SQL Server to Postgres migration: A comprehensive guide
Migrating from SQL Server to Postgres is a significant move for organizations looking to reduce costs, improve scalability, and future-proof their data infrastructure.
But database migrations are costly and time consuming. They frequently run overtime, carry significant business risks, and are a significant opportunity cost. So if you’re going to undertake one, you might want to know that you have an absolutely airtight business case for doing so. And it’s essential to avoid common pitfalls that can result in lengthy outages.
Our experience with large-scale migrations has shown that you can get better performance at a lower cost with Postgres than with SQL Server. If you’re considering a migration to Postgres, get in touch with StepChange’s team for a performance review of your current database and tech stack.
Why migrate from SQL Server to Postgres?
The business case for moving from legacy databases like SQL Server to Postgres has only become more compelling over time. Postgres offers a range of advantages:
- Lower licensing and cloud costs
- Enhanced feature sets (extensibility, support for semi-structured data, and custom functions)
- Long-term strategic advantages (open-source benefits, deployment flexibility, and avoiding vendor lock-in)
SQL Server vs. Postgres
SQL Server is a Relational Database Management System (RDBMS) developed by Microsoft, known for its enterprise features and integration with the Microsoft ecosystem. Postgres (or PostgreSQL) is an Object-Relational Database Management System (ORDBMS) that is open-source and offers advanced extensibility features, making it highly adaptable for various use cases.
Costs
Data infrastructure decisions largely hinge on costs, particularly the sustainability of long term licensing.
Licensing costs
SQL Server is a proprietary product with significant licensing fees, which can range from thousands to tens of thousands of dollars per server core. (need links/numbers). These costs increase with usage, server cores, and premium features–these are pretty much guaranteed to rise over time since your company will continue to add on larger databases or more servers to support its growth.
Postgres is open-source and free, and it’s hard to beat $0 in licensing fees. A typical mid-sized SaaS company uses multiple servers for production and analytics, and migrating to Postgres would mean redirecting licensing savings into other strategic areas, such as enhancing data capabilities or investing in machine learning.
Cloud costs
Another cost-related factor is cloud infrastructure. SQL Server can be more resource-intensive in cloud environments, and when you pair this with the licenses, the overall cost model becomes increasingly unsustainable over time. For instance, some companies that use managed services such as Azure SQL Database find that cloud costs increase over time as their database scales.
Postgres, on the other hand, is well-supported by major cloud providers. Managed services like Amazon RDS, Google Cloud SQL, Azure Database are cost-effective options, and cloud-native versions like Amazon Aurora are optimized for efficiency to keep operational costs low.
If you’re a data team looking to build cloud-native applications and want to avoid vendor lock-in, Postgres is the obvious choice.
Features
Postgres offers many compelling features that set it apart from SQL server.
Extensibility
Postgres is well known for its flexibility–it supports custom data types, user-defined functions, and procedural languages. It offers JSONB for efficient storage and querying of semi-structured data, which is great if you want to combine structured relational data with more flexible document-based formats; you can store and query mixed data without needing to set up a separate NoSQL database.
Scalability and performance
While SQL Server has a slight performance edge in some areas, Postgres is rapidly closing the gap. One you factor in cost and extensibility, the performance differences often become negligible.
With SQL Server, scaling horizontally can be a costly challenge. There are highly Postgres-compatible offerings like Yugabyte (a Distributed SQL database) to enable efficient horizontal scaling for applications. You can also leverage Postgres query optimization techniques for better database performance. For a deeper understanding of Postgres’ capabilities and the scenarios where it might encounter challenges, see our article by Andrew Atkinson on exploring the limits of Postgres.
Open source
SQL Server is proprietary, while Postgres is open-source. This has a few implications beyond customization.
Development
SQL Server’s proprietary nature means your flexibility is limited by Microsoft's development roadmap and release cycle.
Postgres is a highly versatile option that adapts well to a range of use cases. With Postgres, you can modify the database needed as there are no restrictions on what you want to do with it. The ecosystem of extensions and tools is driven by a highly active community of developers.
One reason that prompts our clients to migrate away from SQL Server is requiring a specialized index type for their workload. We typically point them to Postgres because it offers extensions like PostGIS for spatial data, or TimescaleDB for time-series data.
Vendor lock-in
Avoiding vendor-lock in ranks up there with cost as a criteria. This is probably more important than historically given the growing adoption of multi-cloud and hybrid-cloud strategies. If you’re using SQL Server in an Azure environment and want to transition away from Microsoft, you’ll likely face challenges in migration.
Postgres provides true deployment flexibility as you can use it on all major cloud platforms or on-premises. You can migrate between cloud vendors or move back to on-prem as needed without having to rewrite your applications.
Planning your SQL Server to Postgres migration
Migrating from SQL Server to Postgres requires careful planning and execution to minimize risks. Data teams often underestimate the scope of a migration: it’s not just about moving data but about transforming your database environment to take full advantage of the features and cost savings that Postgres offers.
While AI can assist with certain tasks, the complexity of database migrations–particularly when dealing with custom schemas, dependencies, and business logic–requires close human oversight and intervention.
A successful migration typically includes the following stages, each of which must be carefully managed to mitigate risk and minimize downtime:
- Assessment: Evaluate your current SQL server setup, including schema, data types, stored procedures, and application dependencies to identify potential problems early on.
- Schema conversion: Convert your SQL Server schema to Postgres by transforming data types, converting stored procedures to Postgres-compatible functions, and adjusting indexing strategies.
- Data migration: Depending on the size of your database, you may need to use third-party ETL tools to move your data efficiently and ensure data integrity throughout the process.
- Testing & validation: Verify that all data has been correctly transferred and that your applications are functioning as expected, before going live.
- Optimizing & tuning: Once migrated, optimize your Postgres setup by adjusting configuration settings, optimizing queries, and leveraging Postgres-specific features to improve efficiency. (Check out our recent article on how to perform advanced Postgres performance tuning and monitoring which is also a capability of our APX product)
- Training and support: Ensure your team is well-prepared to work with Postgres, this may involve training or check out our Postgres parameter optimization guide to learn best practices for optimizing database performance post-migration.
If you're assessing a potential SQL Server to PostgreSQL migration, we can help you determine whether moving to Postgres is the right step for your organization. Our team of experts has extensive experience handling complex migrations and can manage the entire process–on time and on budget. We also work to ensure that your migration is seamless and optimized to leverage the best of Postgres’ capabilities.
Get your migration started today
Ready to migrate from SQL Server to Postgres? Get in touch with us to learn more about how we can help your company speed up migrations, optimize Postgres databases, and reduce costs while improving performance:
- Engage our team for an in-depth review of your current SQL Server setup to evaluate the benefits of migrating to Postgres
- Book a call to see a demo of our SaaS StepChange APX product which helps improve query performance and reliability while maintaining predictable costs.
