Opaleye.SQLite.Aggregate

Perform aggregations on query results.

Documentation

aggregate :: Aggregator a b -> Query a -> Query b

Given a Query producing rows of type a and an Aggregator accepting rows of type a, apply the aggregator to the results of the query.

groupBy :: Aggregator (Column a) (Column a)

Group the aggregation by equality on the input to groupBy.

sum :: Aggregator (Column a) (Column a)

Sum all rows in a group.

count :: Aggregator (Column a) (Column PGInt8)

Count the number of non-null rows in a group.

avg :: Aggregator (Column PGFloat8) (Column PGFloat8)

Average of a group

max :: PGOrd a => Aggregator (Column a) (Column a)

Maximum of a group

min :: PGOrd a => Aggregator (Column a) (Column a)

Maximum of a group

boolOr :: Aggregator (Column PGBool) (Column PGBool)

boolAnd :: Aggregator (Column PGBool) (Column PGBool)

arrayAgg :: Aggregator (Column a) (Column (PGArray a))

stringAgg :: Column PGText -> Aggregator (Column PGText) (Column PGText)

data Aggregator a b

An Aggregator takes a collection of rows of type a, groups them, and transforms each group into a single row of type b. This corresponds to aggregators using GROUP BY in SQL.

An Aggregator corresponds closely to a Fold from the foldl package. Whereas an Aggregator a b takes each group of type a to a single row of type b, a Fold a b takes a list of a and returns a single row of type b.

Instances

Profunctor Aggregator

Defined in Opaleye.SQLite.Internal.Aggregate

Methods

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

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

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

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

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

ProductProfunctor Aggregator

Defined in Opaleye.SQLite.Internal.Aggregate

Methods

purePP :: b -> Aggregator a b

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

empty :: Aggregator () ()

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

SumProfunctor Aggregator

Defined in Opaleye.SQLite.Internal.Aggregate

Methods

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

Functor (Aggregator a)

Defined in Opaleye.SQLite.Internal.Aggregate

Methods

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

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

Applicative (Aggregator a)

Defined in Opaleye.SQLite.Internal.Aggregate

Methods

pure :: a0 -> Aggregator a a0

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

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

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

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