diff --git a/sql/upgrades/147.sql b/sql/upgrades/147.sql
new file mode 100644
--- /dev/null
+++ b/sql/upgrades/147.sql
@@ -0,0 +1,25 @@
+-- SWH DB schema upgrade
+-- from_version: 146
+-- to_version: 147
+-- description: Make swh_release_add properly idempotent
+
+-- latest schema version
+insert into dbversion(version, release, description)
+      values(147, now(), 'Work In Progress');
+
+-- Create entries in release from tmp_release
+create or replace function swh_release_add()
+    returns void
+    language plpgsql
+as $$
+begin
+    perform swh_person_add_from_release();
+
+    insert into release (id, target, target_type, date, date_offset, date_neg_utc_offset, name, comment, author, synthetic)
+      select distinct t.id, t.target, t.target_type, t.date, t.date_offset, t.date_neg_utc_offset, t.name, t.comment, a.id, t.synthetic
+        from tmp_release t
+        left join person a on a.fullname = t.author_fullname
+        where not exists (select 1 from release where t.id = release.id);
+    return;
+end
+$$;
diff --git a/swh/storage/sql/30-swh-schema.sql b/swh/storage/sql/30-swh-schema.sql
--- a/swh/storage/sql/30-swh-schema.sql
+++ b/swh/storage/sql/30-swh-schema.sql
@@ -17,7 +17,7 @@
 
 -- latest schema version
 insert into dbversion(version, release, description)
-      values(146, now(), 'Work In Progress');
+      values(147, now(), 'Work In Progress');
 
 -- a SHA1 checksum
 create domain sha1 as bytea check (length(value) = 20);
diff --git a/swh/storage/sql/40-swh-func.sql b/swh/storage/sql/40-swh-func.sql
--- a/swh/storage/sql/40-swh-func.sql
+++ b/swh/storage/sql/40-swh-func.sql
@@ -680,9 +680,10 @@
     perform swh_person_add_from_release();
 
     insert into release (id, target, target_type, date, date_offset, date_neg_utc_offset, name, comment, author, synthetic)
-    select t.id, t.target, t.target_type, t.date, t.date_offset, t.date_neg_utc_offset, t.name, t.comment, a.id, t.synthetic
-    from tmp_release t
-    left join person a on a.fullname = t.author_fullname;
+      select distinct t.id, t.target, t.target_type, t.date, t.date_offset, t.date_neg_utc_offset, t.name, t.comment, a.id, t.synthetic
+        from tmp_release t
+        left join person a on a.fullname = t.author_fullname
+        where not exists (select 1 from release where t.id = release.id);
     return;
 end
 $$;
diff --git a/swh/storage/tests/test_storage.py b/swh/storage/tests/test_storage.py
--- a/swh/storage/tests/test_storage.py
+++ b/swh/storage/tests/test_storage.py
@@ -1108,6 +1108,12 @@
         swh_storage.refresh_stat_counters()
         assert swh_storage.stat_counters()['release'] == 2
 
+    def test_release_add_same_twice(self, swh_storage):
+        result = swh_storage.release_add([data.release, data.release])
+
+        assert list(result) == ['release:add']
+        assert 1 <= result['release:add'] <= 2
+
     def test_release_add_from_generator(self, swh_storage):
         def _rel_gen():
             yield data.release