# Turning N+1 queries into 1
for post in Post.find(:all, :include => [ :author, :comments ])
   puts "Post:            " + post.title
   puts "Written by:      " + post.author.name
   puts "Last comment on: " + post.comments.first.created_on
end

Read more:  
http://ar.rubyonrails.com/classes/ActiveRecord/Associations/
ClassMethods.html (Scroll down to Eager loading of associations)

And to match the eager loading, we're introducing a brand new unified  
API for Base.find, which works the same whether you're searching for a  
specific id, the first record, or all the records. By using named  
options we alleviate your poor brain for remembering whether the  
ordering option was argument number 3 or 4.

Person.find(1, :conditions => "administrator = 1", :order =>  
"created_on DESC")
Person.find(1, 5, 6, :conditions => "administrator = 1", :order =>  
"created_on DESC")
Person.find(:first, :order => "created_on DESC", :offset => 5)
Person.find(:all, :conditions => [ "category IN (?)", categories],  
:limit => 50)
Person.find(:all, :offset => 10, :limit => 10)

Read more:  
http://ar.rubyonrails.com/classes/ActiveRecord/Base.html#M000226

Better testing
--------------
We've also slashed the huge number of assertions for testing  
controllers. In one fell swoop, we've gone from around thirty to a shap  
seven. The remaining assertions are more flexible than before, not  
nearly as hard to remember, and are followed on by the fantastic new  
assert_tag, which makes examining the HTML output of an action so much  
easier than the XHTML/REXML fumblings of yesterday.

Read more: http://ap.rubyonrails.com/classes/Test/Unit/Assertions.html

More Ajaxing
------------
Of course, we couldn't make a new release without asserting the  
undisputed position as the number one framework for doing Ajaxed  
applications. This release contains a bunch of new smooth effects  
(http://mir.aculo.us/demos/effects/demo1.html) for visualizing your  
non-refreshing actions. It's now much easier to make Ajaxed  
applications that treat the unfortunate without Javascript nicely with  
request.xml_http_request? and alternative targets for ajax links and  
forms. We've also added periodically_call_remote that can be used to  
Ajax-update a given block every so seconds.

In the next release, which will be not very far off, we're also adding  
awesome support for both Google Suggest-like search boxes and for  
upload progress indicators (http://sean.treadway.info/demo/upload).  
There's a powerful team behind pushing the envelope on this. We have so  
not seen the end of it.

A total of 96 changes, tweaks, and fixes
----------------------------------------
All these goodies are just the tip of the iceberg, though. There's a  
total of 96 new features, changes, tweaks, and fixes packed into this  
monster of a release. And we didn't even have time to push in all of  
the pending patches (http://dev.rubyonrails.com/report/3). How's that  
for an action-packed three weeks since the last release?

Fully backwards compatible!
---------------------------
Despite the true onslaught of new features, fixes, and goodies, we've  
managed to keep this release fully backwards compatible with 0.11.1. So  
you just do a "gem update rails" and all the new stuff is available for  
use in your current application (to take advantage of the new JS  
effects you'll want to copy that one over, though -- use rails . in  
your app dir to get that for free).

See the changelogs for the full story: