Details
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Bug
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Status: Closed
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Major - P3
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Resolution: Works as Designed
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5.0.9
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None
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None
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None
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ALL
Description
db.test.insert({ a: 'a' });
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db.test.aggregate([{ $addFields: { result: { $getField: { field: { $concat: ['$a', 'a'] }, input: { aa: 1 } } } } }]);
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This leads to:
MongoServerError: Invalid $addFields :: caused by :: $getField requires 'field' to evaluate to a constant, but got a non-constant argument
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I don't understand why that happens (and believe it's a bug). According to getField's documentation `field` can be any expression that resolves to a string. In my example it is such but it doesn't work.