Keep views tracked when a pkg or repo is removed (#2572)

Signed-off-by: Sergio Castaño Arteaga <tegioz@icloud.com>

database/migrations/functions/stats/get_stats.sql

@@ -62,6 +62,7 @@ returns setof json as $$
                         sum(total) as total
                     from package_views
                     where day = current_date
+                    and package_id is not null
                     group by package_id
                     order by total desc
                     limit 10
@@ -79,6 +80,7 @@ returns setof json as $$
                     from package_views
                     where date_trunc('year', day) = date_trunc('year', current_date)
                     and date_trunc('month', day) = date_trunc('month', current_date)
+                    and package_id is not null
                     group by package_id
                     order by total desc
                     limit 10

database/migrations/schema/040_keep_views_on_delete.sql

@@ -0,0 +1,18 @@
+alter table package_views alter column package_id drop not null;
+alter table package_views alter column version drop not null;
+alter table package_views drop constraint package_views_package_id_version_fkey;
+alter table package_views add constraint package_views_package_id_version_fkey
+    foreign key (package_id, version)
+    references snapshot (package_id, version)
+    on delete set null;
+
+---- create above / drop below ----
+
+delete from package_views where package_id is null;
+alter table package_views alter column package_id set not null;
+alter table package_views alter column version set not null;
+alter table package_views drop constraint package_views_package_id_version_fkey;
+alter table package_views add constraint package_views_package_id_version_fkey
+    foreign key (package_id, version)
+    references snapshot (package_id, version)
+    on delete cascade;