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Type:
Improvement
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Resolution: Unresolved
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Priority:
Major - P3
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None
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Affects Version/s: None
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Component/s: JavaScript
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Query Optimization
As you can see below - it just happens to return an empty object, but proceeds without error. It seems better to either (a) error or (b) return an array. We don't have a 'set' data type in the BSON spec, so I don't see how we could get it to work and round trip seamlessly, but this experience isn't great.
> db.foo.aggregate([{
$project: {
js_res: {
$function: {
lang: "js",
body: function() {
return new Set([1, 2]);
},
args: []
}
}
}
}])
{ "_id" : ObjectId("5f3c24f10efd1cb7f0a88f4a"), "js_res" : { } }
{ "_id" : ObjectId("5f3c24f60efd1cb7f0a88f4b"), "js_res" : { } }
{ "_id" : ObjectId("5f47f9411945d1527c6b0368"), "js_res" : { } }
{ "_id" : ObjectId("5f47f9c71945d1527c6b0369"), "js_res" : { } }
{ "_id" : ObjectId("5f47fa721945d1527c6b036a"), "js_res" : { } }
As a workaround, you can use the [...set] syntax to expand the set into an array:
> db.foo.aggregate([{
$project: {
js_res: {
$function: {
lang: "js",
body: function() {
return [...new Set([1, 2])];
},
args: []
}
}
}
}])
{ "_id" : ObjectId("5f3c24f10efd1cb7f0a88f4a"), "js_res" : [ 1, 2 ] }
{ "_id" : ObjectId("5f3c24f60efd1cb7f0a88f4b"), "js_res" : [ 1, 2 ] }
{ "_id" : ObjectId("5f47f9411945d1527c6b0368"), "js_res" : [ 1, 2 ] }
{ "_id" : ObjectId("5f47f9c71945d1527c6b0369"), "js_res" : [ 1, 2 ] }
{ "_id" : ObjectId("5f47fa721945d1527c6b036a"), "js_res" : [ 1, 2 ] }
- is related to
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SERVER-34281 ES6 arrow functions (lambdas) do not work with map-reduce
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- Closed
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-
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- Backlog
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- Closed
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- Closed
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- related to
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DOCS-13861 JS objects like 'Set' do not work well in user-defined JS like $accumulator
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- Closed
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