Rails活动记录在内存中的缓存

Question

I have a model which has through relationships to another model through two foreign key relationships. I do a lot of lookups on those tables (which are 3-4K rows) while importing a lot of data, and I'm trying to eliminate spurious repeated database lookups. (Ideally, my database would be doing async writes/INSERTs only)

I have played with doing my own caching by ID, and recently switched to using Rails.cache (with MemoryStore for now. I have no need to sync against other instances, and I'm ram rich on the import machine). However, I find that I am getting multiple copies of the same associated records, and I'd like to get rid of this.

For instance:

irb> p = Phone.includes([:site => :client, :btn => :client]).first. 

irb> p.site.client.object_id => 67190640 

irb> p.btn.client.object_id => 67170780

Ideally, I'd like these to point to the same object in memory. Rails.cache would serialize things in/out, which really just makes this worse, but I was surprised by this. Could I override find_by_id() or some such in a way that the association proxies would make use of my cache?

Maybe there is another caching module that I'm missing?

(please note that there is no web front end involved in this process. It's all models and ORM)

Answer 1

Try using IdentityCache (see https://github.com/Shopify/identity_cache ). We currently have a similar issue. We're using JRuby because it's fast but mallocs are expensive in our target environment... making cacheing these record instances all the more necessary.

There used to be an IdentityMap within ActiveRecord, but it was removed due to issues with unexpected behaviour around associations.

Just noticed you asked this in August, did you find a good solution?