From 3d2a3e5782aaff37c4b27dc9d3858031ab0c9059 Mon Sep 17 00:00:00 2001 From: Andreas Brandl Date: Wed, 1 Aug 2018 12:05:37 +0200 Subject: Docs: FK constraints require an index. Closes #49789. --- doc/development/migration_style_guide.md | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/doc/development/migration_style_guide.md b/doc/development/migration_style_guide.md index a211effdfa7..6f31e5b82e5 100644 --- a/doc/development/migration_style_guide.md +++ b/doc/development/migration_style_guide.md @@ -182,6 +182,34 @@ class MyMigration < ActiveRecord::Migration end ``` +## Adding foreign-key constraints + +When adding a foreign-key constraint to either an existing or new +column remember to also add a index on the column. + +This is _required_ if the foreign-key constraint specifies +`ON DELETE CASCADE` or `ON DELETE SET NULL` behavior. On a cascading +delete, the [corresponding record needs to be retrieved using an +index](https://www.cybertec-postgresql.com/en/postgresql-indexes-and-foreign-keys/) +(otherwise, we'd need to scan the whole table) for subsequent update or +deletion. + +Here's an example where we add a new column with a foreign key +constraint. Note it includes `index: true` to create an index for it. + +```ruby +class Migration < ActiveRecord::Migration + + def change + add_reference :model, :other_model, index: true, foreign_key: { on_delete: :cascade } + end +end +``` + +When adding a foreign-key constraint to an existing column, we +have to employ `add_concurrent_foreign_key` and `add_concurrent_index` +instead of `add_reference`. + ## Adding Columns With Default Values When adding columns with default values you must use the method -- cgit v1.2.1 From e3ff3909862d81036a64f3eab02d5e3e4802f5e6 Mon Sep 17 00:00:00 2001 From: Andreas Brandl Date: Wed, 1 Aug 2018 17:52:54 +0200 Subject: Add rubocop check for add_reference to require index. --- db/migrate/20160317092222_add_moved_to_to_issue.rb | 2 +- rubocop/cop/migration/add_reference.rb | 49 ++++++++++++++++++++ rubocop/rubocop.rb | 1 + spec/rubocop/cop/migration/add_reference_spec.rb | 54 ++++++++++++++++++++++ 4 files changed, 105 insertions(+), 1 deletion(-) create mode 100644 rubocop/cop/migration/add_reference.rb create mode 100644 spec/rubocop/cop/migration/add_reference_spec.rb diff --git a/db/migrate/20160317092222_add_moved_to_to_issue.rb b/db/migrate/20160317092222_add_moved_to_to_issue.rb index 461e7fb3a9b..2bf549d7ecd 100644 --- a/db/migrate/20160317092222_add_moved_to_to_issue.rb +++ b/db/migrate/20160317092222_add_moved_to_to_issue.rb @@ -1,5 +1,5 @@ class AddMovedToToIssue < ActiveRecord::Migration def change - add_reference :issues, :moved_to, references: :issues + add_reference :issues, :moved_to, references: :issues # rubocop:disable Migration/AddReference end end diff --git a/rubocop/cop/migration/add_reference.rb b/rubocop/cop/migration/add_reference.rb new file mode 100644 index 00000000000..4b67270c97a --- /dev/null +++ b/rubocop/cop/migration/add_reference.rb @@ -0,0 +1,49 @@ +# frozen_string_literal: true +require_relative '../../migration_helpers' + +module RuboCop + module Cop + module Migration + # Cop that checks if a foreign key constraint is added and require a index for it + class AddReference < RuboCop::Cop::Cop + include MigrationHelpers + + MSG = '`add_reference` requires `index: true`' + + def on_send(node) + return unless in_migration?(node) + + name = node.children[1] + + return unless name == :add_reference + + opts = node.children.last + + add_offense(node, location: :selector) unless opts && opts.type == :hash + + index_present = false + + opts.each_node(:pair) do |pair| + index_present ||= index_enabled?(pair) + end + + add_offense(node, location: :selector) unless index_present + end + + private + + def index_enabled?(pair) + hash_key_type(pair) == :sym && hash_key_name(pair) == :index && pair.children[1].true_type? + end + + def hash_key_type(pair) + pair.children[0].type + end + + def hash_key_name(pair) + pair.children[0].children[0] + end + end + end + end +end diff --git a/rubocop/rubocop.rb b/rubocop/rubocop.rb index aa7ae601f75..a427208cdab 100644 --- a/rubocop/rubocop.rb +++ b/rubocop/rubocop.rb @@ -11,6 +11,7 @@ require_relative 'cop/migration/add_column' require_relative 'cop/migration/add_concurrent_foreign_key' require_relative 'cop/migration/add_concurrent_index' require_relative 'cop/migration/add_index' +require_relative 'cop/migration/add_reference' require_relative 'cop/migration/add_timestamps' require_relative 'cop/migration/datetime' require_relative 'cop/migration/hash_index' diff --git a/spec/rubocop/cop/migration/add_reference_spec.rb b/spec/rubocop/cop/migration/add_reference_spec.rb new file mode 100644 index 00000000000..8f795bb561e --- /dev/null +++ b/spec/rubocop/cop/migration/add_reference_spec.rb @@ -0,0 +1,54 @@ +require 'spec_helper' + +require 'rubocop' +require 'rubocop/rspec/support' + +require_relative '../../../../rubocop/cop/migration/add_reference' + +describe RuboCop::Cop::Migration::AddReference do + include CopHelper + + let(:cop) { described_class.new } + + context 'outside of a migration' do + it 'does not register any offenses' do + expect_no_offenses(<<~RUBY) + def up + add_reference(:projects, :users) + end + RUBY + end + end + + context 'in a migration' do + before do + allow(cop).to receive(:in_migration?).and_return(true) + end + + it 'registers an offense when using add_reference without index' do + expect_offense(<<~RUBY) + call do + add_reference(:projects, :users) + ^^^^^^^^^^^^^ `add_reference` requires `index: true` + end + RUBY + end + + it 'registers an offense when using add_reference index disabled' do + expect_offense(<<~RUBY) + def up + add_reference(:projects, :users, index: false) + ^^^^^^^^^^^^^ `add_reference` requires `index: true` + end + RUBY + end + + it 'does not register an offense when using add_reference with index enabled' do + expect_no_offenses(<<~RUBY) + def up + add_reference(:projects, :users, index: true) + end + RUBY + end + end +end -- cgit v1.2.1