Reproduction for https://github.com/rails/rails/issues/12261

bug_12261.rb

require 'bundler'
Bundler.setup(:default)

require 'active_record'
require 'minitest/autorun'
require 'logger'

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'postgresql', database: 'rails_bug')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  drop_table "posts"
  create_table :posts do |t|
    t.string :tags, array: true
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class BugTest < Minitest::Test
  def test_array_stuff
    post = Post.create!(tags: ["one", "two", "three"])
    post.update_column(:tags, ["four", "five"])
    assert_equal ["four", "five"], Post.first.tags
  end
end

This investigation was related to: https://meta.discourse.org/t/search-not-working-for-staff-users/11371/5