opaleye-0.5.3.0: An SQL-generating DSL targeting PostgreSQL

Safe HaskellNone
LanguageHaskell2010

Opaleye.RunQuery

Contents

Synopsis

Running Querys

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 [(Int, String)]

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

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

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

runQueryFold :: Default QueryRunner columns haskells => Connection -> Query columns -> b -> (b -> haskells -> IO b) -> IO b #

runQueryFold streams the results of a query incrementally and consumes the results with a left fold.

This fold is not strict. The stream consumer is responsible for forcing the evaluation of its result to avoid space leaks.

Creating new QueryRunnerColumns

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 QueryRunnerColumnDefault Foo Foo where
   queryRunnerColumnDefault =
       queryRunnerColumn (unsafeCoerceColumn
                              :: Column Foo -> Column PGInt4)
                         Foo
                         queryRunnerColumnDefault

Explicit versions

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

runQueryFoldExplicit :: QueryRunner columns haskells -> Connection -> Query columns -> b -> (b -> haskells -> IO b) -> IO b #

Deprecated functions

prepareQuery :: QueryRunner columns haskells -> Query columns -> (Maybe Query, RowParser haskells) #

For internal use only. Do not use. Will be deprecated in version 0.6.

data QueryRunner columns haskells #

A QueryRunner specifies how to convert Postgres values (columns) into Haskell values (haskells). Most likely you will never need to create on of these or handle one directly. It will be provided for you by the Default QueryRunner instance.

Instances

SumProfunctor QueryRunner # 

Methods

(+++!) :: QueryRunner a b -> QueryRunner a' b' -> QueryRunner (Either a a') (Either b b') #

ProductProfunctor QueryRunner # 

Methods

purePP :: b -> QueryRunner a b #

(****) :: QueryRunner a (b -> c) -> QueryRunner a b -> QueryRunner a c #

empty :: QueryRunner () () #

(***!) :: QueryRunner a b -> QueryRunner a' b' -> QueryRunner (a, a') (b, b') #

Profunctor QueryRunner # 

Methods

dimap :: (a -> b) -> (c -> d) -> QueryRunner b c -> QueryRunner a d #

lmap :: (a -> b) -> QueryRunner b c -> QueryRunner a c #

rmap :: (b -> c) -> QueryRunner a b -> QueryRunner a c #

(#.) :: Coercible * c b => (b -> c) -> QueryRunner a b -> QueryRunner a c #

(.#) :: Coercible * b a => QueryRunner b c -> (a -> b) -> QueryRunner a c #

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

Methods

def :: QueryRunner (Column a) b #

Functor (QueryRunner c) # 

Methods

fmap :: (a -> b) -> QueryRunner c a -> QueryRunner c b #

(<$) :: a -> QueryRunner c b -> QueryRunner c a #

Applicative (QueryRunner c) # 

Methods

pure :: a -> QueryRunner c a #

(<*>) :: QueryRunner c (a -> b) -> QueryRunner c a -> QueryRunner c b #

(*>) :: QueryRunner c a -> QueryRunner c b -> QueryRunner c b #

(<*) :: QueryRunner c a -> QueryRunner c b -> QueryRunner c a #

Datatypes

data QueryRunnerColumn pgType 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.

Instances

class QueryRunnerColumnDefault pgType haskellType where #

A QueryRunnerColumnDefault pgType haskellType represents the default way to turn a pgType result from the database into a Haskell value of type haskellType.

Creating an instance of QueryRunnerColumnDefault for your own types is necessary for retrieving those types from the database.

You should use one of the three methods below for writing a QueryRunnerColumnDefault instance.

  1. If you already have a FromField instance for your haskellType, use fieldQueryRunnerColumn. (This is how most of the built-in instances are defined.)
  2. If you don't have a FromField instance, use queryRunnerColumn if possible. See the documentation for queryRunnerColumn for an example.
  3. If you have a more complicated case, but not a FromField instance, write a FieldParser for your type and use fieldParserQueryRunnerColumn. You can also add a FromField instance using this.

Minimal complete definition

queryRunnerColumnDefault

Methods

queryRunnerColumnDefault :: QueryRunnerColumn pgType haskellType #

Instances

QueryRunnerColumnDefault PGJsonb String # 
QueryRunnerColumnDefault PGJsonb Value # 
QueryRunnerColumnDefault PGJson String # 
QueryRunnerColumnDefault PGJson Value # 
QueryRunnerColumnDefault PGBytea ByteString # 
QueryRunnerColumnDefault PGBytea ByteString # 
QueryRunnerColumnDefault PGUuid UUID # 
QueryRunnerColumnDefault PGTimestamptz UTCTime # 
QueryRunnerColumnDefault PGTimestamp LocalTime # 
QueryRunnerColumnDefault PGTime TimeOfDay # 
QueryRunnerColumnDefault PGText String # 
QueryRunnerColumnDefault PGText Text # 
QueryRunnerColumnDefault PGText Text # 
QueryRunnerColumnDefault PGInt4 Int # 
QueryRunnerColumnDefault PGInt4 Int32 # 
QueryRunnerColumnDefault PGInt8 Int64 # 
QueryRunnerColumnDefault PGFloat8 Double # 
QueryRunnerColumnDefault PGDate Day # 
QueryRunnerColumnDefault PGBool Bool # 
QueryRunnerColumnDefault PGCitext (CI Text) # 
QueryRunnerColumnDefault PGCitext (CI Text) # 
QueryRunnerColumnDefault a b => QueryRunnerColumnDefault (Nullable a) (Maybe b) # 
(Typeable * b, FromField b, QueryRunnerColumnDefault a b) => QueryRunnerColumnDefault (PGRange a) (PGRange b) # 
(Typeable * b, QueryRunnerColumnDefault a b) => QueryRunnerColumnDefault (PGArray a) [b] # 

Creating now QueryRunnerColumns