Ruby-on-rails 合并两个 ActiveRecord::Relation 对象

Combine two ActiveRecord::Relation objects

提问by Patrick Klingemann

Suppose I have the following two objects:

假设我有以下两个对象：

first_name_relation = User.where(:first_name => 'Tobias') # ActiveRecord::Relation
last_name_relation  = User.where(:last_name  => 'Fünke') # ActiveRecord::Relation

is it possible to combine the two relations to produce one ActiveRecord::Relationobject containing both conditions?

是否有可能ActiveRecord::Relation将这两种关系结合起来产生一个包含这两种条件的对象？

Note: I'm aware that I can chain the wheres to get this behavior, what I'm really interested in is the case where I have two separate ActiveRecord::Relationobjects.

注意：我知道我可以链接 wheres 来获得这种行为，我真正感兴趣的是我有两个单独的ActiveRecord::Relation对象的情况。

回答by Andrew Marshall

If you want to combine using AND(intersection), use merge:

如果要使用AND(intersection) 组合，请使用merge：

first_name_relation.merge(last_name_relation)

If you want to combine using OR(union), use or^?:

如果要使用OR(union)进行组合，请使用^? ：or

first_name_relation.or(last_name_relation)

---

---

^?Only in ActiveRecord 5+; for 4.2 install the where-orbackport.

^? 仅在 ActiveRecord 5+ 中；对于 4.2 安装where-orbackport。

回答by thatmiddleway

Relation objects can be converted to arrays. This negates being able to use any ActiveRecord methods on them afterwards, but I didn't need to. I did this:

关系对象可以转换为数组。这否定了之后能够对它们使用任何 ActiveRecord 方法，但我不需要。我这样做了：

name_relation = first_name_relation + last_name_relation

Ruby 1.9, rails 3.2

红宝石 1.9，导轨 3.2

回答by Tomasz Ja?kiewicz

mergeactually doesn't work like OR. It's simply intersection (AND)

merge实际上不像OR. 它只是交叉点 ( AND)

I struggled with this problem to combine to ActiveRecord::Relation objects into one and I didn't found any working solution for me.

我努力解决这个问题以将 ActiveRecord::Relation 对象合并为一个，但我没有找到任何适合我的解决方案。

Instead of searching for right method creating an union from these two sets, I focused on algebra of sets. You can do it in different way using De Morgan's law

我没有寻找从这两个集合中创建联合的正确方法，而是专注于集合的代数。你可以使用德摩根定律以不同的方式做到这一点

ActiveRecord provides merge method (AND) and also you can use not method or none_of (NOT).

ActiveRecord 提供合并方法（AND），您也可以使用 not method 或 none_of （NOT）。

search.where.none_of(search.where.not(id: ids_to_exclude).merge(search.where.not("title ILIKE ?", "%#{query}%")))

You have here (A u B)' = A' ^ B'

你在这里 (A u B)' = A' ^ B'

UPDATE: The solution above is good for more complex cases. In your case smth like that will be enough:

更新：上述解决方案适用于更复杂的情况。在你的情况下，这样就足够了：

User.where('first_name LIKE ? OR last_name LIKE ?', 'Tobias', 'Fünke')

回答by 6ft Dan

I've been able to accomplish this, even in many odd situations, by using Rails' built-in Arel.

我已经能够通过使用 Rails 的内置Arel来实现这一点，即使在许多奇怪的情况下。

User.where(
  User.arel_table[:first_name].eq('Tobias').or(
    User.arel_table[:last_name].eq('Fünke')
  )
)

This merges both ActiveRecord relations by using Arel's or.

这通过使用 Arel 的或来合并两个 ActiveRecord 关系。

---

---

Merge, as was suggested here, didn't work for me. It dropped the 2nd set of relation objects from the results.

正如这里建议的那样，合并对我不起作用。它从结果中删除了第二组关系对象。

回答by echo

There is a gem called active_record_unionthat might be what you are looking for.

有一个名为active_record_union的 gem 可能正是您要找的。

It's example usages is the following:

它的示例用法如下：

current_user.posts.union(Post.published)
current_user.posts.union(Post.published).where(id: [6, 7])
current_user.posts.union("published_at < ?", Time.now)
user_1.posts.union(user_2.posts).union(Post.published)
user_1.posts.union_all(user_2.posts)

回答by daveomcd

This is how I've "handled" it if you use pluck to get an identifier for each of the records, join the arrays together and then finally do a query for those joined ids:

如果您使用 pluck 获取每个记录的标识符，将数组连接在一起，然后最后对这些连接的 id 进行查询，这就是我“处理”它的方式：

  transaction_ids = @club.type_a_trans.pluck(:id) + @club.type_b_transactions.pluck(:id) + @club.type_c_transactions.pluck(:id)
  @transactions = Transaction.where(id: transaction_ids).limit(100)

回答by stevenspiel

If you have an array of activerecord relations and want to merge them all, you can do

如果您有一系列 activerecord 关系并希望将它们全部合并，您可以这样做

array.inject(:merge)

回答by Richard Grossman

Brute force it:

蛮力吧：

first_name_relation = User.where(:first_name => 'Tobias') # ActiveRecord::Relation
last_name_relation  = User.where(:last_name  => 'Fünke') # ActiveRecord::Relation

all_name_relations = User.none
first_name_relation.each do |ar|
  all_name_relations.new(ar)
end
last_name_relation.each do |ar|
  all_name_relations.new(ar)
end

回答by Eric Powell

I've stumbled upon this issue a handful of times and the generally accepted responses never quite worked for me.

我曾多次偶然发现这个问题，但普遍接受的回应对我来说从来没有完全奏效。

The proposed solution in the accepted answer seemed like it would work best:

接受的答案中提出的解决方案似乎效果最好：

first_name_relation.or(last_name_relation)

But I could never get this to work and would always receive an 'undefined method' error for 'or'.

但是我永远无法让它工作，并且总是会收到“或”的“未定义方法”错误。

My solution:

我的解决方案：

combined_relation = first_name_relation + (last_name_relation - first_name_relation)

This gives me essentially the results of a UNION between the original queries and the relation objects are still the correct ActiveRecord objects.

这基本上给了我原始查询和关系对象之间的 UNION 结果仍然是正确的 ActiveRecord 对象。

This is similar to the answer provided by @thatmiddleway, though I needed to add the subtraction to get a DISTINCT collection of objects. This does convert the combined collection to an ARRAY, but I could still call model methods on on the individual instances in an 'each' iterator in my view, which solved my issue.

这类似于@thatmiddleway 提供的答案，尽管我需要添加减法以获取 DISTINCT 对象集合。这确实将组合集合转换为 ARRAY，但在我看来，我仍然可以在“每个”迭代器中的各个实例上调用模型方法，这解决了我的问题。

This is my first StackOverflow answer (gasp!), so I welcome your feedback!

这是我的第一个 StackOverflow 答案（喘气！），所以我欢迎您的反馈！