persistent-2.9.1: Type-safe, multi-backend data serialization.

Safe HaskellNone
LanguageHaskell98

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 Source # 
Instance details

Defined in Database.Persist.Types.Base

Enum Checkmark Source # 
Instance details

Defined in Database.Persist.Types.Base

Eq Checkmark Source # 
Instance details

Defined in Database.Persist.Types.Base

Ord Checkmark Source # 
Instance details

Defined in Database.Persist.Types.Base

Read Checkmark Source # 
Instance details

Defined in Database.Persist.Types.Base

Show Checkmark Source # 
Instance details

Defined in Database.Persist.Types.Base

ToHttpApiData Checkmark Source # 
Instance details

Defined in Database.Persist.Types.Base

FromHttpApiData Checkmark Source # 
Instance details

Defined in Database.Persist.Types.Base

PathPiece Checkmark Source # 
Instance details

Defined in Database.Persist.Types.Base

PersistField Checkmark Source # 
Instance details

Defined in Database.Persist.Class.PersistField

PersistFieldSql Checkmark Source # 
Instance details

Defined in Database.Persist.Sql.Class

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.

newtype DBName Source #

Constructors

DBName 

Fields

Instances
Eq DBName Source # 
Instance details

Defined in Database.Persist.Types.Base

Methods

(==) :: DBName -> DBName -> Bool #

(/=) :: DBName -> DBName -> Bool #

Ord DBName Source # 
Instance details

Defined in Database.Persist.Types.Base

Read DBName Source # 
Instance details

Defined in Database.Persist.Types.Base

Show DBName Source # 
Instance details

Defined in Database.Persist.Types.Base

type Attr = Text Source #

data FieldDef Source #

Constructors

FieldDef 

Fields

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).

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

type ForeignFieldDef = (HaskellName, DBName) Source #

Used instead of FieldDef to generate a smaller amount of code

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)
Instances
Eq PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

Ord PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

Read PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

Show PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

ToJSON PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

FromJSON PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

ToHttpApiData PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

FromHttpApiData PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

PathPiece PersistValue Source # 
Instance details

Defined in Database.Persist.Types.Base

PersistField PersistValue Source # 
Instance details

Defined in Database.Persist.Class.PersistField

PersistFieldSql PersistValue Source # 
Instance details

Defined in Database.Persist.Sql.Class

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

data Update record Source #

Updating a database entity.

Persistent users use combinators to create these.

type family BackendSpecificUpdate backend record Source #

data SelectOpt record Source #

Query options.

Persistent users use these directly.

Constructors

Asc (EntityField record 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

PersistField typ => Filter 

Fields

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 family Key record Source #

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

Instances
(PersistEntity a, PersistEntityBackend a ~ backend, IsPersistBackend backend) => RawSql (Key a) Source # 
Instance details

Defined in Database.Persist.Sql.Class

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

Entity 

Fields

Instances
(Eq (Key record), Eq record) => Eq (Entity record) Source # 
Instance details

Defined in Database.Persist.Class.PersistEntity

Methods

(==) :: Entity record -> Entity record -> Bool #

(/=) :: Entity record -> Entity record -> Bool #

(Ord (Key record), Ord record) => Ord (Entity record) Source # 
Instance details

Defined in Database.Persist.Class.PersistEntity

Methods

compare :: Entity record -> Entity record -> Ordering #

(<) :: Entity record -> Entity record -> Bool #

(<=) :: Entity record -> Entity record -> Bool #

(>) :: Entity record -> Entity record -> Bool #

(>=) :: Entity record -> Entity record -> Bool #

max :: Entity record -> Entity record -> Entity record #

min :: Entity record -> Entity record -> Entity record #

(Read (Key record), Read record) => Read (Entity record) Source # 
Instance details

Defined in Database.Persist.Class.PersistEntity

Methods

readsPrec :: Int -> ReadS (Entity record) #

readList :: ReadS [Entity record] #

readPrec :: ReadPrec (Entity record) #

readListPrec :: ReadPrec [Entity record] #

(Show (Key record), Show record) => Show (Entity record) Source # 
Instance details

Defined in Database.Persist.Class.PersistEntity

Methods

showsPrec :: Int -> Entity record -> ShowS #

show :: Entity record -> String #

showList :: [Entity record] -> ShowS #

(Generic (Key record), Generic record) => Generic (Entity record) Source # 
Instance details

Defined in Database.Persist.Class.PersistEntity

Associated Types

type Rep (Entity record) :: Type -> Type #

Methods

from :: Entity record -> Rep (Entity record) x #

to :: Rep (Entity record) x -> Entity record #

(PersistEntity record, PersistField record, PersistField (Key record)) => PersistField (Entity record) Source # 
Instance details

Defined in Database.Persist.Class.PersistEntity

(PersistField record, PersistEntity record) => PersistFieldSql (Entity record) Source # 
Instance details

Defined in Database.Persist.Sql.Class

Methods

sqlType :: Proxy (Entity record) -> SqlType Source #

(PersistEntity record, PersistEntityBackend record ~ backend, IsPersistBackend backend) => RawSql (Entity record) Source # 
Instance details

Defined in Database.Persist.Sql.Class

type Rep (Entity record) Source # 
Instance details

Defined in Database.Persist.Class.PersistEntity

type Rep (Entity record) = D1 (MetaData "Entity" "Database.Persist.Class.PersistEntity" "persistent-2.9.1-apmnZu2X4H1Ac8h1PvpbI" False) (C1 (MetaCons "Entity" PrefixI True) (S1 (MetaSel (Just "entityKey") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (Key record)) :*: S1 (MetaSel (Just "entityVal") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 record)))