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Type:
Task
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Resolution: Cannot Reproduce
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Priority:
Major - P3
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Affects Version/s: None
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Component/s: None
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None
Stack: MongoDB 2.6.5, Mongoid 3.1.6, Ruby 2.1.1
To Reproduce:
class User include Mongoid::Document has_many :given_bonuses, class_name: 'Bonus', inverse_of: :giver has_many :received_bonuses, class_name: 'Bonus', inverse_of: :receiver end class Bonus include Mongoid::Document belongs_to :giver, class_name: 'User', inverse_of: :given_bonuses belongs_to :receiver, class_name: 'User', inverse_of: :received_bonuses end
I'm using the following Map/Reduce code:
map = %Q{
function() {
emit(this.receiver_id, this.giver_id)
}
}
reduce = %Q{
function(key, values) {
var result = {};
values.forEach(function(value) {
if(! result[value]) {
result[value] = 0;
}
result[value] += 1;
});
return result;
}
}
Bonus.all.map_reduce(map, reduce).out(inline: 1)
Let's say I have two or more bonus documents:
> Bonus.count => 2 > Bonus.all.to_a => [#<Bonus _id: 547612a21dbe8b7859000071, giver_id: "547612441dbe8bf35b000005", receiver_id: "547612531dbe8b4a7200006a">, #<Bonus _id: 547612a21dbe8b78590000f9, giver_id: "547612441dbe8bf35b000005", receiver_id: "547612531dbe8b4a7200006a">]
Then the Map/Reduce result is:
=> [{"_id"=>"547612531dbe8b4a7200006a", "value"=>{"ObjectId(\"547612441dbe8bf35b000005\")"=>2.0}}]
Notice that the value key points to a hash of the form
{"ObjectID" => Number}. This is as it should be.
Now let's say I have only one bonus document:
> Bonus.count => 1 > Bonus.first => #<Bonus _id: 547612a21dbe8b7859000071, giver_id: "547612441dbe8bf35b000005", receiver_id: "547612531dbe8b4a7200006a">
Then the Map/Reduce result is:
=> [{"_id"=>"547612531dbe8b4a7200006a", "value"=>"547612441dbe8bf35b000005"}]
Notice that the schema of the result has changed. It should be:
=> [{"_id"=>"547612531dbe8b4a7200006a", "value"=>{"ObjectId(\"547612441dbe8bf35b000005\")"=>1.0}}]
What's going on here?
(Reposted here: https://stackoverflow.com/questions/27156262/mapreduce-gives-odd-result-when-count-1)