Merge pull request #69 from circuithub/exists

Bump Opaleye dependency to 0.7.2.0 to take advantage of new EXISTS support

nix/sources.json

@@ -5,10 +5,10 @@
         "homepage": "https://input-output-hk.github.io/haskell.nix",
         "owner": "input-output-hk",
         "repo": "haskell.nix",
-        "rev": "5b5a18e442df6e27ad8549d69b8868b62adb08c3",
-        "sha256": "055mk7kmjppng66ppnb8kr96v4wwc8pcxfsls5gl77129hsz9aph",
+        "rev": "e7bb8ab2921a11a1d014c70a87898f73e086594d",
+        "sha256": "17c0xqzwnchcy71p8372cydcxc7qf0i8x12d0lf6p1g8yd4al6fa",
         "type": "tarball",
-        "url": "https://github.com/input-output-hk/haskell.nix/archive/5b5a18e442df6e27ad8549d69b8868b62adb08c3.tar.gz",
+        "url": "https://github.com/input-output-hk/haskell.nix/archive/e7bb8ab2921a11a1d014c70a87898f73e086594d.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "niv": {

rel8.cabal

@@ -25,7 +25,7 @@ library
     , case-insensitive
     , contravariant
     , hasql ^>= 1.4.5.1
-    , opaleye ^>= 0.7.1.0
+    , opaleye ^>= 0.7.2.0
     , profunctors
     , scientific
     , semialign

src/Rel8/Query/Exists.hs

@@ -11,23 +11,21 @@ where
 import Prelude hiding ( filter )
 
 -- opaleye
-import qualified Opaleye.Operators as Opaleye
+import qualified Opaleye.Exists as Opaleye
+import qualified Opaleye.Operators as Opaleye hiding ( exists )
 
 -- rel8
 import Rel8.Expr ( Expr )
+import Rel8.Expr.Opaleye ( fromColumn, fromPrimExpr )
 import Rel8.Query ( Query )
 import Rel8.Query.Filter ( filter )
-import Rel8.Query.Maybe ( optional )
 import Rel8.Query.Opaleye ( mapOpaleye )
 import Rel8.Table.Eq ( EqTable, (==:) )
-import Rel8.Table.Maybe ( isJustTable )
 
 
 -- | Checks if a query returns at least one row.
 exists :: Query a -> Query (Expr Bool)
-exists = fmap isJustTable . optional . present
--- FIXME: change this when b7aacc07c6392654cae439fc3b997620c3aa7a87 makes it
--- into a release of Opaleye
+exists = fmap (fromPrimExpr . fromColumn) . mapOpaleye Opaleye.exists
 
 
 inQuery :: EqTable a => a -> Query a -> Query (Expr Bool)