add ON DELETE to relations

backend/priv/repo/migrations/20190809165902_add_on_deletes.exs

@@ -0,0 +1,40 @@
+defmodule Backend.Repo.Migrations.AddOnDeletes do
+  use Ecto.Migration
+
+  def change do
+    # Add ON DELETE CASCADE to foreign key relations.
+
+    # crawls -> instances
+    execute("ALTER TABLE crawls DROP CONSTRAINT crawls_instance_domain_fkey")
+
+    execute(
+      "ALTER TABLE crawls ADD CONSTRAINT crawls_instance_domain_fkey FOREIGN KEY (instance_domain) REFERENCES instances(domain) ON DELETE CASCADE"
+    )
+
+    # instance_peers -> instances
+    execute("ALTER TABLE instance_peers DROP CONSTRAINT instance_peers_source_domain_fkey")
+
+    execute(
+      "ALTER TABLE instance_peers ADD CONSTRAINT instance_peers_source_domain_fkey FOREIGN KEY (source_domain) REFERENCES instances(domain) ON DELETE CASCADE"
+    )
+
+    execute("ALTER TABLE instance_peers DROP CONSTRAINT instance_peers_target_domain_fkey")
+
+    execute(
+      "ALTER TABLE instance_peers ADD CONSTRAINT instance_peers_target_domain_fkey FOREIGN KEY (target_domain) REFERENCES instances(domain) ON DELETE CASCADE"
+    )
+
+    # edges -> instances
+    execute("ALTER TABLE edges DROP CONSTRAINT edges_source_domain_fkey")
+
+    execute(
+      "ALTER TABLE edges ADD CONSTRAINT edges_source_domain_fkey FOREIGN KEY (source_domain) REFERENCES instances(domain) ON DELETE CASCADE"
+    )
+
+    execute("ALTER TABLE edges DROP CONSTRAINT edges_target_domain_fkey")
+
+    execute(
+      "ALTER TABLE edges ADD CONSTRAINT edges_target_domain_fkey FOREIGN KEY (target_domain) REFERENCES instances(domain) ON DELETE CASCADE"
+    )
+  end
+end