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Type:
Bug
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Resolution: Community Answered
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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: None
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Labels:None
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ALL
When inserting a RawBsonDocument that includes duplicated keys, and attempting to exclude said key in a `$project` stage, only the first occurrence of the key is excluded. This appears to be a probable bug.
Tested in the Java driver because the shell doesn't support duplicate keys:
MongoClient client = MongoClients.create("mongodb://mongoUser:hunter1@localhost:37017/?authSource=admin"); RawBsonDocument doc = RawBsonDocument.parse("{a: 5, a: 6, a: 7}"); client.getDatabase("keys").getCollection("fts", RawBsonDocument.class).insertOne(doc); var v = client.getDatabase("keys").getCollection("fts", RawBsonDocument.class) .aggregate(List.of(new BsonDocument("$project", new BsonDocument("a", new BsonInt64(0))))); System.out.println(v.iterator().tryNext());
Results in the output:
{"_id": {"$oid": "659daa98f2c70319473b5206"}, "a": 6, "a": 7}
Or the logically equivalent shell syntax:
keys> db.fts.insert({a: 5, a: 6, a: 7}) # Not supported in shell
keys> db.fts.aggregate({$project: {a: 0}})
[ { _id: ObjectId("659daa98f2c70319473b5206"), a: 6, a: 7 } ]
Tested in version: 7.2.0-rc1
Tested with non-covered $project