Interesting Things
find_in_batches has Evil Scopiness
ActiveRecord::Base#find_in_batches() (and therefore #find_each()) is applying a scope around the block it is given, which applies to any subsequent find call on that model:
Let's say we have a Comment model that act_as_tree so comments can be threaded. In the following code:
Comment.find_each(:conditions => "comments.state = 'published'") do |comment|
puts comment.parent.content
end
The association call to .parent will also have the scope {:conditions => "comments.state = 'published'"} applied to it. This can have highly unexpected side-effects.
The way to get around this is:
Comment.find_each(:conditions => "comments.state = 'published'") do |comment|
Comment.with_exclusive_scope(:find => {}) do
puts comment.parent.content
end
end
Easy Ruby profiling
If you're profiling Ruby code often, here's a code snippet that can be useful:
STDOUTalways points to the file handle that stdout had when ruby was started. Use$stdoutinstead, which allows people to redirect standard output at runtime, which is very useful for e.g. tests, or running a server inside a server.More details at http://blog.segment7.net/articles/2006/08/17/stdout-vs-stdout and http://www.ruby-forum.com/topic/178044#779619.
For example, I use this function a lot in tests, either to assert that a method outputs something, or just to suppress it: http://gist.github.com/514760
Of course, since you are outputting profile information, you may want it to always go to the console (original
STDOUT), no matter what the value of$stdout, even in a test. In which case, nevermind :-)