Opaleye.RunQuery

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

Cursor interface

declareCursor :: Default QueryRunner columns haskells => Connection -> Query columns -> IO (Cursor haskells)

Declare a temporary cursor. The cursor is given a unique name for the given connection.

Returns Nothing when the query returns zero rows.

declareCursorExplicit :: QueryRunner columns haskells -> Connection -> Query columns -> IO (Cursor haskells)

Like declareCursor but takes a QueryRunner explicitly.

closeCursor :: Cursor columns -> IO ()

Close the given cursor.

foldForward :: Cursor haskells -> Int -> (a -> haskells -> IO a) -> a -> IO (Either a a)

Fold over a chunk of rows, calling the supplied fold-like function on each row as it is received. In case the cursor is exhausted, a Left value is returned, otherwise a Right value is returned.

Deprecated functions

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

Deprecated: Will be removed in version 0.7

Datatypes

data Cursor haskells

Cursor within a transaction.

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.

"QueryRunner columns haskells" corresponds to postgresql-simple's "RowParser haskells". "Default QueryRunner columns haskells" corresponds to postgresql-simple's "FromRow haskells".

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

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.

"QueryRunnerColumn pgType haskellType" corresponds to postgresql-simple's "FieldParser haskellType".

Instances

Functor (QueryRunnerColumn u)

Methods

fmap :: (a -> b) -> QueryRunnerColumn u a -> QueryRunnerColumn u b

(<$) :: a -> QueryRunnerColumn u b -> QueryRunnerColumn u a

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.

"QueryRunnerColumnDefault pgType haskellType" corresponds to postgresql-simple's "FromField 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

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGJsonb String

QueryRunnerColumnDefault PGJsonb Value

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGJsonb Value

QueryRunnerColumnDefault PGJson String

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGJson String

QueryRunnerColumnDefault PGJson Value

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGJson Value

QueryRunnerColumnDefault PGBytea ByteString

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGBytea ByteString

QueryRunnerColumnDefault PGBytea ByteString

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGBytea ByteString

QueryRunnerColumnDefault PGUuid UUID

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGUuid UUID

QueryRunnerColumnDefault PGTimestamptz UTCTime

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGTimestamptz UTCTime

QueryRunnerColumnDefault PGTimestamp LocalTime

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGTimestamp LocalTime

QueryRunnerColumnDefault PGTime TimeOfDay

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGTime TimeOfDay

QueryRunnerColumnDefault PGText String

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGText String

QueryRunnerColumnDefault PGText Text

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGText Text

QueryRunnerColumnDefault PGText Text

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGText Text

QueryRunnerColumnDefault PGInt4 Int

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGInt4 Int

QueryRunnerColumnDefault PGInt4 Int32

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGInt4 Int32

QueryRunnerColumnDefault PGInt8 Int64

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGInt8 Int64

QueryRunnerColumnDefault PGFloat8 Double

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGFloat8 Double

QueryRunnerColumnDefault PGDate Day

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGDate Day

QueryRunnerColumnDefault PGBool Bool

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGBool Bool

QueryRunnerColumnDefault PGCitext (CI Text)

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGCitext (CI Text)

QueryRunnerColumnDefault PGCitext (CI Text)

Methods

queryRunnerColumnDefault :: QueryRunnerColumn PGCitext (CI Text)

QueryRunnerColumnDefault a b => QueryRunnerColumnDefault (Nullable a) (Maybe b)

Methods

queryRunnerColumnDefault :: QueryRunnerColumn (Nullable a) (Maybe b)

(Typeable * b, FromField b, QueryRunnerColumnDefault a b) => QueryRunnerColumnDefault (PGRange a) (PGRange b)

Methods

queryRunnerColumnDefault :: QueryRunnerColumn (PGRange a) (PGRange b)

(Typeable * b, QueryRunnerColumnDefault a b) => QueryRunnerColumnDefault (PGArray a) [b]

Methods

queryRunnerColumnDefault :: QueryRunnerColumn (PGArray a) [b]

Creating new QueryRunnerColumns

fieldQueryRunnerColumn :: FromField haskell => QueryRunnerColumn pgType haskell

fieldParserQueryRunnerColumn :: FieldParser haskell -> QueryRunnerColumn pgType haskell