在golang mongodb中过滤

Question

Currently I learn to create restful api with golang and mongodb. Actually I am beginner in both. I use mongodb-go-driver and I learn to use filter when we want to use find() function. But I have some that I don't understand. What is the different between filter := bson.M{"_id": "abcd"} and filter := bson.M{{"_id": "abcd"}}? Thank you

Answer 1

Refer to the source code, https://github.com/mongodb/mongo-go-driver/blob/master/bson/primitive/primitive.go

bson.D, internally is primitive.D, which is []primitive.E, which is a struct. bson.M, internally is primitive.M, which is map[string]interface{}. You put in key/value in bson.M but use document (struct) in bson.D.

It is better to explain it using 2 parameters, e.g. search for a = 1 and b = 2. You syntax will be: bson.M{"a": 1, "b": 2} or bson.D{{"a": 1}, {"b": 2}}