Remove obsolete wiki notes

It seems there are really old wiki notes in the production database.
There is no way to have wiki notes right now with the current
codebase. Besides, it's impossible to create them or interact
with them.

Changelog: other

db/post_migrate/20220322094410_remove_wiki_notes.rb

+# frozen_string_literal: true
+
+class RemoveWikiNotes < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  class Note < ApplicationRecord
+    self.table_name = 'notes'
+    self.inheritance_column = :_type_disabled
+  end
+
+  def up
+    return unless Gitlab.dev_or_test_env? || Gitlab.staging? || Gitlab.com?
+
+    Note.where(noteable_type: 'Wiki', id: [97, 98, 110, 242, 272]).delete_all
+  end
+
+  def down
+    # NO-OP
+  end
+end

db/schema_migrations/20220322094410

+09722b398f82651c433f6b05962827351e6e7c0841f2a6414feb206bb831e523
\ No newline at end of file

spec/migrations/remove_wiki_notes_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require_migration!
+
+RSpec.describe RemoveWikiNotes, :migration do
+  let(:notes) { table(:notes) }
+
+  it 'removes all wiki notes' do
+    notes.create!(id: 97, note: 'Wiki note', noteable_type: 'Wiki')
+    notes.create!(id: 98, note: 'Commit note', noteable_type: 'Commit')
+    notes.create!(id: 110, note: 'Issue note', noteable_type: 'Issue')
+    notes.create!(id: 242, note: 'MergeRequest note', noteable_type: 'MergeRequest')
+
+    expect(notes.where(noteable_type: 'Wiki').size).to eq(1)
+
+    expect { migrate! }.to change { notes.count }.by(-1)
+
+    expect(notes.where(noteable_type: 'Wiki').size).to eq(0)
+  end
+
+  context 'when not staging nor com' do
+    it 'does not remove notes' do
+      allow(::Gitlab).to receive(:com?).and_return(false)
+      allow(::Gitlab).to receive(:dev_or_test_env?).and_return(false)
+      allow(::Gitlab).to receive(:staging?).and_return(false)
+
+      notes.create!(id: 97, note: 'Wiki note', noteable_type: 'Wiki')
+
+      expect { migrate! }.not_to change { notes.count }
+    end
+  end
+end