diff --git a/sql/updates/32.sql b/sql/updates/32.sql
new file mode 100644
--- /dev/null
+++ b/sql/updates/32.sql
@@ -0,0 +1,57 @@
+-- SWH DB schema upgrade
+-- from_version: 31
+-- to_version: 32
+-- description: Use a temporary table to update scheduler_metrics
+
+insert into dbversion (version, release, description)
+       values (32, now(), 'Work In Progress');
+
+create or replace function update_metrics(lister_id uuid default NULL, ts timestamptz default now())
+  returns setof scheduler_metrics
+  language plpgsql
+as $$
+  begin
+    -- If we do the following select as a subquery in the insert statement below,
+    -- PostgreSQL prevents the use of parallel queries. So we do the select into a
+    -- temporary table, which doesn't suffer this limitation.
+
+    create temporary table tmp_update_metrics
+    on commit drop
+    as select
+      lo.lister_id, lo.visit_type, coalesce(ts, now()) as last_update,
+      count(*) as origins_known,
+      count(*) filter (where enabled) as origins_enabled,
+      count(*) filter (where
+        enabled and last_snapshot is NULL
+      ) as origins_never_visited,
+      count(*) filter (where
+        enabled and lo.last_update > last_successful
+      ) as origins_with_pending_changes
+    from listed_origins lo
+    left join origin_visit_stats ovs using (url, visit_type)
+    where
+      -- update only for the requested lister
+      update_metrics.lister_id = lo.lister_id
+      -- or for all listers if the function argument is null
+      or update_metrics.lister_id is null
+    group by (lo.lister_id, lo.visit_type);
+
+    return query
+      insert into scheduler_metrics (
+        lister_id, visit_type, last_update,
+        origins_known, origins_enabled,
+        origins_never_visited, origins_with_pending_changes
+      )
+      select * from tmp_update_metrics
+      on conflict on constraint scheduler_metrics_pkey do update
+        set
+          last_update = EXCLUDED.last_update,
+          origins_known = EXCLUDED.origins_known,
+          origins_enabled = EXCLUDED.origins_enabled,
+          origins_never_visited = EXCLUDED.origins_never_visited,
+          origins_with_pending_changes = EXCLUDED.origins_with_pending_changes
+      returning *;
+  end;
+$$;
+
+comment on function update_metrics(uuid, timestamptz) is 'Update metrics for the given lister_id';
diff --git a/swh/scheduler/sql/30-schema.sql b/swh/scheduler/sql/30-schema.sql
--- a/swh/scheduler/sql/30-schema.sql
+++ b/swh/scheduler/sql/30-schema.sql
@@ -11,7 +11,7 @@
 comment on column dbversion.description is 'Version description';
 
 insert into dbversion (version, release, description)
-       values (31, now(), 'Work In Progress');
+       values (32, now(), 'Work In Progress');
 
 create table task_type (
   type text primary key,
diff --git a/swh/scheduler/sql/40-func.sql b/swh/scheduler/sql/40-func.sql
--- a/swh/scheduler/sql/40-func.sql
+++ b/swh/scheduler/sql/40-func.sql
@@ -363,14 +363,16 @@
 
 create or replace function update_metrics(lister_id uuid default NULL, ts timestamptz default now())
   returns setof scheduler_metrics
-  language sql
+  language plpgsql
 as $$
-  insert into scheduler_metrics (
-    lister_id, visit_type, last_update,
-    origins_known, origins_enabled,
-    origins_never_visited, origins_with_pending_changes
-  )
-    select
+  begin
+    -- If we do the following select as a subquery in the insert statement below,
+    -- PostgreSQL prevents the use of parallel queries. So we do the select into a
+    -- temporary table, which doesn't suffer this limitation.
+
+    create temporary table tmp_update_metrics
+    on commit drop
+    as select
       lo.lister_id, lo.visit_type, coalesce(ts, now()) as last_update,
       count(*) as origins_known,
       count(*) filter (where enabled) as origins_enabled,
@@ -387,15 +389,24 @@
       update_metrics.lister_id = lo.lister_id
       -- or for all listers if the function argument is null
       or update_metrics.lister_id is null
-    group by (lister_id, visit_type)
-  on conflict (lister_id, visit_type) do update
-    set
-      last_update = EXCLUDED.last_update,
-      origins_known = EXCLUDED.origins_known,
-      origins_enabled = EXCLUDED.origins_enabled,
-      origins_never_visited = EXCLUDED.origins_never_visited,
-      origins_with_pending_changes = EXCLUDED.origins_with_pending_changes
-  returning *
+    group by (lo.lister_id, lo.visit_type);
+
+    return query
+      insert into scheduler_metrics (
+        lister_id, visit_type, last_update,
+        origins_known, origins_enabled,
+        origins_never_visited, origins_with_pending_changes
+      )
+      select * from tmp_update_metrics
+      on conflict on constraint scheduler_metrics_pkey do update
+        set
+          last_update = EXCLUDED.last_update,
+          origins_known = EXCLUDED.origins_known,
+          origins_enabled = EXCLUDED.origins_enabled,
+          origins_never_visited = EXCLUDED.origins_never_visited,
+          origins_with_pending_changes = EXCLUDED.origins_with_pending_changes
+      returning *;
+  end;
 $$;
 
 comment on function update_metrics(uuid, timestamptz) is 'Update metrics for the given lister_id';