Cells: Remove `broadcast_messages.namespace_id` foreign key

As part of column removal lets first remove foreign key.

app/models/broadcast_message.rb

@@ -3,6 +3,7 @@
 class BroadcastMessage < MainClusterwide::ApplicationRecord
   include CacheMarkdownField
   include Sortable
+  include IgnorableColumns
 
   ALLOWED_TARGET_ACCESS_LEVELS = [
     Gitlab::Access::GUEST,
@@ -12,6 +13,8 @@ class BroadcastMessage < MainClusterwide::ApplicationRecord
     Gitlab::Access::OWNER
   ].freeze
 
+  ignore_column :namespace_id, remove_with: '16.0', remove_after: '2022-06-22'
+
   cache_markdown_field :message, pipeline: :broadcast_message, whitelisted: true
 
   validates :message,   presence: true

db/post_migrate/20230321095759_remove_namespaces_broadcast_messages_namespace_id_fk.rb

+# frozen_string_literal: true
+
+class RemoveNamespacesBroadcastMessagesNamespaceIdFk < Gitlab::Database::Migration[2.1]
+  disable_ddl_transaction!
+
+  def up
+    return unless foreign_key_exists?(:broadcast_messages, :namespaces, name: "fk_7bf2ec43da")
+
+    with_lock_retries do
+      remove_foreign_key_if_exists(:broadcast_messages, :namespaces,
+        name: "fk_7bf2ec43da", reverse_lock_order: true)
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key(:broadcast_messages, :namespaces,
+      name: "fk_7bf2ec43da", column: :namespace_id,
+      target_column: :id, on_delete: :cascade)
+  end
+end

db/schema_migrations/20230321095759

+f2b7e2856672f294a7686a61d3b953b8341b21b31a60a2f62419e878c3244d64
\ No newline at end of file

db/structure.sql

@@ -34484,9 +34484,6 @@ ALTER TABLE ONLY vulnerabilities
 ALTER TABLE ONLY issue_customer_relations_contacts
     ADD CONSTRAINT fk_7b92f835bb FOREIGN KEY (contact_id) REFERENCES customer_relations_contacts(id) ON DELETE CASCADE;
-ALTER TABLE ONLY broadcast_messages
-    ADD CONSTRAINT fk_7bf2ec43da FOREIGN KEY (namespace_id) REFERENCES namespaces(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY vulnerabilities
     ADD CONSTRAINT fk_7c5bb22a22 FOREIGN KEY (due_date_sourcing_milestone_id) REFERENCES milestones(id) ON DELETE SET NULL;

scripts/decomposition/generate-loose-foreign-key

@@ -168,9 +168,8 @@ def generate_migration(definition)
         return unless foreign_key_exists?(:#{definition.from_table}, :#{definition.to_table}, name: "#{definition.name}")
 
         with_lock_retries do
-          execute('LOCK #{definition.to_table}, #{definition.from_table} IN ACCESS EXCLUSIVE MODE') if transaction_open?
-
-          remove_foreign_key_if_exists(:#{definition.from_table}, :#{definition.to_table}, name: "#{definition.name}")
+          remove_foreign_key_if_exists(:#{definition.from_table}, :#{definition.to_table},
+            name: "#{definition.name}", reverse_lock_order: true)
         end
       end
 

spec/db/schema_spec.rb

@@ -31,6 +31,7 @@
     award_emoji: %w[awardable_id user_id],
     aws_roles: %w[role_external_id],
     boards: %w[milestone_id iteration_id],
+    broadcast_messages: %w[namespace_id],
     chat_names: %w[chat_id team_id user_id integration_id],
     chat_teams: %w[team_id],
     ci_build_needs: %w[partition_id build_id],