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  1. Mongoid
  2. MONGOID-1549

HABTM relations return docs in the wrong order

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      If you have a HABTM relation, Mongoid retrieves the related documents in the wrong order.

      This is because the $in operator is used, which causes the related documents to be sorted by using MongoDB's natural order .

      I'd expect the documents to be returned in the order that their IDs are stored in.

      This was originally reported in MONGOID-248, and fixed in rc.1 , but seems to have regressed since then.

      Here's an example that shows the bug:

      class Post
  include Mongoid::Document

  has_and_belongs_to_many :tags
end

class Tag
  include Mongoid::Document

  field :name, :type => String

  has_and_belongs_to_many :posts
end

Post.delete_all
Tag.delete_all

t1 = Tag.create :name => 'T1'
t2 = Tag.create :name => 'T2'
t3 = Tag.create :name => 'T3'
t4 = Tag.create :name => 'T4'

p = Post.create :tag_ids => [t2.id, t4.id, t1.id, t3.id]
p.reload

# The tags' order in the "tag_ids" field:
p.tag_ids.map {|id| Tag.find(id).name}
=> ["T2", "T4", "T1", "T3"]

# The tags' order from the "tags" relation:
p.tags.map(&:name)
=> ["T1", "T2", "T3", "T4"]

            Assignee:
            Unassigned Unassigned
            Reporter:
            nickh Nick Hoffman
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              Created:
              Updated:
              Resolved: