Opaleye.SQLite.RunQuery

Documentation

runQuery :: Default QueryRunner columns haskells => Connection -> Query columns -> IO [haskells]

runQuery's use of the Default typeclass means that the compiler will have trouble inferring types. It is strongly recommended that you provide full type signatures when using runQuery.

Example type specialization:

runQuery :: Query (Column PGInt4, Column PGText) -> IO [(Column Int, Column String)]

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

runQuery :: Query (Foo (Column PGInt4) (Column PGText) (Column PGBool)
         -> IO [(Foo (Column Int) (Column String) (Column Bool)]

Opaleye types are converted to Haskell types based on instances of the QueryRunnerColumnDefault typeclass.

runQueryExplicit :: QueryRunner columns haskells -> Connection -> Query columns -> IO [haskells]

queryRunnerColumn :: (Column a' -> Column a) -> (b -> b') -> QueryRunnerColumn a b -> QueryRunnerColumn a' b'

Use queryRunnerColumn to make an instance to allow you to run queries on your own datatypes. For example:

newtype Foo = Foo Int
instance Default QueryRunnerColumn Foo Foo where
   def = queryRunnerColumn (unsafeCoerce :: Column Foo -> Column PGInt4) Foo def

data QueryRunner columns haskells

Instances

ProductProfunctor QueryRunner

SumProfunctor QueryRunner

Profunctor QueryRunner

QueryRunnerColumnDefault a b => Default QueryRunner (Column a) b

Functor (QueryRunner c)

Applicative (QueryRunner c)

data QueryRunnerColumn sqlType haskellType

A QueryRunnerColumn pgType haskellType encodes how to turn a value of Postgres type pgType into a value of Haskell type haskellType. For example a value of type QueryRunnerColumn PGText String encodes how to turn a PGText result from the database into a Haskell String.

fieldQueryRunnerColumn :: FromField haskell => QueryRunnerColumn coltype haskell