controller do
    def scoped_collection
      sql = <<-SQL.strip_heredoc
        LEFT JOIN lots on audits.auditable_id = lots.id AND audits.auditable_type = 'Lots::Base'
        LEFT JOIN bills on audits.auditable_id = bills.id AND audits.auditable_type = 'Bill'
        UNION ALL
        SELECT * FROM audits
        LEFT JOIN lots on audits.associated_id = lots.id AND audits.associated_type = 'Lots::Base'
        LEFT JOIN bills on audits.associated_id = bills.id AND audits.associated_type = 'Bill'
      SQL

      Audit
        .joins(sql)
        .where("lots.id is not null or (bills.id is not null and bills.state != 'hidden')")
        .reorder(:created_at)
        .limit(LIMIT)
        .preload(:auditable)
        .preload(:user)
    end
  end

PG::SyntaxError: ERROR:  each UNION query must have the same number of columns
LINE 4: SELECT * FROM audits
               ^
: SELECT  "audits".* FROM "audits" LEFT JOIN lots on audits.auditable_id = lots.id AND audits.auditable_type = 'Lots::Base'
LEFT JOIN bills on audits.auditable_id = bills.id AND audits.auditable_type = 'Bill'
UNION ALL
SELECT * FROM audits
LEFT JOIN lots on audits.associated_id = lots.id AND audits.associated_type = 'Lots::Base'
LEFT JOIN bills on audits.associated_id = bills.id AND audits.associated_type = 'Bill' WHERE (lots.id is not null or (bills.id is not null and bills.state != 'hidden')) ORDER BY "audits"."id" desc LIMIT 30 OFFSET 0