Safe Haskell	None
Language	Haskell98

Database.Persist.Types

Synopsis

Documentation

data Checkmark Source

A Checkmark should be used as a field type whenever a uniqueness constraint should guarantee that a certain kind of record may appear at most once, but other kinds of records may appear any number of times.

NOTE: You need to mark any Checkmark fields as nullable (see the following example).

For example, suppose there's a Location entity that represents where a user has lived:

Location
    user    UserId
    name    Text
    current Checkmark nullable

    UniqueLocation user current

The UniqueLocation constraint allows any number of Inactive Locations to be current. However, there may be at most one current Location per user (i.e., either zero or one per user).

This data type works because of the way that SQL treats NULLable fields within uniqueness constraints. The SQL standard says that NULL values should be considered different, so we represent Inactive as SQL NULL, thus allowing any number of Inactive records. On the other hand, we represent Active as TRUE, so the uniqueness constraint will disallow more than one Active record.

Note: There may be DBMSs that do not respect the SQL standard's treatment of NULL values on uniqueness constraints, please check if this data type works before relying on it.

The SQL BOOLEAN type is used because it's the smallest data type available. Note that we never use FALSE, just TRUE and NULL. Provides the same behavior Maybe () would if () was a valid PersistField.

Constructors

Active	When used on a uniqueness constraint, there may be at most one `Active` record.
Inactive	When used on a uniqueness constraint, there may be any number of `Inactive` records.

Instances

Bounded Checkmark
Enum Checkmark
Eq Checkmark
Ord Checkmark
Read Checkmark
Show Checkmark
PathPiece Checkmark
PersistField Checkmark
PersistFieldSql Checkmark

data IsNullable Source

Constructors

Nullable !WhyNullable
NotNullable

Instances

Eq IsNullable
Show IsNullable

data WhyNullable Source

The reason why a field is nullable is very important. A field that is nullable because of a Maybe tag will have its type changed from A to Maybe A. OTOH, a field that is nullable because of a nullable tag will remain with the same type.

Constructors

ByMaybeAttr
ByNullableAttr

Instances

Eq WhyNullable
Show WhyNullable

data EntityDef Source

Constructors

EntityDef
Fields entityHaskell :: !HaskellName entityDB :: !DBName entityId :: !FieldDef entityAttrs :: ![Attr] entityFields :: ![FieldDef] entityUniques :: ![UniqueDef] entityForeigns :: ![ForeignDef] entityDerives :: ![Text] entityExtra :: !(Map Text [ExtraLine]) entitySum :: !Bool

Instances

Eq EntityDef
Ord EntityDef
Read EntityDef
Show EntityDef

entityPrimary :: EntityDef -> Maybe CompositeDef Source

type ExtraLine = [Text] Source

newtype HaskellName Source

Constructors

HaskellName
Fields unHaskellName :: Text

Instances

Eq HaskellName
Ord HaskellName
Read HaskellName
Show HaskellName

newtype DBName Source

Constructors

DBName
Fields unDBName :: Text

Instances

Eq DBName
Ord DBName
Read DBName
Show DBName

type Attr = Text Source

data FieldType Source

Constructors

FTTypeCon (Maybe Text) Text	Optional module and name.
FTApp FieldType FieldType
FTList FieldType

Instances

Eq FieldType
Ord FieldType
Read FieldType
Show FieldType

data FieldDef Source

Constructors

FieldDef
Fields fieldHaskell :: !HaskellName name of the field fieldDB :: !DBName fieldType :: !FieldType fieldSqlType :: !SqlType fieldAttrs :: ![Attr] user annotations for a field fieldStrict :: !Bool a strict field in the data type. Default: true fieldReference :: !ReferenceDef

Instances

Eq FieldDef
Ord FieldDef
Read FieldDef
Show FieldDef

data ReferenceDef Source

There are 3 kinds of references 1) composite (to fields that exist in the record) 2) single field 3) embedded

Constructors

NoReference
ForeignRef !HaskellName !FieldType	A ForeignRef has a late binding to the EntityDef it references via HaskellName and has the Haskell type of the foreign key in the form of FieldType
EmbedRef EmbedEntityDef
CompositeRef CompositeDef
SelfReference	A SelfReference stops an immediate cycle which causes non-termination at compile-time (issue #311).

Instances

Eq ReferenceDef
Ord ReferenceDef
Read ReferenceDef
Show ReferenceDef

data EmbedEntityDef Source

An EmbedEntityDef is the same as an EntityDef But it is only used for fieldReference so it only has data needed for embedding

Constructors

EmbedEntityDef
Fields embeddedHaskell :: !HaskellName embeddedFields :: ![EmbedFieldDef]

Instances

Eq EmbedEntityDef
Ord EmbedEntityDef
Read EmbedEntityDef
Show EmbedEntityDef

data EmbedFieldDef Source

An EmbedFieldDef is the same as a FieldDef But it is only used for embeddedFields so it only has data needed for embedding

Constructors

EmbedFieldDef
Fields emFieldDB :: !DBName emFieldEmbed :: Maybe EmbedEntityDef emFieldCycle :: Maybe HaskellName `emFieldEmbed` can create a cycle (issue #311) when a cycle is detected, `emFieldEmbed` will be Nothing and `emFieldCycle` will be Just

Instances

Eq EmbedFieldDef
Ord EmbedFieldDef
Read EmbedFieldDef
Show EmbedFieldDef

toEmbedEntityDef :: EntityDef -> EmbedEntityDef Source

data UniqueDef Source

Constructors

UniqueDef
Fields uniqueHaskell :: !HaskellName uniqueDBName :: !DBName uniqueFields :: ![(HaskellName, DBName)] uniqueAttrs :: ![Attr]

Instances

Eq UniqueDef
Ord UniqueDef
Read UniqueDef
Show UniqueDef

data CompositeDef Source

Constructors

CompositeDef
Fields compositeFields :: ![FieldDef] compositeAttrs :: ![Attr]

Instances

Eq CompositeDef
Ord CompositeDef
Read CompositeDef
Show CompositeDef

type ForeignFieldDef = (HaskellName, DBName) Source

Used instead of FieldDef to generate a smaller amount of code

data ForeignDef Source

Constructors

ForeignDef
Fields foreignRefTableHaskell :: !HaskellName foreignRefTableDBName :: !DBName foreignConstraintNameHaskell :: !HaskellName foreignConstraintNameDBName :: !DBName foreignFields :: ![(ForeignFieldDef, ForeignFieldDef)] foreignAttrs :: ![Attr] foreignNullable :: Bool

Instances

Eq ForeignDef
Ord ForeignDef
Read ForeignDef
Show ForeignDef

data PersistException Source

Constructors

PersistError Text	Generic Exception
PersistMarshalError Text
PersistInvalidField Text
PersistForeignConstraintUnmet Text
PersistMongoDBError Text
PersistMongoDBUnsupported Text

Instances

Show PersistException
Exception PersistException
Error PersistException
Typeable * PersistException

data PersistValue Source

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
PersistRational Rational
PersistBool Bool
PersistDay Day
PersistTimeOfDay TimeOfDay
PersistUTCTime UTCTime
PersistNull
PersistList [PersistValue]
PersistMap [(Text, PersistValue)]
PersistObjectId ByteString	Intended especially for MongoDB backend
PersistDbSpecific ByteString	Using `PersistDbSpecific` allows you to use types specific to a particular backend For example, below is a simple example of the PostGIS geography type: data Geo = Geo ByteString instance PersistField Geo where toPersistValue (Geo t) = PersistDbSpecific t fromPersistValue (PersistDbSpecific t) = Right $ Geo $ Data.ByteString.concat ["'", t, "'"] fromPersistValue _ = Left "Geo values must be converted from PersistDbSpecific" instance PersistFieldSql Geo where sqlType _ = SqlOther "GEOGRAPHY(POINT,4326)" toPoint :: Double -> Double -> Geo toPoint lat lon = Geo $ Data.ByteString.concat ["'POINT(", ps $ lon, " ", ps $ lat, ")'"] where ps = Data.Text.pack . show If Foo has a geography field, we can then perform insertions like the following: insert $ Foo (toPoint 44 44)

fromPersistValueText :: PersistValue -> Either Text Text Source

data SqlType Source

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
SqlInt64
SqlReal
SqlNumeric Word32 Word32
SqlBool
SqlDay
SqlTime
SqlDayTime	Always uses UTC timezone
SqlBlob
SqlOther Text	a backend-specific name

Instances

Eq SqlType
Ord SqlType
Read SqlType
Show SqlType
Typeable * SqlType

data PersistFilter Source

Constructors

Eq
Ne
Gt
Lt
Ge
Le
In
NotIn
BackendSpecificFilter Text

Instances

Read PersistFilter
Show PersistFilter

data UpdateException Source

Constructors

KeyNotFound String
UpsertError String

Instances

Show UpdateException
Exception UpdateException
Typeable * UpdateException

data OnlyUniqueException Source

Constructors

OnlyUniqueException String

Instances

Show OnlyUniqueException
Exception OnlyUniqueException
Typeable * OnlyUniqueException

data PersistUpdate Source

Constructors

Assign
Add
Subtract
Multiply
Divide
BackendSpecificUpdate Text

Instances

Read PersistUpdate
Show PersistUpdate

data SomePersistField Source

Constructors

forall a . PersistField a => SomePersistField a

Instances

PersistField SomePersistField

data Update record Source

Updating a database entity

Persistent users use combinators to create these

Constructors

forall typ . PersistField typ => Update
Fields updateField :: EntityField record typ updateValue :: typ updateUpdate :: PersistUpdate
BackendUpdate (BackendSpecificUpdate (PersistEntityBackend record) record)

type family BackendSpecificUpdate backend record Source

data SelectOpt record Source

query options

Persistent users use these directly

Constructors

forall typ . Asc (EntityField record typ)
forall typ . Desc (EntityField record typ)
OffsetBy Int
LimitTo Int

data Filter record Source

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.

Persistent users use combinators to create these

Constructors

forall typ . PersistField typ => Filter
Fields filterField :: EntityField record typ filterValue :: Either typ [typ] filterFilter :: PersistFilter
FilterAnd [Filter record]	convenient for internal use, not needed for the API
FilterOr [Filter record]
BackendFilter (BackendSpecificFilter (PersistEntityBackend record) record)

type family BackendSpecificFilter backend record Source

data Entity record Source

Datatype that represents an entity, with both its Key and its Haskell record representation.

When using a SQL-based backend (such as SQLite or PostgreSQL), an Entity may take any number of columns depending on how many fields it has. In order to reconstruct your entity on the Haskell side, persistent needs all of your entity columns and in the right order. Note that you don't need to worry about this when using persistent's API since everything is handled correctly behind the scenes.

However, if you want to issue a raw SQL command that returns an Entity, then you have to be careful with the column order. While you could use SELECT Entity.* WHERE ... and that would work most of the time, there are times when the order of the columns on your database is different from the order that persistent expects (for example, if you add a new field in the middle of you entity definition and then use the migration code -- persistent will expect the column to be in the middle, but your DBMS will put it as the last column). So, instead of using a query like the one above, you may use rawSql (from the Database.Persist.GenericSql module) with its /entity selection placeholder/ (a double question mark ??). Using rawSql the query above must be written as SELECT ?? WHERE ... Then rawSql will replace ?? with the list of all columns that we need from your entity in the right order. If your query returns two entities (i.e. (Entity backend a, Entity backend b)), then you must you use SELECT ??, ?? WHERE ..., and so on.

Constructors

PersistEntity record => Entity
Fields entityKey :: Key record entityVal :: record

Instances

(PersistEntity record, Eq (Key record), Eq record) => Eq (Entity record)
(PersistEntity record, Ord (Key record), Ord record) => Ord (Entity record)
(PersistEntity record, Read (Key record), Read record) => Read (Entity record)
(PersistEntity record, Show (Key record), Show record) => Show (Entity record)
(PersistEntity record, PersistField record, PersistField (Key record)) => PersistField (Entity record)
(PersistField record, PersistEntity record) => PersistFieldSql (Entity record)
(PersistEntity a, (~) * (PersistEntityBackend a) SqlBackend) => RawSql (Entity a)

Eq PersistValue
Ord PersistValue
Read PersistValue
Show PersistValue
ToJSON PersistValue
FromJSON PersistValue
PathPiece PersistValue
PersistField PersistValue
PersistFieldSql PersistValue
Typeable * PersistValue