[ruby-core:51995] Re: [ruby-trunk - Feature #7797] Hash should be renamed to StrictHash and a new Hash should be created to behave like AS HashWithIndifferentAccess

Em 07-02-2013 13:51, Yorick Peterse escreveu:
> ...
>> And for the performance argument I really believe symbols cause more
>> harm than good to the overall performance given all conversions that
>> it will require in most code bases (even if you don't do that directly
>> it is likely that you rely on some gem that will do that).
>
> I'd be interested in seeing the actual numbers for this. I also find it
> interesting to see that your general opinion seems to be "the
> performance overhead of this change is not important" yet you do seem to
> care about the overhead of converting Symbols to Strings. I find this a
> rather contradicting opinion but maybe I'm misunderstanding things.

https://gist.github.com/rosenfeld/4732737

So, if your program relies on HWIA behavior and is converting regular 
hashes into HWIA, it would perform much worse then if the hash syntax 
already created HWIA. Also libraries like Sequel will call to_sym on 
string values returned from the database as column names. Then the 
overall performance would be slower due to unnecessary conversions 
between symbols and strings that wouldn't be required if regular hashes 
behaved like HWIA.

And this is just a simplistic case. What if I had to scan an entire 
random object resulted from a call to JSON.parse and find all hashes to 
manually replace them by a HWIA version?

This is way more common than you might expect in lots of gems and code 
out there. That is why I believe that the overall performance of most 
Ruby code in the real-world industry have their performance degraded by 
the existence of symbols and by them returning false when compared to 
equivalent strings.

> ...
> On another note, you also seem to be unaware that it's not trivial to
> suddenly replace the usage of Hash with LazyDeveloperHash. Yes, in the
> Ruby source code it might be easier but at least in the C code it's
> going to take time and effort for something that has little value.

You're saying that it has little value. What if someone decides that he 
would like to spend his (not yours) time making the required changes in 
the C code? Would this problem be gone?

> In your other threads I gave you various examples on how you can work
> around your issue

You didn't understand the issue. I showed you a real example where you 
could show me how to optimize it but you haven't done so:

https://bugs.ruby-lang.org/issues/7792#note-23

You just assumed that Sequel took the wrong decision while deciding for 
using symbols as keys instead of strings. Jeremy Evans (Sequel's 
maintainer) doesn't seem to support your opinion on that and explains 
why he thinks Sequel should keep using symbols as keys.

But this is a real gem used in a real-world application published in the 
web. And this application would not only be easier to write and maintain 
if hash syntax created HWIA but this app would also perform better.