Migrating from PostgreSQL to MongoDB

MongoDB may be an excellent choice over PostgreSQL. MongoDB may be especially suitable if:

• Your application is managing structured and unstructured data, and you expect the volume to grow.
• You are working with modern languages that require working with objects that are flexible, requiring a database with rich language support and flexible indexing strategies.
• Your application needs to scale quickly to adjust to changes in traffic and data volume.

Assuming your application is ready to connect to MongoDB and, if necessary, you have restructured your data to fit a MongoDB schema design, these are the steps you will take and the tools you will need:

• You can use Relational Migrator to translate your relational schema into a MongoDB schema design visually.
• Within the psql client, you will perform SELECT queries of your data which are then piped into a COPY command for exporting the query results, either to a tab-separated file TSV) or as JSON.
• If you export to JSON, your queries may need to use some PostgreSQL JSON functions and aggregation functions After your data has been exported, you would use the mongoimport tool to import your data into MongoDB.
• As an alternative to mongoimport, you could use MongoDB's bulkWrite operation to load the data.

The main advantages are in the areas of speed and scalability. Regarding speed:

• Querying data and their associated data objects is often faster in MongoDB than in SQL, which uses expensive JOIN statements.
• MongoDB’s flexible schema enables changes to an application's data model or schema to be deployed quickly and flexibly, without the need for migrations or to update query statements in legacy code.
  

Regarding scalability

• MongoDB's distributed, scale-out architecture allows your database to grow as your application grows. This is in contrast to PostgreSQL, which is not natively distributed.
• MongoDB Atlas supports sharded clusters with multi-node replica sets right out of the box. Shard keys can even be changed in real time without downtime, thanks to live resharding. Starting in MongoDB 7.0, the shard key advisor commands will deliver metrics that will help you refine your shard keys.