Migrate from MongoDBPostgreSQL
Escape MongoDB's licensing changes (SSPL), get true relational queries, schema enforcement, ACID transactions, lower hosting costs.
Step-by-step
- 1
1. Export MongoDB collections
`mongoexport --collection=X --out=X.json` for each collection.
- 2
2. Design relational schema
Denormalize embedded documents into separate tables. Use foreign keys for relationships MongoDB stored implicitly.
- 3
3. Use JSONB for true unstructured fields
Postgres `JSONB` columns handle MongoDB-like unstructured data with full indexing. Don't over-normalize what genuinely doesn't need it.
- 4
4. Bulk import
Write a Node/Python script that reads MongoDB JSON exports and inserts into Postgres with proper FK resolution.
- 5
5. Rewrite queries
MongoDB aggregation pipelines become SQL CTEs + window functions. This is the bulk of the work.
- 6
6. Switch driver
Replace `mongoose`/`mongodb` with `pg`, `postgres.js`, or an ORM like Prisma/Drizzle.
Gotchas to watch
- MongoDB's `_id` ObjectIDs vs Postgres UUIDs — pick one convention.
- Aggregation pipelines are MongoDB's biggest win. SQL is more powerful but you'll write more code.
- Test query performance under load before cutover — JSONB indexing requires GIN indexes.
- If you used MongoDB Change Streams, you need Postgres LISTEN/NOTIFY or Debezium.
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