最近學習在go中操作mongodb，瞭解到主要有第三方mgo和官方mongo-driver兩個庫使用最多。mgo已經停止維護了，因此選擇了mongo-driver。本文記錄一些常用的程式碼操作筆記，以備隨時查閱。

import (
"context"
"fmt"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
"log"
"reflect"
)

// Trainer type is used for later
type Trainer struct {
Name string
Age int
City string
}

func main() {
// Set client options
clientOptions := options.Client().ApplyURI("mongodb://localhost:27017")

// Connect to MongoDB
client, err := mongo.Connect(context.TODO(), clientOptions)

if err != nil {
    log.Fatal(err)
}

// Check the connection
err = client.Ping(context.TODO(), nil)

if err != nil {
    log.Fatal(err)
}

fmt.Println("Connected to MongoDB!")
// Get collection
collection := client.Database("test").Collection("trainers")

ash := Trainer{"Ash", 10, "Pallet Town11"}
misty := Trainer{"misty", 10, "Cerulean City"}
brock := Trainer{"Brock", 15, "Pewter City"}

// Insert
insertResult, err := collection.InsertOne(context.TODO(), ash)
if err != nil {
    log.Fatal(err)
}
fmt.Println("Inserted a single document: ", insertResult.InsertedID)

// InsertMany
trainers := []interface{}{misty, brock}
insertManyResult, err := collection.InsertMany(context.TODO(), trainers)
if err != nil {
    log.Fatal(err)
}
fmt.Println("Inserted multiple documents: ", insertManyResult.InsertedIDs)


// Update
filter := bson.D{{"name", "Ash"}}
fmt.Println("filter:", reflect.TypeOf(filter))
update := bson.D{
    {"$inc", bson.D{
        {"age", 1},
    }},
}
fmt.Println("update:", reflect.TypeOf(update))
updateResult, err := collection.UpdateOne(context.TODO(), filter, update)
if err != nil {
    log.Fatal(err)
}

fmt.Printf("Matched %v documents and updated %v documents.n", updateResult.MatchedCount, updateResult.ModifiedCount)

// Search
var result Trainer
err = collection.FindOne(context.TODO(), filter).Decode(&result)
if err != nil {
    log.Fatal(err)
}
fmt.Printf("Found a single document: %+vn", result)
findOptions := options.Find()
findOptions.SetLimit(5)
var results []*Trainer
cur, err := collection.Find(context.TODO(), bson.D{{}}, findOptions)
if err != nil {
    log.Fatal(err)
}

for cur.Next(context.TODO()) {
    var elem Trainer
    err := cur.Decode(&elem)
    if err != nil {
        log.Fatal(err)
    }

    results = append(results, &elem)
}

if err := cur.Err(); err != nil {
    log.Fatal(err)
}

cur.Close(context.TODO())

fmt.Printf("Found multiple documents (array of pointers): %+vn", results)

// DeleteMany
deleteResult, err := collection.DeleteMany(context.TODO(), bson.D{{}})
if err != nil {
    log.Fatal(err)
}
fmt.Printf("Deleted %v documents in the trainers collectionn", deleteResult.DeletedCount)
 

}