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我的问题是在下面代码块中的巨大横幅之间。
请原谅代码转储,所有这些都粘贴在这里供任何想要复制的人使用,并且此代码确实可以按预期工作,尽管它有点奇怪。注意最后两行,它们打印正确的 SQL。
目标:
我有一些主键类型为 Text
的表,特别是电子邮件。我没有为每个表编写一个新的查询函数,而是承担了泛化该函数的任务,这样我就可以安全地查询任何有电子邮件的表。
问题:
为了让它工作,我必须包括:
instance Default Constant CEmail (Column PGText) where
def = undefined
这让我觉得我做错了什么。对于构建可以从任何包含电子邮件的表中查找记录的查询,有什么建议吗?
{- stack
--resolver lts-8.2
--install-ghc
exec ghci
--package aeson
--package composite-base
--package composite-aeson
--package text
--package string-conversions
--package postgres-simple
--package vinyl
-}
{-# LANGUAGE
Arrows
, DataKinds
, OverloadedStrings
, PatternSynonyms
, TypeOperators
, TemplateHaskell
, FlexibleContexts
, RankNTypes
, ConstraintKinds
, TypeSynonymInstances
, FlexibleInstances
, MultiParamTypeClasses
#-}
import Data.Vinyl (RElem)
import Data.Functor.Identity (Identity)
import Data.Vinyl.TypeLevel (RIndex)
import Composite.Aeson (JsonFormat, defaultJsonFormatRec, recJsonFormat, toJsonWithFormat)
import Composite.Opaleye (defaultRecTable)
import Composite.Record (Record, Rec(RNil), (:->), pattern (:*:))
import Composite.TH (withOpticsAndProxies)
import Control.Arrow (returnA)
import Control.Lens (view)
import Data.Int (Int64)
import Data.Proxy (Proxy(Proxy))
import Data.Text (Text)
import Opaleye
import Opaleye.Internal.TableMaker (ColumnMaker)
import Data.String.Conversions (cs)
import qualified Data.Aeson as Aeson
import qualified Database.PostgreSQL.Simple as PGS -- used for printSql
import Data.Profunctor.Product.Default (Default(def))
--------------------------------------------------
-- | Types
-- | Newtype ClearPassword so it can't be passed around as ordinary Text
newtype ClearPassword a = ClearPassword a
withOpticsAndProxies [d|
type FEmail = "email" :-> Text
type CEmail = "email" :-> Column PGText
type FAge = "age" :-> Text
type CAge = "age" :-> Column PGText
type FClearPassword = "clearpass" :-> ClearPassword Text
type CHashPassword = "hashpass" :-> Column PGText
|]
--------------------------------------------------
-- | Db Setup
-- | Helper Fn
printSql :: Default Unpackspec a a => Query a -> IO ()
printSql = putStrLn . maybe "Empty query" id . showSqlForPostgres
-- | Db Records
type DbUser = '[CEmail, CAge]
type DbPassword = '[CEmail, CHashPassword]
--------------------------------------------------
--------------------------------------------------
--
-- LOOK HERE vvvvvvvvvvvvvvvvvvvvvvvv
--
--------------------------------------------------
--------------------------------------------------
type RecWith f rs = (Default ColumnMaker (Record rs) (Record rs),
Default Constant f (Column PGText),
RElem f rs (RIndex f rs))
-- | queryByEmail needs this, but totally works if `def` is declared
-- as `undefined` ???
instance Default Constant CEmail (Column PGText) where
def = undefined
queryByEmail :: (RecWith CEmail rs) =>
Table a (Record rs) -> Text -> QueryArr () (Record rs)
queryByEmail table email = proc () -> do
u <- queryTable table -< ()
let uEmail = view cEmail u
restrict -< uEmail .=== constant email
returnA -< u
--------------------------------------------------
--------------------------------------------------
--
-- LOOK UP ^^^^^^^^^^^^^^^^^^^^^^^^
--
--------------------------------------------------
--------------------------------------------------
userTable :: Table (Record DbUser) (Record DbUser)
userTable = Table "user" defaultRecTable
-- | Password
passwordTable :: Table (Record DbPassword) (Record DbPassword)
passwordTable = Table "password" defaultRecTable
-- SELECT ... FROM "user" ...
queryUserTest = printSql $ queryByEmail userTable "hi"
-- SELECT ... FROM "password" ...
queryPasswordTest = printSql $ queryByEmail passwordTable "hi"
最佳答案
删除无关的 Default Constant f (Column PGTest)
约束,您应该可以开始了:
#!/usr/bin/env stack
{- stack --resolver lts-8.11 --install-ghc exec ghci --package aeson --package composite-base --package composite-aeson --package text --package string-conversions --package vinyl --package composite-opaleye -}
{-# LANGUAGE Arrows, DataKinds, OverloadedStrings, PatternSynonyms, TypeOperators, TemplateHaskell, FlexibleContexts, RankNTypes, ConstraintKinds, TypeSynonymInstances, FlexibleInstances, MultiParamTypeClasses #-}
import Composite.Opaleye (defaultRecTable)
import Composite.Record (Record, (:->))
import Composite.TH (withOpticsAndProxies)
import Control.Arrow (returnA)
import Control.Lens (view)
import Data.Profunctor.Product.Default (Default)
import Data.Text (Text)
import Data.Vinyl (RElem)
import Data.Vinyl.TypeLevel (RIndex)
import Opaleye.Internal.TableMaker (ColumnMaker)
import Opaleye
newtype ClearPassword a = ClearPassword a
withOpticsAndProxies [d|
type FEmail = "email" :-> Text
type CEmail = "email" :-> Column PGText
type FAge = "age" :-> Text
type CAge = "age" :-> Column PGText
type FClearPassword = "clearpass" :-> ClearPassword Text
type CHashPassword = "hashpass" :-> Column PGText
|]
type DbUser = '[CEmail, CAge]
type DbPassword = '[CEmail, CHashPassword]
printSql :: Default Unpackspec a a => Query a -> IO ()
printSql = putStrLn . maybe "Empty query" id . showSqlForPostgres
queryByEmail :: (RElem CEmail rs (RIndex CEmail rs), Default ColumnMaker (Record rs) (Record rs)) => Table a (Record rs) -> Text -> QueryArr () (Record rs)
queryByEmail table email = proc () -> do
u <- queryTable table -< ()
let uEmail = view cEmail u
restrict -< uEmail .=== constant email
returnA -< u
userTable :: Table (Record DbUser) (Record DbUser)
userTable = Table "user" defaultRecTable
passwordTable :: Table (Record DbPassword) (Record DbPassword)
passwordTable = Table "password" defaultRecTable
queryUserTest = printSql $ queryByEmail userTable "hi"
queryPasswordTest = printSql $ queryByEmail passwordTable "hi"
constant email
调用使用(已经存在的)Default Constant Text (Column PGText)
约束; email
的类型为 CEmail
而不是您需要一个非平凡的非未定义使用实例。
关于postgresql - 如何在 Haskell 中概括 Opaleye 查询(使用 Vinyl)?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44335833/
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我的问题是在下面代码块中的巨大横幅之间。 请原谅代码转储,所有这些都粘贴在这里供任何想要复制的人使用,并且此代码确实可以按预期工作,尽管它有点奇怪。注意最后两行,它们打印正确的 SQL。 目标: 我有
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