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Type:
Bug
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Resolution: Done
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Priority:
Minor - P4
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Affects Version/s: 5.0.0
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Component/s: None
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None
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Environment:{OS: "OS X 10.10.5", Rails: 4.1.7, Mongoid: 5.0.0}
Setup
Consider the has_one/belongs_to relation between the Parent and Child classes, noting that the :dependent option is set to destroy:
parent.rb
class Parent include Mongoid::Document has_one :child, :dependent => :destroy field :name, :type => String end
child.rb
class Child include Mongoid::Document belongs_to :parent field :name, :type => String end
Repro Steps
1. Create two Parent instances, p1 and p2
2. Create one Child instance c, assigning p1 as c's parent
3. Re-assign c to p2} (not the same as assigning {{p2 to c)
4. Call #save() on p2 (not the same as calling #save() on c)
4. Note that c is currently in the DB
5. Destroy p1
6. Note that c is no longer in the DB
Rails Console Example
2.2.2 :001 > p1 = Parent.create!(:name => 'Penny') => #<Parent _id: 56f3299e211d7003eb000003, name: "Penny"> 2.2.2 :002 > p2 = Parent.create!(:name => 'Paige') => #<Parent _id: 56f329a4211d7003eb000004, name: "Paige"> 2.2.2 :003 > c = Child.create!(:name => 'Cindy', :parent => p1) => #<Child _id: 56f329a8211d7003eb000005, parent_id: BSON::ObjectId('56f329a4211d7003eb000004'), name: "Cindy"> 2.2.2 :004 > p2.child = c => #<Child _id: 56f329a8211d7003eb000005, parent_id: BSON::ObjectId('56f329a4211d7003eb000004'), name: "Cindy"> 2.2.2 :005 > p2.save! => true 2.2.2 :006 > Child.find(c.id) => #<Child _id: 56f329a8211d7003eb000005, parent_id: BSON::ObjectId('56f329a4211d7003eb000004'), name: "Cindy"> 2.2.2 :007 > p1.destroy! => true 2.2.2 :008 > Child.find(c.id) => nil
Why Does This Need Fixing?
There is at least one workaround for this (e.g. call #save() on c instead of p2). However, I can attest that it can be difficult for developers to detect when this bug has manifested and understand that a workaround is even required.