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document AR::Base#with_lock in release notes [ci skip]

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1 parent 01d041a commit 1944cbbbe5a49bc6a0644d30c0464d1850cdca64 @vijaydev vijaydev committed Jan 19, 2012
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27 railties/guides/source/3_2_release_notes.textile
@@ -373,6 +373,33 @@ has_many :clients, :class_name => :Client # Note that the symbol need to be capi
User.where(:first_name => "Scarlett").first_or_create!(:last_name => "Johansson")
</ruby>
+* Added a <tt>with_lock</tt> method to Active Record objects, which starts a transaction, locks the object (pessimistically) and yields to the block. The method takes one (optional) parameter and passes it to +lock!+.
+
+This makes it possible to write the following:
+
+<ruby>
+class Order < ActiveRecord::Base
+ def cancel!
+ transaction do
+ lock!
+ # ... cancelling logic
+ end
+ end
+end
+</ruby>
+
+as:
+
+<ruby>
+class Order < ActiveRecord::Base
+ def cancel!
+ with_lock do
+ # ... cancelling logic
+ end
+ end
+end
+</ruby>
+
h4. Deprecations
* Automatic closure of connections in threads is deprecated. For example the following code is deprecated:

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