update sqlc upsert article

content/posts/2024-03-07-upsert-uuids-with-sqlc.md

@@ -52,12 +52,8 @@ And create a `SaveUser` query for saving user records. When a conflict happens o
 
 ```sql
 -- name: SaveUser :one
-INSERT INTO users (
-    id, name, email
-) VALUES (
-    $1, $2, $3
-) ON CONFLICT (id) DO UPDATE 
-  SET name = $2, email = $3
+INSERT INTO users (id, name, email) VALUES (@id, @name, @email) ON CONFLICT (id) DO UPDATE 
+  SET name = @name, email = @email
 RETURNING *;
 ```
 
@@ -76,35 +72,16 @@ As you can see, the ID field is a `uuid.UUID`, not `*uuid.UUID`, so it's not pos
 
 ## The solution 
 
-So how do we perform upserts that account for the zero-value of our types? I've opted to create a function that provides default values when our type's zero-value is encountered. While the below function is explicitly written for `uuid` zero values, it can just as easily be ported to other types.
- 
-```sql
-CREATE OR REPLACE FUNCTION public.uuid_if_empty(id uuid) RETURNS uuid 
-    LANGUAGE plpgsql
-    AS $$BEGIN 
-        IF id = uuid_nil() THEN 
-            RETURN uuid_generate_v4();
-        ELSE 
-            RETURN id;
-        END IF;
-    END$$;
-```
+So how do we perform upserts that account for the zero-value of our types? I've opted to combine `nullif` and `coalesce` to achieve the upsert effect. While the solution below specifically implements upserts for `UUID` types, the `nullif` call can be adapted to any type's zero value. 
 
-> Thanks to [mariusor](https://lobste.rs/~mariusor) on lobste.rs for notifying me about `uuid_nil()`
-
-Now in our upsert statement, we use our new function instead of the raw value passed in
 
 ```sql
 -- name: SaveUser :one
-INSERT INTO users (
-    id, name, email
-) VALUES (
-    -- Note how naming the `id` param changes the numeric value of positional args.
-    -- It may be preferable to use the sqlc.arg macro here to improve readability.
-    uuid_if_empty(sqlc.arg(id))::uuid, $1, $2 
-) ON CONFLICT (id) DO UPDATE 
-  SET name = $2, email = $3
+INSERT INTO users (id, name, email) VALUES (coalesce(nullif(@id, uuid_nil()), uuid_generate_v4()), @name, @email) ON CONFLICT (id) DO UPDATE 
+  SET name = @name, email = @email
 RETURNING *;
 ```
 
+This statement coalesces to `uuid_generate_v4()` when `@id` has the UUID zero value, and uses `@id` as-is otherwise. Using `@id` when it is not the type's zero value is what allows the `ON CONFLICT` portion of the query to activate when we're updating existing records. 
+
 This turned out to be a very simple solution for my current problem. If there's a better or more idiomatic way to achieve the same result, please let me know in the comments!