Remove chat_names -> ci_pipeline_chat_data FK

This change removes the chat_names -> ci_pipeline_chat_data foreign key.
The eventual consistency is already ensured via the loose foreign key
feature.

Changelog: removed

db/post_migrate/20211112113300_remove_ci_pipeline_chat_data_fk_on_chat_names.rb

+# frozen_string_literal: true
+
+class RemoveCiPipelineChatDataFkOnChatNames < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  def up
+    with_lock_retries do
+      remove_foreign_key_if_exists(:ci_pipeline_chat_data, :chat_names, name: "fk_rails_f300456b63")
+    end
+  end
+
+  def down
+    # Remove orphaned rows
+    execute <<~SQL
+    DELETE FROM ci_pipeline_chat_data
+    WHERE
+    NOT EXISTS (SELECT 1 FROM chat_names WHERE chat_names.id=ci_pipeline_chat_data.chat_name_id)
+    SQL
+
+    add_concurrent_foreign_key(:ci_pipeline_chat_data, :chat_names, name: "fk_rails_f300456b63", column: :chat_name_id, target_column: :id, on_delete: "cascade")
+  end
+end

db/schema_migrations/20211112113300

+be11c0b1c7b9c99c28d44c164742815da57bfc4a32afd54df9135e3ce6edeff9
\ No newline at end of file

db/structure.sql

@@ -31103,9 +31103,6 @@ ALTER TABLE ONLY snippet_repositories
 ALTER TABLE ONLY elastic_reindexing_subtasks
     ADD CONSTRAINT fk_rails_f2cc190164 FOREIGN KEY (elastic_reindexing_task_id) REFERENCES elastic_reindexing_tasks(id) ON DELETE CASCADE;
 
-ALTER TABLE ONLY ci_pipeline_chat_data
-    ADD CONSTRAINT fk_rails_f300456b63 FOREIGN KEY (chat_name_id) REFERENCES chat_names(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY approval_project_rules_users
     ADD CONSTRAINT fk_rails_f365da8250 FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;
 

spec/db/schema_spec.rb

@@ -29,6 +29,7 @@ RSpec.describe 'Database schema' do
     ci_builds: %w[erased_by_id runner_id trigger_request_id user_id],
     ci_namespace_monthly_usages: %w[namespace_id],
     ci_pipelines: %w[user_id],
+    ci_pipeline_chat_data: %w[chat_name_id], # it uses the loose foreign key featue
     ci_runner_projects: %w[runner_id],
     ci_trigger_requests: %w[commit_id],
     cluster_providers_aws: %w[security_group_id vpc_id access_key_id],