Rails counter_cache for Model.count 没有任何关联，为了让SELECT COUNT(*)更快 [英] Rails counter_cache for Model.count without any association, in order to make SELECT COUNT (*) faster

问题描述

我正在使用 Model.count 对我的一个模型中的行进行总计，并且有点担心性能，因为最终这个模型会变得非常大，因此 SELECT COUNT (*) 很慢.

I'm totaling the rows in one of my models using Model.count and am a bit concerned about performance, as eventually, this model will get very large, and, therefore, SELECT COUNT (*) very slow.

有没有办法在没有 :belongs_to 关系的情况下使用 counter_cache ?或者另一种性能友好的计算行数的方法?我想制作另一个模型，只是一个我像这样存储计算的模型，但不确定这是最好的方法.

Is there a way to use counter_cache without the :belongs_to relationship? Or another performance-friendly way of counting the rows? I thought about making another model, just one where I store calculations like this but not sure that's the best way.

推荐答案

比创建 Cache 模型更简单的方法是使用 Rails.cache.

Even more trivial than making a Cache model is to just use Rails.cache.

Rails.cache.read("elephant_count") #=> nil
Rails.cache.write("elephant_count", 1) #=> true
Rails.cache.read("elephant_count") #=> 1

Rails 默认使用文件存储(tmp/cache).

Rails uses a file store by default (tmp/cache).

然后您可以将 Rails.cache.write 增量和减量放入模型的 after_create 和 after_destroy 挂钩中，并覆盖 Model.size 调用 Rails.cache.read.

Then you could just place a Rails.cache.write increment and decrement into your model's after_create and after_destroy hooks, and override Model.size with a call to Rails.cache.read.

您可以在 Rails 首次初始化时初始化缓存，方法是在 config/initializers 中放置一个类似于 initialize_cache.rb 的文件，其中包含:

You could initialize the cache whenever Rails first initializes by placing a file named something like initialize_cache.rb in config/initializers containing:

Rails.cache.write('elephant_count', 0) if Rails.cache.read('elephant_count').nil?

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