go.mongodb.org/mongo-driver 是mongo的golang官方包 通过例子我知道连接是这样的
clientOptions := options.Client().ApplyURI("mongodb://tag:[email protected]:27017/tag") client, err := mongo.NewClient(clientOptions) if err != nil { fmt.Println(err) } ctx, _ := context.WithTimeout(context.Background(), 2*time.Second) err = client.Connect(ctx) err = client.Ping(ctx, readpref.Primary()) //tag := UserTag{ // Rid: 1, // Aid: "aid", // Uqid: "", // Values: map[string]string{"1": "a", "2": "b"}, //} collection := client.Database("tag").Collection("usertag") ctx, _ = context.WithTimeout(context.Background(), 5*time.Second) t := UserTag{} //db,usertag.find({$or :[{‘rid‘: 1},{‘aid‘: ‘‘},{‘uqid‘: ‘‘}]}); //err = collection.FindOne(ctx,bson.M{"$or": bson.A{bson.M{"rid":1},bson.M{"aid":"a"}}}).Decode(&t) err = collection.FindOne(ctx,map[string]interface{}{"$or":[]interface{}{map[string]interface{}{"rid":1}}}).Decode(&t) if err != nil { fmt.Println(err) return } fmt.Println(t)
所有的find方法都有一个filer参数, 等同于命令行里的
db.usertag.find({$or :[{‘rid‘: 1},{‘aid‘: ‘‘},{‘uqid‘: ‘‘}]});
但是在代码的实现例filter并不能写成这样
filter := `{$or :[{‘rid‘: 1},{‘aid‘: ‘‘},{‘uqid‘: ‘‘}]}`
这样是不识别的, 我们需要用到bson里提供的几种结构体
type D = primitive.D // E represents a BSON element for a D. It is usually used inside a D. type E = primitive.E // M is an unordered representation of a BSON document. This type should be used when the order of the elements does not // matter. This type is handled as a regular map[string]interface{} when encoding and decoding. Elements will be // serialized in an undefined, random order. If the order of the elements matters, a D should be used instead. // // Example usage: // // bson.M{"foo": "bar", "hello": "world", "pi": 3.14159} type M = primitive.M // An A is an ordered representation of a BSON array. // // Example usage: // // bson.A{"bar", "world", 3.14159, bson.D{{"qux", 12345}}} type A = primitive.A
其中M是map A是列表
所以我们的filter就构造成这样的
filter := bson.M{"$or": bson.A{bson.M{"rid":1},bson.M{"aid":"a"}}}
我们再去看M,A底层数据结构是什
// M is an unordered representation of a BSON document. This type should be used when the order of the elements does not // matter. This type is handled as a regular map[string]interface{} when encoding and decoding. Elements will be // serialized in an undefined, random order. If the order of the elements matters, a D should be used instead. // // Example usage: // // bson.M{"foo": "bar", "hello": "world", "pi": 3.14159}. type M map[string]interface{} // An A is an ordered representation of a BSON array. // // Example usage: // // bson.A{"bar", "world", 3.14159, bson.D{{"qux", 12345}}} type A []interface{}
所以我们的filter也可以写成这样
filter := map[string]interface{}{"$or":[]interface{}{map[string]interface{}{"rid":1}}}
所以我们就可以对照mongo命令文档转成golang代码里的filter了
原因在与mongo底层的通信都是bson(二进制json), 没办法识别字符串, mongo命令行识别是因为client基于json字符串为基础, 去转换成bson格式了
原文地址:https://www.cnblogs.com/leescre/p/12625240.html
时间: 2024-10-31 09:55:55