我们有很多的 report 是由 SQL 直接生成的

class SaleReport < ActiveRecord::Base
  #...
  self.table_name = "sale_report"
  #..。
end

这个 sale_report 是一个 postgresql view，由 10 个以上 table join 生成的，大概这个样子：

SELECT 
       table_a.id,
       #省略若干

FROM abstract_table_a table_a
       LEFT JOIN table_u table_u ON table_u.id = table_a.payer_id
  AND table_a.payer_type = 'Farmer'
       LEFT JOIN table_b table_b ON table_b.id = table_a.order_item_id
       #省略若干LEFT JOIN
  AND table_c.archived_at IS NULL
  AND table_c.staff_id IS NOT NULL
       LEFT JOIN users table_d ON table_d.p_id = orders.p_id
  AND table_d.archived_at IS NULL
    LEFT JOIN table_f table_f ON table_b.p_id = table_f.id
  AND table_b.p_type = 'SUV'
    LEFT JOIN table_l table_f_category ON table_f_category.id = table_f.table_l_id
    LEFT JOIN table_g table_g ON table_b.p_id = table_g.id
  AND table_b.p_type = 'CAR'
       LEFT JOIN table_l table_g_category ON table_g_category.id = table_g.table_l_id
       LEFT JOIN table_h ON table_b.p_id = table_h.id
  AND table_b.p_type = 'TRUCK'
       LEFT JOIN table_r ON table_h.treatment_id = table_r.id
       LEFT JOIN table_l table_h_category
                 ON table_h_category.id = table_r.table_l_id
       LEFT JOIN (
                   #省略若干行
                 ) AS table_x ON table_a.id = table_x.inv_id

       LEFT JOIN (
                   SELECT #省略若干行
                   FROM #省略若干行
                          INNER JOIN #省略若干行
                   WHERE#省略若干行
                 ) table_Z ON table_a.id = table_Z.inv_id
WHERE #省略若干行
ORDER BY #省略若干行;

我希望的是能在 rspec 中，就像用 facotrybot 一样能够

let!(:report) {create(:sale_report)}

我尝试过创建

factory :sale_report, class: SaleReport do

但得到 error

ActiveRecord::StatementInvalid: PG::ObjectNotInPrerequisiteState: ERROR:  cannot insert into view "sale_report"
DETAIL:  Views that do not select from a single table or view are not automatically updatable.
HINT:  To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.
: INSERT INTO "sale_report" DEFAULT VALUES RETURNING "id"

现在如果想要写这个 report 的单元测试需要一个个的 creat join table 的 instance，非常的耗时，而且需要先理解 tables 之间的关系。

请问有什么思路吗？有什么 gem 可以帮助实现吗