persistent-2.9.0: Type-safe, multi-backend data serialization.

Safe Haskell | None
Language | Haskell98

Database.Persist.Class

Contents

- PersistStore
- PersistUnique
- PersistQuery
- DeleteCascade
- PersistEntity
- PersistField
- PersistConfig
- Lifting
- JSON utilities

Synopsis

- class (PersistEntity record, PersistEntityBackend record ~ backend, PersistCore backend) => ToBackendKey backend record where
- class PersistCore backend where
  - data BackendKey backend
- 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
- type PersistRecordBackend record backend = (PersistEntity record, PersistEntityBackend record ~ BaseBackend backend)
- getJust :: (PersistStoreRead backend, Show (Key record), PersistRecordBackend record backend, MonadIO m) => Key record -> ReaderT backend m record
- getJustEntity :: (PersistEntityBackend record ~ BaseBackend backend, MonadIO m, PersistEntity record, PersistStoreRead backend) => Key record -> ReaderT backend m (Entity record)
- getEntity :: (PersistStoreRead backend, PersistRecordBackend e backend, MonadIO m) => Key e -> ReaderT backend m (Maybe (Entity e))
- belongsTo :: (PersistStoreRead backend, PersistEntity ent1, PersistRecordBackend ent2 backend, MonadIO m) => (ent1 -> Maybe (Key ent2)) -> ent1 -> ReaderT backend m (Maybe ent2)
- belongsToJust :: (PersistStoreRead backend, PersistEntity ent1, PersistRecordBackend ent2 backend, MonadIO m) => (ent1 -> Key ent2) -> ent1 -> ReaderT backend m ent2
- insertEntity :: (PersistStoreWrite backend, PersistRecordBackend e backend, MonadIO m) => e -> ReaderT backend m (Entity e)
- insertRecord :: (PersistEntityBackend record ~ BaseBackend backend, PersistEntity record, MonadIO m, PersistStoreWrite backend) => record -> ReaderT backend m record
- type PersistUnique a = PersistUniqueWrite a
- class (PersistCore backend, PersistStoreRead backend) => PersistUniqueRead backend where
- class (PersistUniqueRead backend, PersistStoreWrite backend) => PersistUniqueWrite backend where
- getByValue :: (MonadIO m, PersistUniqueRead backend, PersistRecordBackend record backend) => record -> ReaderT backend m (Maybe (Entity record))
- insertBy :: (MonadIO m, PersistUniqueWrite backend, PersistRecordBackend record backend) => record -> ReaderT backend m (Either (Entity record) (Key record))
- insertUniqueEntity :: (MonadIO m, PersistRecordBackend record backend, PersistUniqueWrite backend) => record -> ReaderT backend m (Maybe (Entity record))
- replaceUnique :: (MonadIO m, Eq record, Eq (Unique record), PersistRecordBackend record backend, PersistUniqueWrite backend) => Key record -> record -> ReaderT backend m (Maybe (Unique record))
- checkUnique :: (MonadIO m, PersistRecordBackend record backend, PersistUniqueRead backend) => record -> ReaderT backend m (Maybe (Unique record))
- onlyUnique :: (MonadIO m, PersistUniqueWrite backend, PersistRecordBackend record backend) => record -> ReaderT backend m (Unique record)
- type PersistQuery a = PersistQueryWrite a
- class (PersistCore backend, PersistStoreRead backend) => PersistQueryRead backend where
- class (PersistQueryRead backend, PersistStoreWrite backend) => PersistQueryWrite backend where
- selectSource :: (PersistQueryRead (BaseBackend backend), MonadResource m, PersistEntity record, PersistEntityBackend record ~ BaseBackend (BaseBackend backend), MonadReader backend m, HasPersistBackend backend) => [Filter record] -> [SelectOpt record] -> ConduitM () (Entity record) m ()
- selectKeys :: (PersistQueryRead (BaseBackend backend), MonadResource m, PersistEntity record, BaseBackend (BaseBackend backend) ~ PersistEntityBackend record, MonadReader backend m, HasPersistBackend backend) => [Filter record] -> [SelectOpt record] -> ConduitM () (Key record) m ()
- selectList :: (MonadIO m, PersistQueryRead backend, PersistRecordBackend record backend) => [Filter record] -> [SelectOpt record] -> ReaderT backend m [Entity record]
- selectKeysList :: (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
- deleteCascadeWhere :: (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 :: * -> *
  - data Unique record
- class PersistField a where
- class PersistConfig c where
  - type PersistConfigBackend c :: (* -> *) -> * -> *
  - type PersistConfigPool c
- entityValues :: PersistEntity record => Entity record -> [PersistValue]
- class HasPersistBackend backend where
  - type BaseBackend backend
- class HasPersistBackend backend => IsPersistBackend backend
- liftPersist :: (MonadIO m, MonadReader backend m, HasPersistBackend backend) => ReaderT (BaseBackend backend) IO b -> m b
- class BackendCompatible sup sub where
- keyValueEntityToJSON :: (PersistEntity record, ToJSON record, ToJSON (Key record)) => Entity record -> Value
- keyValueEntityFromJSON :: (PersistEntity record, FromJSON record, FromJSON (Key record)) => Value -> Parser (Entity record)
- entityIdToJSON :: (PersistEntity record, ToJSON record, ToJSON (Key record)) => Entity record -> Value
- entityIdFromJSON :: (PersistEntity record, FromJSON record, FromJSON (Key record)) => Value -> Parser (Entity record)
- toPersistValueJSON :: ToJSON a => a -> PersistValue
- fromPersistValueJSON :: FromJSON a => PersistValue -> Either Text a

# Documentation

class (PersistEntity record, PersistEntityBackend record ~ backend, PersistCore backend) => ToBackendKey backend record where #

`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`.

Minimal complete definition

toBackendKey, fromBackendKey

Methods

toBackendKey :: Key record -> BackendKey backend #

fromBackendKey :: BackendKey backend -> Key record #

# PersistStore

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 |
    +----+-------+-----+

class PersistCore backend #

Associated Types

data BackendKey backend #

Instances

PersistCore SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Associated Types data BackendKey SqlWriteBackend :: * #
PersistCore SqlReadBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Associated Types data BackendKey SqlReadBackend :: * #
PersistCore SqlBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Associated Types data BackendKey SqlBackend :: * #

type PersistStore a = PersistStoreWrite a #

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 #

Minimal complete definition

get

Methods

get :: (MonadIO m, PersistRecordBackend record backend) => Key record -> ReaderT backend m (Maybe record) #

Get a record by identifier, if available.

### Example usage

Expand

With schema-1 and dataset-1,

    getSpj :: MonadIO m => ReaderT SqlBackend m (Maybe User)
    getSpj = get spjId

    mspj <- getSpj

The above query when applied on dataset-1, will get this:

    +------+-----+
    | name | age |
    +------+-----+
    | SPJ  |  40 |
    +------+-----+

getMany :: (MonadIO m, PersistRecordBackend record backend) => [Key record] -> ReaderT backend m (Map (Key record) record) #

Get many records by their respective identifiers, if available.

### Example usage

Expand

With schema-1 and dataset-1:

    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: persistent-2.8.1

Instances

PersistStoreRead SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods get :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> ReaderT SqlWriteBackend m (Maybe record) # getMany :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [Key record] -> ReaderT SqlWriteBackend m (Map (Key record) record) #
PersistStoreRead SqlReadBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods get :: (MonadIO m, PersistRecordBackend record SqlReadBackend) => Key record -> ReaderT SqlReadBackend m (Maybe record) # getMany :: (MonadIO m, PersistRecordBackend record SqlReadBackend) => [Key record] -> ReaderT SqlReadBackend m (Map (Key record) record) #
PersistStoreRead SqlBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods get :: (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> ReaderT SqlBackend m (Maybe record) # getMany :: (MonadIO m, PersistRecordBackend record SqlBackend) => [Key record] -> ReaderT SqlBackend m (Map (Key record) record) #

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 #

Minimal complete definition

insert, insertKey, repsert, replace, delete, update

Methods

insert :: (MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m (Key record) #

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

### Example usage

Expand

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_ :: (MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m () #

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

### Example usage

Expand

with schema-1 and dataset-1,

    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 :: (MonadIO m, PersistRecordBackend record backend) => [record] -> ReaderT backend m [Key record] #

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

Expand

with schema-1 and dataset-1,

    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_ :: (MonadIO m, PersistRecordBackend record backend) => [record] -> ReaderT backend m () #

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

Expand

With schema-1 and dataset-1,

    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 :: (MonadIO m, PersistRecordBackend record backend) => [Entity record] -> ReaderT backend m () #

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

Expand

With schema-1 and dataset-1,

    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 :: (MonadIO m, PersistRecordBackend record backend) => Key record -> record -> ReaderT backend m () #

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

### Example usage

Expand

With schema-1 and dataset-1,

    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 :: (MonadIO m, PersistRecordBackend record backend) => Key record -> record -> ReaderT backend 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.

### Example usage

Expand

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 :: (MonadIO m, PersistRecordBackend record backend) => [(Key record, record)] -> ReaderT backend m () #

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

Expand

With schema-1 and dataset-1,

    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: persistent-2.8.1

replace :: (MonadIO m, PersistRecordBackend record backend) => Key record -> record -> ReaderT backend 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.

### Example usage

Expand

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 :: (MonadIO m, PersistRecordBackend record backend) => Key record -> ReaderT backend m () #

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

### Example usage

Expand

With schema-1 and dataset-1,

    deleteSpj :: MonadIO m => ReaderT SqlBackend m ()
    deleteSpj = delete spjId

The above query when applied on dataset-1, will produce this:

    +-----+------+-----+
    |id   |name  |age  |
    +-----+------+-----+
    |2    |Simon |41   |
    +-----+------+-----+

update :: (MonadIO m, PersistRecordBackend record backend) => Key record -> [Update record] -> ReaderT backend m () #

Update individual fields on a specific record.

### Example usage

Expand

With schema-1 and dataset-1,

    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 :: (MonadIO m, PersistRecordBackend record backend) => Key record -> [Update record] -> ReaderT backend m record #

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

Expand

With schema-1 and dataset-1,

    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

PersistStoreWrite SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods insert :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => record -> ReaderT SqlWriteBackend m (Key record) # insert_ :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => record -> ReaderT SqlWriteBackend m () # insertMany :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [record] -> ReaderT SqlWriteBackend m [Key record] # insertMany_ :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [record] -> ReaderT SqlWriteBackend m () # insertEntityMany :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [Entity record] -> ReaderT SqlWriteBackend m () # insertKey :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> record -> ReaderT SqlWriteBackend m () # repsert :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> record -> ReaderT SqlWriteBackend m () # repsertMany :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [(Key record, record)] -> ReaderT SqlWriteBackend m () # replace :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> record -> ReaderT SqlWriteBackend m () # delete :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> ReaderT SqlWriteBackend m () # update :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> [Update record] -> ReaderT SqlWriteBackend m () # updateGet :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> [Update record] -> ReaderT SqlWriteBackend m record #
PersistStoreWrite SqlBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods insert :: (MonadIO m, PersistRecordBackend record SqlBackend) => record -> ReaderT SqlBackend m (Key record) # insert_ :: (MonadIO m, PersistRecordBackend record SqlBackend) => record -> ReaderT SqlBackend m () # insertMany :: (MonadIO m, PersistRecordBackend record SqlBackend) => [record] -> ReaderT SqlBackend m [Key record] # insertMany_ :: (MonadIO m, PersistRecordBackend record SqlBackend) => [record] -> ReaderT SqlBackend m () # insertEntityMany :: (MonadIO m, PersistRecordBackend record SqlBackend) => [Entity record] -> ReaderT SqlBackend m () # insertKey :: (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> record -> ReaderT SqlBackend m () # repsert :: (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> record -> ReaderT SqlBackend m () # repsertMany :: (MonadIO m, PersistRecordBackend record SqlBackend) => [(Key record, record)] -> ReaderT SqlBackend m () # replace :: (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> record -> ReaderT SqlBackend m () # delete :: (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> ReaderT SqlBackend m () # update :: (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> [Update record] -> ReaderT SqlBackend m () # updateGet :: (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> [Update record] -> ReaderT SqlBackend m record #

type PersistRecordBackend record backend = (PersistEntity record, PersistEntityBackend record ~ BaseBackend backend) #

A convenient alias for common type signatures

getJust :: (PersistStoreRead backend, Show (Key record), PersistRecordBackend record backend, MonadIO m) => Key record -> ReaderT backend m record #

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

Expand

With schema-1 and dataset-1,

    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 :: (PersistEntityBackend record ~ BaseBackend backend, MonadIO m, PersistEntity record, PersistStoreRead backend) => Key record -> ReaderT backend m (Entity record) #

Same as `getJust`, but returns an `Entity` instead of just the record.

### Example usage

Expand

With schema-1 and dataset-1,

    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: persistent-2.6.1

getEntity :: (PersistStoreRead backend, PersistRecordBackend e backend, MonadIO m) => Key e -> ReaderT backend m (Maybe (Entity e)) #

Like `get`, but returns the complete `Entity`.

### Example usage

Expand

With schema-1 and dataset-1,

    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 :: (PersistStoreRead backend, PersistEntity ent1, PersistRecordBackend ent2 backend, MonadIO m) => (ent1 -> Maybe (Key ent2)) -> ent1 -> ReaderT backend m (Maybe ent2) #

Curry this to make a convenience function that loads an associated model.

    foreign = belongsTo foreignId

belongsToJust :: (PersistStoreRead backend, PersistEntity ent1, PersistRecordBackend ent2 backend, MonadIO m) => (ent1 -> Key ent2) -> ent1 -> ReaderT backend m ent2 #

Same as `belongsTo`, but uses `getJust` and therefore is similarly unsafe.

insertEntity :: (PersistStoreWrite backend, PersistRecordBackend e backend, MonadIO m) => e -> ReaderT backend m (Entity e) #

Like `insert`, but returns the complete `Entity`.

### Example usage

Expand

With schema-1 and dataset-1,

    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 :: (PersistEntityBackend record ~ BaseBackend backend, PersistEntity record, MonadIO m, PersistStoreWrite backend) => record -> ReaderT backend m record #

Like `insertEntity` but just returns the record instead of `Entity`.

### Example usage

Expand

With schema-1 and dataset-1,

    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: persistent-2.6.1

# PersistUnique

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 #

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) => PersistUniqueRead backend where #

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.

Minimal complete definition

getBy

Methods

getBy :: (MonadIO m, PersistRecordBackend record backend) => Unique record -> ReaderT backend m (Maybe (Entity record)) #

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

### Example usage

Expand

With schema-1 and dataset-1:

    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

PersistUniqueRead SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistUnique Methods getBy :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Unique record -> ReaderT SqlWriteBackend m (Maybe (Entity record)) #
PersistUniqueRead SqlReadBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistUnique Methods getBy :: (MonadIO m, PersistRecordBackend record SqlReadBackend) => Unique record -> ReaderT SqlReadBackend m (Maybe (Entity record)) #
PersistUniqueRead SqlBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistUnique Methods getBy :: (MonadIO m, PersistRecordBackend record SqlBackend) => Unique record -> ReaderT SqlBackend m (Maybe (Entity record)) #

class (PersistUniqueRead backend, PersistStoreWrite backend) => PersistUniqueWrite backend where #

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

deleteBy

Methods

deleteBy :: (MonadIO m, PersistRecordBackend record backend) => Unique record -> ReaderT backend m () #

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

### Example usage

Expand

With schema-1 and dataset-1,

    deleteBySpjName :: MonadIO m => ReaderT SqlBackend m ()
    deleteBySpjName = deleteBy UniqueUserName "SPJ"

The above query when applied on dataset-1, will produce this:

    +-----+------+-----+
    |id   |name  |age  |
    +-----+------+-----+
    |2    |Simon |41   |
    +-----+------+-----+

insertUnique :: (MonadIO m, PersistRecordBackend record backend) => record -> ReaderT backend m (Maybe (Key record)) #

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

### Example usage

Expand

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.

upsert #

Arguments

:: (MonadIO m, PersistRecordBackend record backend) |
=> 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.

Throws an exception if there is more than 1 uniqueness constraint.

### Example usage

Expand

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) upadtes

    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]

Then, it throws an error message something like "Expected only one unique key, got"

upsertBy #

Arguments

:: (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

Expand

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  |
    +-----+-----+-----+

putMany #

Arguments

:: (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

PersistUniqueWrite SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistUnique Methods deleteBy :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Unique record -> ReaderT SqlWriteBackend m () # insertUnique :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => record -> ReaderT SqlWriteBackend m (Maybe (Key record)) # upsert :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => record -> [Update record] -> ReaderT SqlWriteBackend m (Entity record) # upsertBy :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Unique record -> record -> [Update record] -> ReaderT SqlWriteBackend m (Entity record) # putMany :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [record] -> ReaderT SqlWriteBackend m () #
PersistUniqueWrite SqlBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistUnique Methods deleteBy :: (MonadIO m, PersistRecordBackend record SqlBackend) => Unique record -> ReaderT SqlBackend m () # insertUnique :: (MonadIO m, PersistRecordBackend record SqlBackend) => record -> ReaderT SqlBackend m (Maybe (Key record)) # upsert :: (MonadIO m, PersistRecordBackend record SqlBackend) => record -> [Update record] -> ReaderT SqlBackend m (Entity record) # upsertBy :: (MonadIO m, PersistRecordBackend record SqlBackend) => Unique record -> record -> [Update record] -> ReaderT SqlBackend m (Entity record) # putMany :: (MonadIO m, PersistRecordBackend record SqlBackend) => [record] -> ReaderT SqlBackend m () #

getByValue :: (MonadIO m, PersistUniqueRead backend, PersistRecordBackend record backend) => record -> ReaderT backend m (Maybe (Entity record)) #

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

Expand

With schema-1 and dataset-1,

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 :: (MonadIO m, PersistUniqueWrite backend, PersistRecordBackend record backend) => record -> ReaderT backend m (Either (Entity record) (Key record)) #

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

Expand

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 :: (MonadIO m, PersistRecordBackend record backend, PersistUniqueWrite backend) => record -> ReaderT backend m (Maybe (Entity record)) #

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

### Example usage

Expand

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: persistent-2.7.1

replaceUnique :: (MonadIO m, Eq record, Eq (Unique record), PersistRecordBackend record backend, PersistUniqueWrite backend) => Key record -> record -> ReaderT backend 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: persistent-1.2.2.0

checkUnique :: (MonadIO m, PersistRecordBackend record backend, PersistUniqueRead backend) => record -> ReaderT backend m (Maybe (Unique record)) #

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

Expand

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

onlyUnique :: (MonadIO m, PersistUniqueWrite backend, PersistRecordBackend record backend) => record -> ReaderT backend m (Unique record) #

Return the single unique key for a record.

### Example usage

Expand

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.

# PersistQuery

type PersistQuery a = PersistQueryWrite a #

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 #

Backends supporting conditional read operations.

Minimal complete definition

selectSourceRes, selectKeysRes, count

Methods

selectSourceRes :: (PersistRecordBackend record backend, MonadIO m1, MonadIO m2) => [Filter record] -> [SelectOpt record] -> ReaderT backend m1 (Acquire (ConduitM () (Entity record) m2 ())) #

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

selectFirst :: (MonadIO m, PersistRecordBackend record backend) => [Filter record] -> [SelectOpt record] -> ReaderT backend m (Maybe (Entity record)) #

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 ())) #

Get the `Key`s of all records matching the given criterion.

count :: (MonadIO m, PersistRecordBackend record backend) => [Filter record] -> ReaderT backend m Int #

The total number of records fulfilling the given criterion.

Instances

PersistQueryRead SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistQuery Methods selectSourceRes :: (PersistRecordBackend record SqlWriteBackend, MonadIO m1, MonadIO m2) => [Filter record] -> [SelectOpt record] -> ReaderT SqlWriteBackend m1 (Acquire (ConduitM () (Entity record) m2 ())) # selectFirst :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [Filter record] -> [SelectOpt record] -> ReaderT SqlWriteBackend m (Maybe (Entity record)) # selectKeysRes :: (MonadIO m1, MonadIO m2, PersistRecordBackend record SqlWriteBackend) => [Filter record] -> [SelectOpt record] -> ReaderT SqlWriteBackend m1 (Acquire (ConduitM () (Key record) m2 ())) # count :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [Filter record] -> ReaderT SqlWriteBackend m Int #
PersistQueryRead SqlReadBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistQuery Methods selectSourceRes :: (PersistRecordBackend record SqlReadBackend, MonadIO m1, MonadIO m2) => [Filter record] -> [SelectOpt record] -> ReaderT SqlReadBackend m1 (Acquire (ConduitM () (Entity record) m2 ())) # selectFirst :: (MonadIO m, PersistRecordBackend record SqlReadBackend) => [Filter record] -> [SelectOpt record] -> ReaderT SqlReadBackend m (Maybe (Entity record)) # selectKeysRes :: (MonadIO m1, MonadIO m2, PersistRecordBackend record SqlReadBackend) => [Filter record] -> [SelectOpt record] -> ReaderT SqlReadBackend m1 (Acquire (ConduitM () (Key record) m2 ())) # count :: (MonadIO m, PersistRecordBackend record SqlReadBackend) => [Filter record] -> ReaderT SqlReadBackend m Int #
PersistQueryRead SqlBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistQuery Methods selectSourceRes :: (PersistRecordBackend record SqlBackend, MonadIO m1, MonadIO m2) => [Filter record] -> [SelectOpt record] -> ReaderT SqlBackend m1 (Acquire (ConduitM () (Entity record) m2 ())) # selectFirst :: (MonadIO m, PersistRecordBackend record SqlBackend) => [Filter record] -> [SelectOpt record] -> ReaderT SqlBackend m (Maybe (Entity record)) # selectKeysRes :: (MonadIO m1, MonadIO m2, PersistRecordBackend record SqlBackend) => [Filter record] -> [SelectOpt record] -> ReaderT SqlBackend m1 (Acquire (ConduitM () (Key record) m2 ())) # count :: (MonadIO m, PersistRecordBackend record SqlBackend) => [Filter record] -> ReaderT SqlBackend m Int #

class (PersistQueryRead backend, PersistStoreWrite backend) => PersistQueryWrite backend where #

Backends supporting conditional write operations

Minimal complete definition

updateWhere, deleteWhere

Methods

updateWhere :: (MonadIO m, PersistRecordBackend record backend) => [Filter record] -> [Update record] -> ReaderT backend m () #

Update individual fields on any record matching the given criterion.

deleteWhere :: (MonadIO m, PersistRecordBackend record backend) => [Filter record] -> ReaderT backend m () #

Delete all records matching the given criterion.

Instances

PersistQueryWrite SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistQuery Methods updateWhere :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [Filter record] -> [Update record] -> ReaderT SqlWriteBackend m () # deleteWhere :: (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [Filter record] -> ReaderT SqlWriteBackend m () #
PersistQueryWrite SqlBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistQuery Methods updateWhere :: (MonadIO m, PersistRecordBackend record SqlBackend) => [Filter record] -> [Update record] -> ReaderT SqlBackend m () # deleteWhere :: (MonadIO m, PersistRecordBackend record SqlBackend) => [Filter record] -> ReaderT SqlBackend m () #

selectSource :: (PersistQueryRead (BaseBackend backend), MonadResource m, PersistEntity record, PersistEntityBackend record ~ BaseBackend (BaseBackend backend), MonadReader backend m, HasPersistBackend backend) => [Filter record] -> [SelectOpt record] -> ConduitM () (Entity record) m () #

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

selectKeys :: (PersistQueryRead (BaseBackend backend), MonadResource m, PersistEntity record, BaseBackend (BaseBackend backend) ~ PersistEntityBackend record, MonadReader backend m, HasPersistBackend backend) => [Filter record] -> [SelectOpt record] -> ConduitM () (Key record) m () #

Get the `Key`s of all records matching the given criterion.

selectList :: (MonadIO m, PersistQueryRead backend, PersistRecordBackend record backend) => [Filter record] -> [SelectOpt record] -> ReaderT backend m [Entity record] #

Call `selectSource` but return the result as a list.

selectKeysList :: (MonadIO m, PersistQueryRead backend, PersistRecordBackend record backend) => [Filter record] -> [SelectOpt record] -> ReaderT backend m [Key record] #

Call `selectKeys` but return the result as a list.

# DeleteCascade

class (PersistStoreWrite backend, PersistEntity record, BaseBackend backend ~ PersistEntityBackend record) => DeleteCascade record backend where #

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.

Minimal complete definition

deleteCascade

Methods

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

Perform cascade-deletion of single database entry.

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

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 #

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 #

Persistent allows multiple different backends (databases).

data Key record #

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

data EntityField record :: * -> * #

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

data Unique record #

Unique keys besides the `Key`.

Methods

keyToValues :: Key record -> [PersistValue] #

A lower-level key operation.

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

A lower-level key operation.

persistIdField :: EntityField record (Key record) #

A meta-operation to retrieve the `Key` `EntityField`.

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

Retrieve the `EntityDef` meta-data for the record.

persistFieldDef :: EntityField record typ -> FieldDef #

Return meta-data for a given `EntityField`.

toPersistFields :: record -> [SomePersistField] #

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

fromPersistValues :: [PersistValue] -> Either Text record #

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

persistUniqueKeys :: record -> [Unique record] #

A meta operation to retrieve all the `Unique` keys.

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

A lower level operation.

persistUniqueToValues :: Unique record -> [PersistValue] #

A lower level operation.

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

Use a `PersistField` as a lens.

# PersistField

class PersistField a where #

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

Expand

##### 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 `PersistField` instances you can look at for examples.
- Typically custom `PersistField` instances will only accept a single `PersistValue` constructor in `fromPersistValue`.
- Internal `PersistField` instances accept a wide variety of `PersistValue`s 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 `PersistFieldSql` to specify the type of the database column.

Minimal complete definition

toPersistValue, fromPersistValue

Methods

toPersistValue :: a -> PersistValue #

fromPersistValue :: PersistValue -> Either Text a #

Instances

PersistField Bool # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Bool -> PersistValue # fromPersistValue :: PersistValue -> Either Text Bool #
PersistField Double # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Double -> PersistValue # fromPersistValue :: PersistValue -> Either Text Double #
PersistField Int # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Int -> PersistValue # fromPersistValue :: PersistValue -> Either Text Int #
PersistField Int8 # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Int8 -> PersistValue # fromPersistValue :: PersistValue -> Either Text Int8 #
PersistField Int16 # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Int16 -> PersistValue # fromPersistValue :: PersistValue -> Either Text Int16 #
PersistField Int32 # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Int32 -> PersistValue # fromPersistValue :: PersistValue -> Either Text Int32 #
PersistField Int64 # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Int64 -> PersistValue # fromPersistValue :: PersistValue -> Either Text Int64 #
PersistField Natural # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Natural -> PersistValue # fromPersistValue :: PersistValue -> Either Text Natural #
PersistField Rational # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Rational -> PersistValue # fromPersistValue :: PersistValue -> Either Text Rational #
PersistField Word # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Word -> PersistValue # fromPersistValue :: PersistValue -> Either Text Word #
PersistField Word8 # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Word8 -> PersistValue # fromPersistValue :: PersistValue -> Either Text Word8 #
PersistField Word16 # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Word16 -> PersistValue # fromPersistValue :: PersistValue -> Either Text Word16 #
PersistField Word32 # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Word32 -> PersistValue # fromPersistValue :: PersistValue -> Either Text Word32 #
PersistField Word64 # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Word64 -> PersistValue # fromPersistValue :: PersistValue -> Either Text Word64 #
PersistField ByteString # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: ByteString -> PersistValue # fromPersistValue :: PersistValue -> Either Text ByteString #
PersistField Text # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Text -> PersistValue # fromPersistValue :: PersistValue -> Either Text Text #
PersistField UTCTime # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: UTCTime -> PersistValue # fromPersistValue :: PersistValue -> Either Text UTCTime #
PersistField Text # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Text -> PersistValue # fromPersistValue :: PersistValue -> Either Text0 Text #
PersistField Html # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Html -> PersistValue # fromPersistValue :: PersistValue -> Either Text Html #
PersistField TimeOfDay # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: TimeOfDay -> PersistValue # fromPersistValue :: PersistValue -> Either Text TimeOfDay #
PersistField Day # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Day -> PersistValue # fromPersistValue :: PersistValue -> Either Text Day #
PersistField PersistValue # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: PersistValue -> PersistValue # fromPersistValue :: PersistValue -> Either Text PersistValue #
PersistField Checkmark # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Checkmark -> PersistValue # fromPersistValue :: PersistValue -> Either Text Checkmark #
PersistField SomePersistField # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: SomePersistField -> PersistValue # fromPersistValue :: PersistValue -> Either Text SomePersistField #
PersistField [Char] # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: [Char] -> PersistValue # fromPersistValue :: PersistValue -> Either Text [Char] #
PersistField a => PersistField [a] # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: [a] -> PersistValue # fromPersistValue :: PersistValue -> Either Text [a] #
PersistField a => PersistField (Maybe a) # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Maybe a -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Maybe a) #
HasResolution a => PersistField (Fixed a) # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Fixed a -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Fixed a) #
PersistField v => PersistField (IntMap v) # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: IntMap v -> PersistValue # fromPersistValue :: PersistValue -> Either Text (IntMap v) #
(Ord a, PersistField a) => PersistField (Set a) # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Set a -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Set a) #
PersistField a => PersistField (Vector a) # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Vector a -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Vector a) #
(PersistEntity record, PersistField record, PersistField (Key record)) => PersistField (Entity record) # |
Instance details Defined in Database.Persist.Class.PersistEntity Methods toPersistValue :: Entity record -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Entity record) #
PersistField (BackendKey SqlWriteBackend) # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods toPersistValue :: BackendKey SqlWriteBackend -> PersistValue # fromPersistValue :: PersistValue -> Either Text (BackendKey SqlWriteBackend) #
PersistField (BackendKey SqlReadBackend) # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods toPersistValue :: BackendKey SqlReadBackend -> PersistValue # fromPersistValue :: PersistValue -> Either Text (BackendKey SqlReadBackend) #
PersistField (BackendKey SqlBackend) # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods toPersistValue :: BackendKey SqlBackend -> PersistValue # fromPersistValue :: PersistValue -> Either Text (BackendKey SqlBackend) #
(PersistField a, PersistField b) => PersistField (a, b) # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: (a, b) -> PersistValue # fromPersistValue :: PersistValue -> Either Text (a, b) #
PersistField v => PersistField (Map Text v) # |
Instance details Defined in Database.Persist.Class.PersistField Methods toPersistValue :: Map Text v -> PersistValue # fromPersistValue :: PersistValue -> Either Text (Map Text v) #

# 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 :: MonadUnliftIO 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) # |
Instance details Defined in Database.Persist.Class.PersistConfig Associated Types type PersistConfigBackend (Either c1 c2) :: (* -> *) -> * -> * # type PersistConfigPool (Either c1 c2) :: * # Methods loadConfig :: Value -> Parser (Either c1 c2) # applyEnv :: Either c1 c2 -> IO (Either c1 c2) # createPoolConfig :: Either c1 c2 -> IO (PersistConfigPool (Either c1 c2)) # runPool :: MonadUnliftIO m => Either c1 c2 -> PersistConfigBackend (Either c1 c2) m a -> PersistConfigPool (Either c1 c2) -> m a #

entityValues :: PersistEntity record => Entity record -> [PersistValue] #

Get list of values corresponding to given entity.

# Lifting

class HasPersistBackend backend where #

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`

Minimal complete definition

persistBackend

Associated Types

type BaseBackend backend #

Methods

persistBackend :: backend -> BaseBackend backend #

Instances

HasPersistBackend SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Types.Internal Associated Types type BaseBackend SqlWriteBackend :: * # Methods persistBackend :: SqlWriteBackend -> BaseBackend SqlWriteBackend #
HasPersistBackend SqlReadBackend # |
Instance details Defined in Database.Persist.Sql.Types.Internal Associated Types type BaseBackend SqlReadBackend :: * # Methods persistBackend :: SqlReadBackend -> BaseBackend SqlReadBackend #
HasPersistBackend SqlBackend # |
Instance details Defined in Database.Persist.Sql.Types.Internal Associated Types type BaseBackend SqlBackend :: * # Methods persistBackend :: SqlBackend -> BaseBackend SqlBackend #

class HasPersistBackend backend => IsPersistBackend backend #

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

mkPersistBackend

Instances

IsPersistBackend SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Types.Internal Methods mkPersistBackend :: BaseBackend SqlWriteBackend -> SqlWriteBackend #
IsPersistBackend SqlReadBackend # |
Instance details Defined in Database.Persist.Sql.Types.Internal Methods mkPersistBackend :: BaseBackend SqlReadBackend -> SqlReadBackend #
IsPersistBackend SqlBackend # |
Instance details Defined in Database.Persist.Sql.Types.Internal Methods mkPersistBackend :: BaseBackend SqlBackend -> SqlBackend #

liftPersist :: (MonadIO m, MonadReader backend m, HasPersistBackend backend) => ReaderT (BaseBackend backend) IO b -> m b #

class BackendCompatible sup sub where #

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 ::
      ( PersistEntity record
      , PeristEntityBackend record ~ BaseBackend backend
      , IsSqlBackend backend
      )

this can be replaced with:

    foo ::
      ( PersistEntity record,
      , PersistEntityBackend record ~ backend
      , BackendCompatible SqlBackend backend
      )

This works for `SqlReadBackend` because of the `instance `BackendCompatible` `SqlBackend` `SqlReadBackend``, without needing to go through the `BaseBackend` type family.

Likewise, functions that are currently hardcoded to use `SqlBackend` can be generalized:

    -- before:
    asdf :: ReaderT SqlBackend m ()
    asdf = pure ()

    -- after:
    asdf' :: BackendCompatible SqlBackend backend => ReaderT backend m ()
    asdf' = withReaderT projectBackend asdf

Since: persistent-2.7.1

Minimal complete definition

projectBackend

Methods

projectBackend :: sub -> sup #

Instances

BackendCompatible SqlBackend SqlWriteBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods projectBackend :: SqlWriteBackend -> SqlBackend #
BackendCompatible SqlBackend SqlReadBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods projectBackend :: SqlReadBackend -> SqlBackend #
BackendCompatible SqlBackend SqlBackend # |
Instance details Defined in Database.Persist.Sql.Orphan.PersistStore Methods projectBackend :: SqlBackend -> SqlBackend #

# JSON utilities

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

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, FromJSON (Key record)) => Value -> Parser (Entity record) #

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, ToJSON (Key record)) => Entity record -> Value #

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, FromJSON (Key record)) => Value -> Parser (Entity record) #

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 #

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 #

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