2009
Give attribute_mapper a try
(For the impatient: skip directly to the `attribute_mapper` gem.)
In the past couple months, I’ve worked on two different projects that needed something like an enumeration, but in their data model. Given the ActiveRecord hammer, they opted to represent the enumeration as a has-many relationship and use a separate table to represent the actual enumeration values.
To a man with an ORM, everything looks like a model
So, their code ended up looking something like this:
class Post < ActiveRecord::Base belongs_to :status end class Status < ActiveRecord::Base has_many :tickets end
From there, the statuses table is populated either from a migration or by seeding the data. Either way, they end up with something like this:
# Supposing statuses has a name column Status.create(:name => 'draft') Status.create(:name => 'reviewed') Status.create(:name => 'published')
With that in place, they can fiddle with posts as such:
post.status = Status.find_by_name('draft')
post.status.name # => 'draft'
It gets the job done, sure. But, it adds a join to a lot of queries and abuses ActiveRecord. Luckily…
I happen to know of a better way
If what you really need is an enumeration, there’s no reason to throw in another table. You can just store the enumeration values as integers in a database column and then map those back to human-friendly labels in your code.
Before I started at FiveRuns, Marcel Molina and Bruce Williams wrote a plugin that does just this. I extracted it and here we are. It’s called attribute_mapper, and it goes a little something like this:
class Post {
:draft => 1,
:reviewed => 2,
:published => 3
}
end
See, no extra table, no need to populate the table, and no extra model. Now, fiddling with posts goes like this:
post.status = :draft post.status # => :draft post.read_attribute(:status) # => 1
Further, we can poke the enumeration directly like so:
Post.statuses # => { :draft => 1, :reviewed => 2, :published => 3 }
Post.statuses.keys # => [:draft, :reviewed, :published]
Pretty handy, friend.
Hey, that looks familiar
If you’ve read Advanced Rails Recipes, you may find this eerily familiar. In fact, recipe #61, “Look Up Constant Data Efficiently” tackles a similar problem. And in fact, I’m migrating a project away from that approach. Well, partially. I’m leaving two models in place where the “constant” model, Status in this case, has actual code on it; that sorta makes sense, though I’m hoping to find a better way.
But, if you don’t need real behavior on your constants, attribute_mapper
is ready to make your domain model slightly simpler.
Just For Fun
This year was my fourth RubyConf. I’ve always come away from RubyConf energized and inspired. But, I’ve yet to follow through on that in a way I found satisfying. I have a feeling I’m not alone in that camp.
This was the first year I’ve given a presentation at RubyConf. At first, I had intended to use this watershed-for-me opportunity to ask whether Ruby was still fun. There’s been a number of “drama moments” since my first RubyConf; I thought it might be worth getting back to my early days of coding with Ruby, when I was exploring and having a great time turning my brain inside out.
As I started researching, it turned out that there are a lot of people having fun with Ruby. Some are doing things like writing games, making music or just tinkering with languages. Others are doing things that only some of us consider fun. Things like hacking on serious virtual machines, garbage collection, and asynchronous IO frameworks.
So, back to my talk. I saw my failure to harness the motivation what I’d seen at previous years at RubyConf as an opportunity to figure out ways to line up some tactics to make sure that after the conference, I was able to create awesome things, contribute them back to the community, and enjoy every minute of it.
Thus, I came up with a sort of “hierarchy of open source developer needs”. At the bottom is enjoyment; there’s little sense doing open source work if you’re not having fun. Once you’re having fun, you probably want to figure out how to find more time for making codes. Once you’re making more codes, you want to figure out how to get people interested in using your stuff. I’ve taken these three needs and identified several tactics that help me when I find myself in a rut or unable to produce. Call them patterns, practices, whatever; for me, they’re just tricks I resort to when the code isn’t flowing like I want to.
The talk I ended up with is equal parts highlighting people in the Ruby community that are having fun and highlight ways to enjoy making things and contributing it back to whatever community you happen to be part of. I hope that I avoided sounding too much like a productivity guru and kept it interesting for the super-technical RubyConf crowd.
If all of this sounds interesting you, grab the slides (which are slightly truncated, no thanks to Keynote) or watch the recording from the conference itself.
I wrote the proposal for this talk right after Why disappeared himself. His way of approaching code is what inspired me to write a talk about getting back to coding for fun. “Just for Fun” starts with a tribute to Why the Lucky Stiff. The sense of fun and playfulness that Why had is important to the Ruby community. I’ve tried to highlight some of his most interesting playful pieces. And in the end, I can’t say “thanks” enough. Why has inspired me a lot and I’m glad I got to meet him, experience him and learn through his works.
Even if you don’t take a look at my presentation, I strongly urge you to give a look at some of Why’s works and let them inspire you. My favorites are Potion and Camping.
Some other things I mentioned in my talk as interesting or fun:
- Greg Borenstein’s code, writings and tumblings
- Project Euler
- Marc-Andre Cournoyer’s codes and book
- Philip Kromer’s Wukung
The Kindle's sweet spot
Given all the hubbub about Kindles, Nooks and their utility, I thought this bears repeating to a wider audience:
The Kindle is great for books that are just a bag of words, but falls short for anything with important visuals.
I’ve really enjoyed reading on my Kindle over the past year. You can’t beat it for dragging a bunch of books with you on vacation or for reading by the poolside. That said, I don’t use it to read anything technical with diagrams or source code listings. I certainly wouldn’t use it to read anything like Tufte, which is exactly why his books aren’t available on the Kindle. Where the Kindle shines is with pop-science books like Freakonomics and Star Wars novels1.
If you love books and reading, the Kindle is a nice addition to your bibliophilic habit, but it’s no replacement for a well-chosen and varied library.
1 Did I say that out loud? Crap.
Testing declarative code
I’m a little conflicted about how and if one should write test code for declarative code. Let’s say I’m writing a MongoMapper document class. It might look something like this:
[sourcecode language=“ruby” gutter=“false”] class Issue
include MongoMapper::Document
key :title, String key :body, String key :created_at, DateTime
end [/sourcecode]
Those key calls. Should I write a test for them? In the past, I’ve said “yes” on the principle that I was test driving the code and I needed something to fail in order to add code. Further, the growing ML-style-typing geek within me likes that writing tests for this is somewhat like constructing my open wacky type system via the test suite.
A Shoulda-flavored test might look something like this:
[sourcecode language=“ruby” gutter=“false”] class IssueTest < Test::Unit::TestCase
context ‘An issue’ do
should_have_keys :title, :body, :created_at
end
end [/sourcecode]
Ignoring the recursive rathole that I’ve now jumped into, I’m left with the question: what use is that should_have_keys? Will it help someone better understand Issue at some point in the future? Will it prevent me from naively breaking the software?
Perhaps this is the crux of the biscuit: by adding code to make certain those key calls are present, have I address the inherent complexity of my application or have I imposed complexity?
I’m going to experiment with swinging back towards leaving these sorts of declarations alone. The jury is still out.
Texas is its own dumb thing
OK, here’s the deal. Wikipedia has it all wrong.
- Texas is not part of the South. Texas is its own unique thing. Sure we have dumbasses, but they are our dumbasses, wholly distinct from your typical Southern dumbass.
- In Texas, the way you refer to “you all” is “ya’ll”; it’s a contraction of “ya all”.
- They neglected to mention the idiomatic pronunciation of words like “oil” (ah-wllllll) or “wash” (warsh).
Please take it under consideration: Wikipedia is edited by a lot of damn Oklahomans.
Curated awesome, the 1st
A bumpy subway wall, loving things for their Unix-y qualities, Kurt Vonnegut looking dapper, the final movement of Dvorak’s Ninth Symphony (originally his fifth), and a music video by Talib Kweli that makes me want to go get my hair cut. Oh, and I can’t leave out the connection between prototyping physical things and applications operating on large data, Ben Scoffield’s take on database taxonomy and a screed on reading one book per week.
(Editor’s note: I recently took to using Tumblr again. For a while, I’ve been curating interesting stuff here. But Tumblr has evolved into a really fantastic application for doing this. So, my policy going forward is to post my stuff here and curate other people’s awesome stuff over there. That said, I’ll probably do “best-of” posts, like this one, to keep you interested and informed.)
Chance Encounter
Another meme-ish “film” by yours truly. This time, the idea is you do something in five seconds, plus a two second intro and a one second outro. Here’s what I came up with:
This is an adaptation of possibly my favorite improvised joke. I deploy this joke when a conversation is interrupted by some disturbance or noisy distraction. Right before the conversation is going to continue, I say “…and that’s how I met the president and the pope on the same day.” Works pretty well.
Funny aside: I found out about this on the Vimeo site, thinking there was a competition this weekend. Turns out, it was last weekend. Figures.
Birthing Born to Run
The birth of Born To Run. On the creation and evolution of the song and album. Great read for Bruce-o-philes.
Representing time in our programs
The time problem is not easy to see in today's mainstream languages because there are no constructs that make time explicit. It is implicit in the system. We don't even know that's what we're doing when we use locks to try to make this work.
I’ve been thinking about how we represent time in programs for a while. The problem is that concurrent programs are all about time, but mostly, we only use two mechanisms to represent it in our programs.
The semi-explicit way is through locks. When we insert locks around some bit of code, we are giving hints to the system that things should only proceed in a certain order. This ordering gives us a notion of time, but it’s not horribly comforting.
The completely implicit way we represent time in our programs is by ordering calls to functions and the lines of code within those functions. Line 10 always executes before line 11, etc.
The problem that Rich Hickey, who has some fantastic ideas about this time stuff, has in the article I quoted is that time is managed manually and implicitly. When you start writing large concurrent programs, this falls apart. We need better constructs to deal with it.
Think of it like the shift from unstructured programming to structured programming to object-oriented programming. At first we just had a long code listing; no functions, just line after line of code. This became mentally untenable, so we shifted to structured, procedural programming. But some of our data was global and it was often hard to tell what functions belong to what data. So we moved to object-oriented programming and encapsulation.
Hopefully Rich Hickey, Simon Peyton-Jones and other functional programming folks can lead us to is a nice way to structure our programs around time. I’m eager to have my brain melted by what they conjure up.
Ain't talkin' 'bout the man
Here’s a fun game. “The Government”:
Try something. Every time somebody complains about the evils or failings of “the government,” strike out “the government” and see what results.
Often, simply striking out “government” reveals a completely different, and far more useful, commentary.
Polyglottin' your data
I think that many of the NoSQL crowd either fail to either recognize, or to properly describe that their preferred databases don’t replace applications like MySQL and Postgres, just as Ruby doesn’t replace Java. Instead, the explosion of these new options for persistence just work better for some domains (and worse for others).
Ben Scofield’s spot-on here. One of the many transitions we’re undergoing is from “I’ll use MySQL most of my career” to “I’ll tinker with a different database for every project over a couple years and then pick and choose the best as time goes on”.
Tons of FP fun
A programming language zoo, a week of FP heaven, rewriting PHP with Haskell and a game for kids of any age to learn the untyped lambda calculus. Did I ever mention it’s a good time to have a fascination with functional programming languages?
iPod Spaceman
(With due apologies to the creators of New Math, the writers of 30 Rock and the lovely iPod people.)
On American political insanity
Still crazy after all these years:
Politicians should tone down the rhetoric. Protesters should read some history before making Hitler comparisons. Talk-show hosts should stop pretending that paranoid nitwits are asking reasonable questions.
The Economist does well to explain the insanity that is propagated by American political media. Reading articles like this help me stay sane. Also: ignoring media with deadlines shorter than a week, and consuming as much constructive satire as possible.
It's not NoSQL, it's post-relational
Almost five years ago, we were witness to the reinvention of web frameworks. A couple upstarts named Django and Rails appeared at almost the same time, espousing many of the same values. In the typical Gandhi-cycle, they were first ignored, the incumbents fought them, and then they achieved victory over the incumbents. Today, any framework that’s used on new projects is likely to have more than a hint of Django and Rails in it.
Today, we’re seeing the same thing for databases. Something is going on and things are changing. Barring an unprecedented departure of fashion from software development, I’ll look back five years from now and write about some other shift in the development landscape.
But, all shifts like this need a name. Right now, the best we have is NoSQL. The problem with that name is that it only defines what it is not. That makes it confrontational and not amazingly particular to what it includes or excludes.
Damien Katz, the creator of CouchDB, has noted the need for a better name for this storage revolution. Allow me to proffer mine:
Post-relational
What we’re seeing its the end of the assumption that valuable data should go in some kind of relational database. The end of the assumption that SQL and ACID are the only tools for solving our problems. The end of the viability of master/slave scaling. The end of weaving the relational model through our application code.
We’re seeing an explosion in the ideas about how one should store important data. We’re looking at data to see if it’s even worth persisting. We’re experimenting with new semantics around structure, consistency and concurrency.
In the same way that post-modernism is about reconsidering the ways of the past in art and architecture, post-relational is a chance for software developers to reconsider our own ways. Just as post-modernism didn’t invalidate the entire history of art, post-relational won’t invalidate the usefulness of relational databases.
However, it’s likely that those working in some domains will decide that non-relational databases better fit their needs. That’s progress in our field. It’s fun to watch.
Say it with me: post-relational databases, post-relational storage, post-relational thinking, or simply, post-relational.