If you try to delete a system which has updatable packages it crashes with a PG::ForeignKeyViolation.
Started DELETE "/systems/5" for 10.0.3.1 at 2016-10-28 15:20:05 +0200
Processing by SystemsController#destroy as HTML
Parameters: {"authenticity_token"=>"Uk1Ypi8sOCKFeI+JQc5l4OM6bMM/RWj3UcnMN7zG7+ZzRsYHb9NcX2q6sZh72va8DbDXqO5UL1LqUyCKRBApeA==", "id"=>"5"}
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1 [["id", 11]]
System Load (0.2ms) SELECT "systems".* FROM "systems" WHERE "systems"."id" = $1 LIMIT 1 [["id", 5]]
SystemGroup Load (0.3ms) SELECT "system_groups".* FROM "system_groups" WHERE "system_groups"."id" = $1 LIMIT 1 [["id", 9]]
Role Load (0.2ms) SELECT "roles".* FROM "roles" WHERE "roles"."id" = $1 LIMIT 1 [["id", 5]]
(0.1ms) BEGIN
SQL (1.7ms) DELETE FROM "systems" WHERE "systems"."id" = $1 [["id", 5]]
PG::ForeignKeyViolation: ERROR: update or delete on table "systems" violates foreign key constraint "fk_rails_0e3a405992" on table "concrete_package_versions"
DETAIL: Key (id)=(5) is still referenced from table "concrete_package_versions".
: DELETE FROM "systems" WHERE "systems"."id" = $1
(0.1ms) ROLLBACK
Completed 500 Internal Server Error in 13ms (ActiveRecord: 2.8ms)
ActiveRecord::InvalidForeignKey (PG::ForeignKeyViolation: ERROR: update or delete on table "systems" violates foreign key constraint "fk_rails_0e3a405992" on table "concrete_package_versions"
DETAIL: Key (id)=(5) is still referenced from table "concrete_package_versions".
: DELETE FROM "systems" WHERE "systems"."id" = $1):
app/controllers/systems_controller.rb:56:in `destroy'
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/actionpack-4.2.4/lib/action_dispatch/middleware/templates/rescues/_source.erb (6.9ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/actionpack-4.2.4/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (2.9ms)
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Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/actionpack-4.2.4/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout (27.1ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/web-console-2.3.0/lib/web_console/templates/_markup.html.erb (0.4ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/web-console-2.3.0/lib/web_console/templates/_inner_console_markup.html.erb within layouts/inlined_string (0.3ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/web-console-2.3.0/lib/web_console/templates/_prompt_box_markup.html.erb within layouts/inlined_string (0.3ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/web-console-2.3.0/lib/web_console/templates/style.css.erb within layouts/inlined_string (0.3ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/web-console-2.3.0/lib/web_console/templates/console.js.erb within layouts/javascript (20.0ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/web-console-2.3.0/lib/web_console/templates/main.js.erb within layouts/javascript (0.4ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/web-console-2.3.0/lib/web_console/templates/error_page.js.erb within layouts/javascript (0.4ms)
Rendered /var/www/upd89-web/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/web-console-2.3.0/lib/web_console/templates/index.html.erb (44.2ms)
If you try to delete a system which has updatable packages it crashes with a PG::ForeignKeyViolation.