Hasql.Decoders

A DSL for declaration of result decoders.

Result

data Result a

Decoder of a query result.

Instances

Functor Result

Defined in Hasql.Decoders

Methods

fmap :: (a -> b) -> Result a -> Result b

(<$) :: a -> Result b -> Result a

Default (Result Int64)

Maps to rowsAffected.

Defined in Hasql.Decoders

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def :: Result Int64

Default (Row a) => Default (Result [a])

Maps to (rowList def).

Defined in Hasql.Decoders

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def :: Result [a]

Default (Row a) => Default (Result (Maybe a))

Maps to (rowMaybe def).

Defined in Hasql.Decoders

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def :: Result (Maybe a)

Default (Result ())

Maps to unit.

Defined in Hasql.Decoders

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def :: Result ()

Default (Row a) => Default (Result (Identity a))

Maps to (fmap Identity (singleRow def).

Defined in Hasql.Decoders

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def :: Result (Identity a)

Default (Row a) => Default (Result (Vector a))

Maps to (rowVector def).

Defined in Hasql.Decoders

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def :: Result (Vector a)

unit :: Result ()

Decode no value from the result.

Useful for statements like INSERT or CREATE.

rowsAffected :: Result Int64

Get the amount of rows affected by such statements as UPDATE or DELETE.

singleRow :: Row a -> Result a

Exactly one row. Will raise the UnexpectedAmountOfRows error if it's any other.

Specialized multi-row results

rowMaybe :: Row a -> Result (Maybe a)

Maybe one row or none.

rowVector :: Row a -> Result (Vector a)

Zero or more rows packed into the vector.

It's recommended to prefer this function to rowList, since it performs notably better.

rowList :: Row a -> Result [a]

Zero or more rows packed into the list.

Multi-row traversers

foldlRows :: (a -> b -> a) -> a -> Row b -> Result a

Foldl multiple rows.

foldrRows :: (b -> a -> a) -> a -> Row b -> Result a

Foldr multiple rows.

Row

data Row a

Decoder of an individual row, which gets composed of column value decoders.

E.g.:

x :: Row (Maybe Int64, Text, TimeOfDay)
x =
  (,,) <$> nullableColumn int8 <*> column text <*> column time

Instances

Monad Row

Defined in Hasql.Decoders

Methods

(>>=) :: Row a -> (a -> Row b) -> Row b

(>>) :: Row a -> Row b -> Row b

return :: a -> Row a

fail :: String -> Row a

Functor Row

Defined in Hasql.Decoders

Methods

fmap :: (a -> b) -> Row a -> Row b

(<$) :: a -> Row b -> Row a

Applicative Row

Defined in Hasql.Decoders

Methods

pure :: a -> Row a

(<*>) :: Row (a -> b) -> Row a -> Row b

liftA2 :: (a -> b -> c) -> Row a -> Row b -> Row c

(*>) :: Row a -> Row b -> Row b

(<*) :: Row a -> Row b -> Row a

Default (Value a) => Default (Row (Maybe a))

Defined in Hasql.Decoders

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def :: Row (Maybe a)

(Default (Value a1), Default (Value a2)) => Default (Row (a1, a2))

Defined in Hasql.Decoders

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def :: Row (a1, a2)

Default (Value a) => Default (Row (Identity a))

Defined in Hasql.Decoders

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def :: Row (Identity a)

column :: Value a -> Row a

Lift an individual non-nullable value decoder to a composable row decoder.

nullableColumn :: Value a -> Row (Maybe a)

Lift an individual nullable value decoder to a composable row decoder.

Value

data Value a

Decoder of an individual value.

Instances

Functor Value

Defined in Hasql.Decoders

Methods

fmap :: (a -> b) -> Value a -> Value b

(<$) :: a -> Value b -> Value a

Default (Value Bool)

Maps to bool.

Defined in Hasql.Decoders

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def :: Value Bool

Default (Value Char)

Maps to char.

Defined in Hasql.Decoders

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def :: Value Char

Default (Value Double)

Maps to float8.

Defined in Hasql.Decoders

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def :: Value Double

Default (Value Float)

Maps to float4.

Defined in Hasql.Decoders

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def :: Value Float

Default (Value Int16)

Maps to int2.

Defined in Hasql.Decoders

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def :: Value Int16

Default (Value Int32)

Maps to int4.

Defined in Hasql.Decoders

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def :: Value Int32

Default (Value Int64)

Maps to int8.

Defined in Hasql.Decoders

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def :: Value Int64

Default (Value (TimeOfDay, TimeZone))

Maps to timetz.

Defined in Hasql.Decoders

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def :: Value (TimeOfDay, TimeZone)

Default (Value ByteString)

Maps to bytea.

Defined in Hasql.Decoders

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def :: Value ByteString

Default (Value Scientific)

Maps to numeric.

Defined in Hasql.Decoders

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def :: Value Scientific

Default (Value Text)

Maps to text.

Defined in Hasql.Decoders

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def :: Value Text

Default (Value UTCTime)

Maps to timestamptz.

Defined in Hasql.Decoders

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def :: Value UTCTime

Default (Value Value)

Maps to json.

Defined in Hasql.Decoders

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def :: Value Value0

Default (Value UUID)

Maps to uuid.

Defined in Hasql.Decoders

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def :: Value UUID

Default (Value Day)

Maps to date.

Defined in Hasql.Decoders

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def :: Value Day

Default (Value DiffTime)

Maps to interval.

Defined in Hasql.Decoders

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def :: Value DiffTime

Default (Value TimeOfDay)

Maps to time.

Defined in Hasql.Decoders

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def :: Value TimeOfDay

Default (Value LocalTime)

Maps to timestamp.

Defined in Hasql.Decoders

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def :: Value LocalTime

bool :: Value Bool

Decoder of the BOOL values.

int2 :: Value Int16

Decoder of the INT2 values.

int4 :: Value Int32

Decoder of the INT4 values.

int8 :: Value Int64

Decoder of the INT8 values.

float4 :: Value Float

Decoder of the FLOAT4 values.

float8 :: Value Double

Decoder of the FLOAT8 values.

numeric :: Value Scientific

Decoder of the NUMERIC values.

char :: Value Char

Decoder of the CHAR values. Note that it supports UTF-8 values.

text :: Value Text

Decoder of the TEXT values.

bytea :: Value ByteString

Decoder of the BYTEA values.

date :: Value Day

Decoder of the DATE values.

timestamp :: Value LocalTime

Decoder of the TIMESTAMP values.

timestamptz :: Value UTCTime

Decoder of the TIMESTAMPTZ values.

NOTICE

Postgres does not store the timezone information of TIMESTAMPTZ. Instead it stores a UTC value and performs silent conversions to the currently set timezone, when dealt with in the text format. However this library bypasses the silent conversions and communicates with Postgres using the UTC values directly.

time :: Value TimeOfDay

Decoder of the TIME values.

timetz :: Value (TimeOfDay, TimeZone)

Decoder of the TIMETZ values.

Unlike in case of TIMESTAMPTZ, Postgres does store the timezone information for TIMETZ. However the Haskell's "time" library does not contain any composite type, that fits the task, so we use a pair of TimeOfDay and TimeZone to represent a value on the Haskell's side.

interval :: Value DiffTime

Decoder of the INTERVAL values.

uuid :: Value UUID

Decoder of the UUID values.

inet :: Value (NetAddr IP)

Decoder of the INET values.

json :: Value Value

Decoder of the JSON values into a JSON AST.

jsonBytes :: (ByteString -> Either Text a) -> Value a

Decoder of the JSON values into a raw JSON ByteString.

jsonb :: Value Value

Decoder of the JSONB values into a JSON AST.

jsonbBytes :: (ByteString -> Either Text a) -> Value a

Decoder of the JSONB values into a raw JSON ByteString.

array :: Array a -> Value a

Lifts the Array decoder to the Value decoder.

composite :: Composite a -> Value a

Lifts the Composite decoder to the Value decoder.

hstore :: (forall m. Monad m => Int -> m (Text, Maybe Text) -> m a) -> Value a

A generic decoder of HSTORE values.

Here's how you can use it to construct a specific value:

x :: Value [(Text, Maybe Text)]
x =
  hstore replicateM

enum :: (Text -> Maybe a) -> Value a

Given a partial mapping from text to value, produces a decoder of that value.

custom :: (Bool -> ByteString -> Either Text a) -> Value a

Lifts a custom value decoder function to a Value decoder.

Array

data Array a

A generic array decoder.

Here's how you can use it to produce a specific array value decoder:

x :: Value [[Text]]
x =
  array (dimension replicateM (dimension replicateM (element text)))

Instances

Functor Array

Defined in Hasql.Decoders

Methods

fmap :: (a -> b) -> Array a -> Array b

(<$) :: a -> Array b -> Array a

dimension :: (forall m. Monad m => Int -> m a -> m b) -> Array a -> Array b

A function for parsing a dimension of an array. Provides support for multi-dimensional arrays.

Accepts:

• An implementation of the replicateM function (Control.Monad.replicateM, Data.Vector.replicateM), which determines the output value.
• A decoder of its components, which can be either another dimension, element or nullableElement.

element :: Value a -> Array a

Lift a Value decoder into an Array decoder for parsing of non-nullable leaf values.

nullableElement :: Value a -> Array (Maybe a)

Lift a Value decoder into an Array decoder for parsing of nullable leaf values.

Composite

data Composite a

Composable decoder of composite values (rows, records).

Instances

Monad Composite

Defined in Hasql.Decoders

Methods

(>>=) :: Composite a -> (a -> Composite b) -> Composite b

(>>) :: Composite a -> Composite b -> Composite b

return :: a -> Composite a

fail :: String -> Composite a

Functor Composite

Defined in Hasql.Decoders

Methods

fmap :: (a -> b) -> Composite a -> Composite b

(<$) :: a -> Composite b -> Composite a

Applicative Composite

Defined in Hasql.Decoders

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pure :: a -> Composite a

(<*>) :: Composite (a -> b) -> Composite a -> Composite b

liftA2 :: (a -> b -> c) -> Composite a -> Composite b -> Composite c

(*>) :: Composite a -> Composite b -> Composite b

(<*) :: Composite a -> Composite b -> Composite a

field :: Value a -> Composite a

Lift a Value decoder into a Composite decoder for parsing of non-nullable leaf values.

nullableField :: Value a -> Composite (Maybe a)

Lift a Value decoder into a Composite decoder for parsing of nullable leaf values.