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Type:
Task
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Resolution: Done
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Affects Version/s: None
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Component/s: None
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Labels:None
According to the MongoDB documentation, the _id field is returned by default when using projections.
Using version 3.1.5
irb(main):010:0> m = Member.only('email').first MOPED: QUERY database=xxx collection=members selector={"$query"=>{}, "$orderby"=>{:_id=>1}} flags=[:slave_ok] limit=-1 skip=0 batch_size=nil fields={"email"=>1} (1.0500ms) irb(main):011:0> m.attributes => {"_id"=>"5140fcd180fcd02f93000001", "email"=>"x@x.com"}
the id attribute is available
irb(main):012:0> m.id
=> "5140fcd180fcd02f93000001"
Using version 4.0.0beta1
pry(main)> m = Member.only('email').first MOPED: QUERY database=xxx collection=members selector={"$query"=>{}, "$orderby"=>{:_id=>1}} flags=[] limit=-1 skip=0 batch_size=nil fields={"email"=>1} runtime: 0.6460ms pry(main)> m.attributes => {"_id"=>BSON::ObjectId('51350cef9ebea4769b000001'), "email"=>"x@x.com"} pry(main)> m.id ActiveModel::MissingAttributeError: Missing attribute: '_id'.
But now, you must explicitly include 'id' or '_id' in the only call
pry(main)> m = Member.only('email', 'id').first pry(main)> m.attributes => {"_id"=>BSON::ObjectId('51350cef9ebea4769b000001'), "email"=>"x@x.com"} pry(main)> m.id => BSON::ObjectId('51350cef9ebea4769b000001')
The 3.1.5 behavior seems more consistent with what MongoDB is doing in that the id attribute is available by default instead of having to explicitly include 'id' in all calls to only.