September 8th, 2008
Simplified finders in DataMapper
It seems I’m spending lots of time reading about DataMapper currently, while planning the first refactoring of Ribs. While reading I keep seeing Sam’s examples of simplified finders compared to the ActiveRecord versions. A typical example of the kind of thing I’m talking about is something like this with ActiveRecord:
Exibition.find(:all, :conditions => ["run_time > ? AND run_time < ?", 2, 5])
Which with DataMapper would be:
Exibition.all(:run_time.gt => 2, :run_time.lt => 5)
Oh, and yeah, it the typo is directly from the DataMapper documentation. So what’s wrong here? Well, in most cases it probably does exactly what you want it too. And that’s the problem in itself. If you use these simplified finders with more than one argument, you will get subpar SQL queries in some cases. Simply, if you don’t control the order of the clauses separated by AND, you might get queries that perform substantially worse than they should. Of course, that doesn’t happen often, but it’s important to keep it in mind.
And incidentally, I really do hate the methods added to Symbol.
