mgo-减少更新并仅查找一个查询

Question

I find myself having to write two db queries and I would like to know whether it's possible to reduce to one.

I am updating a document and then finding the document again in the database. Is it possible to update and receive the full updated document in the response of the update query? This would save a call to the db.

I should explain that the document I'm saving won't be a complete document which is why I'm having to retrieve it from the database to get all the fields.

Answer 1

Yes, it is possible. Please have a look at the documentation of the Query.Apply method, which runs the findAndModify MongoDB command.

Straight from the documentation, this example increments a counter and prints its new value:

change := mgo.Change{
        Update: bson.M{"$inc": bson.M{"n": 1}},
        ReturnNew: true,
}
info, err = col.Find(M{"_id": id}).Apply(change, &doc)
fmt.Println(doc.N)