if $props does not exists it should return blank array instead null value how can we fix it
db.collection.aggregate([
{
"$group": {
"_id": "$prop3"
}
}
])
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John
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Can you please [edit] your question to include the input documents and the expected output? – chridam Apr 14 '22 at 13:31
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please check the fiddle $prop3 does not have value it should return [] insread [ { "_id": null } ] – John Apr 14 '22 at 13:40
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From the marked answer in the duplicate `db.collection.aggregate([{$match:{prop3:{$exists:true,$ne:null}}},{$group:{_id:'$prop3'}}])` [Mongo Playground](https://mongoplayground.net/p/X5xX0VqONq3) – chridam Apr 14 '22 at 13:45