Opaleye.Distinct

Documentation

distinct :: Default Distinctspec fields fields => Select fields -> Select fields

Remove duplicate rows from the Select.

Example type specialization:

distinct :: Select (Field a, Field b) -> Select (Field a, Field b)

Assuming the makeAdaptorAndInstance splice has been run for the product type Foo:

distinct :: Select (Foo (Field a) (Field b) (Field c)) -> Select (Foo (Field a) (Field b) (Field c))

If you want to run distinct on SelectArrs you should apply laterally to it:

laterally distinct :: Default Distinctspec fields fields => SelectArr i fields -> SelectArr i fields

distinctOnCorrect :: Default Unpackspec b b => (a -> b) -> Select a -> Select a

Keep a row from each set where the given function returns the same result. No ordering is guaranteed. Multiple fields may be distinguished by projecting out tuples of Field_s. Use distinctOnBy to control how the rows are chosen.

distinctOnByCorrect :: Default Unpackspec b b => (a -> b) -> Order a -> Select a -> Select a

Keep the row from each set where the given function returns the same result. The row is chosen according to which comes first by the supplied ordering. However, no output ordering is guaranteed. Mutliple fields may be distinguished by projecting out tuples of Field_s.

data Distinctspec a b

Instances

Profunctor Distinctspec

Defined in Opaleye.Internal.Distinct

Methods

dimap :: (a -> b) -> (c -> d) -> Distinctspec b c -> Distinctspec a d

lmap :: (a -> b) -> Distinctspec b c -> Distinctspec a c

rmap :: (b -> c) -> Distinctspec a b -> Distinctspec a c

(#.) :: forall a b c q. Coercible c b => q b c -> Distinctspec a b -> Distinctspec a c

(.#) :: forall a b c q. Coercible b a => Distinctspec b c -> q a b -> Distinctspec a c

ProductProfunctor Distinctspec

Defined in Opaleye.Internal.Distinct

Methods

purePP :: b -> Distinctspec a b

(****) :: Distinctspec a (b -> c) -> Distinctspec a b -> Distinctspec a c

empty :: Distinctspec () ()

(***!) :: Distinctspec a b -> Distinctspec a' b' -> Distinctspec (a, a') (b, b')

SumProfunctor Distinctspec

Defined in Opaleye.Internal.Distinct

Methods

(+++!) :: Distinctspec a b -> Distinctspec a' b' -> Distinctspec (Either a a') (Either b b')

Default Distinctspec (Column a) (Column a)

Defined in Opaleye.Internal.Distinct

Methods

def :: Distinctspec (Column a) (Column a)

Default (WithNulls Distinctspec) a b => Default Distinctspec (MaybeFields a) (MaybeFields b)

Defined in Opaleye.Internal.Distinct

Methods

def :: Distinctspec (MaybeFields a) (MaybeFields b)

Functor (Distinctspec a)

Defined in Opaleye.Internal.Distinct

Methods

fmap :: (a0 -> b) -> Distinctspec a a0 -> Distinctspec a b

(<$) :: a0 -> Distinctspec a b -> Distinctspec a a0

Applicative (Distinctspec a)

Defined in Opaleye.Internal.Distinct

Methods

pure :: a0 -> Distinctspec a a0

(<*>) :: Distinctspec a (a0 -> b) -> Distinctspec a a0 -> Distinctspec a b

liftA2 :: (a0 -> b -> c) -> Distinctspec a a0 -> Distinctspec a b -> Distinctspec a c

(*>) :: Distinctspec a a0 -> Distinctspec a b -> Distinctspec a b

(<*) :: Distinctspec a a0 -> Distinctspec a b -> Distinctspec a a0

Explicit versions

distinctExplicit :: Distinctspec fields fields' -> Select fields -> Select fields'

Adaptors

distinctspecField :: Distinctspec (Column a) (Column a)

distinctspecMaybeFields :: WithNulls Distinctspec a b -> Distinctspec (MaybeFields a) (MaybeFields b)