PostgreSQL is an interesting choice in this section because, technically, there is no separate NoSQL version of PostgreSQL, but rather PostgreSQL has added various features in recent releases that have added NoSQL capabilities to the existing Postgres implementation.

Proponents of PostgreSQL rightly point out that it is a much older, and, by extension tested technology, having been first released in the mid-1990s. Postgres now supports hierarchical document data storage, JSON, a key-value store (called HStore), and sharding, and includes interfaces for various programming languages as well as diverse data sources. In other words, PostgreSQL has been extended to support NoSQL-like functionalities while maintaining its existing capabilities as a traditional RDBMS.

PostgreSQL is available as a fully-functional, open source product.

Business use cases: While most of the technologies in this section are available under commercial licensing (to get access to all their capabilities), PostgreSQL, being open source, is a very cost-effective way to try out a mature database without making large initial investments. It can also serve as a testing platform for trying out NoSQL features, such as handling JSON data prior to making a final decision. In either case, PostgreSQL is a formidable platform and can support enterprise needs. There are also commercial derivatives of PostgreSQL—databases that build on top of PostgreSQL such as Greenplum, which is also available as an open source product.