| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Hasql.Interpolate
Synopsis
- sql :: QuasiQuoter
- data Sql
- interp :: DecodeResult b => Bool -> Sql -> Statement () b
- interpFoldl :: DecodeRow a => Bool -> (b -> a -> b) -> b -> Sql -> Statement () b
- interpWith :: Bool -> Result b -> Sql -> Statement () b
- class DecodeValue a where
- decodeValue :: Value a
- class DecodeField a where
- class DecodeRow a where
- class DecodeResult a where
- decodeResult :: Result a
- class EncodeValue a where
- encodeValue :: Value a
- class EncodeField a
- newtype OneRow a = OneRow {
- getOneRow :: a
- newtype OneColumn a = OneColumn {
- getOneColumn :: a
- newtype RowsAffected = RowsAffected {}
- newtype Json = Json Value
- newtype Jsonb = Jsonb Value
- newtype AsJson a = AsJson a
- newtype AsJsonb a = AsJsonb a
- newtype CompositeValue a = CompositeValue a
- toTable :: EncodeRow a => [a] -> Sql
- class EncodeRow a where
- unzipWithEncoder :: (forall x. (a -> x -> x) -> x -> Params x -> Int -> r) -> r
QuasiQuoters
sql :: QuasiQuoter Source #
QuasiQuoter that supports interpolation and splices. Produces a
Sql.
#{..} interpolates a haskell expression into a sql query.
example1 :: EncodeValue a => a -> Sql
example1 x = [sql| select #{x} |]
^{..} introduces a splice, which allows us to inject a sql
snippet along with the associated parameters into another sql
snippet.
example2 :: Sql
example2 = [sql| ^{example1 True} where true |]
A SQL string with interpolated expressions.
Interpolators
Interpolate a Sql into a Statement using the DecodeResult
type class to determine the appropriate decoder.
example :: Int64 -> Statement () [(Int64, Int64)]
example bonk = interp False [sql| select x, y from t where t.x > #{bonk} |]
interpFoldl :: DecodeRow a => Bool -> (b -> a -> b) -> b -> Sql -> Statement () b Source #
interpolate then consume with foldlRows
interpWith :: Bool -> Result b -> Sql -> Statement () b Source #
A more general version of interp that allows for passing an
explicit decoder.
Decoders
class DecodeValue a where Source #
This type class determines which decoder we will apply to a query field by the type of the result.
Example
data ThreatLevel = None | Midnight
instance DecodeValue ThreatLevel where
decodeValue = enum \case
"none" -> Just None
"midnight" -> Just Midnight
_ -> Nothing
Methods
decodeValue :: Value a Source #
Instances
class DecodeField a where Source #
You do not need to define instances for this class; The two
instances exported here cover all uses. The class only exists to
lift Value to hasql's NullableOrNot GADT.
Methods
decodeField :: NullableOrNot Value a Source #
Instances
| DecodeValue a => DecodeField a Source # | Overlappable instance for parsing non-nullable values |
Defined in Hasql.Interpolate.Internal.Decoder Methods decodeField :: NullableOrNot Value a Source # | |
| DecodeValue a => DecodeField (Maybe a) Source # | Instance for parsing nullable values |
Defined in Hasql.Interpolate.Internal.Decoder Methods decodeField :: NullableOrNot Value (Maybe a) Source # | |
class DecodeRow a where Source #
Determine a row decoder from a Haskell type. Derivable with generics for any product type.
Examples
Minimal complete definition
Nothing
Methods
Instances
class DecodeResult a where Source #
Determine a result decoder from a Haskell type.
Methods
decodeResult :: Result a Source #
Instances
Encoders
class EncodeValue a where Source #
This type class determines which encoder we will apply to a field by its type.
Example
data ThreatLevel = None | Midnight
instance EncodeValue ThreatLevel where
encodeValue = enum \case
None -> "none"
Midnight -> "midnight"
Methods
encodeValue :: Value a Source #
Instances
class EncodeField a Source #
You do not need to define instances for this class; The two
instances exported here cover all uses. The class only exists to
lift Value to hasql's NullableOrNot GADT.
Minimal complete definition
encodeField
Instances
| EncodeValue a => EncodeField a Source # | Overlappable instance for all non-nullable types. |
Defined in Hasql.Interpolate.Internal.Encoder Methods | |
| EncodeValue a => EncodeField (Maybe a) Source # | Instance for all nullable types. |
Defined in Hasql.Interpolate.Internal.Encoder Methods encodeField :: NullableOrNot Value (Maybe a) | |
Newtypes for decoding/encoding
Instances
| Eq a => Eq (OneRow a) Source # | |
| Show a => Show (OneRow a) Source # | |
| Generic (OneRow a) Source # | |
| DecodeRow a => DecodeResult (OneRow a) Source # | Parse a single row result, throw
|
Defined in Hasql.Interpolate.Internal.OneRow Methods decodeResult :: Result (OneRow a) Source # | |
| type Rep (OneRow a) Source # | |
Defined in Hasql.Interpolate.Internal.OneRow | |
Constructors
| OneColumn | |
Fields
| |
newtype RowsAffected Source #
Constructors
| RowsAffected | |
Fields | |
Instances
Newtype for DecodeValue /
EncodeValue instances that converts
between a postgres json type and an Aeson Value
Instances
| DecodeValue Json Source # | Parse a postgres |
Defined in Hasql.Interpolate.Internal.Json Methods decodeValue :: Value Json Source # | |
| EncodeValue Json Source # | |
Defined in Hasql.Interpolate.Internal.Json Methods encodeValue :: Value Json Source # | |
Newtype for DecodeValue /
EncodeValue instances that converts
between a postgres json type and an Aeson Value
Instances
| DecodeValue Jsonb Source # | Parse a postgres |
Defined in Hasql.Interpolate.Internal.Json Methods decodeValue :: Value Jsonb Source # | |
| EncodeValue Jsonb Source # | |
Defined in Hasql.Interpolate.Internal.Json Methods encodeValue :: Value Jsonb Source # | |
Newtype for DecodeValue /
EncodeValue instances that converts
between a postgres json type and anything that is an instance of
FromJSON / ToJSON
Constructors
| AsJson a |
Instances
| FromJSON a => DecodeValue (AsJson a) Source # | Parse a postgres |
Defined in Hasql.Interpolate.Internal.Json Methods decodeValue :: Value (AsJson a) Source # | |
| ToJSON a => EncodeValue (AsJson a) Source # | Encode anything that is an instance of |
Defined in Hasql.Interpolate.Internal.Json Methods encodeValue :: Value (AsJson a) Source # | |
Newtype for DecodeValue /
EncodeValue instances that converts
between a postgres jsonb type and anything that is an instance of
FromJSON / ToJSON
Constructors
| AsJsonb a |
Instances
| FromJSON a => DecodeValue (AsJsonb a) Source # | Parse a postgres |
Defined in Hasql.Interpolate.Internal.Json Methods decodeValue :: Value (AsJsonb a) Source # | |
| ToJSON a => EncodeValue (AsJsonb a) Source # | Encode anything that is an instance of |
Defined in Hasql.Interpolate.Internal.Json Methods encodeValue :: Value (AsJsonb a) Source # | |
newtype CompositeValue a Source #
Useful with DerivingVia to get a DecodeValue instance for any
product type by parsing it as a composite.
Example
data Point = Point Int64 Int64 deriving stock (Generic) deriving (DecodeValue) via CompositeValue Point
Constructors
| CompositeValue a |
Instances
| (Generic a, GToComposite (Rep a)) => DecodeValue (CompositeValue a) Source # | |
Defined in Hasql.Interpolate.Internal.CompositeValue Methods decodeValue :: Value (CompositeValue a) Source # | |
toTable
toTable :: EncodeRow a => [a] -> Sql Source #
toTable takes some list of products into the corresponding
relation in sql. It is applying the unnest based technique
described in the hasql
documentation.
Example
Here is a small example that takes a haskell list and inserts it
into a table blerg which has columns x, y, and z of type
int8, boolean, and text respectively.
toTableExample :: [(Int64, Bool, Text)] -> Statement () ()
toTableExample rowsToInsert =
interp [sql| insert into blerg (x, y, z) select * from ^{toTable rowsToInsert} |]
This is driven by the EncodeRow type class that has a
default implementation for product types that are an instance of
Generic. So the following also works:
data Blerg
= Blerg Int64 Bool Text
deriving stock (Generic)
deriving anyclass (EncodeRow)
toTableExample :: [Blerg] -> Statement () ()
toTableExample blergs =
interp [sql| insert into blerg (x, y, z) select * from ^{toTable blergs} |]
class EncodeRow a where Source #
Minimal complete definition
Nothing
Methods
unzipWithEncoder :: (forall x. (a -> x -> x) -> x -> Params x -> Int -> r) -> r Source #
The continuation (forall x. (a -> x -> x) -> x -> E.Params x
-> Int -> r) is given cons (a -> x -> x) and nil (x) for some
existential type x and an encoder (Params xx. An
Int is also given to tally up how many sql fields are in the
unzipped structure.
Example
Consider the following manually written instance:
data Blerg = Blerg Int64 Bool Text Char
instance EncodeRow Blerg where
unzipWithEncoder k = k cons nil enc 4
where
cons (Blerg a b c d) ~(as, bs, cs, ds) =
(a : as, b : bs, c : cs, d : ds)
nil = ([], [], [], [])
enc =
(((x, _, _, _) -> x) >$< param encodeField)
<> (((_, x, _, _) -> x) >$< param encodeField)
<> (((_, _, x, _) -> x) >$< param encodeField)
<> (((_, _, _, x) -> x) >$< param encodeField)
We chose ([Int64], [Bool], [Text], [Char]) as our existential
type. If we instead use the default instance based on
GEncodeRow then we would produce the same code as the
instance below:
instance EncodeRow Blerg where
unzipWithEncoder k = k cons nil enc 4
where
cons (Blerg a b c d) ~(~(as, bs), ~(cs, ds)) =
((a : as, b : bs), (c : cs, d : ds))
nil = (([], []), ([], []))
enc =
((((x, _), _) -> x) >$< param encodeField)
<> ((((_, x), _) -> x) >$< param encodeField)
<> (((_ , (x, _)) -> x) >$< param encodeField)
<> (((_ , (_, x)) -> x) >$< param encodeField)
The notable difference being we don't produce a flat tuple, but
instead produce a balanced tree of tuples isomorphic to the
balanced tree of :*:Rep of Blerg.
Instances
| (EncodeValue x1, EncodeValue x2) => EncodeRow (x1, x2) Source # | |
Defined in Hasql.Interpolate.Internal.EncodeRow Methods unzipWithEncoder :: (forall x. ((x1, x2) -> x -> x) -> x -> Params x -> Int -> r) -> r Source # | |
| (EncodeValue x1, EncodeValue x2, EncodeValue x3) => EncodeRow (x1, x2, x3) Source # | |
Defined in Hasql.Interpolate.Internal.EncodeRow Methods unzipWithEncoder :: (forall x. ((x1, x2, x3) -> x -> x) -> x -> Params x -> Int -> r) -> r Source # | |
| (EncodeValue x1, EncodeValue x2, EncodeValue x3, EncodeValue x4) => EncodeRow (x1, x2, x3, x4) Source # | |
Defined in Hasql.Interpolate.Internal.EncodeRow Methods unzipWithEncoder :: (forall x. ((x1, x2, x3, x4) -> x -> x) -> x -> Params x -> Int -> r) -> r Source # | |
| (EncodeValue x1, EncodeValue x2, EncodeValue x3, EncodeValue x4, EncodeValue x5) => EncodeRow (x1, x2, x3, x4, x5) Source # | |
Defined in Hasql.Interpolate.Internal.EncodeRow Methods unzipWithEncoder :: (forall x. ((x1, x2, x3, x4, x5) -> x -> x) -> x -> Params x -> Int -> r) -> r Source # | |
| (EncodeValue x1, EncodeValue x2, EncodeValue x3, EncodeValue x4, EncodeValue x5, EncodeValue x6) => EncodeRow (x1, x2, x3, x4, x5, x6) Source # | |
Defined in Hasql.Interpolate.Internal.EncodeRow Methods unzipWithEncoder :: (forall x. ((x1, x2, x3, x4, x5, x6) -> x -> x) -> x -> Params x -> Int -> r) -> r Source # | |
| (EncodeValue x1, EncodeValue x2, EncodeValue x3, EncodeValue x4, EncodeValue x5, EncodeValue x6, EncodeValue x7) => EncodeRow (x1, x2, x3, x4, x5, x6, x7) Source # | |
Defined in Hasql.Interpolate.Internal.EncodeRow Methods unzipWithEncoder :: (forall x. ((x1, x2, x3, x4, x5, x6, x7) -> x -> x) -> x -> Params x -> Int -> r) -> r Source # | |
| (EncodeValue x1, EncodeValue x2, EncodeValue x3, EncodeValue x4, EncodeValue x5, EncodeValue x6, EncodeValue x7, EncodeValue x8) => EncodeRow (x1, x2, x3, x4, x5, x6, x7, x8) Source # | |
Defined in Hasql.Interpolate.Internal.EncodeRow Methods unzipWithEncoder :: (forall x. ((x1, x2, x3, x4, x5, x6, x7, x8) -> x -> x) -> x -> Params x -> Int -> r) -> r Source # | |