Golang vs. MongoDB: Deleting documents

In the process of using Golang as an application development language, a very common database is MongoDB. By using MongoDB we can easily store and retrieve data and it also has the advantage of being quickly used in applications. In this post, we will learn how to delete documents using Golang and MongoDB.

In MongoDB, documents are stored in collections. Collections are similar to tables in relational databases, but the data stored in collections does not need to follow a specific schema. This gives developers more flexibility, which also makes deleting documents easier.

In Golang, we use the mgo (mongo-go-driver) library to interact with MongoDB. The mgo library is a lightweight, high-performance, and easy-to-use MongoDB driver that supports all MongoDB functionality. In the following example, we will use the mgo library to delete documents.

First, we need to install the mgo library using the following command:

go get go.mongodb.org/mongo-driver/mongo

Next, we will create a structure containing the MongoDB connection details.

type MongoDBConfig struct {
    Host        string
    Database    string
    Collection  string
}

func (c *MongoDBConfig) getMongoSession() (*mongo.Database, error) {
    client, err := mongo.NewClient(options.Client().ApplyURI(c.Host))
    if err != nil {
        return nil, err
    }

    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()

    err = client.Connect(ctx)
    if err != nil {
        return nil, err
    }

    return client.Database(c.Database), nil
}

In this code, we define a structure called MongoDBConfig to store MongoDB connection details such as the name of the host, database, and collection. The getMongoSession method is responsible for establishing a connection to the database and returning the connection to the caller.

The next step is to delete the document in MongoDB. We can use the following code to delete a document:

func deleteDocument(m MongoDBConfig, id string) (bool, error) {
    session, err := m.getMongoSession()
    if err != nil {
        return false, err
    }

    filter := bson.M{"_id": bson.ObjectIdHex(id)}
    result, err := session.Collection(m.Collection).DeleteOne(context.Background(), filter)
    if err != nil {
        return false, err
    }

    if result.DeletedCount == 0 {
        return false, nil
    }

    return true, nil
}

In this code, we have established a connection to the database using the getMongoSession method. We also define a method called deleteDocument that passes the MongoDBConfig structure with the ID string as parameters. We find the document matching the ID in the specified collection and delete it using the DeleteOne method. If the deletion is successful, it returns true, otherwise it returns False.

Before calling the deleteDocument function, we need to ensure that the ID exists in the collection. Here is the code on how to check ID existence:

func documentExists(m MongoDBConfig, id string) (bool, error) {
    session, err := m.getMongoSession()
    if err != nil {
        return false, err
    }

    filter := bson.M{"_id": bson.ObjectIdHex(id)}
    count, err := session.Collection(m.Collection).CountDocuments(context.Background(), filter)
    if err != nil {
        return false, err
    }

    if count == 0 {
        return false, nil
    }

    return true, nil
}

In this code, we have defined a method called documentExists which passes MongoDBConfig structure with ID string as parameters. We find documents matching the ID in the specified collection and get the count from the number of documents. If the count is zero, the document does not exist.

Before executing the deleteDocument method, we need to execute the documentExists method to check whether the document exists. If the document exists, it can be safely deleted. Here is the code on how to execute these two methods:

func main() {
    m := MongoDBConfig{
        Host: "mongodb://localhost:27017",
        Database: "test",
        Collection: "users",
    }

    id := "5fd7bcb3c28082702d0f0e6b"
    exists, err := documentExists(m, id)
    if err != nil {
        log.Fatal(err)
    }

    if exists {
        deleted, err := deleteDocument(m, id)
        if err != nil {
            log.Fatal(err)
        }

        if deleted {
            fmt.Println("Document deleted successfully.")
        } else {
            fmt.Println("Failed to delete document.")
        }
    } else {
        fmt.Println("Document does not exist.")
    }
}

In this code, we set some example values ​​for the MongoDBConfig structure and specify the ID of the document to be deleted. We use the documentExists method to check if the document exists. If the document exists, delete it using the deleteDocument method. If the deletion is successful, we print a message to the screen.

In this article, we learned how to delete documents using Golang and MongoDB. By using mgo library, we can easily interact with MongoDB and achieve fast deletion of documents. Now you can use this simple code snippet to manage documents in your MongoDB database.

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