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58 lines
1.9 KiB
Haskell
58 lines
1.9 KiB
Haskell
module Hasql.Query
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(
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Query.Query,
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statement,
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)
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where
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import Hasql.Prelude
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import qualified Hasql.Private.Query as Query
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import qualified Hasql.Decoders.Results as Decoders.Results
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import qualified Hasql.Decoders as Decoders
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import qualified Hasql.Encoders.Params as Encoders.Params
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import qualified Hasql.Encoders as Encoders
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-- |
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-- A specification of a strictly single-statement query, which can be parameterized and prepared.
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--
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-- Consists of the following:
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--
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-- * SQL template,
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-- * params encoder,
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-- * result decoder,
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-- * a flag, determining whether it should be prepared.
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--
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-- The SQL template must be formatted according to Postgres' standard,
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-- with any non-ASCII characters of the template encoded using UTF-8.
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-- According to the format,
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-- parameters must be referred to using the positional notation, as in the following:
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-- @$1@, @$2@, @$3@ and etc.
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-- Those references must be used to refer to the values of the 'Encoders.Params' encoder.
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--
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-- Following is an example of the declaration of a prepared statement with its associated codecs.
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--
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-- @
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-- selectSum :: Hasql.Query.'Query.Query' (Int64, Int64) Int64
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-- selectSum =
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-- Hasql.Query.'statement' sql encoder decoder True
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-- where
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-- sql =
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-- "select ($1 + $2)"
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-- encoder =
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-- 'contramap' 'fst' (Hasql.Encoders.'Hasql.Encoders.value' Hasql.Encoders.'Hasql.Encoders.int8') '<>'
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-- 'contramap' 'snd' (Hasql.Encoders.'Hasql.Encoders.value' Hasql.Encoders.'Hasql.Encoders.int8')
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-- decoder =
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-- Hasql.Decoders.'Hasql.Decoders.singleRow' (Hasql.Decoders.'Hasql.Decoders.value' Hasql.Decoders.'Hasql.Decoders.int8')
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-- @
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--
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-- The statement above accepts a product of two parameters of type 'Int64'
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-- and produces a single result of type 'Int64'.
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--
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{-# INLINE statement #-}
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statement :: ByteString -> Encoders.Params a -> Decoders.Result b -> Bool -> Query.Query a b
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statement =
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unsafeCoerce Query.statement
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