For the past four months, I’ve worked as a backend engineering intern with the incredibly talented engineers of the Cockroach Labs SQL Execution team to unlock the full potential of the vectorized engine ahead of the CockroachDB 20.1 release. During this time, I focused on improving the algorithm behind some of CockroachDB’s SQL operators, to reduce memory usage and speed up query execution. In this blog post, I will go over the improvements that I made to the algorithm behind the unordered distinct operator, as well as new algorithms that address some existing inefficiencies.