Question

Is it a good idea to warm up cache in the BEGIN block, when it gets used?

Answer 1

You didn’t really provide any information on what kind of environment you’re talking about, which I think is important. In most cases the answer is probably “no”, but I can think of one case where it’s a definite yes, which is preforking servers — web applications and the like. In that case, any work that you can do “before the fork” not only saves the cost of having the children recompute the same values individually, it alo saves memory, since the pages containing the results can be shared across all of the child processes by the OS’s COW mechanism.

If you’re talking about a module you’re writing and not an application, then I’d say no, don’t lift things to compilation time without the user’s permission unless they’re things that have to be done for the module to work. Instead, provide a preheat_cache class method, and if your caller has a reason to need a hot cache at compile time they can put the call into a BEGIN block themselves. You could also use a :preheat_cache import tag but that’s unnecessarily fancy in my book.