Ruby on Rails 2.0 is Done

Jamie noted that ruby on rails 2.0 is done. In addition to upgrade and installation instructions, the article lists a number of the more interesting new features in the release which appears to be quite extensive.

Comments

ORM still broken?

[poet]

I wonder if they still disallow proper database design by having a requirement of an autoincrementing number for the primary key.... The Rails developers could learn a thing about databases. Start here: http://en.wikipedia.org/wiki/Database_normalization . Yes I know that a serial/autoincrementing key makes it easy for the app... it makes it a lot harder for the DBA in a lot of cases.

Re:ORM still broken?

[K. S. Kyosuke]

Making the huge mistake that everyone would only ever want to do something your way is how you kill a programming language.

What a relief... As a lisper and rubyist, I'm glad to hear that Python is going to die! Good riddance!

Re:ORM still broken?

[FooBarWidget]

People have discussed this over and over and over again. I presume you're talking about support for composite primary keys. They aren't necessarily a good thing. Go read http://rapidapplicationdevelopment.blogspot.com/2007/08/in-case-youre-new-to-series-ive.html

I don't even consider normalization taken to the extreme, to be a good thing. It's a trade off, just like everything else - what you gain by normalization, you might lose in the form of added application complexity, or perhaps even something else. Just because normalization is "good" according to ivory-tower database theory, doesn't mean that anything that isn't fully normalized is "bad" or "broken".

"Yes I know that a serial/autoincrementing key makes it easy for the app... it makes it a lot harder for the DBA in a lot of cases."

Can you explain what exactly it is that makes it a lot harder? (And isn't a DBA paid to do his job?)

Re:ORM still broken?

[FooBarWidget]

That's great for you, but Ruby on Rails is not - and isn't intended to be - a framework for redundant distributed DB applications. Ruby on Rails is not trying to be the thing for everybody. And that's exactly what makes it so powerful and easy. Indeed - turning it into something for everybody actually makes it worse. I'd like to see some proof that composite primary keys are so important in web applications. So far I've seen no convincing evidence. Despite all the complaints about composite primary keys, new Rails websites are written everything, even by high-profile organizations like IBM, NASA, Oracle and Yahoo. And they seem to function just fine.

If you really, really, really, really need composite primary keys, you can still fallback to raw SQL queries in Rails.

Re:ORM still broken?

[thammoud]

A DBA that uses composite primary keys does not deserve the title. You should never designate a primary key whose value can change. Use business keys for that.

Re:ORM still broken?

[crayz]

If you do a search for "composite keys rails", hit #1 is this, a gem written by a fairly prominent ruby programmer that makes it trivially easy to use composite primary keys within ActiveRecord. My guess is if you actually cared about this issue, rather than just raising it as a canard to bash Rails with, you would have found this solution to your problem and wouldn't be posting here

Re:ORM still broken?

[coryking]

That stored procedure is awesome (well, it actually isn't very good sql, but it doesn't matter right now). As the developer, you just need to worry about passing the monster name and the database spits out everything you want.

If you do most of the logic in your stored procedures, it makes it easy to bolt on new features written in various languages. If you decide to have a perl script for a cron job, you just call the same stored procedures your ruby app is calling. If you want a windows front end for your admin staff, the windows app calls the same stored procedure too.

Once you bury the database logic in the application code, you have to rewrite it for every application. It is, in a way, a very evil form of copy & paste programming. Now every change in the database requires you to go into every single application and change something. Kinda like when you get slutty with your code and copy & paste it rather than abstract it out into a library.

And I'm aware stored procedures don't play nice if you are worried about cross-database issues because you sell the software. This only works when you get complete control over the application & database stack.

PS: MySQL stored procedures suck. Use a real database with a better stored procedure language.

Re:ORM still broken?

[CarpetShark]

A DBA that uses composite primary keys does not deserve the title. You should never designate a primary key whose value can change.

You're assuming that all composite primary keys use values that do change. That's highly unlikely, given the number of tables in the world filled with historical data. That said, I agree (for other reasons) that surrogate keys are much better.

Re:ORM still broken?

[Ilan Volow]

When you as a DBA use anything other than a surrogate primary key, you are making the exceptionally dangerous assumption that the client has the correct understanding of what their model entails, that there will be no exceptions to the rules of that model, and that the model they gave you will never, ever change.

Borrowing from your SSN example, let's say that your client tells you the main way they identify customers is through the SSN, and you go by that, and then there's a case of identity theft and the customer's SSN number has to be changed? Now you've got potentially thousands of records with a bad primary key that you have to change (and mitigate constraint issues as well). What if privacy issues require the company dropping SSN's as an identifier, and now the company will be forbidden from asking customers their SSN's? You'll no longer be able to generate primary keys compatible with the same ones used before.

What truly separates a good DBA from a bad one is the good DBA's ability to anticipate change, design for change, insulate existing stuff from change, and basically save the client from any flaws in their own conceptual model (while making it look like they've followed the client's conceptual model to the letter). A bad DBA simply trusts whatever his client says and believes it to be correct and forever immutable.

Re:ORM still broken?

[Allador]

If the client says that "orders have order items, numbered 1,2,3,4..." then your model should have (ORDER#, LINE#) as the compound key for order items. If the client says "customers are identified by an arbitrary customer number", then it's okay to use an artificial ID. If the client says "customers are identified by SSNs" then that's your key. I hate to feed the cowards, but I just cant let this go.

You are completely incorrect.

If your domain model describes the way an actor finds an entry is by Order# and Line#, that should in no way, shape, or form decree what your technical artifacts look like.

The correct thing to do in that case is to have a unique, opaque, identity key (numeric or guid, just so long as its unrelated to the record data, and has no additional meaning beyond the unique value of that record).

Then you can also add unique constraints or indexes to the composite key, and/or you can enforce that unique constraint in the application. Or both, for the smart ones.

But you need to have a unique way to identify the record THAT IS NOT SUBJECT TO CHANGE. In your example, you could re-order the lines, or one line could have been a mistake and you need to move it to a different order.

If you've used composite keys on order# and line#, then you've got alot of cleanup work to do after your change.

If you've used proper opaque identity keys, then you just change the data, and there are no side effects.

Since in that case your joins are also done on the identity keys, your relatinoships are stable even when you change order# or line#.

The SSN one is even worse. I can guarantee you that if you do that, someone will have the wrong SSN, and it will need to be changed in your data.

If you've used SSN as the primary key, then its a pain in the ass, and you have to do data integrity cleanup.

If you've used a proper opaque identity key, then you just change the SSN, and there are no side effects.

This is stuff you learn the first time you write an app as a junior developer without a mentor, and use SSN as a key. A year or two later you come to regret it, and the lesson is learned for a lifetime.

I don't understand the fuss.

[Russ Nelson]

I don't understand the fuss behind Ruby on Rails. Ruby is a programming language. Rails is a framework. Frameworks are a dime a dozen. Is RoR all that wonderful or are we being marketed-to?

Re:I don't understand the fuss.

[JudicatorX]

You are, or at least so far as hype == marketing.

Re:I don't understand the fuss.

[pestilence669]

"Web guys" will never understand the hype behind RoR. For the average PHP coder, RoR is slower and more restrictive... A hindrance. To a software engineer, however, RoR's great use of design patterns and best practices compliments what they should be doing already. Just as an example, if you're not writing unit tests, then you aren't very serious about your software to begin with. RoR's test facilities will bore you and nag you death. What Rails does is force you to consciously decide to not do something you should probably be doing, like testing. If MVC and encapsulation mean nothing to you, then RoR can't help you much. You still need you own discipline, or you can still write abominable code. RoR embodies many practices from how the big boys write software, few from the basement hackers.

Re:I don't understand the fuss.

[crayz]

Please just try Rails for a little while. While Rails has its flaws, overall it's a highly productive framework - and much of the credit for the terrific code clarity goes to Ruby, which is much more powerful and dynamic than almost any other mainstream language(other than maybe Javascript)

Some things to read about and try within Rails:
* ActiveRecord's ability to introspect the DB schema at runtime. e.g. autocreating the method to allow: User.find_by_name('Joe')
* ActiveRecord's magic-fields, e.g. created_at/updated_at
* the ActiveRecord associations, and the easy DB queries that come with them, e.g. @user.posts.find(:all, :conditions => {:status => 'pending'})
* the scope_out plugin, which provides some nice additions to 'with_scope'. e.g. in the Post model you could do scope_out :pending, :conditions => {:status => :pending}, and then be able to change the previous example to:
@user.posts.pending
* ActiveRecord callbacks and the controller before/after filters
* the RESTful routing and easy links that come with it, e.g. link_to(@user.name, @user) will create a hyperlink to the correct URL for that user record's 'show' page
* the form/field helpers which also integrate with the routing, so you can now do just form_for(@user) - it will create a proper form tag for hitting either the create or update method for that @user, depending on whether the record has already been saved to the database - the form_for/fields_for block syntax is also very powerful, especially when you add your own form helper methods
* all the convenience methods provided by active_support, like 5.minutes or 1.month.ago
* Ruby itself - Ruby is simply a joy to code in. even if I were going to dump Rails, I would now strongly prefer to find a new Ruby framework(like Merb) than using another language

I'd strongly urge you to pick one or more of the PHP MVC frameworks to look at while you read about Rails. Most of them are copies or at least inspired off Rails to some degree, so they often use similar conventions. You'll see the difference between what's possible in PHP and Ruby - PHP doesn't come out looking too good at the end

RRN?

[raftpeople]

Back when I was a young whippersnapper, we called that thing a relative record number!

Sites Moved to Rails?

[markmcb]

OmniNerd.com, a site I do hobby development for, is running on Rails 2.0. We switched over from PHP this fall and site maintenance has been a dream since. Our site has even survived a few Slashdottings and Diggs since the switch, which used to murder it before. (Granted, the PHP code wasn't the best.) I've heard the "doesn't scale" debate a million times, but I'm curious if there is anyone out there who has recently moved a project from one language/framework to Ruby/Rails and whether you're glad you did or if it's been a nightmare. We're a medium-to-low traffic site with big surges every few weeks and it's worked well for us.

Scaling matters if you're Digg. Are you Digg?

[patio11]

While Rails might not be my first framework of choice to implement Digg in, I prefer to build sites which actually, you know, make money by solving problems for paying customers. When you do that, you don't really have to worry about scaling to infinity and beyond, but you do have to worry about expressiveness, maintainability, and time to market. (If you have too many customers relative to servers, heck, easy solution there -- the engineer in me says "just throw up more boxes", but the businessman in me says "pay somebody to worry about it so I can go back to counting my benjamins".)

I have a Rails site, my first (hopefully of many) for my small business, which plugs along at about 20 requests a second in tests. If I could saturate those 20 requests a second, I would quit my day job on the spot. Scaling? Eh, who cares.

(P.S. Day job is writing enterprise level crud apps for Japanese universities on the J2EE stack. They worry a bit about, e.g., getting hit with 8k users signing in simultaneously during class registration. You know what we do? Exactly what I'd do for a Rails app in the same situation ("don't do anything stupid like an n+1 queries loop, cache the important stuff, and buy enough hardware for the job"). Only difference in Rails is I have never wanted to poke my eye out with a spoon while writing it.

Re:Scaling matters if you're Digg. Are you Digg?

[pestilence669]

Ever notice how those most "concerned" about scalability tend to have never profiled or benchmarked their own code? ... or understand why you want to scale horizontally, rather than vertically? Whenever I build services that can handle 120,000 requests/sec., they usually just end up being 99% underutilized. Everyone likes to think THEY will be the next MySpace, with no server budget apparently. I highly doubt that any who argue Rails can't scale has ever had to deal with real distributed clusters. The database cluster will have many more scalablity issues than the webservers. This is such a non-issue, I cannot believe it. If you can scale JAVA!!!... You know what I mean.

Re:You don't have to use ActiveRecord

[Bill, Shooter of Bul]

Yeah, and thats what I don't really like about frameworks in general. They have all of these awesome cool fast easy to use things built in. But sometimes you discover that your needs are too complex for the framework, and someone instantly replies " you don't have to use feature X". Well sooner or later you aren't using many of the cool features of the framework anymore. So why are you using the framework?

I guess they didn't fix the scalability issues

[ThinkFr33ly]

Perhaps a web development framework's web site should be designed in such a way that it can handle a burst of traffic from Slashdot.org and Digg.com.

Otherwise, one might think that RoR doesn't scale.

Re:Scaling matters if you're Digg. Are you Digg?

[slaingod]

Every time a RoR article hits Slashdot, there is a scale/speed question that gets raised. Realistically, there are a ton of things you can do to get performance where you want it to be. The first is to dump mongrel and use FastCGI or similar. FastCGI is 3-5x faster than mongrel. Mongrel is great for low traffic sites, and for dev, don't get me wrong.

The upper limit I see with RoR/FCGI is around 2500 requests per sec, for a 'is the server alive' ping, that simply returns 'Yes'. Typical, results are in the ~100 requests per second range with moderate db access, and rendering to xml or html. 100 requests per second was enough to handle a 24 hour media buy on the frontpage of myspace for example (100,000k unique visitors-ish).

Moving your static assets off of your server and on to S3 or another CDN is obviously a big help here, so your server/bandwidth is only taken up with requests that need/affect the db. From the example above, with the MySpace media buy, the total for that day was $20-30 I believe in bandwidth costs, and this was a site with a video mixer that had tons of images/video/mp3 and large flash objects. Obviously, mongrel shouldn't be delivering your assets locally anyway, apache/lighty etc should be.

Ultimately it comes down to design and caching when it comes to getting that top performance out of it. My 100 requests/sec wasn't using MemCached or fragment caching, and the mysql db was local. Caching in Rails is a little less than helpful for highly customized for each user sites, but there are plugins that extend it like extended_fragment_cache(ing?), that allow you to templatize things like ID's, etc. Think of say a forum topic listing, where only the topics change as you paginate. With extended fragment caching, you basically draw the page once, and then pass in a hash of the variables that replace the placeholders each time you draw a new page.

Another big thing with ajax sites, is to use link_to_remote with the :update => 'some_div', rather than using the rjs/render :update stuff in the controller. escape_javascript is one of the BIG performance issues in Rails, as it is basically just multiple gsubs. Designing around that is a big win. A native C escape_javascript should be a high priority for the rails/ruby devs, with optimization for the memory allocations (ie. scan the string to see how much it will grow, allocate, and just do one pass to expand).

Re:You don't have to use ActiveRecord

[smackjer]

I agree. That's why I build all of my computers by hand with raw transistors and whatnot.

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