Import backend code inside the repository.

backend/resources/sql/workers.sql

@@ -0,0 +1,53 @@
+-- :name acquire-task :? :1
+with recursive locked_tasks as (
+  select (j).*, pg_try_advisory_lock((j).id) as locked
+    from (
+      select j
+        from tasks as j
+       where queue = :queue
+         and status = 'pending'
+         and created_at <= now()
+       order by created_at, id
+       limit 1
+    ) as t1
+  union all (
+    select (j).*, pg_try_advisory_lock((j).id) as locked
+      from (
+        select (
+          select j
+            from tasks as j
+           where queue = :queue
+             and status = 'pending'
+             and created_at <= now()
+             and (created_at, id) > (locked_tasks.created_at, locked_tasks.id)
+          order by created_at, id
+          limit 1
+        ) as j
+        from locked_tasks
+        where locked_tasks.id is not null
+        limit 1
+      ) as t1
+  )
+)
+select id, status, error, created_at
+  from locked_tasks
+ where locked
+ limit 1;
+
+-- :name create-task :? :1
+insert into tasks (queue)
+values (:queue)
+returning *;
+
+-- :name mark-task-done
+update tasks
+   set status = 'completed',
+       completed_at = clock_timestamp()
+ where id = :id;
+
+-- :name mark-task-failed
+update tasks
+   set status = 'failed',
+       error = :error,
+       completed_at = clock_timestamp()
+ where id = :id;