Rails-获取具有重复项的对象 [英] Rails - get objects of objects WITH duplicates

问题描述

在解决我需要获取一次查询中来自对象的对象。

这是该问题的后续措施。我选择为此创建一个新问题，因为根据我以前的规范回答了最后一个问题。

This is a follow up to that question. I chose to create a new question to this since the last one was answered according to my previous specification. Please do refer to that previous question for details.

基本上，我想在一个查询中获取多个对象的所有对象。例如。如果某个产品具有多个类别，而该类别又具有多个产品，那么我想获得该关系中的所有产品，并且更容易（且错误地）放入：

Basically, I wanted to get all the objects of multiple objects in one single query. E.g. if a Product has several Categories which in turn has several Products, I want to get all the Products in that relation, easier (and erronously) put:

all_products = @my_product.categories.products

此查询已解决。我想（最好是）更改此查询：

This was solved with this query. It is this query I would (preferably) like to alter:

Product.includes(:categories).where(categories: { id: @my_product.categories.pluck(:id) } )

现在，我意识到我错过了一些东西使用此解决方案的原因是，我仅获得一份独特的产品列表（也可以期望得到）。但是，我想也获取可能重复的列表。

Now, I realized something I missed using this solution was that I only get a list of unique Products (which one would expect as well). I would however like to get a list with possible duplicates as well.

基本上，如果类别中包括蓝色电动车 （蓝色，电动和汽车）我想返回该对象的三个实例，而不是一个唯一的实例。

Basically, if a "Blue, Electric Car" is included in categories ("Blue", "Electric" and "Car") I would like to get three instances of that object returned, instead of one unique.

我想这不是使Rails感觉，但有没有办法改变上面的查询，以便它不为我提供返回列表中唯一对象的列表，而是完整列表？

I guess this does not make Rails-sense but is there a way to alter the query above so that it does not serve me a list of unique objects in the returned list but rather the "complete" list?

推荐答案

由于要重复，只需将 includes 更改为 joins ， （我刚刚对此进行了测试）。 joins 本质上将合并（内部联接）这两个表，从而为您提供一个唯一的记录列表（按产品和类别）。 includes 确实渴望加载，它只是已经加载了关联的表，但是进行了外部联接，因此，检索到的记录也是唯一的（但仅针对每个Product）。

Since you want duplicates, just change includes to joins, (I tested this just now). joins will essentially combine (inner-join) the two tables giving you a list of records that are all unique (per Product and Category). includes does eager loading which just loads the associated tables already but does an outer-join, and therefore, the retrieved records are also unique (but only per Product).

Product.joins(:categories).where(categories: { id: @my_product.categories.pluck(:id) } )

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