Tomas Vondra


Tomas first met PostgreSQL in 2003 and quickly became a big fan. He participated in porting various applications to PostgreSQL from other databases, tuning and fixing performance issues etc. He is also a member of the executive committee of CSPUG (Czech and Slovak PostgreSQL Users Group), an "umbrella" organization for the local PostgreSQL community. Tomas currently works as a database engineer for EDB, working on various PostgreSQL-related tasks.

Talk Description: Where do the performance cliffs come from?

When running queries on a Postgres database, chances are you have experience with hitting a "performance cliff" - an abrupt change of performance for a given query, after only a small change in data and/or query parameters.

In this talk I'll explain why performance cliffs happen - after a brief explanation of how cost-based optimizers work and what assumptions that relies on, I'll show a couple examples why/how it fails. I'll share some recommendations on how to mitigate these issues.

If time permits, I'll talk about a couple interesting improvements & possible solutions proposed in recent research projects, focused on making query execution more adaptive & robust.