[deploy] Add unique index on articles canonical_url (#10161)

app/models/article.rb

@@ -51,8 +51,8 @@ class Article < ApplicationRecord
 
   validates :body_markdown, length: { minimum: 0, allow_nil: false }, uniqueness: { scope: %i[user_id title] }
   validates :cached_tag_list, length: { maximum: 126 }
-  validates :canonical_url, url: { allow_blank: true, no_local: true,
-                                   schemes: %w[https http] }, uniqueness: { allow_blank: true }
+  validates :canonical_url, uniqueness: { allow_nil: true }
+  validates :canonical_url, url: { allow_blank: true, no_local: true, schemes: %w[https http] }
   validates :feed_source_url, uniqueness: { allow_blank: true }
   validates :main_image, url: { allow_blank: true, schemes: %w[https http] }
   validates :main_image_background_hex_color, format: /\A#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})\z/

db/migrate/20200902132326_add_unique_index_to_articles_canonical_url.rb

@@ -0,0 +1,15 @@
+class AddUniqueIndexToArticlesCanonicalUrl < ActiveRecord::Migration[6.0]
+  disable_ddl_transaction!
+
+  def up
+    unless index_exists?(:articles, :canonical_url, unique: true)
+      add_index :articles, :canonical_url, unique: true, algorithm: :concurrently
+    end
+  end
+
+  def down
+    if index_exists?(:articles, :canonical_url, unique: true)
+      remove_index :articles, column: :canonical_url, algorithm: :concurrently
+    end
+  end
+end

db/schema.rb

@@ -154,6 +154,7 @@ ActiveRecord::Schema.define(version: 2020_09_02_204028) do
     t.string "video_state"
     t.string "video_thumbnail_url"
     t.index ["boost_states"], name: "index_articles_on_boost_states", using: :gin
+    t.index ["canonical_url"], name: "index_articles_on_canonical_url", unique: true
     t.index ["comment_score"], name: "index_articles_on_comment_score"
     t.index ["featured_number"], name: "index_articles_on_featured_number"
     t.index ["feed_source_url"], name: "index_articles_on_feed_source_url"

spec/models/article_spec.rb

@@ -37,7 +37,7 @@ RSpec.describe Article, type: :model do
     it { is_expected.to validate_length_of(:title).is_at_most(128) }
     it { is_expected.to validate_presence_of(:title) }
     it { is_expected.to validate_presence_of(:user_id) }
-    it { is_expected.to validate_uniqueness_of(:canonical_url).allow_blank }
+    it { is_expected.to validate_uniqueness_of(:canonical_url).allow_nil }
     it { is_expected.to validate_uniqueness_of(:feed_source_url).allow_blank }
     it { is_expected.to validate_uniqueness_of(:slug).scoped_to(:user_id) }