How to choose between PostgreSQL and CockroachDB

Originally published on Aug 15, 2019 at ObjectRocket.com/blog

As CockroachDB® and PostgreSQL® have consolidated a place in the market when it comes to relational workloads, many folks have started asking which they should choose. CockroachDB offers true global-scale SQL with distributed transactions and horizontal read/write scaling built-in for unprecedented scale, resiliency, and performance for SQL workloads. However, there are still some scenarios where PostgreSQL might just be a better fit.

Similarities between CockroachDB and PostgreSQL

These two technologies overlap quite a bit. First and foremost, both boast:

• SQL compliance
• ACID transactions
• PostgreSQL wire protocol compatibility
• Broad client driver and ORM support

This functionality covers most major points, which means the choice comes down to more nuanced decision points. With only a few exceptions, you can try an app on top of either database and later transition to the other without having to rewrite your app.

Want to check out CockroachDB, but decide that PostgreSQL is a better fit? The chances are pretty good that you won’t run into any trouble. Do you have an app running on PostgreSQL, but you’re looking for better scaling and failover? CockroachDB could be a better fit.

Differentiators to help you decide

Compatibility, complex queries, scale, and flexibility might help you choose one option over the other.

Scale

The biggest difference is how the products handle scaling, replication, and high availability (HA). CockroachDB was built from the ground up to provide a global SQL datastore with distributed transactions. You can spread your data across clouds and regions with fine-grained control over what data is allowed to reside in each region or cloud. Though solutions and extensions do exist for providing some of the same functionality with PostgreSQL, it’s not as complete nor as straightforward to configure and manage.

CockroachDB’s focus on global scale allows it to be a lot more cloud-friendly. CockroachDB expects a large number of smaller, disposable nodes, so scaling and HA are just handled effortlessly behind the scenes for you.

PostgreSQL, on the other hand, does provide a number of solutions for multi-master, scaling, and HA, but most of that functionality is not included in PostgreSQL and requires third-party extensions. Also, the setup, configuration, and day-to-day management are a bit more complex for an HA PostgreSQL deployment.

Flexibility

A real benefit of PostgreSQL is its many years of battle hardening and the scope of tunables and extensions. Just compare the documentation for Server Configuration on PostgreSQL, and you see a vast array of options and tuning parameters for your cluster. Want Isolation levels? You’ve got four options, whereas CockroachDB gives you only one. Want replication? PostgreSQL gives you eight alternatives, while CockroachDB handles it behind the scenes.

PostgreSQL also offers a huge ecosystem of extensions to expand the product. Hundreds of extensions are publicly available, and you can also write your own. These range from adding clustering (like Citus) to new objects (postGIS) to optimizing PostgreSQL for a specific use case (Timescale). This flexibility definitely comes with a cost, though. It can introduce complexity and impact the performance and stability of your instance. You could also end up misconfiguring your environment. The CockroachDB approach simplifies things so that building and managing a cluster is straightforward.

Compatibility

If you need complete PostgreSQL or fuller SQL conformance, PostgreSQL is a better bet. Whether you’ve got a legacy app or you need a backend store for a standard CMS or web framework, there could be a heavy reliance on the corners of PostgreSQL or SQL that Cockroach might not support yet. Though Cockroach Labs continues to add more features and functionality to the product, it’s not 100% compatible with PostgreSQL yet. Another area where you might see a difference is how CockroachDB handles roles, users, groups, and authentication. The PostgreSQL authentication options are extremely robust, and though CockroachDB does offer RBAC, there are some significant differences between the two technologies.

You can overcome compatibility challenges, but it is ultimately up to your app and your ability to identify and address potential incompatibilities.

Complex queries

An area where Cockroach Labs has invested a ton of effort has been the ability to perform joins and improve performance with their cost-based SQL query optimizer. However, if you have a Business Intelligence or analytics workload with extremely complex queries and multiple joins, views, aggregations, and expression evaluations, PostgreSQL might be the better option.

This is an area where you can easily test with an evaluation or proof of concept. The closer your use case leans towards analytics queries and OLAP, PostgreSQL might be the better bet. With quick OLTP-style transactions, CockroachDB can help the most.

Summary comparison

* Since no datastore that I know of 100% conforms to the full SQL:2011 spec, I just looked at how much of the spec each product supports.

You have two great options before you. Both can be used in concert to create an amazing datastore portfolio. If you’re building from scratch today and you don’t have extremely unique or PostgreSQL-specific needs and scaling matters, then look seriously at CockroachDB as an amazing opportunity. However, if you already know what you need and want to focus on the broad flexibility of PostgreSQL, we can help there as well.

Both PostgreSQL and CockroachDB are available now. Find which is the right fit for you.

Conclusion

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