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Why migrate to qmgo

• Mgo is a convenient library for golang to operate mongodb, but it does not support the latest features of mongodb, such as Transaction.
• My old project is written in mgo. If I want to migrate to the official mongo-driver, its syntax is more primitive, the usage difference is large, and the migration cost will be higher.
• I found a library called qmgo, which is based on the official mongo-driver package, but it is closer to mgo in terms of syntax and suitable for simple and rude migrations.

Below I will record the methods used in the migration process, which I found out by myself. If you have any questions,
please correct me.

Batch replacement

• Batch replace github.com/globalsign/mgo/bson with go.mongodb.org/mongo-driver/bson
• Batch replace bson.NewObjectId() with primitive.NewObjectID()
• Batch replace bson.ObjectId with primitive.ObjectID
• Batch replace .Find(bson.M with .Find(c, bson.M
• Batch replace .Find(search to .Find(c, search
• Batch replace .Insert( to .InsertOne(c,
• Batch replace .Update( to .UpdateOne(c,
• Batch replace .RemoveAll( to .RemoveAll(c,
• Batch replace .Remove( to .Remove(c,
• Batch replace errors.Is(err, mgo.ErrNotFound) with qmgo.IsErrNoDocuments(err)
• Batch replace .EnsureIndex(mgo.Index{ for .CreateOneIndex(c, options.IndexModel{

Copy and paste

• Where there is no context, copy and paste everywhere c := context.Background()
• If it is in the interface method of gin, you can directly use gin's c *gin.Context (but if multi-coroutine operation needs to Copy gin's Context)

Function substitution

• Replace the bson.IsObjectIdHex() method:

package db

import (
    "go.mongodb.org/mongo-driver/bson/primitive"
)

func IsObjectIDHex(hex string) bool {
    _, err := primitive.ObjectIDFromHex(hex)
    if err != nil {
        return false
    }
    return true
}

• Replace the bson.ObjectIdHex() method:

package db

import (
    "fmt"
    "go.mongodb.org/mongo-driver/bson/primitive"
)

func ObjectIDHex(hex string) primitive.ObjectID {
    id, err := primitive.ObjectIDFromHex(hex)
    if err != nil {
        panic(fmt.Sprintf("Invalid input to ObjectIDHex: %+v", hex))
    }
    return id
}

These functions can be placed in the package of the auxiliary method or the package of the database operation, and then
replace the references in batches.

Summary

At this point, the project completed the migration within two hours and started running smoothly.

Thanks to the author of qmgo for making the wheels for me.

If I have the opportunity, I will also open up some wheels.