Difference between local and instance variables in ruby

I am working on a script that creates several fairly complex nested hash datastructures and then iterates through them conditionally creating database records. This is a standalone script using active record. After several minutes of running I noticed a significant lag in server responsiveness and discovered that the script, while being set to be nice +19, was enjoying a steady %85 - %90 total server memory.

In this case I am using instance variables simply for readability. It helps knowing what is going to be re-used outside of the loop vs. what won't. Is there a reason to not use instance variables when they are not needed? Are there differences in memory allocation and management between local and instance variables? Would it help setting @variable = nil when its开发者_如何学Python no longer needed?

An instance variable continues to exist for the life of the object that holds it. A local variable exists only within a single method, block or module body.

If you're assuming objects in your object's instance variables will be garbage-collected just because you don't intend to refer to them in the future, that isn't how it works. The garbage collector only knows whether there's a reachable reference to the object — and there is if it's in an instance variable.

Setting @variable = nil destroys the reference to the object that the instance variable once pointed to. When there are no more remaining references to an object, it should be collected by the garbage collector eventually. I say "eventually" because the GC is somewhat unpredictable. However, it's easy to have a memory leak by a "dangling reference" and possibly (depending on how the GC is implemented) circular references. What else refers to this object?