| Safe Haskell | Safe |
|---|---|
| Language | Haskell98 |
Opaleye.Internal.Aggregate
- newtype Aggregator a b = Aggregator (PackMap (Maybe AggrOp, PrimExpr) PrimExpr a b)
- makeAggr' :: Maybe AggrOp -> Aggregator (Column a) (Column b)
- makeAggr :: AggrOp -> Aggregator (Column a) (Column b)
- runAggregator :: Applicative f => Aggregator a b -> ((Maybe AggrOp, PrimExpr) -> f PrimExpr) -> a -> f b
- aggregateU :: Aggregator a b -> (a, PrimQuery, Tag) -> (b, PrimQuery, Tag)
- extractAggregateFields :: Tag -> (Maybe AggrOp, PrimExpr) -> PM [(Symbol, (Maybe AggrOp, PrimExpr))] PrimExpr
Documentation
newtype Aggregator a b Source
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.
runAggregator :: Applicative f => Aggregator a b -> ((Maybe AggrOp, PrimExpr) -> f PrimExpr) -> a -> f b Source
aggregateU :: Aggregator a b -> (a, PrimQuery, Tag) -> (b, PrimQuery, Tag) Source