Database.Groundhog

This module exports the most commonly used functions and datatypes.

See http://github.com/lykahb/groundhog/blob/master/examples/.

Core datatypes and functions

class (Monad m, Applicative m, Functor m, MonadIO m, ConnectionManager (Conn m), PersistBackendConn (Conn m)) => PersistBackend m where

This class helps to shorten the type signatures of user monadic code. If your monad has several connections, e.g., for main and audit databases, create run*Db function runAuditDb :: Action conn a -> m a

Minimal complete definition

getConnection

Associated Types

type Conn m

Methods

getConnection :: m (Conn m)

Instances

(Monad m, Applicative m, Functor m, MonadIO m, PersistBackendConn conn) => PersistBackend (ReaderT * conn m)

Associated Types

type Conn (ReaderT * conn m :: * -> *) :: *

Methods

getConnection :: ReaderT * conn m (Conn (ReaderT * conn m))

class (DbDescriptor conn, ConnectionManager conn) => PersistBackendConn conn where

Minimal complete definition

insert, insert_, insertBy, insertByAll, replace, replaceBy, select, selectStream, selectAll, selectAllStream, get, getBy, update, delete, deleteBy, deleteAll, count, countAll, project, projectStream, migrate, executeRaw, queryRaw, insertList, getList

Methods

insert :: (PersistEntity v, PersistBackend m, Conn m ~ conn) => v -> m (AutoKey v)

Insert a new record to a database and return its autogenerated key or ()

insert_ :: (PersistEntity v, PersistBackend m, Conn m ~ conn) => v -> m ()

Insert a new record to a database. For some backends it may be faster than insert.

insertBy :: (PersistEntity v, IsUniqueKey (Key v (Unique u)), PersistBackend m, Conn m ~ conn) => u (UniqueMarker v) -> v -> m (Either (AutoKey v) (AutoKey v))

Try to insert a record and return Right newkey. If there is a constraint violation for the given constraint, Left oldkey is returned , where oldkey is an identifier of the record with the matching values.

insertByAll :: (PersistEntity v, PersistBackend m, Conn m ~ conn) => v -> m (Either (AutoKey v) (AutoKey v))

Try to insert a record and return Right newkey. If there is a constraint violation for any constraint, Left oldkey is returned , where oldkey is an identifier of the record with the matching values. Note that if several constraints are violated, a key of an arbitrary matching record is returned.

replace :: (PersistEntity v, PrimitivePersistField (Key v BackendSpecific), PersistBackend m, Conn m ~ conn) => Key v BackendSpecific -> v -> m ()

Replace a record with the given autogenerated key. Result is undefined if the record does not exist.

replaceBy :: (PersistEntity v, IsUniqueKey (Key v (Unique u)), PersistBackend m, Conn m ~ conn) => u (UniqueMarker v) -> v -> m ()

Replace a record. The unique key marker defines what unique key of the entity is used.

select :: (PersistEntity v, EntityConstr v c, HasSelectOptions opts conn (RestrictionHolder v c), PersistBackend m, Conn m ~ conn) => opts -> m [v]

Return a list of the records satisfying the condition. Example: select $ (FirstField ==. "abc" &&. SecondField >. "def") `orderBy` [Asc ThirdField] `limitTo` 100

selectAll :: (PersistEntity v, PersistBackend m, Conn m ~ conn) => m [(AutoKey v, v)]

Return a list of all records. Order is undefined. It can be useful for datatypes with multiple constructors.

get :: (PersistEntity v, PrimitivePersistField (Key v BackendSpecific), PersistBackend m, Conn m ~ conn) => Key v BackendSpecific -> m (Maybe v)

Fetch an entity from a database

getBy :: (PersistEntity v, IsUniqueKey (Key v (Unique u)), PersistBackend m, Conn m ~ conn) => Key v (Unique u) -> m (Maybe v)

Fetch an entity from a database by its unique key

update :: (PersistEntity v, EntityConstr v c, PersistBackend m, Conn m ~ conn) => [Update conn (RestrictionHolder v c)] -> Cond conn (RestrictionHolder v c) -> m ()

Update the records satisfying the condition. Example: update [FirstField =. "abc"] $ FirstField ==. "def"

delete :: (PersistEntity v, EntityConstr v c, PersistBackend m, Conn m ~ conn) => Cond conn (RestrictionHolder v c) -> m ()

Remove the records satisfying the condition

deleteBy :: (PersistEntity v, PrimitivePersistField (Key v BackendSpecific), PersistBackend m, Conn m ~ conn) => Key v BackendSpecific -> m ()

Remove the record with given key. No-op if the record does not exist

deleteAll :: (PersistEntity v, PersistBackend m, Conn m ~ conn) => v -> m ()

Remove all records. The entity parameter is used only for type inference.

count :: (PersistEntity v, EntityConstr v c, PersistBackend m, Conn m ~ conn) => Cond conn (RestrictionHolder v c) -> m Int

Count total number of records satisfying the condition

countAll :: (PersistEntity v, PersistBackend m, Conn m ~ conn) => v -> m Int

Count total number of records with all constructors. The entity parameter is used only for type inference

project :: (PersistEntity v, EntityConstr v c, Projection' p conn (RestrictionHolder v c) a, HasSelectOptions opts conn (RestrictionHolder v c), PersistBackend m, Conn m ~ conn) => p -> opts -> m [a]

Fetch projection of some fields. Example: project (SecondField, ThirdField) $ (FirstField ==. "abc" &&. SecondField >. "def") `orderBy` [Asc ThirdField] `offsetBy` 100

migrate :: (PersistEntity v, PersistBackend m, Conn m ~ conn) => v -> Migration m

Check database schema and create migrations for the entity and the entities it contains

executeRaw :: (PersistBackend m, Conn m ~ conn) => Bool -> String -> [PersistValue] -> m ()

Execute raw query

queryRaw :: (PersistBackend m, Conn m ~ conn) => Bool -> String -> [PersistValue] -> m (RowStream [PersistValue])

Execute raw query with results

insertList :: (PersistField a, PersistBackend m, Conn m ~ conn) => [a] -> m Int64

getList :: (PersistField a, PersistBackend m, Conn m ~ conn) => Int64 -> m [a]

data Unique u

A holder for Unique constraints

data UniqueMarker v a

A phantom datatype to make instance head different u (UniqueMarker v)

Instances

(PersistEntity v, DbDescriptor db, IsUniqueKey k, (~) * k (Key v (Unique u)), (~) * (RestrictionHolder v c) r') => Expression db r' (u (UniqueMarker v))

Methods

toExpr :: u (UniqueMarker v) -> UntypedExpr db r'

type ProjectionDb (u (UniqueMarker v)) db

type ProjectionDb (u (UniqueMarker v)) db = ()

type ProjectionRestriction (u (UniqueMarker v)) (RestrictionHolder v' c)

type ProjectionRestriction (u (UniqueMarker v)) (RestrictionHolder v' c) = (~) * v v'

data BackendSpecific

Key marked with this type can have value for any backend

extractUnique :: (IsUniqueKey uKey, uKey ~ Key v u) => v -> uKey

Creates value of unique key using the data extracted from the passed value

data Cond db r

Represents condition for a query.

Constructors

And (Cond db r) (Cond db r)

Or (Cond db r) (Cond db r)

Not (Cond db r)

Compare ExprRelation (UntypedExpr db r) (UntypedExpr db r)

CondRaw (QueryRaw db r)

CondEmpty

Instances

((~) * db' db, (~) * r' r) => Expression db' r' (Cond db r)

Methods

toExpr :: Cond db r -> UntypedExpr db' r'

(~) * db' db => HasSelectOptions (Cond db r) db' r

Associated Types

type HasLimit (Cond db r) :: *

type HasOffset (Cond db r) :: *

type HasOrder (Cond db r) :: *

type HasDistinct (Cond db r) :: *

Methods

getSelectOptions :: Cond db r -> SelectOptions db' r (HasLimit (Cond db r)) (HasOffset (Cond db r)) (HasOrder (Cond db r)) (HasDistinct (Cond db r))

type HasLimit (Cond db r)

type HasLimit (Cond db r) = HFalse

type HasOffset (Cond db r)

type HasOffset (Cond db r) = HFalse

type HasOrder (Cond db r)

type HasOrder (Cond db r) = HFalse

type HasDistinct (Cond db r)

type HasDistinct (Cond db r) = HFalse

type ProjectionDb (Cond db r) db'

type ProjectionDb (Cond db r) db' = (~) * db db'

type ProjectionRestriction (Cond db r) r'

type ProjectionRestriction (Cond db r) r' = (~) * r r'

data Order db r

Defines sort order of a result-set

Constructors

Projection' f db r a => Asc f

Projection' f db r a => Desc f

data AutoKeyField v c where

It can be used in expressions like a regular field. For example, delete (AutoKeyField ==. k) or delete (AutoKeyField ==. k ||. SomeField ==. "DUPLICATE")

Constructors

AutoKeyField :: AutoKeyField v c

Instances

(EntityConstr v c, DbDescriptor db, (~) * (RestrictionHolder v c) r') => Expression db r' (AutoKeyField v c)

Methods

toExpr :: AutoKeyField v c -> UntypedExpr db r'

type ProjectionDb (AutoKeyField v c) db

type ProjectionDb (AutoKeyField v c) db = ()

type ProjectionRestriction (AutoKeyField v c) r

type ProjectionRestriction (AutoKeyField v c) r = (~) * r (RestrictionHolder v c)

(~>) :: (EntityConstr v c, FieldLike f a, DbDescriptor db, Projection' f db (RestrictionHolder v c) a, Embedded a) => f -> Selector a a' -> SubField db v c a' infixl 5

Accesses fields of the embedded datatypes. For example, SomeField ==. ("abc", "def") ||. SomeField ~> Tuple2_0Selector ==. "def"

limitTo :: (HasSelectOptions a db r, HasLimit a ~ HFalse) => a -> Int -> SelectOptions db r HTrue (HasOffset a) (HasOrder a) (HasDistinct a)

offsetBy :: (HasSelectOptions a db r, HasOffset a ~ HFalse) => a -> Int -> SelectOptions db r (HasLimit a) HTrue (HasOrder a) (HasDistinct a)

orderBy :: (HasSelectOptions a db r, HasOrder a ~ HFalse) => a -> [Order db r] -> SelectOptions db r (HasLimit a) (HasOffset a) HTrue (HasDistinct a)

deleteByKey :: (PersistBackend m, PersistEntity v, PrimitivePersistField (Key v BackendSpecific)) => Key v BackendSpecific -> m ()

Deprecated: Use deleteBy instead

Expressions

(=.) :: (Assignable f a', ProjectionDb f db, ProjectionRestriction f r, Expression db r b, Unifiable f b) => f -> b -> Update db r infixr 3

Update field

(&&.) :: Cond db r -> Cond db r -> Cond db r infixr 3

Boolean "and" operator.

(||.) :: Cond db r -> Cond db r -> Cond db r infixr 2

Boolean "or" operator.

(==.) :: (Expression db r a, Expression db r b, Unifiable a b) => a -> b -> Cond db r infix 4

(/=.) :: (Expression db r a, Expression db r b, Unifiable a b) => a -> b -> Cond db r infix 4

(<.) :: (Expression db r a, Expression db r b, Unifiable a b) => a -> b -> Cond db r infix 4

(<=.) :: (Expression db r a, Expression db r b, Unifiable a b) => a -> b -> Cond db r infix 4

(>.) :: (Expression db r a, Expression db r b, Unifiable a b) => a -> b -> Cond db r infix 4

(>=.) :: (Expression db r a, Expression db r b, Unifiable a b) => a -> b -> Cond db r infix 4

isFieldNothing :: (Expression db r f, Projection f (Maybe a), PrimitivePersistField (Maybe a), Unifiable f (Maybe a)) => f -> Cond db r

This function more limited than (==.), but has better type inference. If you want to compare your value to Nothing with (==.) operator, you have to write the types explicitly myExpr ==. (Nothing :: Maybe Int). TODO: restrict db r

liftExpr :: ExpressionOf db r a a' => a -> Expr db r a'

Converts value to Expr. It can help to pass values of different types into functions which expect arguments of the same type, like (+).

toArith :: ExpressionOf db r a a' => a -> Expr db r a'

Deprecated: Please use liftExpr instead

It is kept for compatibility with older Groundhog versions and can be replaced with "liftExpr".

Migration

createMigration :: Monad m => Migration m -> m NamedMigrations

Produce the migrations but not execute them. Fails when an unsafe migration occurs.

executeMigration :: (PersistBackend m, MonadIO m) => NamedMigrations -> m ()

Execute the migrations with printing to stderr. Fails when an unsafe migration occurs.

executeMigrationUnsafe :: (PersistBackend m, MonadIO m) => NamedMigrations -> m ()

Execute migrations. Executes the unsafe migrations without warnings and prints them to stderr

runMigration :: (PersistBackend m, MonadIO m) => Migration m -> m ()

Creates migrations and executes them with printing to stderr. Fails when an unsafe migration occurs. > runMigration m = createMigration m >>= executeMigration

runMigrationUnsafe :: (PersistBackend m, MonadIO m) => Migration m -> m ()

Creates migrations and executes them with printing to stderr. Executes the unsafe migrations without warnings > runMigrationUnsafe m = createMigration m >>= executeMigrationUnsafe

printMigration :: MonadIO m => NamedMigrations -> m ()

Pretty print the migrations