Add arrayAggDistinct wrapper for PostgreSQL function

esqueleto.cabal

@@ -1,5 +1,5 @@
 name:                esqueleto
-version:             2.5.2
+version:             2.5.3
 synopsis:            Type-safe EDSL for SQL queries on persistent backends.
 homepage:            https://github.com/bitemyapp/esqueleto
 license:             BSD3

src/Database/Esqueleto/PostgreSQL.hs

@@ -4,7 +4,8 @@
 --
 -- /Since: 2.2.8/
 module Database.Esqueleto.PostgreSQL
-  ( arrayAgg
+  ( arrayAggDistinct
+  , arrayAgg
   , stringAgg
   , chr
   , now_
@@ -14,6 +15,15 @@ import Database.Esqueleto.Internal.Language
 import Database.Esqueleto.Internal.Sql
 import Data.Time.Clock (UTCTime)
 
+-- | (@array_agg@) Concatenate distinct input values, including @NULL@s, into
+-- an array.
+--
+-- /Since: 2.5.3/
+arrayAggDistinct :: SqlExpr (Value a) -> SqlExpr (Value [a])
+arrayAggDistinct = arrayAgg . distinct
+  where
+    distinct = unsafeSqlBinOp " " (unsafeSqlValue "DISTINCT")
+
 -- | (@array_agg@) Concatenate input values, including @NULL@s,
 -- into an array.
 --

test/Test.hs

@@ -1446,6 +1446,16 @@ main = do
 #else
         (return () :: IO ())
 
+      it "arrayAggDistinct looks sane" $
+        run $ do
+          let people1 = fmap (\p -> p { personName = "John" }) [p1, p2, p3]
+              people2 = fmap (\p -> p { personName = "Rachel" }) [p4, p5]
+          mapM_ insert $ people1 <> people2
+          [Value ret] <-
+            select . from $ \p -> return (EP.arrayAggDistinct (p ^. PersonName))
+          liftIO $ L.sort ret `shouldBe` ["John", "Rachel"]
+
+
       it "arrayAgg looks sane" $
         run $ do
           let people = [p1, p2, p3, p4, p5]