Rails通过序列化数组查找 [英] Rails look up by serialized array

问题描述

我正在尝试基于序列化的数组文本字段（如果需要的话，请使用Postgres）执行Rails查找。因此：

I'm trying to perform a Rails lookup based on a serialized array text field (Postgres, if it matters). So:

class Foo < ActiveRecord::Base
  serialize :arr, Array
end

然后：

> f = Foo.create!(arr: [[1, 2], [3, 4]])
=> #<Foo id: 1, arr: [[1, 2], [3, 4]]>
> f.arr
=> [[1, 2], [3, 4]]

一切顺利。但我似乎无法根据该字段进行查找：

All's well. But I can't seem to do a lookup based on that field:

> Foo.where(arr: [[1, 2], [3, 4]])
=> ActiveRecord::StatementInvalid Exception: PG::UndefinedFunction: ERROR:  operator does not exist: text = integer
   "foos"."arr" IN (1, 2, ...
                ^
   HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.

Rails似乎正在尝试将其转换为IN查询。无论如何，我们知道Rails是使用Yaml序列化的（还是我们？）。让我们尝试：

It seems Rails is trying to convert it into an IN query. No matter, we know Rails serializes with Yaml (or do we?). So let's try:

> Foo.where(arr: [[1, 2], [3, 4]].to_yaml)
=> #<ActiveRecord::Relation []>

更仔细的检查似乎使我转向换行符，因为此查找失败的原因。我可以找到一个带有复杂LIKE子句的解决方法，但那时候我想我可能走错了路。

Closer inspection seems to lead me towards newlines as the reason why this lookup fails. I could find a way around this with a complex LIKE clause but at that point I think I'm probably headed down the wrong path.

有没有一种查找模型的标准方法在Rails中基于序列化的属性（我应该使用不是Yaml的东西进行序列化吗？）非常感谢！

Is there a standard way to look up a model in Rails based on a serialized attribute? (Should I just serialize with something that isn't Yaml?) Many thanks!

推荐答案

我目前使用的解决方案（肯定对其他方法开放！）是强制Rails使用Yaml之外的其他东西进行序列化，以允许进行字符串查询：

The solution I'm using for now (definitely open to other approaches!) is to force Rails to serialize with something other than Yaml, to allow for string queries:

class Foo < ActiveRecord::Base
  serialize :arr, SerializedArray

  def self.find_by_arr
    self.where(arr: SerializedArray.dump(arr)).take
  end
end

class SerializedArray
  def self.load(arr)
    arr ? JSON.load(arr) : nil
  end

  def self.dump(arr)
    arr ? JSON.dump(arr) : nil
  end
end

有点简直就是我必须使用自定义 find_by_arr 进行查询，但是它可以工作。

It's a little janky in that I have to query with the custom find_by_arr, but it works.

（编辑：删除了错误的示例代码。）

( removed bad example code.)

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