大型模型存在参数时的Rails过滤器 [英] Rails filter when param is present for large model

问题描述

此博客文章说明了如何根据此代码中存在的参数进行过滤。

This blog post explains how to filter based on the parameters that are present with this code.

def index
  @products = Product.where(nil) # creates an anonymous scope
  @products = @products.status(params[:status]) if params[:status].present?
  @products = @products.location(params[:location]) if params[:location].present?
  @products = @products.starts_with(params[:starts_with]) if params[:starts_with].present?
end

Product.where（nil）该解决方案的一部分是有问题的，因为如果模型很大，它将把所有内容加载到内存中并导致服务器崩溃。

The Product.where(nil) part of the solution is problematic because it will load everything into memory and cause your server to crash if the model is big.

其中一个博客评论者说：使用 Product.none 代替 Product.where（nil）更好吗？但我无法使用该解决方案。

One of the blog post commenters said "Isn't it better to use Product.none instead of Product.where(nil)?" but I couldn't get that solution to work.

此Stackoverflow答案通过 joins 方法访问 ActiveRecord :: Relation 对象。我没有加入，所以此解决方案对我不起作用。

This Stackoverflow answer accesses the ActiveRecord::Relation object via the joins method. I'm not doing a join, so this solution won't work for me.

请告诉我是否有更好的方法或完全不同的方法我应该解决这个问题。谢谢！

Let me know if there is a better way to do this or a completely different way I should approach this problem. Thanks!

推荐答案

为什么不只使用 .all 并合并

def filter_by_params
  params.slice(:status, :location, :starts_with)
    .compact # removes keys with nil values
    # iterates though the hash and returns a scope
    .each_with_object(Product.all) do |(key, value), scope|
      scope.merge(Product.send(key, value))
    end
end

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