ActiveRecord `add_index` patch for PostgreSQL JSONB GIN indexes

add_index_patch.rb

# This patch detects {index_columns} that match something like
# the example below, then strips the surrounding double quotes.
#
#   "(settings->'example')"
#
# The resulting CREATE INDEX sql looks something like:
#
#   CREATE INDEX "idx_users_on_settings_example" ON "users" USING gin ((settings->>'example'))
#
# Your {add_index} call should looks something like:
#
#   add_index :users, "(settings->'example')", name: 'idx_users_on_settings_example', using: :gin
module AddIndexPatch
  def add_index_options(*args)
    super.tap do |options|
      index_columns = 2

      if options[index_columns] =~ /^"(\(\w+\-\>'\w+'\))"$/
        options[index_columns] = $1
      end
    end
  end
end

ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.send(:include, AddIndexPatch)