Safe Haskell	None

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 sqlType Source

Constructors

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

Instances

Functor EntityDef
Eq sqlType => Eq (EntityDef sqlType)
Ord sqlType => Ord (EntityDef sqlType)
Read sqlType => Read (EntityDef sqlType)
Show sqlType => Show (EntityDef sqlType)

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 sqlType 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 fieldEmbedded :: Maybe (EntityDef ()) indicates that the field uses an embedded entity

Instances

Functor FieldDef
Eq sqlType => Eq (FieldDef sqlType)
Ord sqlType => Ord (FieldDef sqlType)
Read sqlType => Read (FieldDef sqlType)
Show sqlType => Show (FieldDef sqlType)

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 PersistException Source

Constructors

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

Instances

Show PersistException
Typeable PersistException
Exception PersistException
Error PersistException

newtype ZT Source

Avoid orphan instances.

Constructors

ZT ZonedTime

Instances

Eq ZT
Ord ZT
Read ZT
Show ZT
Typeable ZT

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
PersistZonedTime ZT
PersistNull
PersistList [PersistValue]
PersistMap [(Text, PersistValue)]
PersistObjectId ByteString	intended especially for MongoDB backend

fromPersistValueText :: PersistValue -> Either String 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
SqlDayTimeZoned
SqlBlob
SqlOther Text	a backend-specific name

Instances

Eq SqlType
Ord SqlType
Read SqlType
Show SqlType
Typeable SqlType

newtype KeyBackend backend entity Source

Constructors

Key
Fields unKey :: PersistValue

Instances

Eq (KeyBackend backend entity)
Ord (KeyBackend backend entity)
Read (KeyBackend backend entity)
Show (KeyBackend backend entity)
ToJSON (KeyBackend backend entity)
FromJSON (KeyBackend backend entity)
PathPiece (KeyBackend SqlBackend entity)
PersistField (KeyBackend backend entity)

type family KeyEntity key Source

data PersistFilter Source

Constructors

Eq
Ne
Gt
Lt
Ge
Le
In
NotIn
BackendSpecificFilter Text

Instances

Read PersistFilter
Show PersistFilter

data UpdateGetException Source

Constructors

KeyNotFound String

Instances

Show UpdateGetException
Typeable UpdateGetException
Exception UpdateGetException

data PersistUpdate Source

Constructors

Assign
Add
Subtract
Multiply
Divide

Instances

Bounded PersistUpdate
Enum PersistUpdate
Read PersistUpdate
Show PersistUpdate

data SomePersistField Source

Constructors

forall a . PersistField a => SomePersistField a

Instances

PersistField SomePersistField

data Update v Source

Constructors

forall typ . PersistField typ => Update
Fields updateField :: EntityField v typ updateValue :: typ updateUpdate :: PersistUpdate

data SelectOpt v Source

Constructors

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

type family BackendSpecificFilter b v Source

data Filter v 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.

Constructors

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

type Key val = KeyBackend (PersistEntityBackend val) valSource

Helper wrapper, equivalent to Key (PersistEntityBackend val) val.

Since 1.1.0

data Entity entity Source

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

When using the an 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

Entity
Fields entityKey :: Key entity entityVal :: entity

Instances

Eq entity => Eq (Entity entity)
Ord entity => Ord (Entity entity)
Read entity => Read (Entity entity)
Show entity => Show (Entity entity)
ToJSON e => ToJSON (Entity e)
FromJSON e => FromJSON (Entity e)
PersistEntity a => RawSql (Entity a)

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