PgConf.Russia 2020

We would like to share our test results (including performance testing) of PostgreSQL/Citrus and MongoDB for our company's data. It has been a very exciting process with unexpected turns and a somewhat controversial outcome.

To build a decent query plan, the optimizer has to understand statistical characteristics of underlying data. It is interesting to observe how the structure of the collected information became more complicated over time: what the optimizer relied on back in its early days and what is at his disposal now with the release of the 12th version. We will also talk about how and when statistics are collected, how to manage this process and whether it is necessary to think about it at all.

Porting applications from Oracle to Postgres is common work today. Unfortunately it is not without problems. In presentation I'll try to show the basic performance problems related to differences between Oracle and Postgres and PL/SQL and PL/pgSQL.

pg_repack is one of the most popular instruments for removing bloat of tables and indexes in Postgres. In most cases, it works perfectly. But if you use such a feature of Postgres as deferred constraints, using pg_repack becomes more difficult or even impossible. I will talk about how we encountered the problem and will describe some workarounds - from internal instruments of Postgres to a small patch for pg_repack.