Hi there. I made a Pull Request to fix bug on ActiveSupport::Cache::MemCacheStore#increment and decrement for initialization of not stored value.
https://github.com/rails/rails/pull/30716 Regarding initialization, the current document says as follows. ``` # Increment a cached value. This method uses the memcached incr atomic # operator and can only be used on values written with the :raw option. # Calling it on a value not stored with :raw will initialize that value # to zero. ``` However, I would rather initialize the value with `amount` for increment and `- amount` for decrement as if the not stored value is initialized to 0 prior to the specified operation. ``` # Before @data.incr(normalize_key(name, options), amount, options[:expires_in], 0) @data.decr(normalize_key(name, options), amount, options[:expires_in], 0) # After @data.incr(normalize_key(name, options), amount, options[:expires_in], amount) @data.decr(normalize_key(name, options), amount, options[:expires_in], -amount) ``` The reason is that we want to implement appropriate lazy initialization. For example, simple counter with lazy initialization can be written with instance variable as follows. ``` def increment(amount) @counter ||= 0 @counter += amount end ``` If we implement the above counter with current ActiveSupport::Cache::MemCacheStore, it can be written as follows. ``` def increment(amount) result = @cache.increment(amount) result != 0 ? result : @cache.increment(amount) end ``` As you can see, the initialization to 0 inside @cache actually does not help us write lazy initialization. We should still handle 0 instead of nil. What is worse, if we use increment and decrement concurrently on the same key, there is no way to calculate the accurate count. With the proposed feature request the above code can be simplified as follows. ``` def increment(amount) @cache.increment(amount) end ``` Also, I have found the same specification on incr of Redis. https://redis.io/commands/incr If the idea is O.K., I will submit another PR or change the current PR to address the issue. IMHO, as this initialization has been disabled for a long time, it is about time to improve the specification. -- Best Regards, Takumasa Ochi -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Core" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-core+unsubscr...@googlegroups.com. To post to this group, send email to rubyonrails-core@googlegroups.com. Visit this group at https://groups.google.com/group/rubyonrails-core. For more options, visit https://groups.google.com/d/optout.
