如何使用具有不同值的联接表获取值? [英] How to get value using join table with different values?

问题描述

我有一个产品，用户和product_click模型. 在product_click中，我有一个count列，我在其中记录一个记录，哪个用户单击哪个产品多少次.

I have a product, user and product_click model. In product_click, I have column count where I'm keeping a record, which user click which product how many times.

我也尝试过

Product.sort_by{ |r|  r.product_clicks.where(user_id: user.id).first.try(:count).to_i

给出期望的结果，但在运行时创建大量查询.

which giving desire result but creating lots of query on running.

product_click.rb

product_click.rb

belongs_to :product
  belongs_to :user

product.rb

product.rb

has_many :product_clicks, dependent: :destroy

user.rb

has_many :product_clicks, dependent: :destroy

模式

create_table "product_clicks", force: :cascade do |t|
    t.bigint "product_id"
    t.bigint "user_id"
    t.bigint "count", default: 0
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

在控制器中

Product.left_outer_joins(:product_clicks).order("count DESC NULLS LAST")

现在我正在寻找类似的东西.

Now i am looking something like this to work.

但是在这里，我无法检查计数是否属于哪个特定用户. 如果我要添加

But here i can't able to check whether the count was of which particular user. If i'm adding

Product.left_outer_joins(:product_clicks).where(resource_clicks: { user_id: user.id }).order("count DESC NULLS LAST")

然后显示用户点击过的产品，但没有显示零"(我从未点击过)的产品.

Then it showing a product which user clicked but not the 'nil' ones(which i never clicked).

我也尝试过

Product.left_outer_joins(:product_clicks).where(product_clicks: { user_id: [user.id, nil] }).order("count DESC NULLS LAST")

但给我我所单击的所有内容，而所有其他都没有其他人单击.如果有人点击了我没有点击的内容，那么它不会显示给我.

but giving me all i clicked and all which no one else clicked. If someone click which i didn't then it not displaying to me.

推荐答案

虽然我在考虑其他方法，但一种直接方法是两步解决方案.

While I am thinking of other ways, one straight way would be a 2 step solution.

product_ids = ProductClick.where(user_id: user.id).order('count desc').pluck(:product_id)

products = Product.where(id: product_ids)

它肯定会改善您的时间，并且比您的查询(N + 1)要好.

It'll definitely improve your time and is better than your query (which is N+1).

使用预加载

Product.includes(:product_clicks).where('product_clicks.user_id' => user.id).order('product_clicks.count desc')

上面的查询也应该以相同的方式产生结果，但是无论如何它可能在内部命中2个查询.

The above query should also result in the same way, however, it may internally hit 2 queries anyway.

使用Haveing子句-推荐

Product.includes(:product_clicks).having('product_clicks.user_id' => user.id).order('product_clicks.count desc')

更新-使用OR

Product.includes(:product_clicks).where('product_clicks.user_id' => user.id)
       .order('product_clicks.count desc')
       .or(
        Product.includes(:product_clicks)
               .where('product_clicks.user_id' => user.id)
               .where(product_clicks: { id: nil })
       )

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