Rails 5 IN-clause subquery

[jaredbeck]

ransack 1.8.0: In rails 4, it is possible to use a SqlLiteral node as the formatter of a custom ransacker. In rails 5 it is not. There may be an issue with rails 5's new attribute type system.

Consider this contrived, yet complete and executable example. The formatter is a subquery of Post ids.

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  # gem 'rails', '4.2.7'
  gem 'rails', '5.0.0'
  gem 'ransack', '1.8.0', require: false
  gem 'sqlite3'
end

require 'active_record'
require "ransack"
require 'minitest/autorun'
require 'logger'

ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.string :title
  end
end

class Post < ActiveRecord::Base
  ransacker(
    :banana,
    callable: -> (x) { x.table[:id] },
    formatter: ->(value) {
      ::Arel::Nodes::SqlLiteral.new(
        arel_table.project(:id).where(arel_table[:title].eq(value)).to_sql
      )
    }
  )
end

class BugTest < Minitest::Test
  def test_association_stuff
    a = Post.create!(title: 'apple')
    b = Post.create!(title: 'banana')
    c = Post.create!(title: 'coconut')

    # rails 4 passes. query is:
    # SELECT "posts".* FROM "posts" WHERE "posts"."id" IN (
    #   SELECT id FROM "posts" WHERE "posts"."title" = 'banana'
    # )

    # rails 5 fails. query is:
    # SELECT "posts".* FROM "posts" WHERE "posts"."id" IN (0)

    assert_equal [b], Post.ransack(banana_in: "banana").result
  end
end

I know there are better ways to use ransack to search post titles :) as I said, this is a contrived example.

[jonatack]

Reproduced. On Rails 5.0.0 and master (5.1.0.alpha) too.

[jonatack]

With both Ransack 1.8.1 (latest release) and also 1.7.0 from a year ago.

[jonatack]

@jaredbeck This appears to be coming from a change in Arel or Active Record between Rails 4 and 5, not a bug in Ransack. It's a bit of a strange example. You might need to formulate your Arel query differently. Ransackers just provide a conduit to Arel. The Rails team has clarified over the past couple years that Arel methods are :nodoc: and likely to change without warning. So closing for now unless this is a bug in ransackers not correctly providing access to Arel.

P.S. - This works fine, though I imagine you are trying to do something else:

Post.ransack(title_in: 'banana').result

[jaredbeck]

I know there are better ways to use ransack to search post titles :) as I said, this is a contrived example.

P.S. - This works fine, though I imagine you are trying to do something else:
Post.ransack(title_in: 'banana').result

Correct, my admittedly contrived example does not require an IN-clause subquery. My app does.

You might need to formulate your Arel query differently. Ransackers just provide a conduit to Arel. The Rails team has clarified over the past couple years that Arel methods are :nodoc: and likely to change without warning.

Yeah, my colleagues keep writing complicated custom ransackers that break every time I upgrade arel. Maybe there should be a warning about this in the custom ransacker docs. Would you like a PR with such a warning?

[jonatack]

There might be news from the front. If I recall @sgrif's remarks in the latest http://bikeshed.fm/74 podcast discussing Ransack and Arel -- and I could be wrong -- the Arel API is planned to stabilize and return from :nodoc: back to public. Yay! -- to symbolically celebrate I added Sean's vintage Arel blog post to the two other Arel resources in the Ransack wiki today.

PR proposal: There is already a warning in the ransackers section of the wiki about complicated Arel ransackers not being a cure-all with mention of a few alternate solutions, so I think we're fine.

On the other hand, any of the TODO or FIXME comments in the code base would be wonderful PRs to work on.

On Monday, August 8, 2016, Jared Beck notifications@github.com wrote:

I know there are better ways to use ransack to search post titles :) as I
said, this is a contrived example.

P.S. - This works fine, though I imagine you are trying to do something
else:
Post.ransack(title_in: 'banana').result

Correct, my admittedly contrived example does not require an IN-clause
subquery. My app does.

You might need to formulate your Arel query differently. Ransackers just
provide a conduit to Arel. The Rails team has clarified over the past
couple years that Arel methods are :nodoc: and likely to change without
warning.

Yeah, my colleagues keep writing complicated custom ransackers that break
every time I upgrade arel. Maybe there should be a warning about this in
the custom ransacker docs. Would you like a PR with such a warning?

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[jaredbeck]

.. news from the front.

🎺 🎵📰! 😀

.. the Arel API is planned to stabilize and return from :nodoc: back to public ..

That's great news, thanks.