Incorrect default value inserted for JSON column types

[fschwahn]

In case of a JSON column, bulk_insert will incorrectly insert the default value. It inserts "{}" (ie. a string) instead of {} (ie. an object).

Here's a failing test:

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"
  gem "sqlite3"
  gem "bulk_insert"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :profiles, force: true do |t|
    t.string :name
    t.json :json_data, default: {}, null: false
  end
end

class Profile < ActiveRecord::Base
end

class BugTest < Minitest::Test
  def test_bulk_insert_json_default
    worker = Profile.bulk_insert
    worker.add(name: "Foo", json_data: {})
    worker.add(name: "Bar")
    worker.save!

    profile1 = Profile.find_by!(name: "Foo")
    profile2 = Profile.find_by!(name: "Bar")
    assert_equal profile1.json_data, {}
    assert_equal profile2.json_data, {}
  end
end

The reason is the following code: https://github.com/jamis/bulk_insert/blob/ab5db0873098701904ac2fcdcab86e417d342895/lib/bulk_insert/worker.rb#L51-L64

In case a value does not exist, the column default is used. The column default in rails is expressed as a string (ie. in the example above: Profile.columns_hash["json_data"].default == {}). This is problematic for JSON columns, as both "{}" and {} are valid JSON (one a string, the other an object).