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rel8/src/Rel8/Query/These.hs
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1{-# language FlexibleContexts #-}
3module Rel8.Query.These
4 ( alignBy
5 , keepHereTable, loseHereTable
6 , keepThereTable, loseThereTable
7 , keepThisTable, loseThisTable
8 , keepThatTable, loseThatTable
9 , keepThoseTable, loseThoseTable
10 , bitraverseTheseTable
11 )
12where
14-- base
15import Prelude
17-- opaleye
18import qualified Opaleye.Internal.Join as Opaleye
19import qualified Opaleye.Internal.PrimQuery as Opaleye
21-- rel8
22import Rel8.Expr ( Expr )
23import Rel8.Expr.Bool ( boolExpr, not_ )
24import Rel8.Expr.Eq ( (==.) )
25import Rel8.Expr.Opaleye ( toColumn, toPrimExpr )
26import Rel8.Expr.Serialize ( litExpr )
27import Rel8.Query ( Query )
28import Rel8.Query.Filter ( where_ )
29import Rel8.Query.Maybe ( optional )
30import Rel8.Query.Opaleye ( zipOpaleyeWith )
31import Rel8.Table ( Table )
32import Rel8.Table.Either ( EitherTable( EitherTable ) )
33import Rel8.Table.Maybe ( MaybeTable( MaybeTable ), isJustTable )
34import Rel8.Table.Opaleye ( unpackspec )
35import Rel8.Table.Tag ( Tag(..) )
36import Rel8.Table.These
37 ( TheseTable( TheseTable )
38 , hasHereTable, hasThereTable
39 , isThisTable, isThatTable, isThoseTable
40 )
41import Rel8.Type.Tag ( EitherTag( IsLeft, IsRight ) )
44-- | Corresponds to a @FULL OUTER JOIN@ between two queries.
45alignBy :: (Table Expr a, Table Expr b)
46 => (a -> b -> Expr Bool)
47 -> Query a -> Query b -> Query (TheseTable a b)
48alignBy condition as bs =
49 uncurry TheseTable <$> zipOpaleyeWith fullOuterJoin as bs
50 where
51 fullOuterJoin a b =
52 Opaleye.joinExplicit unpackspec unpackspec pure pure full a b on
53 where
54 full = Opaleye.FullJoin
55 on = toColumn . toPrimExpr . uncurry condition
58-- | Filter 'TheseTable's, keeping only 'thisTable's and 'thoseTable's.
59keepHereTable :: TheseTable a b -> Query (a, MaybeTable b)
60keepHereTable = loseThatTable
63-- | Filter 'TheseTable's, keeping on
64loseHereTable :: TheseTable a b -> Query b
65loseHereTable = keepThatTable
68keepThereTable :: TheseTable a b -> Query (MaybeTable a, b)
69keepThereTable = loseThisTable
72loseThereTable :: TheseTable a b -> Query a
73loseThereTable = keepThisTable
76keepThisTable :: TheseTable a b -> Query a
77keepThisTable t@(TheseTable (MaybeTable _ a) _) = do
78 where_ $ isThisTable t
79 pure a
82loseThisTable :: TheseTable a b -> Query (MaybeTable a, b)
83loseThisTable t@(TheseTable ma (MaybeTable _ b)) = do
84 where_ $ not_ $ isThisTable t
85 pure (ma, b)
88keepThatTable :: TheseTable a b -> Query b
89keepThatTable t@(TheseTable _ (MaybeTable _ b)) = do
90 where_ $ isThatTable t
91 pure b
94loseThatTable :: TheseTable a b -> Query (a, MaybeTable b)
95loseThatTable t@(TheseTable (MaybeTable _ a) mb) = do
96 where_ $ not_ $ isThatTable t
97 pure (a, mb)
100keepThoseTable :: TheseTable a b -> Query (a, b)
101keepThoseTable t@(TheseTable (MaybeTable _ a) (MaybeTable _ b)) = do
102 where_ $ isThoseTable t
103 pure (a, b)
106loseThoseTable :: TheseTable a b -> Query (EitherTable a b)
107loseThoseTable t@(TheseTable (MaybeTable _ a) (MaybeTable _ b)) = do
108 where_ $ not_ $ isThoseTable t
109 pure $ EitherTable result a b
110 where
111 tag = boolExpr (litExpr IsLeft) (litExpr IsRight) (isThatTable t)
112 result = (mempty `asTypeOf` result) {expr = tag}
115bitraverseTheseTable :: ()
116 => (a -> Query c)
117 -> (b -> Query d)
118 -> TheseTable a b
119 -> Query (TheseTable c d)
120bitraverseTheseTable f g t = do
121 mc <- optional (f . fst =<< keepHereTable t)
122 md <- optional (g . snd =<< keepThereTable t)
123 where_ $ isJustTable mc ==. hasHereTable t
124 where_ $ isJustTable md ==. hasThereTable t
125 pure $ TheseTable mc md