #
Create a new record in the database using the given key.
Example usage
insertAliceKey :: MonadIO m => Key User -> ReaderT SqlBackend m () insertAliceKey key = insertKey key $ User "Alice" 20
insertAliceKey $ UserKey {unUserKey = SqlBackendKey {unSqlBackendKey = 3}}
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |Alice |20 | +-----+------+-----+
repsert :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> record -> 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.
Example usage
We try to explain
upsertBy
using
schema-1
and
dataset-1
.
First, we insert Philip to dataset-1 .
insertPhilip :: MonadIO m => ReaderT SqlBackend m (Key User) insertPhilip = insert $ User "Philip" 42
philipId <- insertPhilip
This query will produce:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |Philip|42 | +-----+------+-----+
repsertHaskell :: MonadIO m => Key record -> ReaderT SqlBackend m () repsertHaskell id = repsert id $ User "Haskell" 81
repsertHaskell philipId
This query will replace Philip's record with Haskell's one:
+-----+-----------------+--------+ |id |name |age | +-----+-----------------+--------+ |1 |SPJ |40 | +-----+-----------------+--------+ |2 |Simon |41 | +-----+-----------------+--------+ |3 |Philip -> Haskell|42 -> 81| +-----+-----------------+--------+
repsert
inserts the given record if the key doesn't exist.
repsertXToUnknown :: MonadIO m => ReaderT SqlBackend m () repsertXToUnknown = repsert unknownId $ User "X" 999
For example, applying the above query to dataset-1 will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |X |999 | +-----+------+-----+
repsertMany :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => [( Key record, record)] -> ReaderT backend m () Source #
Put many entities into the database.
Batch version of
repsert
for SQL backends.
Useful when migrating data from one entity to another and want to preserve ids.
Example usage
repsertManyUsers :: MonadIO m =>ReaderT SqlBackend m () repsertManyusers = repsertMany [(simonId, User "Philip" 20), (unknownId999, User "Mr. X" 999)]
The above query when applied on dataset-1 , will produce this:
+-----+----------------+---------+ |id |name |age | +-----+----------------+---------+ |1 |SPJ |40 | +-----+----------------+---------+ |2 |Simon -> Philip |41 -> 20 | +-----+----------------+---------+ |999 |Mr. X |999 | +-----+----------------+---------+
Since: 2.8.1
replace :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> record -> 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.
Example usage
With schema-1 schama-1 and dataset-1 ,
replaceSpj :: MonadIO m => User -> ReaderT SqlBackend m () replaceSpj record = replace spjId record
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |Mike |45 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+
delete :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> ReaderT backend m () Source #
Delete a specific record by identifier. Does nothing if record does not exist.
Example usage
update :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> [ Update record] -> ReaderT backend m () Source #
Update individual fields on a specific record.
Example usage
updateSpj :: MonadIO m => [Update User] -> ReaderT SqlBackend m () updateSpj updates = update spjId updates
updateSpj [UserAge +=. 100]
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |140 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+
updateGet :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Key record -> [ Update record] -> ReaderT backend m record Source #
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.
Example usage
updateGetSpj :: MonadIO m => [Update User] -> ReaderT SqlBackend m User updateGetSpj updates = updateGet spjId updates
spj <- updateGetSpj [UserAge +=. 100]
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |140 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+
Instances
type PersistRecordBackend record backend = ( PersistEntity record, PersistEntityBackend record ~ BaseBackend backend) Source #
A convenient alias for common type signatures
getJust :: forall record backend m. ( PersistStoreRead backend, PersistRecordBackend record backend, MonadIO m) => Key record -> ReaderT backend m record Source #
Same as
get
, but for a non-null (not Maybe) foreign key.
Unsafe unless your database is enforcing that the foreign key is valid.
Example usage
getJustSpj :: MonadIO m => ReaderT SqlBackend m User getJustSpj = getJust spjId
spj <- getJust spjId
The above query when applied on dataset-1 , will get this record:
+----+------+-----+ | id | name | age | +----+------+-----+ | 1 | SPJ | 40 | +----+------+-----+
getJustUnknown :: MonadIO m => ReaderT SqlBackend m User getJustUnknown = getJust unknownId
mrx <- getJustUnknown
This just throws an error.
getJustEntity :: forall record backend m. ( PersistEntityBackend record ~ BaseBackend backend, MonadIO m, PersistEntity record, PersistStoreRead backend) => Key record -> ReaderT backend m ( Entity record) Source #
Same as
getJust
, but returns an
Entity
instead of just the record.
Example usage
getJustEntitySpj :: MonadIO m => ReaderT SqlBackend m (Entity User) getJustEntitySpj = getJustEntity spjId
spjEnt <- getJustEntitySpj
The above query when applied on dataset-1 , will get this entity:
+----+------+-----+ | id | name | age | +----+------+-----+ | 1 | SPJ | 40 | +----+------+-----+
Since: 2.6.1
getEntity :: forall e backend m. ( PersistStoreRead backend, PersistRecordBackend e backend, MonadIO m) => Key e -> ReaderT backend m ( Maybe ( Entity e)) Source #
Like
get
, but returns the complete
Entity
.
Example usage
getSpjEntity :: MonadIO m => ReaderT SqlBackend m (Maybe (Entity User)) getSpjEntity = getEntity spjId
mSpjEnt <- getSpjEntity
The above query when applied on dataset-1 , will get this entity:
+----+------+-----+ | id | name | age | +----+------+-----+ | 1 | SPJ | 40 | +----+------+-----+
belongsTo :: forall ent1 ent2 backend m. ( PersistStoreRead backend, PersistEntity ent1, PersistRecordBackend ent2 backend, 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 foreignId
belongsToJust :: forall ent1 ent2 backend m. ( PersistStoreRead backend, PersistEntity ent1, PersistRecordBackend ent2 backend, MonadIO m) => (ent1 -> Key ent2) -> ent1 -> ReaderT backend m ent2 Source #
Same as
belongsTo
, but uses
getJust
and therefore is similarly unsafe.
insertEntity :: forall e backend m. ( PersistStoreWrite backend, PersistRecordBackend e backend, MonadIO m) => e -> ReaderT backend m ( Entity e) Source #
Like
insert
, but returns the complete
Entity
.
Example usage
insertHaskellEntity :: MonadIO m => ReaderT SqlBackend m (Entity User) insertHaskellEntity = insertEntity $ User "Haskell" 81
haskellEnt <- insertHaskellEntity
The above query when applied on dataset-1 , will produce this:
+----+---------+-----+ | id | name | age | +----+---------+-----+ | 1 | SPJ | 40 | +----+---------+-----+ | 2 | Simon | 41 | +----+---------+-----+ | 3 | Haskell | 81 | +----+---------+-----+
insertRecord :: forall record backend m. ( PersistEntityBackend record ~ BaseBackend backend, PersistEntity record, MonadIO m, PersistStoreWrite backend) => record -> ReaderT backend m record Source #
Like
insertEntity
but just returns the record instead of
Entity
.
Example usage
insertDaveRecord :: MonadIO m => ReaderT SqlBackend m User insertDaveRecord = insertRecord $ User "Dave" 50
dave <- insertDaveRecord
The above query when applied on dataset-1 , will produce this:
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |Dave |50 | +-----+------+-----+
Since: 2.6.1
PersistUnique
The
PersistUnique
type class is relevant for database backends that
offer uniqueness keys. Uniquenes keys allow us to perform operations like
getBy
,
deleteBy
, as well as
upsert
and
putMany
.
All the examples present here will be explained based on these two schemas and the dataset:
schema-1
This schema has single unique constraint.
share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistLowerCase|
User
name String
age Int
UniqueUserName name
deriving Show
|]
schema-2
This schema has two unique constraints.
share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistLowerCase|
User
name String
age Int
UniqueUserName name
UniqueUserAge age
deriving Show
|]
dataset-1
+-----+-----+-----+ |id |name |age | +-----+-----+-----+ |1 |SPJ |40 | +-----+-----+-----+ |2 |Simon|41 | +-----+-----+-----+
type PersistUnique a = PersistUniqueWrite a Source #
A backwards-compatible alias for those that don't care about distinguishing between read and write queries. It signifies the assumption that, by default, a backend can write as well as read.
class PersistStoreRead backend => PersistUniqueRead backend where Source #
Queries against
Unique
keys (other than the id
Key
).
Please read the general Persistent documentation to learn how to create
Unique
keys.
Using this with an Entity without a Unique key leads to undefined
behavior. A few of these functions require a
single
Unique
, so using
an Entity with multiple
Unique
s is also undefined. In these cases
persistent's goal is to throw an exception as soon as possible, but
persistent is still transitioning to that.
SQL backends automatically create uniqueness constraints, but for MongoDB you must manually place a unique index on a field to have a uniqueness constraint.
Methods
getBy :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Unique record -> ReaderT backend m ( Maybe ( Entity record)) Source #
Get a record by unique key, if available. Returns also the identifier.
Example usage
getBySpjName :: MonadIO m => ReaderT SqlBackend m (Maybe (Entity User)) getBySpjName = getBy $ UniqueUserName "SPJ"
mSpjEnt <- getBySpjName
The above query when applied on dataset-1 , will get this entity:
+----+------+-----+ | id | name | age | +----+------+-----+ | 1 | SPJ | 40 | +----+------+-----+
Instances
class ( PersistUniqueRead backend, PersistStoreWrite backend) => PersistUniqueWrite backend where Source #
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
Methods
deleteBy :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => Unique record -> ReaderT backend m () Source #
Delete a specific record by unique key. Does nothing if no record matches.
Example usage
insertUnique :: forall record m. ( MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m ( Maybe ( Key record)) Source #
Like
insert
, but returns
Nothing
when the record
couldn't be inserted because of a uniqueness constraint.
Example usage
With schema-1 and dataset-1 , we try to insert the following two records:
linusId <- insertUnique $ User "Linus" 48 spjId <- insertUnique $ User "SPJ" 90
+-----+------+-----+ |id |name |age | +-----+------+-----+ |1 |SPJ |40 | +-----+------+-----+ |2 |Simon |41 | +-----+------+-----+ |3 |Linus |48 | +-----+------+-----+
Linus's record was inserted to dataset-1 , while SPJ wasn't because SPJ already exists in dataset-1 .
Arguments
| :: forall record m. ( MonadIO m, PersistRecordBackend record backend, OnlyOneUniqueKey record) | |
| => record |
new record to insert |
| -> [ Update record] |
updates to perform if the record already exists |
| -> ReaderT backend m ( Entity record) |
the record in the database after the operation |
Update based on a uniqueness constraint or insert:
- insert the new record if it does not exist;
- If the record exists (matched via it's uniqueness constraint), then update the existing record with the parameters which is passed on as list to the function.
Example usage
First, we try to explain
upsert
using
schema-1
and
dataset-1
.
upsertSpj :: MonadIO m => [Update User] -> ReaderT SqlBackend m (Maybe (Entity User)) upsertSpj updates = upsert (User "SPJ" 999) upadtes
mSpjEnt <- upsertSpj [UserAge +=. 15]
The above query when applied on dataset-1 , will produce this:
+-----+-----+--------+ |id |name |age | +-----+-----+--------+ |1 |SPJ |40 -> 55| +-----+-----+--------+ |2 |Simon|41 | +-----+-----+--------+
upsertX :: MonadIO m => [Update User] -> ReaderT SqlBackend m (Maybe (Entity User)) upsertX updates = upsert (User "X" 999) updates
mXEnt <- upsertX [UserAge +=. 15]
The above query when applied on dataset-1 , will produce this:
+-----+-----+--------+ |id |name |age | +-----+-----+--------+ |1 |SPJ |40 | +-----+-----+--------+ |2 |Simon|41 | +-----+-----+--------+ |3 |X |999 | +-----+-----+--------+
Next, what if the schema has two uniqueness constraints? Let's check it out using schema-2 :
mSpjEnt <- upsertSpj [UserAge +=. 15]
This fails with a compile-time type error alerting us to the fact
that this record has multiple unique keys, and suggests that we look for
upsertBy
to select the unique key we want.
Arguments
| :: forall record m. ( MonadIO m, PersistRecordBackend record backend) | |
| => Unique record |
uniqueness constraint to find by |
| -> record |
new record to insert |
| -> [ Update record] |
updates to perform if the record already exists |
| -> ReaderT backend m ( Entity record) |
the record in the database after the operation |
Update based on a given uniqueness constraint or insert:
- insert the new record if it does not exist;
- update the existing record that matches the given uniqueness constraint.
Example usage
We try to explain
upsertBy
using
schema-2
and
dataset-1
.
upsertBySpjName :: MonadIO m => User -> [Update User] -> ReaderT SqlBackend m (Entity User) upsertBySpjName record updates = upsertBy (UniqueUserName "SPJ") record updates
mSpjEnt <- upsertBySpjName (Person "X" 999) [PersonAge += .15]
The above query will alter dataset-1 to:
+-----+-----+--------+ |id |name |age | +-----+-----+--------+ |1 |SPJ |40 -> 55| +-----+-----+--------+ |2 |Simon|41 | +-----+-----+--------+
upsertBySimonAge :: MonadIO m => User -> [Update User] -> ReaderT SqlBackend m (Entity User) upsertBySimonAge record updates = upsertBy (UniqueUserName "SPJ") record updates
mPhilipEnt <- upsertBySimonAge (User "X" 999) [UserName =. "Philip"]
The above query will alter dataset-1 to:
+----+-----------------+-----+ | id | name | age | +----+-----------------+-----+ | 1 | SPJ | 40 | +----+-----------------+-----+ | 2 | Simon -> Philip | 41 | +----+-----------------+-----+
upsertByUnknownName :: MonadIO m => User -> [Update User] -> ReaderT SqlBackend m (Entity User) upsertByUnknownName record updates = upsertBy (UniqueUserName "Unknown") record updates
mXEnt <- upsertByUnknownName (User "X" 999) [UserAge +=. 15]
This query will alter dataset-1 to:
+-----+-----+-----+ |id |name |age | +-----+-----+-----+ |1 |SPJ |40 | +-----+-----+-----+ |2 |Simon|41 | +-----+-----+-----+ |3 |X |999 | +-----+-----+-----+
Arguments
| :: forall record m. ( MonadIO m, PersistRecordBackend record backend) | |
| => [record] |
A list of the records you want to insert or replace. |
| -> ReaderT backend m () |
Put many records into db
- insert new records that do not exist (or violate any unique constraints)
- replace existing records (matching any unique constraint)
Since: 2.8.1
Instances
class PersistEntity record => OnlyOneUniqueKey record where Source #
This class is used to ensure that
upsert
is only called on records
that have a single
Unique
key. The quasiquoter automatically generates
working instances for appropriate records, and generates
TypeError
instances for records that have 0 or multiple unique keys.
Since: 2.10.0
Methods
onlyUniqueP :: record -> Unique record Source #
class PersistEntity record => AtLeastOneUniqueKey record where Source #
This class is used to ensure that functions requring at least one
unique key are not called with records that have 0 unique keys. The
quasiquoter automatically writes working instances for appropriate
entities, and generates
TypeError
instances for records that have
0 unique keys.
Since: 2.10.0
Methods
requireUniquesP :: record -> NonEmpty ( Unique record) Source #
onlyOneUniqueDef :: ( OnlyOneUniqueKey record, Monad proxy) => proxy record -> UniqueDef Source #
Given a proxy for a
PersistEntity
record, this returns the sole
UniqueDef
for that entity.
Since: 2.13.0.0
type NoUniqueKeysError ty = ((' Text "The entity " :<>: ' ShowType ty) :<>: ' Text " does not have any unique keys.") :$$: (' Text "The function you are trying to call requires a unique key " :<>: ' Text "to be defined on the entity.") Source #
This is an error message. It is used when writing instances of
OnlyOneUniqueKey
for an entity that has no unique keys.
Since: 2.10.0
type MultipleUniqueKeysError ty = (((' Text "The entity " :<>: ' ShowType ty) :<>: ' Text " has multiple unique keys.") :$$: (' Text "The function you are trying to call requires only a single " :<>: ' Text "unique key.")) :$$: ((' Text "There is probably a variant of the function with 'By' " :<>: ' Text "appended that will allow you to select a unique key ") :<>: ' Text "for the operation.") Source #
This is an error message. It is used when an entity has multiple unique keys, and the function expects a single unique key.
Since: 2.10.0
getByValue :: forall record m backend. ( MonadIO m, PersistUniqueRead backend, PersistRecordBackend record backend, AtLeastOneUniqueKey record) => record -> ReaderT backend m ( Maybe ( Entity record)) Source #
A modification of
getBy
, which takes the
PersistEntity
itself instead
of a
Unique
record. Returns a record matching
one
of the unique keys. This
function makes the most sense on entities with a single
Unique
constructor.
Example usage
getBySpjValue :: MonadIO m => ReaderT SqlBackend m (Maybe (Entity User)) getBySpjValue = getByValue $ User SPJ 999
mSpjEnt <- getBySpjValue
The above query when applied on dataset-1 , will get this record:
+----+------+-----+ | id | name | age | +----+------+-----+ | 1 | SPJ | 40 | +----+------+-----+
insertBy :: forall record backend m. ( MonadIO m, PersistUniqueWrite backend, PersistRecordBackend record backend, AtLeastOneUniqueKey record) => record -> ReaderT backend m ( Either ( Entity record) ( Key record)) 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
.
Example usage
With schema-2 and dataset-1 , we have following lines of code:
l1 <- insertBy $ User "SPJ" 20 l2 <- insertBy $ User "XXX" 41 l3 <- insertBy $ User "SPJ" 40 r1 <- insertBy $ User "XXX" 100
First three lines return
Left
because there're duplicates in given record's uniqueness constraints. While the last line returns a new key as
Right
.
insertUniqueEntity :: forall record backend m. ( MonadIO m, PersistRecordBackend record backend, PersistUniqueWrite backend) => record -> ReaderT backend m ( Maybe ( Entity record)) Source #
Like
insertEntity
, but returns
Nothing
when the record
couldn't be inserted because of a uniqueness constraint.
Example usage
We use schema-2 and dataset-1 here.
insertUniqueSpjEntity :: MonadIO m => ReaderT SqlBackend m (Maybe (Entity User)) insertUniqueSpjEntity = insertUniqueEntity $ User "SPJ" 50
mSpjEnt <- insertUniqueSpjEntity
The above query results
Nothing
as SPJ already exists.
insertUniqueAlexaEntity :: MonadIO m => ReaderT SqlBackend m (Maybe (Entity User)) insertUniqueAlexaEntity = insertUniqueEntity $ User "Alexa" 3
mAlexaEnt <- insertUniqueSpjEntity
Because there's no such unique keywords of the given record, the above query when applied on dataset-1 , will produce this:
+----+-------+-----+ | id | name | age | +----+-------+-----+ | 1 | SPJ | 40 | +----+-------+-----+ | 2 | Simon | 41 | +----+-------+-----+ | 3 | Alexa | 3 | +----+-------+-----+
Since: 2.7.1
replaceUnique :: forall record backend m. ( MonadIO m, Eq ( Unique record), PersistRecordBackend record backend, PersistUniqueWrite backend) => Key record -> record -> ReaderT backend m ( Maybe ( Unique record)) Source #
checkUnique :: forall record backend m. ( MonadIO m, PersistRecordBackend record backend, PersistUniqueRead 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
Example usage
checkUniqueUpdateable :: forall record backend m. ( MonadIO m, PersistRecordBackend record backend, PersistUniqueRead backend) => Entity 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 stay unique, and could thus safely be updated.
on a conflict returns the conflicting key
This is similar to
checkUnique
, except it's useful for updating - when the
particular entity already exists, it would normally conflict with itself.
This variant ignores those conflicts
Example usage
We use schema-1 and dataset-1 here.
This would be
Nothing
:
mAlanConst <- checkUnique $ User "Alan" 70
While this would be
Just
because SPJ already exists:
mSpjConst <- checkUnique $ User "SPJ" 60
Since: 2.11.0.0
onlyUnique :: forall record backend m. ( MonadIO m, PersistUniqueWrite backend, PersistRecordBackend record backend, OnlyOneUniqueKey record) => record -> ReaderT backend m ( Unique record) Source #
Return the single unique key for a record.
Example usage
We use shcema-1 and dataset-1 here.
onlySimonConst :: MonadIO m => ReaderT SqlBackend m (Unique User) onlySimonConst = onlyUnique $ User "Simon" 999
mSimonConst <- onlySimonConst
mSimonConst
would be Simon's uniqueness constraint. Note that
onlyUnique
doesn't work if there're more than two constraints. It will
fail with a type error instead.
PersistQuery
The
PersistQuery
type class allows us to select lists and filter
database models.
selectList
is the canonical read operation, and we
can write
updateWhere
and
deleteWhere
to modify based on filters.
selectList :: forall record backend m. ( MonadIO m, PersistQueryRead backend, PersistRecordBackend record backend) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m [ Entity record] Source #
Returns a
[
corresponding to the filters and options
provided.
Entity
record]
Filters are constructed using the operators defined in Database.Persist (and re-exported from Database.Persist.Sql ). Let's look at some examples:
usersWithAgeOver40 ::SqlPersistTIO[EntityUser] usersWithAgeOver40 =selectList[UserAge>=.40] []
If you provide multiple values in the list, the conditions are
AND
ed
together.
usersWithAgeBetween30And50 ::SqlPersistTIO[EntityUser] usersWithAgeBetween30And50 =selectList[ UserAge>=.30 , UserAge<=.50 ] []
The second list contains the
SelectOpt
for a record. We can select the
first ten records with
LimitTo
firstTenUsers =
selectList [] [LimitTo 10]
And we can select the second ten users with
OffsetBy
.
secondTenUsers =
selectList [] [LimitTo 10, OffsetBy 10]
Warning that LIMIT/OFFSET is bad for pagination!
With
Asc
and
Desc
, we can provide the field we want to sort on. We can
provide multiple sort orders - later ones are used to sort records that are
equal on the first field.
newestUsers =
selectList [] [Desc UserCreatedAt, LimitTo 10]
oldestUsers =
selectList [] [Asc UserCreatedAt, LimitTo 10]
selectKeys :: forall record backend m. ( PersistQueryRead backend, MonadResource m, PersistRecordBackend record backend, MonadReader backend m) => [ Filter record] -> [ SelectOpt record] -> ConduitM () ( Key record) m () Source #
Get the
Key
s of all records matching the given criterion.
For an example, see
selectList
.
type PersistQuery a = PersistQueryWrite a Source #
A backwards-compatible alias for those that don't care about distinguishing between read and write queries. It signifies the assumption that, by default, a backend can write as well as read.
class ( PersistCore backend, PersistStoreRead backend) => PersistQueryRead backend where Source #
Backends supporting conditional read operations.
Minimal complete definition
Methods
selectSourceRes :: ( PersistRecordBackend record backend, MonadIO m1, MonadIO m2) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m1 ( Acquire ( ConduitM () ( Entity record) m2 ())) Source #
Get all records matching the given criterion in the specified order. Returns also the identifiers.
NOTE: This function returns an
Acquire
and a
ConduitM
, which implies
that it streams from the database. It does not. Please use
selectList
to simplify the code. If you want streaming behavior, consider
persistent-pagination
which efficiently chunks a query into ranges, or
investigate a backend-specific streaming solution.
selectFirst :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m ( Maybe ( Entity record)) Source #
Get just the first record for the criterion.
selectKeysRes :: ( MonadIO m1, MonadIO m2, PersistRecordBackend record backend) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m1 ( Acquire ( ConduitM () ( Key record) m2 ())) Source #
Get the
Key
s of all records matching the given criterion.
count :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> ReaderT backend m Int Source #
The total number of records fulfilling the given criterion.
exists :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> ReaderT backend m Bool Source #
Check if there is at least one record fulfilling the given criterion.
Since: 2.11
Instances
class ( PersistQueryRead backend, PersistStoreWrite backend) => PersistQueryWrite backend where Source #
Backends supporting conditional write operations
Methods
updateWhere :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> [ Update record] -> ReaderT backend m () Source #
Update individual fields on any record matching the given criterion.
deleteWhere :: ( MonadIO m, PersistRecordBackend record backend) => [ Filter record] -> ReaderT backend m () Source #
Delete all records matching the given criterion.
Instances
selectSource :: forall record backend m. ( PersistQueryRead backend, MonadResource m, PersistRecordBackend record backend, MonadReader backend m) => [ Filter record] -> [ SelectOpt record] -> ConduitM () ( Entity record) m () Source #
Get all records matching the given criterion in the specified order. Returns also the identifiers.
WARNING: This function returns a
ConduitM
, which implies that it streams
the results. It does not stream results on most backends. If you need
streaming, see
persistent-pagination
for a means of chunking results based
on indexed ranges.
selectKeysList :: forall record backend m. ( MonadIO m, PersistQueryRead backend, PersistRecordBackend record backend) => [ Filter record] -> [ SelectOpt record] -> ReaderT backend m [ Key record] Source #
Call
selectKeys
but return the result as a list.
DeleteCascade
class ( PersistStoreWrite backend, PersistEntity record, BaseBackend backend ~ PersistEntityBackend record) => DeleteCascade record backend where Source #
For combinations of backends and entities that support cascade-deletion. “Cascade-deletion” means that entries that depend on other entries to be deleted will be deleted as well.
deleteCascadeWhere :: forall record backend m. ( MonadIO m, DeleteCascade record backend, PersistQueryWrite backend) => [ Filter record] -> ReaderT backend m () Source #
Cascade-deletion of entries satisfying given filters.
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 where Source #
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.
Minimal complete definition
keyToValues , keyFromValues , persistIdField , entityDef , persistFieldDef , toPersistFields , fromPersistValues , persistUniqueKeys , persistUniqueToFieldNames , persistUniqueToValues , fieldLens
Associated Types
type PersistEntityBackend record Source #
Persistent allows multiple different backends (databases).
By default, a backend will automatically generate the key Instead you can specify a Primary key made up of unique values.
data EntityField record :: Type -> Type Source #
An
EntityField
is parameterised by the Haskell record it belongs to
and the additional type of that field.
As of
persistent-2.11.0.0
, it's possible to use the
OverloadedLabels
language extension to refer to
EntityField
values polymorphically. See
the documentation on
SymbolToField
for more information.
Unique keys besides 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 :: proxy record -> EntityDef Source #
Retrieve the
EntityDef
meta-data for the record.
persistFieldDef :: EntityField record typ -> FieldDef Source #
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 record Source #
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 -> NonEmpty ( FieldNameHS , FieldNameDB ) 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.
keyFromRecordM :: Maybe (record -> Key record) Source #
Extract a
from a
Key
record
record
value. Currently, this is
only defined for entities using the
Primary
syntax for
natural/composite keys. In a future version of
persistent
which
incorporates the ID directly into the entity, this will always be Just.
Since: 2.11.0.0
class SymbolToField (sym :: Symbol ) rec typ | sym rec -> typ where Source #
This type class is used with the
OverloadedLabels
extension to
provide a more convenient means of using the
EntityField
type.
EntityField
definitions are prefixed with the type name to avoid
ambiguity, but this ambiguity can result in verbose code.
If you have a table
User
with a
name Text
field, then the
corresponding
EntityField
is
UserName
. With this, we can write
#name ::
.
EntityField
User Text
What's more fun is that the type is more general: it's actually
#name
:: (
SymbolToField
"name" rec typ)
=> EntityField rec typ
Which means it is *polymorphic* over the actual record. This allows you to write code that can be generic over the tables, provided they have the right fields.
Since: 2.11.0.0
Methods
symbolToField :: EntityField rec typ Source #
PersistField
class PersistField a where Source #
This class teaches Persistent how to take a custom type and marshal it to and from a
PersistValue
, allowing it to be stored in a database.
Examples
Simple Newtype
You can use
newtype
to add more type safety/readability to a basis type like
ByteString
. In these cases, just derive
PersistField
and
PersistFieldSql
:
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
newtype HashedPassword = HashedPassword ByteString
deriving (Eq, Show, PersistField, PersistFieldSql)
Smart Constructor Newtype
In this example, we create a
PersistField
instance for a newtype following the "Smart Constructor" pattern.
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
import qualified Data.Text as T
import qualified Data.Char as C
-- | An American Social Security Number
newtype SSN = SSN Text
deriving (Eq, Show, PersistFieldSql)
mkSSN :: Text -> Either Text SSN
mkSSN t = if (T.length t == 9) && (T.all C.isDigit t)
then Right $ SSN t
else Left $ "Invalid SSN: " <> t
instance PersistField SSN where
toPersistValue (SSN t) = PersistText t
fromPersistValue (PersistText t) = mkSSN t
-- Handle cases where the database does not give us PersistText
fromPersistValue x = Left $ "File.hs: When trying to deserialize an SSN: expected PersistText, received: " <> T.pack (show x)
Tips:
-
This file contain dozens of
PersistFieldinstances you can look at for examples. -
Typically custom
PersistFieldinstances will only accept a singlePersistValueconstructor infromPersistValue. -
Internal
PersistFieldinstances accept a wide variety ofPersistValues to accomodate e.g. storing booleans as integers, booleans or strings. -
If you're making a custom instance and using a SQL database, you'll also need
PersistFieldSqlto specify the type of the database column.
Methods
toPersistValue :: a -> PersistValue Source #
fromPersistValue :: PersistValue -> Either Text a Source #
Instances
PersistConfig
class PersistConfig c where Source #
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
Associated Types
type PersistConfigBackend c :: ( Type -> Type ) -> Type -> Type Source #
type PersistConfigPool c Source #
Methods
loadConfig :: Value -> Parser c Source #
Load the config settings from a
Value
, most likely taken from a YAML
config file.
applyEnv :: c -> IO c Source #
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 :: MonadUnliftIO m => c -> PersistConfigBackend c m a -> PersistConfigPool c -> m a Source #
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) Source # | |
|
Defined in Database.Persist.Class.PersistConfig Associated Types type PersistConfigBackend ( Either c1 c2) :: ( Type -> Type ) -> Type -> Type Source # type PersistConfigPool ( Either c1 c2) Source # Methods loadConfig :: Value -> Parser ( Either c1 c2) Source # applyEnv :: Either c1 c2 -> IO ( Either c1 c2) Source # createPoolConfig :: Either c1 c2 -> IO ( PersistConfigPool ( Either c1 c2)) Source # runPool :: MonadUnliftIO m => Either c1 c2 -> PersistConfigBackend ( Either c1 c2) m a -> PersistConfigPool ( Either c1 c2) -> m a Source # |
|
entityValues :: PersistEntity record => Entity record -> [ PersistValue ] Source #
Get list of values corresponding to given entity.
Lifting
class HasPersistBackend backend where Source #
Class which allows the plucking of a
BaseBackend backend
from some larger type.
For example,
instance HasPersistBackend (SqlReadBackend, Int) where
type BaseBackend (SqlReadBackend, Int) = SqlBackend
persistBackend = unSqlReadBackend . fst
Associated Types
type BaseBackend backend Source #
Methods
persistBackend :: backend -> BaseBackend backend Source #
Instances
| HasPersistBackend SqlBackend Source # | |
|
Defined in Database.Persist.SqlBackend.Internal Associated Types type BaseBackend SqlBackend Source # Methods persistBackend :: SqlBackend -> BaseBackend SqlBackend Source # |
|
| HasPersistBackend SqlWriteBackend Source # | |
|
Defined in Database.Persist.Sql.Types.Internal Associated Types Methods persistBackend :: SqlWriteBackend -> BaseBackend SqlWriteBackend Source # |
|
| HasPersistBackend SqlReadBackend Source # | |
|
Defined in Database.Persist.Sql.Types.Internal Associated Types type BaseBackend SqlReadBackend Source # Methods persistBackend :: SqlReadBackend -> BaseBackend SqlReadBackend Source # |
|
| ( BackendCompatible b s, HasPersistBackend b) => HasPersistBackend ( Compatible b s) Source # | |
|
Defined in Database.Persist.Compatible.Types Associated Types type BaseBackend ( Compatible b s) Source # Methods persistBackend :: Compatible b s -> BaseBackend ( Compatible b s) Source # |
|
withBaseBackend :: HasPersistBackend backend => ReaderT ( BaseBackend backend) m a -> ReaderT backend m a Source #
Run a query against a larger backend by plucking out
BaseBackend backend
This is a helper for reusing existing queries when expanding the backend type.
Since: 2.12.0
class HasPersistBackend backend => IsPersistBackend backend Source #
Class which witnesses that
backend
is essentially the same as
BaseBackend backend
.
That is, they're isomorphic and
backend
is just some wrapper over
BaseBackend backend
.
Minimal complete definition
Instances
| IsPersistBackend SqlBackend Source # | |
|
Defined in Database.Persist.SqlBackend.Internal Methods mkPersistBackend :: BaseBackend SqlBackend -> SqlBackend Source # |
|
| IsPersistBackend SqlWriteBackend Source # | |
|
Defined in Database.Persist.Sql.Types.Internal Methods mkPersistBackend :: BaseBackend SqlWriteBackend -> SqlWriteBackend Source # |
|
| IsPersistBackend SqlReadBackend Source # | |
|
Defined in Database.Persist.Sql.Types.Internal Methods mkPersistBackend :: BaseBackend SqlReadBackend -> SqlReadBackend Source # |
|
liftPersist :: ( MonadIO m, MonadReader backend m) => ReaderT backend IO b -> m b Source #
class BackendCompatible sup sub where Source #
This class witnesses that two backend are compatible, and that you can
convert from the
sub
backend into the
sup
backend. This is similar
to the
HasPersistBackend
and
IsPersistBackend
classes, but where you
don't want to fix the type associated with the
PersistEntityBackend
of
a record.
Generally speaking, where you might have:
foo :: (PersistEntityrecord ,PeristEntityBackendrecord ~BaseBackendbackend ,IsSqlBackendbackend )
this can be replaced with:
foo :: (PersistEntityrecord, ,PersistEntityBackendrecord ~ backend ,BackendCompatibleSqlBackendbackend )
This works for
SqlReadBackend
because of the
instance
, without needing to go through the
BackendCompatible
SqlBackend
SqlReadBackend
BaseBackend
type family.
Likewise, functions that are currently hardcoded to use
SqlBackend
can be generalized:
-- before: asdf ::ReaderTSqlBackendm () asdf = pure () -- after: asdf' ::BackendCompatibleSqlBackend backend => ReaderT backend m () asdf' =withCompatibleBackendasdf
Since: 2.7.1
Methods
projectBackend :: sub -> sup Source #
Instances
| BackendCompatible SqlBackend SqlBackend Source # | |
|
Defined in Database.Persist.Sql.Orphan.PersistStore Methods |
|
| BackendCompatible SqlBackend SqlWriteBackend Source # | |
|
Defined in Database.Persist.Sql.Orphan.PersistStore Methods |
|
| BackendCompatible SqlBackend SqlReadBackend Source # | |
|
Defined in Database.Persist.Sql.Orphan.PersistStore Methods |
|
withCompatibleBackend :: BackendCompatible sup sub => ReaderT sup m a -> ReaderT sub m a Source #
Run a query against a compatible backend, by projecting the backend
This is a helper for using queries which run against a specific backend type that your backend is compatible with.
Since: 2.12.0
PersistCore
PersistCore
is a type class that defines a default database
BackendKey
type. For SQL databases, this is currently an
auto-incrementing inteer primary key. For MongoDB, it is the default
ObjectID.
class PersistCore backend Source #
Associated Types
data BackendKey backend Source #
Instances
| PersistCore SqlBackend Source # | |
|
Defined in Database.Persist.Sql.Orphan.PersistStore Associated Types data BackendKey SqlBackend Source # |
|
| PersistCore SqlWriteBackend Source # | |
|
Defined in Database.Persist.Sql.Orphan.PersistStore Associated Types data BackendKey SqlWriteBackend Source # |
|
| PersistCore SqlReadBackend Source # | |
|
Defined in Database.Persist.Sql.Orphan.PersistStore Associated Types data BackendKey SqlReadBackend Source # |
|
| ( BackendCompatible b s, PersistCore b) => PersistCore ( Compatible b s) Source # | |
|
Defined in Database.Persist.Compatible.Types Associated Types data BackendKey ( Compatible b s) Source # |
|
class ( PersistEntity record, PersistEntityBackend record ~ backend, PersistCore backend) => ToBackendKey backend record where Source #
ToBackendKey
converts a
PersistEntity
Key
into a
BackendKey
This can be used by each backend to convert between a
Key
and a plain
Haskell type. For Sql, that is done with
toSqlKey
and
fromSqlKey
.
By default, a
PersistEntity
uses the default
BackendKey
for its Key
and is an instance of ToBackendKey
A
Key
that instead uses a custom type will not be an instance of
ToBackendKey
.
Methods
toBackendKey :: Key record -> BackendKey backend Source #
fromBackendKey :: BackendKey backend -> Key record Source #
JSON utilities
keyValueEntityToJSON :: ( PersistEntity record, ToJSON record) => Entity record -> Value Source #
Predefined
toJSON
. The resulting JSON looks like
{"key": 1, "value": {"name": ...}}
.
The typical usage is:
instance ToJSON (Entity User) where
toJSON = keyValueEntityToJSON
keyValueEntityFromJSON :: ( PersistEntity record, FromJSON record) => Value -> Parser ( Entity record) Source #
Predefined
parseJSON
. The input JSON looks like
{"key": 1, "value": {"name": ...}}
.
The typical usage is:
instance FromJSON (Entity User) where
parseJSON = keyValueEntityFromJSON
entityIdToJSON :: ( PersistEntity record, ToJSON record) => Entity record -> Value Source #
Predefined
toJSON
. The resulting JSON looks like
{"id": 1, "name": ...}
.
The typical usage is:
instance ToJSON (Entity User) where
toJSON = entityIdToJSON
entityIdFromJSON :: ( PersistEntity record, FromJSON record) => Value -> Parser ( Entity record) Source #
Predefined
parseJSON
. The input JSON looks like
{"id": 1, "name": ...}
.
The typical usage is:
instance FromJSON (Entity User) where
parseJSON = entityIdFromJSON
toPersistValueJSON :: ToJSON a => a -> PersistValue Source #
Convenience function for getting a free
PersistField
instance
from a type with JSON instances.
Example usage in combination with
fromPersistValueJSON
:
instance PersistField MyData where fromPersistValue = fromPersistValueJSON toPersistValue = toPersistValueJSON
fromPersistValueJSON :: FromJSON a => PersistValue -> Either Text a Source #
Convenience function for getting a free
PersistField
instance
from a type with JSON instances. The JSON parser used will accept JSON
values other that object and arrays. So, if your instance serializes the
data to a JSON string, this will still work.
Example usage in combination with
toPersistValueJSON
:
instance PersistField MyData where fromPersistValue = fromPersistValueJSON toPersistValue = toPersistValueJSON