Preql.Wire.Internal

The types in this module have invariants which cannot be checked if their constructors are in scope. Preql.Wire exports the type names only.

Documentation

newtype Query (n :: Nat)

The IsString instance does no validation; the limited instances discourage directly manipulating strings, with the high risk of SQL injection. A Query is tagged with a Nat representing the width of its return type.

Constructors

Query ByteString

Instances

Show (Query n)

Defined in Preql.Wire.Internal

Methods

showsPrec :: Int -> Query n -> ShowS

show :: Query n -> String

showList :: [Query n] -> ShowS

IsString (Query n)

Defined in Preql.Wire.Internal

Methods

fromString :: String -> Query n

data RowDecoder (n :: Nat) a

RowDecoder is Functor but not Monad so that we can index the type by the number of columns that it consumes. We also know & verify all of the OIDs before we read any of the field data sent by Postgres, which would admit an Applicative instance but not Monad

Constructors

RowDecoder (Vector n PgType) (InternalDecoder a)

Instances

Functor (RowDecoder n)

Defined in Preql.Wire.Internal

Methods

fmap :: (a -> b) -> RowDecoder n a -> RowDecoder n b

(<$) :: a -> RowDecoder n b -> RowDecoder n a

pureDecoder :: a -> RowDecoder 0 a

Analogous to pure, pureDecoder a returns the value a without consuming any input from Postgres.

applyDecoder :: RowDecoder m (a -> b) -> RowDecoder n a -> RowDecoder (m + n) b

Analogous to <*>, pureDecoder Constructor applyDecoder a applyDecoder b supplies two arguments to Constructor, from the RowDecoder a and b.

type InternalDecoder = ReaderT (IORef DecoderState) IO

Internal because we need IO for the libpq FFI, but we promise not to do any IO besides decoding. We don't even make network calls to Postgres in InternalDecoder

data DecoderState

Constructors

DecoderState

Fields

• result :: !Result
• row :: !Row
• column :: !Column

Instances

Eq DecoderState

Defined in Preql.Wire.Internal

Methods

(==) :: DecoderState -> DecoderState -> Bool

(/=) :: DecoderState -> DecoderState -> Bool

Show DecoderState

Defined in Preql.Wire.Internal

Methods

showsPrec :: Int -> DecoderState -> ShowS

show :: DecoderState -> String

showList :: [DecoderState] -> ShowS

incrementColumn :: DecoderState -> DecoderState

incrementRow :: DecoderState -> DecoderState

decodeRow :: IORef DecoderState -> RowDecoder n a -> Result -> IO a

Can throw FieldError

getNextValue :: InternalDecoder (Maybe ByteString)