Rails/Arel：选择所有记录作为 ActiveRecord::Relation
在 Rails 中使用 Arel - 我正在寻找一种创建 ActiveRecord::Relation 的方法，该方法可以有效地生成 SELECT * FROM table，我仍然可以进一步操作它。
例如，我有一个分为多个类别的模型，我通过以下方式返回这些类别的计数：
relation = Model.where(:archived => false) # all non-archived records
record_counts = {
:total => relation.count,
:for_sale => relation.where(:for_sale => true).count
:on_auction => relation.where(:on_auction => true).count
}
这工作正常，并且具有向 MySQL 发出 COUNT 查询的优点，而不是实际上自己选择记录。
但是，我现在需要在计数中包含存档记录，但 relation = Model.all 会生成 Array，并且我正在寻找 ActiveRecord： ：关系。
我能想到的唯一方法是 model.where(model.arel_table[:id].not_eq(nil)) ，它有效，但似乎有点荒谬。
任何人都可以阐明这一点吗？
Using Arel in Rails - I'm looking for a way of creating an ActiveRecord::Relation that effectively results in SELECT * FROM table, which I can still manipulate further.
For example, I have a model that's split up into multiple categories, and I return counts for these in the following manner:
relation = Model.where(:archived => false) # all non-archived records
record_counts = {
:total => relation.count,
:for_sale => relation.where(:for_sale => true).count
:on_auction => relation.where(:on_auction => true).count
}
This works fine, and has the advantage of firing off COUNT queries to MySQL, rather than actually selecting the records themselves.
However, I now need to include archived records in the counts, but relation = Model.all results in an Array, and I'm looking for an ActiveRecord::Relation.
The only way I can think of doing this is model.where(model.arel_table[:id].not_eq(nil)), which works, but seems slightly absurd.
Can anyone shed any light on this?
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尝试
relation = Model.scoped。这将为您提供关系而不是实际结果。Try
relation = Model.scoped. That will give you the relation instead of the actual results.对于 Rails 4.1 及更高版本：
Model.all返回一个关系（以前没有）对于 Rails 4.0：
Model.where(nil)对于 Rails 3.x：<代码>模型.范围
For Rails 4.1 and above:
Model.allreturns a relation (where it previously did not)For Rails 4.0:
Model.where(nil)For Rails 3.x:
Model.scoped您可能会想要：
如果您看到关系是什么，它实际上是一个
ActiveRecord::Relation。正如您可以从此页面看到：
http://api .rubyonrails.org/classes/ActiveRecord/NamedScope/ClassMethods.html#method-i-scoped
它表示以下内容：
You would want:
which if you see what relation is, it is in fact an
ActiveRecord::Relation.As you can see from this page:
http://api.rubyonrails.org/classes/ActiveRecord/NamedScope/ClassMethods.html#method-i-scoped
It says the following: