mysql-haskell-nem-0.1.0.0: src/Database/MySQL/Nem/QueryResults.hs
{-# LANGUAGE BangPatterns, OverloadedStrings #-}
-- |
-- Module: Database.MySQL.Simpe.QueryResults
-- Copyright: (c) 2011 MailRank, Inc.
-- License: BSD3
-- Maintainer: José Lorenzo Rodríguez
-- Stability: experimental
-- Portability: portable
--
-- The 'QueryResults' typeclass, for converting a row of results
-- returned by a SQL query into a more useful Haskell representation.
--
-- Predefined instances are provided for tuples containing up to 24
-- elements.
module Database.MySQL.Nem.QueryResults
( QueryResults(..)
, convertError
) where
import Control.Exception (throw)
import Database.MySQL.Base (ColumnDef(..), MySQLValue)
import Database.MySQL.Nem.Result (ResultError(..), Result(..))
import qualified Data.ByteString as B
import qualified Data.ByteString.Char8 as B8
-- | A collection type that can be converted from a MySQL row result.
--
-- Instances should use the 'convert' method of the 'Result' class
-- to perform conversion of each element of the collection.
--
-- This example instance demonstrates how to convert a two-column row
-- into a Haskell pair. Each field in the metadata is paired up with
-- each value from the row, and the two are passed to 'convert'.
--
-- @
-- instance ('Result' a, 'Result' b) => 'QueryResults' (a,b) where
-- 'convertResults' [fa,fb] [va,vb] = (a,b)
-- where !a = 'convert' fa va
-- !b = 'convert' fb vb
-- 'convertResults' fs vs = 'convertError' fs vs 2
-- @
--
-- Notice that this instance evaluates each element to WHNF before
-- constructing the pair. By doing this, we guarantee two important
-- properties:
--
-- * Keep resource usage under control by preventing the construction
-- of potentially long-lived thunks.
--
-- * Ensure that any 'ResultError' that might arise is thrown
-- immediately, rather than some place later in application code
-- that cannot handle it.
--
-- You can also declare Haskell types of your own to be instances of
-- 'QueryResults'.
--
-- @
--data User = User { firstName :: String, lastName :: String }
--
--instance 'QueryResults' User where
-- 'convertResults' [fa,fb] [va,vb] = User <$> a <*> b
-- where !a = 'convert' fa va
-- !b = 'convert' fb vb
-- 'convertResults' fs vs = 'convertError' fs vs 2
-- @
class QueryResults a
-- Convert values from a row into a Haskell collection.
--
-- This function will throw a 'ResultError' if conversion of the
-- collection fails.
where
convertResults :: [ColumnDef] -> [MySQLValue] -> a
instance (Result a, Result b) =>
QueryResults (a, b) where
convertResults [fa, fb] [va, vb] = (a, b)
where
!a = convert fa va
!b = convert fb vb
convertResults fs vs = convertError fs vs 2
instance (Result a, Result b, Result c) =>
QueryResults (a, b, c) where
convertResults [fa, fb, fc] [va, vb, vc] = (a, b, c)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
convertResults fs vs = convertError fs vs 3
instance (Result a, Result b, Result c, Result d) =>
QueryResults (a, b, c, d) where
convertResults [fa, fb, fc, fd] [va, vb, vc, vd] = (a, b, c, d)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
convertResults fs vs = convertError fs vs 4
instance (Result a, Result b, Result c, Result d, Result e) =>
QueryResults (a, b, c, d, e) where
convertResults [fa, fb, fc, fd, fe] [va, vb, vc, vd, ve] = (a, b, c, d, e)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
convertResults fs vs = convertError fs vs 5
instance (Result a, Result b, Result c, Result d, Result e, Result f) =>
QueryResults (a, b, c, d, e, f) where
convertResults [fa, fb, fc, fd, fe, ff] [va, vb, vc, vd, ve, vf] =
(a, b, c, d, e, f)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
convertResults fs vs = convertError fs vs 6
instance (Result a, Result b, Result c, Result d, Result e, Result f, Result g) =>
QueryResults (a, b, c, d, e, f, g) where
convertResults [fa, fb, fc, fd, fe, ff, fg] [va, vb, vc, vd, ve, vf, vg] =
(a, b, c, d, e, f, g)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
convertResults fs vs = convertError fs vs 7
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h) =>
QueryResults (a, b, c, d, e, f, g, h) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh] [va, vb, vc, vd, ve, vf, vg, vh] =
(a, b, c, d, e, f, g, h)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
convertResults fs vs = convertError fs vs 8
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i) =>
QueryResults (a, b, c, d, e, f, g, h, i) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi] [va, vb, vc, vd, ve, vf, vg, vh, vi] =
(a, b, c, d, e, f, g, h, i)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
convertResults fs vs = convertError fs vs 9
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j) =>
QueryResults (a, b, c, d, e, f, g, h, i, j) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj] =
(a, b, c, d, e, f, g, h, i, j)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
convertResults fs vs = convertError fs vs 10
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk] =
(a, b, c, d, e, f, g, h, i, j, k)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
convertResults fs vs = convertError fs vs 11
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl] =
(a, b, c, d, e, f, g, h, i, j, k, l)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
convertResults fs vs = convertError fs vs 12
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm] =
(a, b, c, d, e, f, g, h, i, j, k, l, m)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
convertResults fs vs = convertError fs vs 13
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
convertResults fs vs = convertError fs vs 14
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n
,Result o) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn, fo] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn, vo] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
!o = convert fo vo
convertResults fs vs = convertError fs vs 15
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n
,Result o
,Result p) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn, fo, fp] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn, vo, vp] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
!o = convert fo vo
!p = convert fp vp
convertResults fs vs = convertError fs vs 16
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n
,Result o
,Result p
,Result q) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn, fo, fp, fq] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn, vo, vp, vq] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
!o = convert fo vo
!p = convert fp vp
!q = convert fq vq
convertResults fs vs = convertError fs vs 17
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n
,Result o
,Result p
,Result q
,Result r) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn, fo, fp, fq, fr] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn, vo, vp, vq, vr] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
!o = convert fo vo
!p = convert fp vp
!q = convert fq vq
!r = convert fr vr
convertResults fs vs = convertError fs vs 18
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n
,Result o
,Result p
,Result q
,Result r
,Result s) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn, fo, fp, fq, fr, fs] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn, vo, vp, vq, vr, vs] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
!o = convert fo vo
!p = convert fp vp
!q = convert fq vq
!r = convert fr vr
!s = convert fs vs
convertResults fs_ vs_ = convertError fs_ vs_ 19
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n
,Result o
,Result p
,Result q
,Result r
,Result s
,Result t
,Result u
,Result v) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn, fo, fp, fq, fr, fs, ft, fu, fv] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn, vo, vp, vq, vr, vs, vt, vu, vv] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
!o = convert fo vo
!p = convert fp vp
!q = convert fq vq
!r = convert fr vr
!s = convert fs vs
!t = convert ft vt
!u = convert fu vu
!v = convert fv vv
convertResults fs_ vs_ = convertError fs_ vs_ 22
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n
,Result o
,Result p
,Result q
,Result r
,Result s
,Result t
,Result u
,Result v
,Result w) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn, fo, fp, fq, fr, fs, ft, fu, fv, fw] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn, vo, vp, vq, vr, vs, vt, vu, vv, vw] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
!o = convert fo vo
!p = convert fp vp
!q = convert fq vq
!r = convert fr vr
!s = convert fs vs
!t = convert ft vt
!u = convert fu vu
!v = convert fv vv
!w = convert fw vw
convertResults fs_ vs_ = convertError fs_ vs_ 23
instance (Result a
,Result b
,Result c
,Result d
,Result e
,Result f
,Result g
,Result h
,Result i
,Result j
,Result k
,Result l
,Result m
,Result n
,Result o
,Result p
,Result q
,Result r
,Result s
,Result t
,Result u
,Result v
,Result w
,Result x) =>
QueryResults (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x) where
convertResults [fa, fb, fc, fd, fe, ff, fg, fh, fi, fj, fk, fl, fm, fn, fo, fp, fq, fr, fs, ft, fu, fv, fw, fx] [va, vb, vc, vd, ve, vf, vg, vh, vi, vj, vk, vl, vm, vn, vo, vp, vq, vr, vs, vt, vu, vv, vw, vx] =
(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x)
where
!a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
!m = convert fm vm
!n = convert fn vn
!o = convert fo vo
!p = convert fp vp
!q = convert fq vq
!r = convert fr vr
!s = convert fs vs
!t = convert ft vt
!u = convert fu vu
!v = convert fv vv
!w = convert fw vw
!x = convert fx vx
convertResults fs_ vs_ = convertError fs_ vs_ 24
-- | Throw a 'ConversionFailed' exception, indicating a mismatch
-- between the number of columns in the 'Field' and row, and the
-- number in the collection to be converted to.
convertError
:: [ColumnDef]
-- ^ Descriptors of fields to be converted.
-> [MySQLValue]
-- ^ Contents of the row to be converted.
-> Int
-- ^ Number of columns expected for conversion. For
-- instance, if converting to a 3-tuple, the number to
-- provide here would be 3.
-> a
convertError fs vs n =
throw $
ConversionFailed
(show (map (B8.unpack . columnName) fs))
("Tried to create a Tuple of " ++ show n ++ " elements")
("Mismatch between number of columns to convert and number in target type. Source: " ++
(show . length) vs ++ " columns, Target: " ++ show n ++ " elements")