Add insertUnique_ to PersistUniqueWrite (#1469)

* Add insertUnique_ to PersistUniqueWrite

- Works the same as insertUnique, but doesn't return a key
- For SQL databases this can be twice as fast since there is no SELECT
  to get the key after the original INSERT

commit 093b2347762e15a12fc4422c718d6adeb3e7fb89
Author: Luke Seale <19484084+lbseale@users.noreply.github.com>
Date:   Tue Jan 24 17:33:41 2023 -0800

    Add a test for insertUnique_

commit 75ffc4f3eb5048d1983fab6d8b0df22e1d6f4517
Author: Luke Seale <19484084+lbseale@users.noreply.github.com>
Date:   Tue Jan 24 17:33:19 2023 -0800

    Add help for insertUnique_

    - Also fix incorrect type annotation

commit bc81b359f454d0984062ab4f32980df75a6a85d8
Author: Luke Seale <19484084+lbseale@users.noreply.github.com>
Date:   Tue Jan 24 17:31:50 2023 -0800

    Add insertUnique_ to PersistUniqueWrite typeclass

    - Works the same way is insertUnique, but calls insert_ instead of
      insert
    - Return type is Maybe (), since it insert_ doesn't return a key

* Add since tag for insertUnqiue_

* Add change to ChangeLog

persistent-test/src/ReadWriteTest.hs

@@ -53,3 +53,14 @@ specsWith originalRunDb = describe "ReadWriteTest" $ do
                 mkey1 @== Nothing
                 mperson <- selectFirst [PersonName ==. name_] []
                 fmap entityVal mperson @== Just person
+
+                let nameLuke = "Luke Seale New"
+                    personLuke = Person nameLuke 31 Nothing
+                mkey2 <- insertUnique_ personLuke
+                mkey3 <- insertUnique_ personLuke
+                mkey3 @== Nothing
+                mpersonLuke <- selectFirst [PersonName ==. nameLuke] []
+                fmap entityVal mpersonLuke @== Just personLuke
+
+
+

persistent/ChangeLog.md

@@ -8,6 +8,12 @@
 * [#1476](https://github.com/yesodweb/persistent/pull/1476)
     * Fix `mkRecordName` to suffix `_` if the field name matches any of Haskell keywords.
 
+## 2.14.5.0
+
+* [#1469] https://github.com/yesodweb/persistent/pull/1469
+    * Change default implementation for `insertUnique_` to not perform
+      unecessary queries (mirrors 1449)
+
 ## 2.14.4.4
 
 * [#1460] https://github.com/yesodweb/persistent/pull/1460

persistent/Database/Persist/Class/PersistUnique.hs

@@ -140,6 +140,37 @@ class (PersistUniqueRead backend, PersistStoreWrite backend) =>
             Nothing -> Just `liftM` insert datum
             Just _ -> return Nothing
 
+    -- | Same as 'insertUnique' but doesn't return a @Key@.
+    --
+    -- === __Example usage__
+    --
+    -- With <#schema-persist-unique-1 schema-1> and <#dataset-persist-unique-1 dataset-1>, we try to insert the following two records:
+    --
+    -- > linusId <- insertUnique_ $ User "Linus" 48
+    -- > spjId   <- insertUnique_ $ User "SPJ" 90
+    --
+    -- > +-----+------+-----+
+    -- > |id   |name  |age  |
+    -- > +-----+------+-----+
+    -- > |1    |SPJ   |40   |
+    -- > +-----+------+-----+
+    -- > |2    |Simon |41   |
+    -- > +-----+------+-----+
+    -- > |3    |Linus |48   |
+    -- > +-----+------+-----+
+    --
+    -- Linus's record was inserted to <#dataset-persist-unique-1 dataset-1>, while SPJ wasn't because SPJ already exists in <#dataset-persist-unique-1 dataset-1>.
+    --
+    -- @since 2.14.5.0
+    insertUnique_
+        :: forall record m. (MonadIO m, PersistRecordBackend record backend, SafeToInsert record)
+        => record -> ReaderT backend m (Maybe ())
+    insertUnique_ datum = do
+        conflict <- checkUnique datum
+        case conflict of
+            Nothing -> Just `liftM` insert_ datum
+            Just _ -> return Nothing
+
     -- | Update based on a uniqueness constraint or insert:
     --
     -- * insert the new record if it does not exist;