Safe Haskell | None |
---|---|
Language | Haskell98 |
- runQuery :: Default QueryRunner columns haskells => Connection -> Query columns -> IO [haskells]
- runQueryExplicit :: QueryRunner columns haskells -> Connection -> Query columns -> IO [haskells]
- runQueryFold :: Default QueryRunner columns haskells => Connection -> Query columns -> b -> (b -> haskells -> IO b) -> IO b
- runQueryFoldExplicit :: QueryRunner columns haskells -> Connection -> Query columns -> b -> (b -> haskells -> IO b) -> IO b
- queryRunnerColumn :: (Column a' -> Column a) -> (b -> b') -> QueryRunnerColumn a b -> QueryRunnerColumn a' b'
- prepareQuery :: QueryRunner columns haskells -> Query columns -> (Maybe Query, RowParser haskells)
- data QueryRunner columns haskells
- data QueryRunnerColumn pgType haskellType
- class QueryRunnerColumnDefault pgType haskellType where
- queryRunnerColumnDefault :: QueryRunnerColumn pgType haskellType
- fieldQueryRunnerColumn :: FromField haskell => QueryRunnerColumn coltype haskell
Documentation
runQuery :: Default QueryRunner columns haskells => Connection -> Query columns -> IO [haskells] Source
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 (ColumnPGInt4
, ColumnPGText
) -> IO [(Column Int, Column String)]
Assuming the makeAdaptorAndInstance
splice has been run for the product type Foo
:
runQuery :: Query (Foo (ColumnPGInt4
) (ColumnPGText
) (ColumnPGBool
) -> 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] Source
runQueryFold :: Default QueryRunner columns haskells => Connection -> Query columns -> b -> (b -> haskells -> IO b) -> IO b Source
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.
runQueryFoldExplicit :: QueryRunner columns haskells -> Connection -> Query columns -> b -> (b -> haskells -> IO b) -> IO b Source
queryRunnerColumn :: (Column a' -> Column a) -> (b -> b') -> QueryRunnerColumn a b -> QueryRunnerColumn a' b' Source
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
prepareQuery :: QueryRunner columns haskells -> Query columns -> (Maybe Query, RowParser haskells) Source
For internal use only. Do not use. Will be removed in a subsequent release.
data QueryRunner columns haskells Source
data QueryRunnerColumn pgType haskellType Source
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
.
class QueryRunnerColumnDefault pgType haskellType where Source
A QueryRunnerColumnDefault
pgType
haskellType
represents
the default way to turn a pgType
result from the database into a
Haskell value of type haskelType
.
queryRunnerColumnDefault :: QueryRunnerColumn pgType haskellType Source
fieldQueryRunnerColumn :: FromField haskell => QueryRunnerColumn coltype haskell Source