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Type:
Bug
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Resolution: Works as Designed
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Priority:
Major - P3
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None
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Affects Version/s: 1.3.3
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Component/s: BSON
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Labels:None
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Environment:ubuntu 18.04
go 1.14
MongoDB server version 4.2.5
Hi,
I've noticed a weird behavior when decoding result to bson.M
for some reason, all the field of the bson.M document are sorted when fetched from a collection. Not sure if the reordering happens during Find or Decode though
go code to reproduce the issue:
package main import ( "context" "fmt" "go.mongodb.org/mongo-driver/bson" "go.mongodb.org/mongo-driver/mongo" "go.mongodb.org/mongo-driver/mongo/options" ) func main() { client, _ := mongo.Connect(context.Background(), options.Client().ApplyURI("mongodb://localhost:27017")) doc := bson.M{ "b": 1, "a": 2, } c := client.Database("test").Collection("collection") c.Drop(context.Background()) c.InsertOne(context.Background(), doc) result := bson.M{} cursor, _ := c.Find(context.Background(), bson.M{}) if cursor.Next(context.Background()) { cursor.Decode(result) } fmt.Printf("%+v", result) client.Disconnect(context.Background()) }
output:
map[_id:ObjectID("5eb498f45f45605b861334f4") a:2 b:1]
expected behavior (mongo shell): the field order should not change
> use test switched to db test > db.collection.drop() true > db.test.insert({"b":1, "a":2}) WriteResult({ "nInserted" : 1 }) > db.test.find() { "_id" : ObjectId("5eb4993ff3c0910e14193d5b"), "b" : 1, "a" : 2 }
the old mgo driver was not changing the field order
This was initially noticed here: mongoplayground.net/p/6--axoMYpDZ