From: Stephen Sykes <sdsykes@...>
Date: 2009-08-08T04:44:07+09:00
Subject: [ruby-core:24809] Re: [Feature #1906] Kernel#backtrace: Objectifying 	Kernel#caller

>
> Rationale
> =========
>
> `caller` has two principle uses:
>
> * Allowing users to display the backtrace at a given point, e.g. `puts caller`.
> * Introspection to determine the callpath that lead the current method.
>

Yes we use exactly this kind of introspection when optimising SQL
queries in scrooge (
http://github.com/methodmissing/scrooge/tree/master ).

For our purposes we need to determine if one backtrace is different
from another - we want to make sure that we optimise each callsite
from user code individually.

Storing and comparing the output of caller is not ideal for this -
those arrays of strings can get large.  Currently we hash the top 11
items in the list and store the hash as a signature.  But even so
dozens (or however deep the stack is) of strings must be created each
time by caller anyway - it's not terribly fast.

What would be most advantageous to us would be if Backtrace#hash were
added, and generated a hash faster without having to create so many
strings as is the current case.

-Stephen