From: "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>
Date: 2013-02-06T23:58:44+09:00
Subject: [ruby-core:51922] [ruby-trunk - Feature #7792] Make symbols and strings the same thing


Issue #7792 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


I'd just like to highlight what performance impact we may be referring to:

https://gist.github.com/rosenfeld/4723061

I'll copy it here:

require 'benchmark'
 
hashes = []
1_000_000.times { hashes << { some_key_name: 1, 'some_key_name' => 2 }}
Benchmark.bmbm do |x|
  x.report { hashes.map{|h| h[:some_key_name]} }
  x.report { hashes.map{|h| h['some_key_name']} }
end

Result:

ruby symbols-performance.rb 
Rehearsal ------------------------------------
   0.540000   0.010000   0.550000 (  0.543421)
   0.680000   0.020000   0.700000 (  0.705931)
--------------------------- total: 1.250000sec
 
       user     system      total        real
   0.240000   0.000000   0.240000 (  0.244554)
   0.380000   0.000000   0.380000 (  0.391517)

Does this small hit in performance worth all the hassle that it is to have to differentiate symbols from strings?
----------------------------------------
Feature #7792: Make symbols and strings the same thing
https://bugs.ruby-lang.org/issues/7792#change-35921

Author: rosenfeld (Rodrigo Rosenfeld Rosas)
Status: Open
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: Next Major


Recently I had to replace several of my symbols to plain strings in my project. Here is what happened:

I generated some results with some class that would add items to an array like this:

results << {id: 1, name: 'abc'}

Then I would store such results in cache using Redis, encoded as a JSON string. But then when I restore the data from cache the hash will be {'id' => 1, 'name' => 'abc'}.

This wasn't a problem until recently because I never used the results directly in the same request before and would always use the value stored on Redis and parsed by JSON.

But recently I had to use the values directly in a view. But then I had a problem because I would have to use symbols in the results for the first time and strings the next times when the result was available on cache. I really don't want to care about memory management in Ruby if possible and symbols forces me to abandon the new sexy hash syntax many times. Now I have to write

results << {'id' => 1, 'name' => 'abc}

when I'd prefer to write

results << {id: 1, name: 'abc}

This is not the first time I had a bad user experience due to symbols being different from strings. And I'm not the only one or ActiveSupport Hash#with_indifferent_access wouldn't be so popular and Rails wouldn't use it all the time internally.

It is really bad when you have to constantly check how you store your keys in your hashes. Am I using symbols or strings as keys? If you use the wrong type on plain hashes you can find a bad time debugging your code. Or you could just use Hash#with_indifferent_access everywhere, thus reducing performance (I guess) and it is pretty inconvenient anyway.

Or if you're comparing the keys of your hash in some "each" closure you have to worry about it being a symbol or a string too.

Ruby is told to be programmers' friendly and it usually is. But symbols are certainly a big exception.


-- 
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