我有一个表ticketlines，其中包含列：
ID, TICKET, PRODUCT, REASON, UNITS, PRICE
Controller Ticketlines：
@q = Ticketline.joins(:product, :ticket).group(:PRODUCT).select("PRODUCT, products.CONSIGNOR, SUM(UNITS) AS TOTALUNITS").ransack(params[:q])
@product_sales = @q.result.paginate(:page => params[:page], :per_page => 30)
在我看来，我想展示@product_sales.count
生成查询：
SELECT COUNT(*) AS count_all, `ticketlines`.`PRODUCT` AS ticketlines_product FROM `ticketlines` INNER JOIN `products` ON `products`.`ID` = `ticketlines`.`PRODUCT` INNER JOIN `tickets` ON `tickets`.`ID` = `ticketlines`.`TICKET` GROUP BY `ticketlines`.`PRODUCT`
显示@product_sales的结果数。
问题是当我尝试使用ransack过滤结果时。
产品表包含列ID, NAME, CATEGORY, CONSIGNOR
如果我按照PRODUCT过滤Ticketlines则可行。如果我按CATEGORY或CONSIGNOR过滤则不会。
例如，如果我在按@product_sales.count时按类别进行过滤，则会生成查询：
SELECT COUNT(DISTINCT ) AS count, `ticketlines`.`PRODUCT` AS ticketlines_product FROM `ticketlines` INNER JOIN `products` ON `products`.`ID` = `ticketlines`.`PRODUCT` INNER JOIN `tickets` ON `tickets`.`ID` = `ticketlines`.`TICKET` LEFT OUTER JOIN `categories` ON `categories`.`ID` = `products`.`CATEGORY` WHERE `categories`.`ID` = '289108c2-6be3-4baf-b053-96f70dc2cc5a' GROUP BY `ticketlines`.`PRODUCT`
对我来说没有意义的是，如果我从view @ product_sales.count中删除，则没有错误。我可以使用类别过滤器，它可以工作。
执行的查询是：
SELECT PRODUCT, SUM(UNITS) AS TOTALUNITS FROM `ticketlines` INNER JOIN `products` ON `products`.`ID` = `ticketlines`.`PRODUCT` INNER JOIN `tickets` ON `tickets`.`ID` = `ticketlines`.`TICKET` LEFT OUTER JOIN `categories` ON `categories`.`ID` = `products`.`CATEGORY` WHERE `categories`.`ID` = '289108c2-6be3-4baf-b053-96f70dc2cc5a' GROUP BY `ticketlines`.`PRODUCT` LIMIT 30 OFFSET 0
只有在使用count时才能使@product_sales为零的原因是什么？