PgConf.Russia 2019

Workshop on Server-Side development in procedural languages PL/Perl ,PL/Python, PL / v8 inside PostgreSQL and Postgres Pro. You will not only learn what they are for but also how to use them correctly and what results can be achieved using them.

As any ordinary software developers, we just pursued a goal to develop a system robust for high loads, and even succeeded. The system architecture was fine, but the data volume was keeping increased and revealed the painful issues and errors that nobody had expected. We faced very strange queries seemed to be unbelievable. In my short talk I would like to share sad experience of arised-from-nothing high loads in DBMS and solving the challenge.

A major responsibility of a database engine is to convert a declarative SQL query to an efficient execution plan, employing various methods to scan and join the relations. There is always a development effort to improve this area. What clever execution plans can PostgreSQL generate, what's new in version 11 and what is in development? To name a few things, the joins are optimized by removing unneeded outer and inner joins, and reducing joins from outer and semi to inner. There is work to enable merge joins on inequality and range overlap, and to improve join selectivity estimates with multi-column statistics. When it comes to scanning a single relation, covering indexes allow to use index-only scans more often. Incremental sort and more precise estimation of sorting costs help generate better paths when sorted output is required, e.g. when using GROUP BY and ORDER BY or performing merge joins. This talk aims to give an overview of such optimizations that already exist and that are being developed now.

My talk will be about different cases of usage and setup of the standby server; examples how to setup standby linked to your archive( to make an opportunity to recreate standby from archive after primary crashing and promoting your old standby); Avito experience of usage of standby server for read-only queries: problems and solutions; monitoring of standby.