Database.Persist.Class.PersistStore

Documentation

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

Associated Types

type BaseBackend backend

Methods

persistBackend :: backend -> BaseBackend backend

Instances

HasPersistBackend SqlBackend

Defined in Database.Persist.SqlBackend.Internal

Associated Types

type BaseBackend SqlBackend

Methods

persistBackend :: SqlBackend -> BaseBackend SqlBackend

HasPersistBackend SqlWriteBackend

Defined in Database.Persist.Sql.Types.Internal

Associated Types

type BaseBackend SqlWriteBackend

Methods

persistBackend :: SqlWriteBackend -> BaseBackend SqlWriteBackend

HasPersistBackend SqlReadBackend

Defined in Database.Persist.Sql.Types.Internal

Associated Types

type BaseBackend SqlReadBackend

Methods

persistBackend :: SqlReadBackend -> BaseBackend SqlReadBackend

(BackendCompatible b s, HasPersistBackend b) => HasPersistBackend (Compatible b s)

Defined in Database.Persist.Compatible.Types

Associated Types

type BaseBackend (Compatible b s)

Methods

persistBackend :: Compatible b s -> BaseBackend (Compatible b s)

withBaseBackend :: HasPersistBackend backend => ReaderT (BaseBackend backend) m a -> ReaderT backend m a

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 where

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.

Methods

mkPersistBackend :: BaseBackend backend -> backend

This function is how we actually construct and tag a backend as having read or write capabilities. It should be used carefully and only when actually constructing a backend. Careless use allows us to accidentally run a write query against a read-only database.

Instances

IsPersistBackend SqlBackend

Defined in Database.Persist.SqlBackend.Internal

Methods

mkPersistBackend :: BaseBackend SqlBackend -> SqlBackend

IsPersistBackend SqlWriteBackend

Defined in Database.Persist.Sql.Types.Internal

Methods

mkPersistBackend :: BaseBackend SqlWriteBackend -> SqlWriteBackend

IsPersistBackend SqlReadBackend

Defined in Database.Persist.Sql.Types.Internal

Methods

mkPersistBackend :: BaseBackend SqlReadBackend -> SqlReadBackend

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

A convenient alias for common type signatures

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

class PersistCore backend

Associated Types

data BackendKey backend

Instances

PersistCore SqlBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Associated Types

data BackendKey SqlBackend

PersistCore SqlWriteBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Associated Types

data BackendKey SqlWriteBackend

PersistCore SqlReadBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Associated Types

data BackendKey SqlReadBackend

(BackendCompatible b s, PersistCore b) => PersistCore (Compatible b s)

Defined in Database.Persist.Compatible.Types

Associated Types

data BackendKey (Compatible b s)

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

Get a record by identifier, if available.

Example usage

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 :: forall record m. (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

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: 2.8.1

Instances

PersistStoreRead SqlBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Methods

get :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> ReaderT SqlBackend m (Maybe record)

getMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => [Key record] -> ReaderT SqlBackend m (Map (Key record) record)

PersistStoreRead SqlWriteBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Methods

get :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> ReaderT SqlWriteBackend m (Maybe record)

getMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [Key record] -> ReaderT SqlWriteBackend m (Map (Key record) record)

PersistStoreRead SqlReadBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Methods

get :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlReadBackend) => Key record -> ReaderT SqlReadBackend m (Maybe record)

getMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlReadBackend) => [Key record] -> ReaderT SqlReadBackend m (Map (Key record) record)

(HasPersistBackend b, BackendCompatible b s, PersistStoreRead b) => PersistStoreRead (Compatible b s)

Defined in Database.Persist.Compatible.Types

Methods

get :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => Key record -> ReaderT (Compatible b s) m (Maybe record)

getMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => [Key record] -> ReaderT (Compatible b s) 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 :: forall record m. (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

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 ()

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

Example usage

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

Create multiple records in the database and return their Keys.

If you don't need the inserted Keys, 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

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

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

The MongoDB, PostgreSQL, SQLite and MySQL backends insert all records in one database query.

Example usage

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 :: forall record m. (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

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

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

Example usage

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 :: forall record m. (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

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 ()

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

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: 2.8.1

replace :: forall record m. (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

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 ()

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

Example usage

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

Update individual fields on a specific record.

Example usage

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 :: forall record m. (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

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 SqlBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Methods

insert :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => record -> ReaderT SqlBackend m (Key record)

insert_ :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => record -> ReaderT SqlBackend m ()

insertMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => [record] -> ReaderT SqlBackend m [Key record]

insertMany_ :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => [record] -> ReaderT SqlBackend m ()

insertEntityMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => [Entity record] -> ReaderT SqlBackend m ()

insertKey :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> record -> ReaderT SqlBackend m ()

repsert :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> record -> ReaderT SqlBackend m ()

repsertMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => [(Key record, record)] -> ReaderT SqlBackend m ()

replace :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> record -> ReaderT SqlBackend m ()

delete :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> ReaderT SqlBackend m ()

update :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> [Update record] -> ReaderT SqlBackend m ()

updateGet :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlBackend) => Key record -> [Update record] -> ReaderT SqlBackend m record

PersistStoreWrite SqlWriteBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Methods

insert :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => record -> ReaderT SqlWriteBackend m (Key record)

insert_ :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => record -> ReaderT SqlWriteBackend m ()

insertMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [record] -> ReaderT SqlWriteBackend m [Key record]

insertMany_ :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [record] -> ReaderT SqlWriteBackend m ()

insertEntityMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [Entity record] -> ReaderT SqlWriteBackend m ()

insertKey :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> record -> ReaderT SqlWriteBackend m ()

repsert :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> record -> ReaderT SqlWriteBackend m ()

repsertMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => [(Key record, record)] -> ReaderT SqlWriteBackend m ()

replace :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> record -> ReaderT SqlWriteBackend m ()

delete :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> ReaderT SqlWriteBackend m ()

update :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> [Update record] -> ReaderT SqlWriteBackend m ()

updateGet :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record SqlWriteBackend) => Key record -> [Update record] -> ReaderT SqlWriteBackend m record

(HasPersistBackend b, BackendCompatible b s, PersistStoreWrite b) => PersistStoreWrite (Compatible b s)

Defined in Database.Persist.Compatible.Types

Methods

insert :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => record -> ReaderT (Compatible b s) m (Key record)

insert_ :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => record -> ReaderT (Compatible b s) m ()

insertMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => [record] -> ReaderT (Compatible b s) m [Key record]

insertMany_ :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => [record] -> ReaderT (Compatible b s) m ()

insertEntityMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => [Entity record] -> ReaderT (Compatible b s) m ()

insertKey :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => Key record -> record -> ReaderT (Compatible b s) m ()

repsert :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => Key record -> record -> ReaderT (Compatible b s) m ()

repsertMany :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => [(Key record, record)] -> ReaderT (Compatible b s) m ()

replace :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => Key record -> record -> ReaderT (Compatible b s) m ()

delete :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => Key record -> ReaderT (Compatible b s) m ()

update :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => Key record -> [Update record] -> ReaderT (Compatible b s) m ()

updateGet :: forall record (m :: Type -> Type). (MonadIO m, PersistRecordBackend record (Compatible b s)) => Key record -> [Update record] -> ReaderT (Compatible b s) m record

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

Like get, but returns the complete Entity.

Example usage

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

getJust :: forall record backend m. (PersistStoreRead backend, 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

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 :: forall record backend m. (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

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: 2.6.1

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)

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

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)

Like insert, but returns the complete Entity.

Example usage

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 :: forall record backend m. (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

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: 2.6.1

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.

Methods

toBackendKey :: Key record -> BackendKey backend

fromBackendKey :: BackendKey backend -> Key record

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' = withCompatibleBackend asdf

Since: 2.7.1

Methods

projectBackend :: sub -> sup

Instances

BackendCompatible SqlBackend SqlBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Methods

projectBackend :: SqlBackend -> SqlBackend

BackendCompatible SqlBackend SqlWriteBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Methods

projectBackend :: SqlWriteBackend -> SqlBackend

BackendCompatible SqlBackend SqlReadBackend

Defined in Database.Persist.Sql.Orphan.PersistStore

Methods

projectBackend :: SqlReadBackend -> SqlBackend

withCompatibleBackend :: BackendCompatible sup sub => ReaderT sup m a -> ReaderT sub m a

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