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Mongoid 7.0
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.. default-domain:: mongodb

.. contents:: On this page
   :local:
   :backlinks: none
   :depth: 2
   :class: singlecol

This page describes significant changes and improvements in Mongoid 7.0.
The complete list of releases is available `on GitHub
<https://github.com/mongodb/mongoid/releases>`_ and `in JIRA
<https://jira.mongodb.org/projects/MONGOID?selectedItem=com.atlassian.jira.jira-projects-plugin:release-page>`_;
please consult GitHub releases for detailed release notes and JIRA for
the complete list of issues fixed in each release, including bug fixes.

Please note that improvements that have been backported to Mongoid 6.x are
not included in this list.

The behavior of :ref:`read-only attributes <read-only>` now matches that of
ActiveRecord.

Referenced associations now support all :ref:`dependent behaviors <dependent-behavior>`
that `ActiveRecord supports <http://guides.rubyonrails.org/association_basics.html>`_.

:ref:`$unwind <unwind-dsl>` operator support added to the :ref:`aggregation
pipeline builder DSL <aggregation-pipeline-builder-dsl>`.

``background_indexing`` Mongoid :ref:`configuration option
<configuration-options>` added.

Mongoid 7.0 requires MongoDB server 2.6 or newer, Ruby 2.2.2 or higher and
supports Rails 5.1-6.0.

New in version 7.0.3: Embedded matchers now support the ``$eq`` operator.

New in version 7.0.5: Mongoid now officially supports Rails 6.0.


``set`` Overwrites Complete Document
------------------------------------

**Breaking change:** In Mongoid 7.0.2 and higher, ``set`` fully overwrites
the targeted attributes in the database, including any nested documents
and nested attributes. This behavior matches that of MongoDB ``$set`` operator.
In Mongoid 7.0.1 and lower, ``set`` retained other attributes present in the
database below the document being written:

.. code-block:: ruby

  class Product
    include Mongoid::Document
    
    field :tags, type: Hash
  end
  
  product = Product.new(tags: {color: 'black'})
  product.set(tags: {size: 'large'})
  
  product
  # Mongoid 7.0.2+:
  # => #<Product _id: 62ab9770ce4ef31ac572679c, tags: {:size=>"large"}>
  #
  # Mongoid 7.0.1:
  # => #<Product _id: 62ab9770ce4ef31ac572679c, tags: {:color=>"black", :size=>"large"}>