Citus Blog

Distributed PostgreSQL has become a hot topic. Several distributed database vendors have added support for the PostgreSQL protocol as a convenient way to gain access to the PostgreSQL ecosystem. Others (like us) have built a distributed database on top of PostgreSQL itself.

For the Citus database team, distributed PostgreSQL is primarily about achieving high performance at scale. The unique thing about Citus, the technology powering Azure Cosmos DB for PostgreSQL, is that it is fully implemented as an open-source extension to PostgreSQL. It also leans entirely on PostgreSQL for storage, indexing, low-level query planning and execution, and various performance features. As such, Citus inherits the performance characteristics of a single PostgreSQL server but applies them at scale.

That all sounds good in theory, but to see whether this holds up in practice, you need benchmark numbers. We therefore asked GigaOM to run performance benchmarks comparing Azure Cosmos DB for PostgreSQL to other distributed implementations. GigaOM compared the transaction performance and price-performance of these popular managed services of distributed PostgreSQL, using the HammerDB benchmark software:

Keep reading

One of the most important improvements in Citus 11.3 is that Citus offers more reliable metadata sync. Before 11.3, when a Citus cluster had thousands of distributed objects (such as distributed tables), Citus occasionally experienced memory problems while running metadata sync. Due to these memory errors, some users with very large numbers of tables were sometimes unable to add new nodes or upgrade beyond Citus 11.0.

To address the memory issues, we added an alternative "non-transactional" mode to the current metadata sync in Citus 11.3.

The default mode for metadata sync is still the original single transaction mode that we introduced in Citus 11.0. But now in 11.3 or later, if you have a very large number of tables and you run into the memory error, you can choose to optionally switch to the non-transactional mode, which syncs the metadata via many transactions. While most of you who use Citus will not need to enable this alternative metadata sync mode, this is how to do it:

Keep reading