I'm trying to insert some data in MongoDB using mgo but the outcome is not what I wanted.
My struct
type Slow struct {
Endpoint string
Time string
}
My insert statement
err := collection.Insert(&Slow{endpoint, e})
if err != nil {
panic(err)
}
How I'm trying to print it
var results []Slow
err := collection.Find(nil).All(&results)
if err != nil {
panic(err)
}
s, _ := json.MarshalIndent(results, " ", " ")
w.Write(s)
My output (Marshaled JSON)
[{
"Endpoint": "/api/endpoint1",
"Time": "0.8s"
},
{
"Endpoint": "/api/endpoint2",
"Time": "0.7s"
}]
What I wanted
{
"/api/endpoint1":"0.8s",
"/api/endpoint2":"0.7s"
}
//No brackets
Thank you.
First, you seem to want the results sorted by Endpoint. If you don't specify any sort order when querying, you can have no guarantee of any specific order. So query them like this:
err := collection.Find(nil).Sort("endpoint").All(&results)
Next, what you want is not the JSON representation of the results. To get the format you want, use the following loop:
w.Write([]byte{'{'})
for i, slow := range results {
if i > 0 {
w.Write([]byte{','})
}
w.Write([]byte(fmt.Sprintf("\n\t\"%s\":\"%v\"", slow.Endpoint, slow.Time)))
}
w.Write([]byte("\n}"))
Output is as you expect it (try it on the Go Playground):
{
"/api/endpoint1":"0.8s",
"/api/endpoint2":"0.7s"
}
Related
This is function that tries to update the code matching by its value
the res collection as having the code of Marque it will be compared with doc.Marque if it is the case it will be replaced by the value of the marque.
This code is working perfectly in mongoDB CLI, but as i am working with GO.
I tried to convert it into mgo as you may see below but it is not working , i did not find the foreach function in mgo , is there something to be replaced with in this case ? thanks for the help
db.res.find().forEach(function(doc){
var v = db.brands.findOne({code: doc.Marque});
if(v){
db.res.update({"Marque": doc.Marque},
{$set: {"Marque":v.value}}, {multi: true});
}
});
Here is what i tried :
result:=Results{}
pipe:=res.find(bson.M{}).Iter()
for pipe.Next(&result) {
brands:=brands.findOne({code: doc.Marque});
if(v){
pipe.update({"Marque": doc.Marque},
{$set: {"Marque": v.value}}, {multi: true});
}
}
Visit the mgo Godoc may help you understand how it works.
Second, exported types/functions in Golang are begin with a capital letter. So res.find, brands.findOne, ... should be res.Find, brands.FineOne respectively, if such functions exist.
// let's say you have a type like this
type myResult struct {
ID bson.ObjectId `bson:"_id"`
Marque string `bson:"Marque"`
// other fields...
}
// and another type like this
type myCode struct {
Code string `bson:"code"`
// other fields...
}
res := db.C("res")
brands := db.C("brands")
result := myResult{}
// iterate all documents
iter := res.Find(nil).Iter()
for iter.Next(&result) {
var v myCode
err := brands.Find(bson.M{"code": result.Marque}).One(&v)
if err != nil {
// maybe not found or other reason,
// it is recommend to have additional check
continue
}
query := bson.M{"_id": result.ID}
update := bson.M{"Marque": v.value}
if err = res.Update(query, update); err != nil {
// handle error
}
}
if err := iter.Close(); err != nil {
fmt.Println(err)
}
Now I'm doing:
sess := mongodb.DB("mybase").C("mycollection")
var users []struct {
Username string `bson:"username"`
}
err = sess.Find(nil).Select(bson.M{"username": 1, "_id": 0}).All(&users)
if err != nil {
fmt.Println(err)
}
var myUsers []string
for _, user := range users{
myUsers = append(myUsers, user.Username)
}
Is there a more effective way to get slice with usernames from Find (or another search function) directly, without struct and range loop?
The result of a MongoDB find() is always a list of documents. So if you want a list of values, you have to convert it manually just as you did.
Using a custom type (derived from string)
Also note that if you would create your own type (derived from string), you could override its unmarshaling logic, and "extract" just the username from the document.
This is how it could look like:
type Username string
func (u *Username) SetBSON(raw bson.Raw) (err error) {
doc := bson.M{}
if err = raw.Unmarshal(&doc); err != nil {
return
}
*u = Username(doc["username"].(string))
return
}
And then querying the usernames into a slice:
c := mongodb.DB("mybase").C("mycollection") // Obtain collection
var uns []Username
err = c.Find(nil).Select(bson.M{"username": 1, "_id": 0}).All(&uns)
if err != nil {
fmt.Println(err)
}
fmt.Println(uns)
Note that []Username is not the same as []string, so this may or may not be sufficient to you. Should you need a user name as a value of string instead of Username when processing the result, you can simply convert a Username to string.
Using Query.Iter()
Another way to avoid the slice copying would be to call Query.Iter(), iterate over the results and extract and store the username manually, similarly how the above custom unmarshaling logic does.
This is how it could look like:
var uns []string
it := c.Find(nil).Select(bson.M{"username": 1, "_id": 0}).Iter()
defer it.Close()
for doc := (bson.M{}); it.Next(&doc); {
uns = append(uns, doc["username"].(string))
}
if err := it.Err(); err != nil {
fmt.Println(err)
}
fmt.Println(uns)
I don't see what could be more effective than a simple range loop with appends. Without all the Mongo stuff your code basically is this and that's exactly how I would do this.
package main
import (
"fmt"
)
type User struct {
Username string
}
func main() {
var users []User
users = append(users, User{"John"}, User{"Jane"}, User{"Jim"}, User{"Jean"})
fmt.Println(users)
// Interesting part starts here.
var myUsers []string
for _, user := range users {
myUsers = append(myUsers, user.Username)
}
// Interesting part ends here.
fmt.Println(myUsers)
}
https://play.golang.com/p/qCwENmemn-R
As I know, we can use
> db['twitter-3'].find({}, {"text": 1})
to select all texts in collection.
How can we use mgo to find specific field in golang?
I tried
var result []string
err = conn.Find(bson.M{}, bson.M{"text", 1}).All(&result)
But it is not correct.
Use the query Select method to specify the fields to return:
var result []struct{ Text string `bson:"text"` }
err := c.Find(nil).Select(bson.M{"text": 1}).All(&result)
if err != nil {
// handle error
}
for _, v := range result {
fmt.Println(v.Text)
}
In this example, I declared an anonymous type with the one selected field. It's OK to use a type with all document fields.
to select multiple fields:
var result []struct{
Text string `bson:"text"`
Otherfield string `bson:"otherfield"`
}
err := c.Find(nil).Select(bson.M{"text": 1, "otherfield": 1}).All(&result)
if err != nil {
// handle error
}
for _, v := range result {
fmt.Println(v.Text)
}
var result interface{}
err = c.Find(nil).Select(bson.M{"text": 1}).All(&result)
So here is my question. I have an array which are stored the _ids of mongodbs objects. Whats the right way to retrieve them all in one query using the mgo and bson package?
So if the array is like that: ids:=["543d171c5b2c12420dd016","543d171c5b2dd016"]
How we make the query ? I tried that but I know its wrong.
query := bson.M{"_id": bson.M{"$in": ids}}
c.Find(query).All()
Thanks in advance
If the documents are stored with string ids, then the code looks correct.
The ids look like hex encoded object ids. If the object identifiers are object ids, then you need to the convert the hex strings to object ids:
oids := make([]bson.ObjectId, len(ids))
for i := range ids {
oids[i] = bson.ObjectIdHex(ids[i])
}
query := bson.M{"_id": bson.M{"$in": oids}}
MongoDB syntax for go.mongodb.org/mongo-driver has been updated, this should work using the official driver.
oids := make([]primitive.ObjectID, len(ids))
for i := range ids {
objID, err := primitive.ObjectIDFromHex(ids[i])
if err == nil {
oids = append(oids, objID)
}
}
This is to convert back to a struct that can be used through out the app
type MongoUser struct {
ID *primitive.ObjectID `json:"id" bson:"_id"`
FirstName string `json:"first_name" bson:"firstName"`
LastName string `json:"last_name" bson:"lastName"`
Email string `json:"email" bson:"email"`
}
This is a helper method that takes your slice of ids and turns it into the object id type.
func formatObjectIdMultiple(hex []string) ([]primitive.ObjectID, error) {
var list []primitive.ObjectID
oids := make([]primitive.ObjectID, len(hex))
for _, i := range hex {
objectId, err := primitive.ObjectIDFromHex(i)
if err != nil {
return nil, err
}
oids = append(oids, objectId)
}
return list, nil
}
Here is my method for the db. Its important you use bson.M for some reason bson.D does not work with this. Also dont forget to close your cursor the defer function will close it at the end of your GetMultipleUser function.
func (mongo *Mongo) GetMultipleUser(ids []string) ([]*MongoUser, error) {
objectIDs, err := formatObjectIdMultiple(ids)
if err != nil {
return nil, err
}
query := bson.M{"_id": bson.M{"$in": objectIDs}}
coll := mongo.Con.Database("dbName").Collection("users")
cursor, err := coll.Find(context.Background(), query)
if err != nil {
return nil, err
}
defer func() {
cursor.Close(context.Background())
}()
var output []*MongoUser
for cursor.Next(context.Background()) {
var temp *MongoUser
cursor.Decode(&temp)
output = append(output, temp)
}
return output, nil
}
In MongoDB doing something like db.mycollection.find() returns all documents in a collection.
When working in GoLang using the package labix.org/v2/mgo and I do for example:
query := db.C("client").Find();
It complains that it requires input in the form of an interface. All I need to do is retrieve all documents and iterate through them and display each one for now. How do I achieve this effect? All examples I have seen seem to have filters in place.
Found a solution:
var results []client
err := db.C("client").Find(nil).All(&results)
if err != nil {
// TODO: Do something about the error
} else {
fmt.Println("Results All: ", results)
}
func (uc UserController) GetUsersList(w http.ResponseWriter,r *http.Request,p httprouter.Params){
var u []models.User
// Fetch user
if err := uc.session.DB("mydb").C("users").Find(nil).All(&u); err != nil {
w.WriteHeader(404)
fmt.Println("Results All: ", u)
return
}
uj, _ := json.Marshal(u)
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(200)
fmt.Fprintf(w, "%s", uj)
}