Question

让我们想象一下具有两个具有HABTM关联的资源（用户和书籍）的Ruby模式。

当我基于这种关联进行过滤时，无论用户是否有一本书，Ruby的行为都会有些奇怪：

2.5.3 :007 > Contact.includes(:books).count
(4.7ms)  SELECT COUNT(*) FROM "contacts"
=> 36880

这很好，因为它返回与任何图书关联的联系人的总价值。

2.5.3 :010 > Contact.includes(:books).where(books: {"id":[1,2] }).count
(34.0ms)  SELECT COUNT(DISTINCT "contacts"."id") FROM "contacts" LEFT OUTER JOIN "contacts_books" ON "contacts_books"."contact_id" = "contacts"."id" LEFT OUTER JOIN "books" ON "books"."id" = "contacts_books"."book_id" WHERE "books"."id" IN (?, ?)  [["id", 1], ["id", 2]]
=> 24864

这还可以，因为它返回ID为1或2的所有联系人。

2.5.3 :011 > Contact.includes(:books).where.not(books: {"id":[1,2] }).count
(13.0ms)  SELECT COUNT(DISTINCT "contacts"."id") FROM "contacts" LEFT OUTER JOIN "contacts_books" ON "contacts_books"."contact_id" = "contacts"."id" LEFT OUTER JOIN "books" ON "books"."id" = "contacts_books"."book_id" WHERE "books"."id" NOT IN (?, ?)  [["id", 1], ["id", 2]]
=> 0

现在这部分没有意义，因为它应该是总数-#associations，所以36880-24864给我留下了12016条记录，而不是0。

或者我想念什么？

Rails 5.2.2 红宝石2.5.3p105（2018-10-18修订版65156）[x86_64-darwin17]

Answer 1

where条件将要求加载的联系人至少有一本书，例如如果没有书号，则无法检查书号是否在数组中。

我如何调试的：

当我尝试重现您的问题时，我有一个小仓库：

$client = new SoapClient("https://etrack.postaplus.net/APIService/PostaWebClient.svc?singleWsdl", array("trace" => 1, "exception" => 0));

$params = array(
        "CodeStation" => `BEY`,
        "PickupNumber" => `1`,
        "Reason" => `test reason`,
        "Password" => `sss`,
        "ShipperAccount" => `acc`,
        "UserName" => `acc`,
    );

$client->Pickup_Cancel($params);

最小复制回购：https://github.com/localhostdotdev/bug/tree/has-and-belongs-to-many-includes-count

Ruby HATBM-负过滤行为很奇怪

1 个答案: