Database.Persist.Base

This defines the API for performing database actions. There are two levels to this API: dealing with fields, and dealing with entities. In SQL, a field corresponds to a column, and should be a single, non-composite value. An entity corresponds to a SQL table. In other words: An entity is a collection of fields.

Documentation

data PersistValue

A raw value which can be stored in any backend and can be marshalled to and from a PersistField.

Constructors

PersistText Text

PersistByteString ByteString

PersistInt64 Int64

PersistDouble Double

PersistBool Bool

PersistDay Day

PersistTimeOfDay TimeOfDay

PersistUTCTime UTCTime

PersistNull

PersistList [PersistValue]

PersistMap [(Text, PersistValue)]

PersistForeignKey ByteString

intended especially for MongoDB backend

Instances

Eq PersistValue

Ord PersistValue

Read PersistValue

Show PersistValue

Typeable PersistValue

PersistField PersistValue

data SqlType

A SQL data type. Naming attempts to reflect the underlying Haskell datatypes, eg SqlString instead of SqlVarchar. Different SQL databases may have different translations for these types.

Constructors

SqlString

SqlInt32

SqlInteger

FIXME 8-byte integer; should be renamed SqlInt64

SqlReal

SqlBool

SqlDay

SqlTime

SqlDayTime

SqlBlob

Instances

Eq SqlType

Read SqlType

Show SqlType

Typeable SqlType

class PersistField a where

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

Methods

toPersistValue :: a -> PersistValue

fromPersistValue :: PersistValue -> Either String a

sqlType :: a -> SqlType

isNullable :: a -> Bool

Instances

PersistField Bool

PersistField Double

PersistField Int

PersistField Int8

PersistField Int16

PersistField Int32

PersistField Int64

PersistField Word8

PersistField Word16

PersistField Word32

PersistField Word64

PersistField String

PersistField Text

PersistField ByteString

PersistField Html

PersistField TimeOfDay

PersistField UTCTime

PersistField Day

PersistField SomePersistField

PersistField PersistValue

PersistField a => PersistField (Maybe a)

class Show (Key val) => PersistEntity val where

A single database entity. For example, if writing a blog application, a blog entry would be an entry, containing fields such as title and content.

Associated Types

data Key val

The unique identifier associated with this entity. In general, backends also define a type synonym for this, such that "type MyEntityId = Key MyEntity".

data Update val

Fields which can be updated using the update and updateWhere functions.

data Filter val

Filters which are available for select, updateWhere and deleteWhere. Each filter constructor specifies the field being filtered on, the type of comparison applied (equals, not equals, etc) and the argument for the comparison.

data Order val

How you can sort the results of a select.

data Unique val

Unique keys in existence on this entity.

Methods

entityDef :: val -> EntityDef

toPersistFields :: val -> [SomePersistField]

fromPersistValues :: [PersistValue] -> Either String val

halfDefined :: val

toPersistKey :: PersistValue -> Key val

fromPersistKey :: Key val -> PersistValue

persistFilterToFieldName :: Filter val -> String

persistFilterToFilter :: Filter val -> PersistFilter

persistFilterToValue :: Filter val -> Either PersistValue [PersistValue]

persistOrderToFieldName :: Order val -> String

persistOrderToOrder :: Order val -> PersistOrder

persistUpdateToFieldName :: Update val -> String

persistUpdateToUpdate :: Update val -> PersistUpdate

persistUpdateToValue :: Update val -> PersistValue

persistUniqueToFieldNames :: Unique val -> [String]

persistUniqueToValues :: Unique val -> [PersistValue]

persistUniqueKeys :: val -> [Unique val]

data EntityDef

Constructors

EntityDef

Fields

entityName :: String

entityAttribs :: [String]

entityColumns :: [(String, String, [String])]

name, type, attribs

entityUniques :: [(String, [String])]

name, columns

entityDerives :: [String]

Instances

Show EntityDef

class Monad m => PersistBackend m where

Methods

insert :: PersistEntity val => val -> m (Key val)

Create a new record in the database, returning the newly created identifier.

replace :: PersistEntity val => Key val -> val -> m ()

Replace the record in the database with the given key. Result is undefined if such a record does not exist.

update :: PersistEntity val => Key val -> [Update val] -> m ()

Update individual fields on a specific record.

updateWhere :: PersistEntity val => [Filter val] -> [Update val] -> m ()

Update individual fields on any record matching the given criterion.

delete :: PersistEntity val => Key val -> m ()

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

deleteBy :: PersistEntity val => Unique val -> m ()

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

deleteWhere :: PersistEntity val => [Filter val] -> m ()

Delete all records matching the given criterion.

get :: PersistEntity val => Key val -> m (Maybe val)

Get a record by identifier, if available.

getBy :: PersistEntity val => Unique val -> m (Maybe (Key val, val))

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

selectEnum

Arguments

:: PersistEntity val

=> [Filter val]

-> [Order val]

-> Int

limit

-> Int

offset

-> Enumerator (Key val, val) m a

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

selectKeys :: PersistEntity val => [Filter val] -> Enumerator (Key val) m a

Get the Keys of all records matching the given criterion.

count :: PersistEntity val => [Filter val] -> m Int

The total number of records fulfilling the given criterion.

Instances

MonadControlIO m => PersistBackend (SqlPersist m)

data PersistFilter

Constructors

Eq

Ne

Gt

Lt

Ge

Le

In

NotIn

Instances

Read PersistFilter

Show PersistFilter

data PersistUpdate

Constructors

Update

Add

Subtract

Multiply

Divide

Instances

Read PersistUpdate

Show PersistUpdate

data PersistOrder

Constructors

Asc

Desc

Instances

Read PersistOrder

Show PersistOrder

data SomePersistField

Constructors

forall a . PersistField a => SomePersistField a

Instances

PersistField SomePersistField

selectList

Arguments

:: (PersistEntity val, PersistBackend m, Monad m)

=> [Filter val]

-> [Order val]

-> Int

limit

-> Int

offset

-> m [(Key val, val)]

Call select but return the result as a list.

insertBy :: (PersistEntity v, PersistBackend m) => v -> m (Either (Key v, v) (Key v))

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.

getByValue :: (PersistEntity v, PersistBackend m) => v -> m (Maybe (Key v, v))

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

checkUnique :: (PersistEntity val, PersistBackend m) => val -> m Bool

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

Returns True if the entity would be unique, and could thus safely be inserted; returns False on a conflict.

class PersistEntity a => DeleteCascade a where

Methods

deleteCascade :: PersistBackend m => Key a -> m ()

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

data PersistException

Constructors

PersistMarshalException String

Instances

Show PersistException

Typeable PersistException

Exception PersistException