Step-by-Step Guide to Converting from Couchbase to MongoDB

Introduction

Transitioning from one technology to another is a significant decision for any organization. The move from Couchbase to MongoDB is no exception. Both are powerful NoSQL databases that offer flexibility, scalability, and high performance. However, MongoDB has gained popularity due to its dynamic schema, document-oriented storage, and extensive community support. This article aims to guide you through the process of converting from Couchbase to MongoDB, highlighting the key differences and providing a step-by-step approach to ensure a smooth transition.

Overview of Differences

Aspect	Couchbase	MongoDB
Data Model	Document and Key-Value	Document
Query Language	N1QL (SQL-like)	MongoDB Query Language
Indexing	Primary and Secondary	Secondary only
Consistency	Eventual and Strong	Eventual
Replication	Multi-master	Primary-secondary
Transactions	Supports multi-document transactions	Supports multi-document transactions (since version 4.0)

Differences in Syntax

Operation	Couchbase	MongoDB
Insert Document	INSERT INTO `bucket_name` (KEY, VALUE) VALUES ("doc_id", {"field": "value"});	db.collection.insertOne({"_id": "doc_id", "field": "value"});
Query Document	SELECT * FROM `bucket_name` WHERE field = "value";	db.collection.find({"field": "value"});
Update Document	UPDATE `bucket_name` SET field = "new_value" WHERE field = "value";	db.collection.updateOne({"field": "value"}, {$set: {"field": "new_value"}});
Delete Document	DELETE FROM `bucket_name` WHERE field = "value";	db.collection.deleteOne({"field": "value"});

Converting from Couchbase to MongoDB

Converting your database from Couchbase to MongoDB involves several steps, including data migration, application code adjustment, and learning the new query language. Here are the key steps to consider:

1. Data Migration: Export your data from Couchbase and import it into MongoDB. This can be done using tools like Couchbase's cbexport and MongoDB's mongoimport.
2. Adjusting Application Code: Update your application code to use MongoDB's query language and APIs.
3. Learning MongoDB: Familiarize yourself with MongoDB's documentation and community resources to understand its query language and best practices.

Example Code Conversion

Below are examples of how to convert Couchbase queries to MongoDB queries:

// Couchbase Insert Document
INSERT INTO `bucket_name` (KEY, VALUE) VALUES ("doc_id", {"field": "value"});

// MongoDB Insert Document
db.collection.insertOne({"_id": "doc_id", "field": "value"});

// Couchbase Query Document
SELECT * FROM `bucket_name` WHERE field = "value";

// MongoDB Query Document
db.collection.find({"field": "value"});

// Couchbase Update Document
UPDATE `bucket_name` SET field = "new_value" WHERE field = "value";

// MongoDB Update Document
db.collection.updateOne({"field": "value"}, {$set: {"field": "new_value"}});

// Couchbase Delete Document
DELETE FROM `bucket_name` WHERE field = "value";

// MongoDB Delete Document
db.collection.deleteOne({"field": "value"});