update_all

For example: having two models, User and Message (user has_many messages, each message has a boolean flag called 'read'). You want to mark all messages as read for a particular user.

==== Mark all messages as read for a particular user

Message.update_all({:read => true}, {:id => user.messages})

The examples are unfortunate, because passing a string as the updates argument is an invitation to SQL injection attacks. Don't do this!

Billing.update_all("author='#{author}'")

Use the hash form of updates instead:

Billing.update_all(:author => author)

Then the SQL adapter will quote everything safely. Even if [you think] you're sure there's no quoting issue, it's better to cultivate the habit of using the hash form just in case you missed something.

Same with conditions--use the hash or array form rather than a string if there are variables involved.

BTW, to do this and give options, of course you'll need to put the braces back in:

Billing.update_all({:author => author},
                 ['title like ?', "#{prefix}%"])

If you use update_all to change an attribute marked as serialized ( using ActiveRecord::Base.serialize ), you need to call to_yaml yourself:

User.update_all({ :preferences => { :first_name => 'John', :last_name => 'Doe' }.to_yaml })

If you have

class Topic < ActiveRecord::Base
default_scope :conditions => "forums.preferences > 1", :include => [:forum]
end

and you do a

Topic.update_all(...)

it’ll fail with

Mysql::Error: Unknown column 'forums.preferences' in 'where clause'

The work around for this is:

Topic.send(:with_exclusive_scope) { Topic.update_all(...) }

You can monkey patch this using this code (and requiring it in environment.rb or else where)

module ActiveRecordMixins
class ActiveRecord::Base
  def self.update_all!(*args)
    self.send(:with_exclusive_scope) { self.update_all(*args) }
  end
  def self.delete_all!(*args)
    self.send(:with_exclusive_scope) { self.delete_all(*args) }
  end
end
end
end

Then just you update_all! or delete_all! when it has a default scope.

If you're on Rails 3, you should look into http://apidock.com/rails/ActiveRecord/Relation/update_all

I would like to point out that if you are on rails 2.3.11 or lower you will not be able to run ledermann code.

==== Ledermann Code user.messages.update_all(:read => true)

If you are running 2.3 or later it you will have to use James code

==== James Code

Message.update_all({:read => true}, {:id => user.messages})

thanks guys for all the code help

With enum fields you must use integer values: ==== code Model.update_all(type: Model.types[specific_type])

update_all : skip validations, and will save the object to the database regardless of its validity. They should be used with caution.