Fix #219 (#240)

We need to `rebind` immediately after calling `UNNEST`, before we call `fromColumns`.

src/Rel8/Query/List.hs

@@ -25,7 +25,7 @@ import Rel8.Expr.Opaleye ( mapPrimExpr )
 import Rel8.Query ( Query )
 import Rel8.Query.Aggregate ( aggregate )
 import Rel8.Query.Maybe ( optional )
-import Rel8.Query.Rebind ( rebind )
+import Rel8.Query.Rebind ( hrebind, rebind )
 import Rel8.Schema.HTable.Vectorize ( hunvectorize )
 import Rel8.Schema.Null ( Sql, Unnullify )
 import Rel8.Schema.Spec ( Spec( Spec, info ) )
@@ -86,7 +86,7 @@ someExpr = aggregate . fmap nonEmptyAggExpr
 -- @catListTable@ is an inverse to 'many'.
 catListTable :: Table Expr a => ListTable Expr a -> Query a
 catListTable (ListTable as) =
-  rebind "unnest" $ fromColumns $ runIdentity $
+  fmap fromColumns $ hrebind "unnest" $ runIdentity $
     hunvectorize (\Spec {info} -> pure . sunnest info) as
 
 
@@ -96,7 +96,7 @@ catListTable (ListTable as) =
 -- @catNonEmptyTable@ is an inverse to 'some'.
 catNonEmptyTable :: Table Expr a => NonEmptyTable Expr a -> Query a
 catNonEmptyTable (NonEmptyTable as) =
-  rebind "unnest" $ fromColumns $ runIdentity $
+  fmap fromColumns $ hrebind "unnest" $ runIdentity $
     hunvectorize (\Spec {info} -> pure . sunnest info) as
 
 

src/Rel8/Query/Rebind.hs

@@ -2,6 +2,7 @@
 
 module Rel8.Query.Rebind
   ( rebind
+  , hrebind
   )
 where
 
@@ -15,7 +16,9 @@ import qualified Opaleye.Internal.Rebind as Opaleye
 -- rel8
 import Rel8.Expr ( Expr )
 import Rel8.Query ( Query )
+import Rel8.Schema.HTable (HTable)
 import Rel8.Table ( Table )
+import Rel8.Table.Cols (Cols (Cols))
 import Rel8.Table.Opaleye ( unpackspec )
 import Rel8.Query.Opaleye (fromOpaleye)
 
@@ -25,3 +28,7 @@ import Rel8.Query.Opaleye (fromOpaleye)
 -- variables. It's essentially a @let@ binding for Postgres expressions.
 rebind :: Table Expr a => String -> a -> Query a
 rebind prefix a = fromOpaleye (Opaleye.rebindExplicitPrefix prefix unpackspec <<< pure a)
+
+
+hrebind :: HTable t => String -> t Expr -> Query (t Expr)
+hrebind prefix = fmap (\(Cols a) -> a) . rebind prefix . Cols