Suggest checking the partitioning doc when adding CI tables

New CI tables that reference large tables should be
should be partitioned from the start.

danger/ci_tables/Dangerfile

+# frozen_string_literal: true
+
+SEE_DB_DOC = "See the [database dictionary documentation](https://docs.gitlab.com/ee/development/database/database_dictionary.html)."
+
+PARTITIONING_COMMENT = <<~SUGGEST_COMMENT
+When adding new CI tables, consider [partitioning](https://docs.gitlab.com/ee/development/cicd/cicd_tables.html) the table
+from the start if it references any of the larger CI tables: `ci_pipelines`, `ci_stages`, `ci_builds`, `p_ci_builds_metadata`, `ci_job_artifacts`, `ci_pipeline_variables`.
+SUGGEST_COMMENT
+
+def check_database_dictionary_yaml(database_dictionary)
+  return unless database_dictionary.ci_schema?
+  # `p_` prefix is used by the partitioned tables, so we can assume that the table is already partitioned
+  return if database_dictionary.table_name.to_s.start_with?('p_')
+
+  mr_line = database_dictionary.raw.lines.find_index { |line| line.start_with?('table_name:') }
+  return unless mr_line
+
+  markdown(PARTITIONING_COMMENT, file: database_dictionary.path, line: mr_line.succ)
+rescue Psych::Exception
+  # YAML could not be parsed, fail the build.
+  fail "#{helper.html_link(database_ditionary.path)} isn't valid YAML! #{SEE_DB_DOC}" # rubocop:disable Style/SignalException
+rescue StandardError => e
+  warn "There was a problem trying to check the database dictionary file. Exception: #{e.class.name} - #{e.message}"
+end
+
+def added_database_dictionary_files
+  database_dictionary.database_dictionary_files(change_type: :added)
+end
+
+added_database_dictionary_files.each do |database_dictionary|
+  check_database_dictionary_yaml(database_dictionary)
+end

danger/plugins/database_dictionary.rb

+# frozen_string_literal: true
+
+require_relative '../../tooling/danger/database_dictionary'
+
+module Danger
+  class DatabaseDictionary < Plugin
+    # Put the helper code somewhere it can be tested
+    include Tooling::Danger::DatabaseDictionary
+  end
+end

spec/tooling/danger/database_dictionary_spec.rb

+# frozen_string_literal: true
+
+require 'gitlab-dangerfiles'
+require 'gitlab/dangerfiles/spec_helper'
+
+require_relative '../../../tooling/danger/database_dictionary'
+
+RSpec.describe Tooling::Danger::DatabaseDictionary, feature_category: :shared do
+  include_context "with dangerfile"
+
+  let(:fake_danger) { DangerSpecHelper.fake_danger.include(described_class) }
+
+  subject(:database_dictionary) { fake_danger.new(helper: fake_helper) }
+
+  describe '#database_dictionary_files' do
+    let(:database_dictionary_files) do
+      [
+        'db/docs/ci_pipelines.yml',
+        'db/docs/projects.yml'
+      ]
+    end
+
+    let(:other_files) do
+      [
+        'app/models/model.rb',
+        'app/assets/javascripts/file.js'
+      ]
+    end
+
+    shared_examples 'an array of Found objects' do |change_type|
+      it 'returns an array of Found objects' do
+        expect(database_dictionary.database_dictionary_files(change_type: change_type))
+          .to contain_exactly(
+            an_instance_of(described_class::Found),
+            an_instance_of(described_class::Found)
+          )
+
+        expect(database_dictionary.database_dictionary_files(change_type: change_type).map(&:path))
+          .to eq(database_dictionary_files)
+      end
+    end
+
+    shared_examples 'an empty array' do |change_type|
+      it 'returns an array of Found objects' do
+        expect(database_dictionary.database_dictionary_files(change_type: change_type)).to be_empty
+      end
+    end
+
+    describe 'retrieves added database dictionary files' do
+      context 'with added added database dictionary files' do
+        let(:added_files) { database_dictionary_files }
+
+        include_examples 'an array of Found objects', :added
+      end
+
+      context 'without added added database dictionary files' do
+        let(:added_files) { other_files }
+
+        include_examples 'an empty array', :added
+      end
+    end
+
+    describe 'retrieves modified database dictionary files' do
+      context 'with modified modified database dictionary files' do
+        let(:modified_files) { database_dictionary_files }
+
+        include_examples 'an array of Found objects', :modified
+      end
+
+      context 'without modified modified database dictionary files' do
+        let(:modified_files) { other_files }
+
+        include_examples 'an empty array', :modified
+      end
+    end
+
+    describe 'retrieves deleted database dictionary files' do
+      context 'with deleted deleted database dictionary files' do
+        let(:deleted_files) { database_dictionary_files }
+
+        include_examples 'an array of Found objects', :deleted
+      end
+
+      context 'without deleted deleted database dictionary files' do
+        let(:deleted_files) { other_files }
+
+        include_examples 'an empty array', :deleted
+      end
+    end
+  end
+
+  describe described_class::Found do
+    let(:database_dictionary_path) { 'db/docs/ci_pipelines.yml' }
+    let(:gitlab_schema) { 'gitlab_ci' }
+
+    let(:yaml) do
+      {
+
+        'table_name' => 'ci_pipelines',
+        'classes' => ['Ci::Pipeline'],
+        'feature_categories' => ['continuous_integration'],
+        'description' => 'TODO',
+        'introduced_by_url' => 'https://gitlab.com/gitlab-org/gitlab/-/commit/c6ae290cea4b88ecaa9cfe0bc9d88e8fd32070c1',
+        'milestone' => '9.0',
+        'gitlab_schema' => gitlab_schema
+      }
+    end
+
+    let(:raw_yaml) { YAML.dump(yaml) }
+
+    subject(:found) { described_class.new(database_dictionary_path) }
+
+    before do
+      allow(File).to receive(:read).and_call_original
+      allow(File).to receive(:read).with(database_dictionary_path).and_return(raw_yaml)
+    end
+
+    described_class::ATTRIBUTES.each do |attribute|
+      describe "##{attribute}" do
+        it 'returns value from the YAML' do
+          expect(found.public_send(attribute)).to eq(yaml[attribute])
+        end
+      end
+    end
+
+    describe '#raw' do
+      it 'returns the raw YAML' do
+        expect(found.raw).to eq(raw_yaml)
+      end
+    end
+
+    describe '#ci_schema?' do
+      it { expect(found.ci_schema?).to be_truthy }
+
+      context 'with main schema' do
+        let(:gitlab_schema) { 'gitlab_main' }
+
+        it { expect(found.ci_schema?).to be_falsey }
+      end
+    end
+
+    describe '#main_schema?' do
+      it { expect(found.main_schema?).to be_falsey }
+
+      context 'with main schema' do
+        let(:gitlab_schema) { 'gitlab_main' }
+
+        it { expect(found.main_schema?).to be_truthy }
+      end
+    end
+  end
+end

tooling/danger/database_dictionary.rb

+# frozen_string_literal: true
+
+require 'yaml'
+
+module Tooling
+  module Danger
+    module DatabaseDictionary
+      DICTIONARY_PATH_REGEXP = %r{db/docs/.*\.yml}
+
+      # `change_type` can be:
+      #   - :added
+      #   - :modified
+      #   - :deleted
+      def database_dictionary_files(change_type:)
+        files = helper.public_send("#{change_type}_files") # rubocop:disable GitlabSecurity/PublicSend
+
+        files.filter_map { |path| Found.new(path) if path =~ DICTIONARY_PATH_REGEXP }
+      end
+
+      class Found
+        ATTRIBUTES = %w[
+          table_name classes feature_categories description introduced_by_url milestone gitlab_schema
+        ].freeze
+
+        attr_reader :path
+
+        def initialize(path)
+          @path = path
+        end
+
+        ATTRIBUTES.each do |attribute|
+          define_method(attribute) do
+            yaml[attribute]
+          end
+        end
+
+        def raw
+          @raw ||= File.read(path)
+        end
+
+        def ci_schema?
+          gitlab_schema == 'gitlab_ci'
+        end
+
+        def main_schema?
+          gitlab_schema == 'gitlab_main'
+        end
+
+        private
+
+        def yaml
+          @yaml ||= YAML.safe_load(raw)
+        end
+      end
+    end
+  end
+end