如何在 Rails 遷移中創建這個特定的 PostGres 索引？

Question

我正在使用 Rails 4.2.7 和 PostGres 9.5。 我試圖在我的表上創建一個 trqm 索引（以方便 LIKE 搜索）所以我創建了這個遷移

class AddTrqmIndexOnRaceTimes < ActiveRecord::Migration
  def change
    CREATE INDEX my_object_times_name_gin_trgm_idx ON my_object_times USING gin (name gin_trgm_ops);
  end
end

當我運行“rake db:migrate”時，這會導致以下錯誤……

StandardError: An error has occurred, this and all later migrations canceled:

undefined local variable or method `gin_trgm_ops' for #<AddTrqmIndexOnRaceTimes:0x007fdc34b40600>
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/migration.rb:664:in `block in method_missing'
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/migration.rb:634:in `block in say_with_time'
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/migration.rb:634:in `say_with_time'
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/migration.rb:654:in `method_missing'
/Users/mikeb/Documents/workspace/runtrax/db/migrate/20161012185951_add_trqm_index_on_my_object_times.rb:3:in `change'
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/migration.rb:608:in `exec_migration'
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/migration.rb:592:in `block (2 levels) in migrate'
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/migration.rb:591:in `block in migrate'
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:292:in `with_connection'
/Users/mikeb/.rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/migration.rb:590:in `migrate'

在 Rails 遷移中創建此索引的正確方法是什么？

Answer 1

您不能在 ruby​​ 方法change直接添加 SQL。 要么使用add_index方法，或者如果您需要超出幫助程序的功能，請使用 ActiveRecord 執行您的查詢，如下所示：

class AddTrqmIndexOnRaceTimes < ActiveRecord::Migration
  def change
    MyObjectTime.connection.execute("CREATE INDEX my_object_times_name_gin_trgm_idx ON my_object_times USING gin (name gin_trgm_ops);")
  end
end

Answer 2

Rails 5 添加了對在表達式索引上指定運算符類的支持

例如：

def change
  add_index :patients, 'lower(last_name) varchar_pattern_ops', name: "index_patients_on_name_unique", unique: true
end

來源

Answer 3

你需要對你的代碼做些小改動。 將 sql 查詢包裝在execute 。

class AddTrqmIndexOnRaceTimes < ActiveRecord::Migration
  def change
    execute "CREATE INDEX my_object_times_name_gin_trgm_idx ON my_object_times USING gin (name gin_trgm_ops);"
  end
end